Chemical Engineering

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This is the collection for the University of Waterloo's Department of Chemical Engineering.

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Modelling and Performance of a Hydrogel-Based Photobioreactor
(University of Waterloo, 2024-07-05) Rasmussen, Nicholas
This work is motivated by the need for in situ food production with respect to future space activities due to the technical and economic in-feasibility of long-term earth-based resupply. The unique size constraints of space have prevented conventional food systems from demonstrating feasibility. Owing to their high growth rates and phototropic activity, microalgae are a promising candidate to meet the caloric and respiratory needs of astronauts as part of a biological life support systems (BLSS). However, the gravity dependence and size of transitional photobioreactors poses a challenged to their utilization in space. As such, a solid-state hydrogel-based photobioreactor (hPBR) is proposed to achieve inherent phase separation allowing for extra-terrestial use. Initially proposed for the Canadian Space Agency (CSA) Deep Space Food Challenge (DSFC) (Design A), this design was further iterated to improve productivity and reactor performance (Design B). Using Chlorella vulgaris, Design B achieved a biomass productivity of 2.4 and 3.2 g m−2d −1 when using physically (pPVA) and chemically (cPVA) crosslinked poly(vinyl) alcohol (PVA) respectively with a water demand of 0.44 kg g−1 biomass. Over 23 days of growth, the lipid content increased from 18.9% to 56.6% and 13.8% to 43.2% for pPVA and cPVA respectively, and the chlorophyll content also decreased. However, cell viability remained high at over 97% and surface coverage analysis showed good coverage within a few days. Observations made with the prototype suggested mass transport limitations were impacting growth, and that poor humidity control led to the hydrogels drying out. To this end, a continuum model of the hydrogel was proposed to better understand mass transfer and to inform future design iterations. Hydrogels are two phase systems where the polymer is fixed due to crosslinking leading to a moving boundary with changes in water content. The proposed model did not require any parameter fitting as values were determined with independent experiments. The model enabled the prediction of the transient material response to changing relative humidity. This helped to explain why humidity control was critical in maintaining cell viability. Humidity impacted the water content of the gel’s surface which needed to be high enough to support algae growth. Using the steady-state solution to the model, the solute transport through the system was also modelled. The solute profile suggested that nutrient concentrations throughout the hydrogel were similar to that in the media tank. This suggests nutrient supply was not the cause of the diminishing biomass quality and that other factors such as photo-inhibition, and mechanical stresses from solid-state cultivation may be issues to address in future work.
Rational Design of Engineered Porous Transition Metal-based Electrocatalysts for Rechargeable Zinc-air Batteries
(University of Waterloo, 2024-06-27) Zhang, Yatian
The adoption of primary zinc-air batteries (ZABs) for telecommunication and medical applications underscores their commercial viability. However, the progress of ZABs have been hindered by challenges associated with air electrodes. The substantial electrode polarizations of the Oxygen Reduction Reaction (ORR) and the Oxygen Evolution Reaction (OER) pose significant energy barriers, impeding the efficiency of charge and discharge processes. Hence, there's an urgent need to develop bifunctional electrocatalysts with superior performance, energy efficiency, and long-term stability for ZABs. In the first work, three-dimensional interconnected and ordered mesoporous Fe2Nx decorated on TiOy with the introduced nitrogen vacancies was constructed (Fe2Nx@TiOy). By creating defects in ordered porous materials, the increased surface area, pore volume, and active sites boost the kinetics of the ORR. Fe2Nx@TiOy with created nitrogen defects reveals a superior ORR performance, including a high half-wave potential (0.88 V vs reversible hydrogen electrode) and high current density (71 mA cm-2 at 0.8 V). The zinc-air battery assembled with Fe2Nx@TiOy catalysts presents a high specific capacity of 809 mAh g-1. Density functional theory (DFT) analysis and X-ray absorption spectroscopy further confirm that the engineering of nitrogen vacancies modulates the electronic environment of Fe and regulates the adsorption and desorption of intermediates to facilitate the ORR activity. The Fe d-band center moving toward the Fermi energy level strengthens the interaction between the adsorbate and substrate, allowing oxygen species to be favorably stabilized onto Fe2Nx@TiOy, while significantly reducing the kinetic barrier. This work serves as a guideline for developing effective defect engineering and ordered porous materials for efficient energy conversion and storage. In the second work, among a series of ternary Cu-Ti-O electrocatalysts, a hierarchical macroporous Cu0.3Ti0.7O2 catalyst achieves a balance between structural stability and active sites exposure, showing an electron density reconfiguration in the Cu-Ti-O system. X-ray absorption fine structure analyses reveal the partial electron density reconfiguration presented among Cu, Ti, and O atoms can be the dominant reason for the peaks shift. It was demonstrated that Ti atoms tended to delocalize maximum charge by releasing it to the Cu atoms in the compositions of Cu0.3Ti0.7O2, which lower the thermodynamic barrier of the total reaction, and hence contributes to a remarkable enhancement in zinc-air battery. This work offers an attractive approach to developing the nonprecious transitional metal-based ORR/OER catalysts, and zinc-air battery for the design of performance-oriented electrocatalysts for wider electrochemical energy applications. In the last work, a unique Mg-decorated three-dimensionally ordered mesoporous (3DOM) Co3O4 electrocatalyst is engineered and evaluated as cathodic material for zinc-air batteries. The modulation of electronic structure and bonding configuration of Co sites through coordination with substituted Mg atoms effectively enhance the interaction with oxygen species and, therefore, the ORR/OER activity. Meanwhile, the substitution of Co2+ with Mg2+ creates abundant, more catalytically active octahedral sites (Co3+) in 3DOM-MgxCo3-xO4. Moreover, the tailored 3D interpenetrating porous structure endows the electrocatalyst with large diffusion channels for oxygen species and highly accessible active sites. The as-prepared catalyst retains 99% and 98% of its initial ORR and OER current, respectively, after 16 h under chronoamperometric measurement. The zinc-air battery assembled with 3DOM-MgxCo3-xO4 exhibits a high power density of 253 mW cm-2 and long-term cyclability over 236 h, outperforming the commercial noble-metal-based catalysts in terms of performance and stability. This work offers a straightforward and promising design strategy for the development of robust bifunctional electrocatalysts toward practical applications of zinc-air batteries. In summary, this thesis exhibits three types of transition metal-based materials with hierarchical three-dimensional porous structures applied in rechargeable zinc-air batteries. The main emphasis is focused on the synthesis and electrocatalytic activity as well as the underlying mechanisms for these materials in zinc-air batteries. It gives a prospect that is expected to engineer and synthesize porous transition metal-based materials for zinc-air batteries.
Synthesis and Characterization of Polymeric Sensing Materials for Detection of Gases in Energy Storage Devices
(University of Waterloo, 2024-06-21) Ghodrati, Shahrzad
The increasing popularity of portable electronic devices, electric vehicles, and smart grids has created a need for energy storage systems including battery technology with lithium-ion batteries (LIBs) being one of the most common battery types. However, enhancing the safety of these LIBs remains a prominent aspect that requires advancements in battery technology as it has been shown that gas evolution occurs in LIBs. The identification and detection of these gases (which can be hazardous in different ways) are critical to protecting human and environmental health. Hence, there is an urgent need for gas-sensing devices (i.e., gas sensors) to minimize concerns regarding health, safety, and the environment. This thesis presents an investigation on the design, evaluation, and characterization of polymeric gas sensing materials for the room-temperature detection of harmful gases (in ppm levels) generated in energy storage devices (e.g., lithium-ion batteries). The importance of gas sensing materials is well recognized as the sensing material is the ‘heart’ of a sensor that interacts with the target analyte, leading to a detection signal generated by the sensor. Four gases, namely, hydrogen (H2), ethylene (C2H4), carbon monoxide (CO), and carbon dioxide (CO2), were found to be the main gases released in LIBs and identified as target gases for detection. Polymers modified/doped with metal oxides have displayed reasonable sensing behavior making them promising sensing materials in gas sensor applications. Polyaniline (PANI) doped with various concentrations of different metal oxide nanoparticles were synthesized and evaluated as sensing materials for target analytes, along with other polymeric materials like polypyrrole (PPy), polythiophene (PTh), and polyvinylpyrrolidone (PVP). Gas sorption characteristics were evaluated using formaldehyde as a "simulant" or "surrogate" due to safety concerns associated with testing target analytes in an academic environment. The doped PANI materials, in particular, exhibited enhanced gas sorption properties, attributed to the synergistic effects of the dopants, which improved the interaction between the polymer matrix and gas molecules. The effect of environmental factors (e.g., ageing), on the sensing performance, related to the sensing material stability, was also evaluated for selected sensing materials. Other property characteristics of the sensing materials were also determined using different techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-rays (EDX), dynamic light scattering (DLS), and Brunauer-Emmett-Teller (BET) tests, to provide a more detailed explanation and additional confirmation of the sorption trends. In the final step, optimal sensing materials were deposited on a MEMS (micro-electro-mechanical system) sensor, which is efficient, inexpensive, and of small size. The sensor as a whole was then evaluated for its sensing performance towards 50 ppm ethylene.
Robust NMPC of Large-Scale Systems and Surrogate Embedding Strategies for NMPC
(University of Waterloo, 2024-06-20) Elorza Casas, Carlos Andrés
Non-linear model predictive control (NMPC) is a promising control algorithm due to its ability to deal with constrained multivariable problems. However, NMPC can be computationally expensive to solve due to its non-linear nature, multiple interacting process units and the presence of model uncertainty. Real-world NMPC applications also necessitate state estimation for feedback control. While robust NMPC and state estimators have been studied individually for large-scale problems, understanding their combined impact is crucial for wider NMPC adoption. Integrating tractable Machine Learning (ML) surrogates, particularly Neural Networks (NNs), into NMPC to reduce the computational load is an emerging strategy. However, embedding NN surrogates in NMPC, in a form amenable to simultaneous solution approaches, remains unresolved. This thesis aims to address two major NMPC implementation issues. First, this work analyses the combined impact of uncertainty and state estimation on the performance of NMPC on large-scale systems. Two scenario-based robust approaches to NMPC, multi-scenario NMPC (MSc-NMPC) and multi-stage NMPC (MS-NMPC), are implemented on the benchmark Tennessee-Eastman (TE) process in closed-loop using two standard state estimation algorithms, Extended Kalman Filter (EKF) and Moving Horizon Estimation (MHE). Robust NMPC with MHE is shown to prevent constraint violation while closely tracking the set-points under process uncertainty where traditional NMPC failed. The additional computational time required to solve the robust NMPC and MHE does not cause significant delays for the sampling time considered, demonstrating their applicability to challenging large-scale industrial chemical and manufacturing processes. This work also aims to benchmark various strategies for embedding NN surrogates in NMPC. One strategy embeds NN models as explicit algebraic constraints within the optimization framework, leveraging the auto differentiation (AD) of algebraic modelling languages (AMLs) to evaluate the derivatives. Alternatively, the surrogate can be evaluated externally from the optimization framework, using the efficient AD of ML environments. Physics-informed NNs (PINNs) and Physics-informed Convolutional NNs (PICNNs) are used as NN surrogates due to their ability to maintain fidelity to fundamental physics laws while reducing the need for historical/process data. The study reveals that replacing mechanistic models with NN surrogates may not always offer computational advantages, even with highly nonlinear systems. Smooth activation functions provide little to no advantage over the mechanistic equations when a local non-linear program (NLP) solver is used. Moreover, the external evaluation of the NN surrogates often outperforms the embedding as algebraic constraints, likely due, to the difficulty in initializing the auxiliary variables and constraints introduced with the explicit algebraic reformulations.
Rheology of Suspensions of Solid Particles in Liquids Thickened by Starch Nanoparticles
(University of Waterloo, 2024-05-24) Ghanaatpishehsanaei, Ghazaleh
This study explores the rheological characteristics of suspensions containing solid particles dispersed in aqueous matrix phase thickened with starch nanoparticles (SNP). The SNP concentration ranged from 5 to 35 wt% relative to the aqueous matrix phase, while the solids concentration of the suspensions varied from 0 to 57 vol%. Two different size solid particles were used in the experiments. Observations revealed that suspensions at constant SNP concentrations exhibited Newtonian behavior at low solids concentrations but transitioned to non-Newtonian shear-thinning behavior at higher solids concentrations. Notably, an increase in SNP concentration led to an earlier onset of non-Newtonian behavior at lower solids concentrations. The rheological properties of non-Newtonian suspensions were effectively characterized using a power-law model, with the consistency index showing a positive correlation with suspension solids concentration at any given SNP level. Furthermore, the flow behavior index, indicative of shear-thinning behavior, decreased with increasing solids concentration, suggesting an amplification of shear-thinning tendencies in the suspensions. The effect of particle size on the rheological behavior of suspensions was found to be insignificant. Experimental viscosity and consistency data for both Newtonian and non-Newtonian suspensions aligned well with predictions from the Pal model.
Modification Strategy for Mn-based Layered Transition Metal Oxide as Sodium-ion Battery Cathodes
(University of Waterloo, 2024-05-23) Wong, Ka Ho
Sodium-ion batteries (SIBs) are being touted as the future of energy storage. However, the lackluster performance of current cathode technology is a major roadblock to their widespread use. Among the promising candidates for cathodes, layered sodium manganese oxide stands out due to its low cost and higher energy density. However, its cycling performance is limited due to structural and surface instabilities. To overcome these challenges, researchers are exploring various strategies, such as doping, coating, and heterostructure design, to enhance the performance of manganese-based oxide. Doping involves introducing foreign atoms to enhance structural stability and electrochemical performance. Coating is a surface protection method, while heterostructure design involves developing a composite material composed of different crystal phases of sodium manganese oxide to leverage the intrinsic advantage of each phase. By analyzing the latest research, a novel coating approach of utilizing functionalized polymer (polyamic acid) as an encapsulation layer for P2-Na0.7MnO2 cathode is demonstrated. The polymer is equipped with abundant functional groups such as hydroxyl, carboxyl, amide, fluoromethyl, and aromatic, that endow a high oxidative stability and high toughness, thereby mitigating structural transition and electrolyte decomposition. Additionally, a high percentage of polar groups enable ionic conduction of Na+ through the polymer coating, as well as reducing active material dissolution through a chelation mechanism. Hence, the encapsulated cathode exhibits significant improvement in its cycling performance, maintaining stable discharge capacity for 500 cycles at 1000 mA g-1.
Recovery of Volatile Aroma Compounds by Membranes
(University of Waterloo, 2024-05-03) Davari, Susan
This research investigates the potential application of poly(ether block amide) (PEBA) membranes for the separation of volatile aroma compounds from wine and the effect of non-volatile components on the separation performance using the pervaporation process. The study examined the selective retrieval of two aroma compounds (4-ethyl guaiacol and 4-ethyl phenol) from binary dilute aqueous solutions through pervaporation utilizing the PEBA 2533 membrane. It was observed that this membrane effectively recovers hydrophobic aroma compounds. The influence of feed concentration and temperature on aroma recovery was also analyzed. The performance of PEBA 2533 for aroma recovery was assessed, and experimental data were analyzed using a batch pervaporation model. It was discovered that both the flux of aroma compounds and their selectivity were notably influenced by the concentration of aroma compounds in the feed. The permeation flux and their selectivity in separating the volatile aroma compound in a binary solution followed the sequence of 4-ethyl phenol > 4-ethyl guaiacol, showing an inverse relationship with their molecular size. Generally, the permeation flux of aroma was found to be directly proportional to the concentration of aroma compounds in the solution within the tested concentration range (10-110 ppm). The impact of temperature on permeation flux followed an Arrhenius-type relationship and 4-EG with larger molecular size showed higher apparent activation energy than 4-EP and water. It was observed that the recovery of 4-Ethyl guaiacol from its dilute aqueous solution was affected by non-volatile wine components (sugar, yeast, and salt) and alcohol. Specifically, the presence of glucose as a model sugar and NaCl as a model salt in the feed solution did not notably affect the pervaporative performance of 4-EG, maybe because of their low contents in the feed mixture and low interactions with aroma. The addition of agar initially increased the permeate flux of 4-EG due to its insolubility and ability to absorb water molecules, boosting the concentration of 4-EG and enhancing the driving force. However, at higher agar concentrations, precipitation formed a thick layer of swollen agar in the tank, trapping 4-EG molecules and reducing their concentration in the solution. This led to a peak flux followed by a decline, reaching a maximum turning point at a specific agar concentration. Finally, the presence of ethanol as a model alcohol in the binary solution of 4-ethyl guaiacol was found to significantly reduce the permeation of 4-ethyl guaiacol. However, the total flux of the mixture considerably increased. The presence of ethanol affected the partitioning and activity coefficients of the components in the mixture as well as membrane swelling and plasticization, which ultimately affected the solubility and diffusivity properties of the membrane.
Structurally Enhanced Electrodes for Redox Flow Batteries Produced via Electrospinning
(University of Waterloo, 2024-04-29) Lee, Kyu Min
The vanadium redox flow battery is one of the most promising secondary batteries for energy storage system due to its design flexibility attributed to the large adjustable capacity of the storage tanks filled with electrolyte solution. However, the vanadium redox flow battery is not yet widely deployed owing to its low power density. This thesis describes the way of constructing the fibrous electrode with novel structure to overcome the flaw. The general electrospun materials of polyacrylonitrile were synthesized with substantially lower porosity than standard materials by applying compression during the stabilization stage. This objective was to create flow battery electrodes with higher volumetric surface area. The flexibility of the electrospinning technique combined with adjustable post-processing steps such as stabilization and carbonization allowed for the creation of layers with very specific structural and transport properties. In-plane permeability was found to remain relatively constant compared to the original uncompressed fibrous structure. On the other hand, the fibers compacted and compressed down to the flat ribbon shape hurt the through-plane permeability, so artificial holes were created using a CO_2 laser to perforate the structure. The loss of specific surface area caused by laser perforation was quite negligible and still showed improvement. Overall, the novel flow-through electrode provided from this study successfully contributed to improving the transport properties as well as the electrochemical reaction rate, leading to the optimal power density of a vanadium redox flow battery. In addition to that, 2-dimensional half-cell model was created with multi-physics simulation to predict the change in performance with respect to the structural properties of fibrous electrode. The performance was evaluated based on polarization behavior, required pumping power to operate the cell, and operating efficiency. Moreover, electrode was constructed to multi-layered structure in profiles of permeability, fiber size, and porosity. The vanadium ion could be distributed uniformly over the entire region of electrode, which enabled more portion of fiber surface to be utilized for reaction to improve power density while maintaining low pumping power for operation. Based on the prediction from the model, the actual experimental work was invested for multi-layered structure built with novel electrospun fibrous layers. Two different flow channel designs were considered: interdigitated and parallel. The convective flow was induced with the interdigitated flow channel design. Thus, the vanadium ions could be distributed effectively to the region of electrode, resulting in the higher power density. The electrode created in multi-layer provided higher net power density even though the increased pumping power requirement compared to the case of single layer. The body of work presented in this thesis has contributed significantly to understanding the mass transport phenomena taking place in electrodes built in novel fibrous structures. It highlights the preparation of this media through electrospinning as well as numerical and experimental methods for characterizing and understanding these processes. All the work presented here promoted the development of flow batteries through better understanding of the flow battery electrode.
Novel Copolymers Based on Methoxythiophene-Flanked Diketopyrrolopyrrole for Wearable Resistive Sensors
(University of Waterloo, 2024-04-25) Stella, Andrew
The exposure that firefighters experience due to their occupation has recently been identified by the World Health Organization as a Group 1 carcinogen. One factor is colorless, odorless, toxic gases in “warm zones” near enough to fires where awareness and protection are lowered but the actual risks are still high. The current gas sensors available are based on metal oxides, and are bulky, inflexible, and costly to produce. By contrast, gas sensors based on conjugated polymers promise to be lightweight and flexible enough to weave directly into clothing and could be manufactured using low cost roll-to-roll printing. However, they require improvements in stability. This work first establishes a baseline of stability for previously reported conjugated polymers. Common p-type dopant molecules are used to dope diketopyrrolopyrrole (DPP) copolymers, which are known for their stability. It was found that the longest the sensors could last was ~10 days. Believing that the stability could be improved through increasing the energy level of the polymer’s Highest Occupied Molecular Orbital (HOMO), this thesis extends a recent report of a novel DPP-flanking group, methoxythiophene. The potential of methoxythiophene-flanking groups as a method to raise DPP polymer HOMO energy has several advantages. They are sterically small (only extending the length of the thiophene molecule by < 2.5 Å) and by using the flanking group to raise the HOMO, both the choice of solubilizing side chain and choice of comonomer remain free. A solubilizing side chain with thermally/chemically removable groups could therefore be used. The removal process could introduce stable pores, enhancing gas transport in and out of the polymer film. Likewise, a comonomer could be selected for its interaction with a target gas. Three novel conjugated DPP-based copolymers were then synthesized, using methoxythiophene as a flanking group to the DPP unit. Two were produced through Stille coupling and one was produced through the more environmentally friendly Direct Arylation Polymerization (DArP). As hypothesized, these copolymers show high HOMO levels, which are anticipated to grant them high stability once doped with common p-dopants. One, C8-EDOT shows conductivity stable in air over 2 months (~1%/day decrease in current) even without exogenous dopant, having been doped by trace HCl in chloroform used to coat films. The three polymers also show ultralow bandgaps, which could make them useful in Near Infrared detection or Organic Photovoltaic applications.
Highly Crosslinked Natural Rubber-Cellulose Nanocrystals Composites for Sustainable Material Applications
(University of Waterloo, 2024-04-24) Ojogbo, Ewomazino
In a bid to develop environmentally friendly rubber materials, the use of renewable and sustainable additives and reinforcing fillers that could provide suitable mechanical property enhancement is of great interest. In this thesis, cellulose nanocrystals (CNCs) are employed as reinforcing fillers due to their availability, sustainability, high aspect ratio, and excellent mechanical properties. In the first part of this study, various processing and fabrication methods of natural rubber (NR) – CNCs nanocomposite formulations were investigated to obtain optimal dispersion of CNCs and hence physical properties. Rheology, morphology, and various physico-mechanical property testing were also employed to understand the effects of the processing method on the NR-CNC vulcanizates. While co-coagulation and extrusion provided improved reinforcement of the nanocomposites attributed to the optimal dispersion of CNCs, batch mixing processed samples exhibited poor dispersion even at low CNCs loadings as observed from transmission electron microscopy and inferior composite properties. The second and third part of this thesis involved chemical modification of the CNCs to enhance hydrophobicity and increase dispersion. Firstly, CNC was grafted on epoxidized natural rubber (ENR) in a base thermo-catalyzed reactive extrusion process. Successful grafting was confirmed using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and toluene swelling experiments. The new covalently grafted ENR – CNC was then added as a masterbatch into a rubber formulation. The ENR acted as a carrier of CNCs in the rubber leading to efficient dispersion of the CNCs and subsequently improved the tensile strength and rheological properties of the composite. In a separate study, CNC was modified with 3-isocyanotopropyltriethoxysilane (IPTS) and employed as a reinforcing filler for natural rubber. Successful modification was verified using FTIR and nuclear magnetic resonance (NMR) spectroscopy. As it is important to retain the crystalline structure of the CNC after modification, X-ray diffraction (XRD) studies showed that the crystal structure of the CNC was retained. The composition of the modified CNC with natural rubber improved the mechanical properties, reduced the cure time, and had no negative effect on the processability. Overall, this study aimed to develop environmentally friendly and renewable nanocomposite systems based on rubber and CNCs in a bid to replace or complement the incumbent fillers in the rubber industry. Particularly, to generate knowledge on the chemical modification, processing, and applications of CNC in highly crosslinked rubber compounds, and investigate their suitability in material applications such as tires.
A Study of the Solubility and Mobility of Silver Ions in Chitosan and Fibroin Membranes
(University of Waterloo, 2024-04-24) Li, Xiaojia
Chitosan and fibroin are biopolymers widely applied in wound healing and wastewater treatment with silver ions (Ag+). The solubility and mobility of Ag+ in these polymers are important parameters for designing and optimizing related applications, but they are seldom studied. This study investigates and compares the sorption and transport properties of Ag+ in chitosan and fibroin membranes to reveal the unique interactions between these polymers and ions. The solubility and mobility of NaCl are also studied for comparison. The sorption performance was evaluated through sorption uptake and sorption isotherms at different Ag+ concentrations. The Ag+ equilibrium uptake and solubility in chitosan membranes were higher than those in fibroin membranes. The sorption of Ag+ in fibroin membranes followed the Freundlich isotherms, but neither the Langmuir nor the Freundlich isotherm applied to the sorption of Ag+ in chitosan membranes due to strong Ag+-chitosan complexation interactions. The permeance, permeability and diffusivity were studied through permeation/diffusion tests. The permeance, permeability and diffusivity of Ag+ in chitosan membranes were found to be dependent on the Ag+ concentration, while those values in fibroin membranes were relatively constant lower than those in chitosan, except the transient diffusivity coefficients and steady-state diffusivity coefficients. The transient diffusivity coefficients of Ag+ in chitosan ranged from 0.7 to 7.1 μm/s2, while those values in fibroin were in the range of 42.0 to 48.5 μm/s2. The steady-diffusivity coefficients of Ag+ were 2.7 to 31.7 μm/s2 in chitosan and 32.8 to 49.9 μm/s2 in fibroin. The diffusivity of Ag+ in chitosan was further studied by desorption tests. The diffusivity coefficients obtained from different methods were compared to gain better understanding of the diffusion process. The formation of Ag+-chitosan complexes played an important role and it significantly affected solubility and mobility of Ag+ in chitosan.
A Droplet Microfluidic Platform Used to Encapsulate Single Pre-formed Cancer Spheroids in Hydrogel Microenvironments
(University of Waterloo, 2024-04-19) Ezzo, Noura
Cancer has been a leading cause of death around the world for many years. Even with the emerging technologies seen in these times, there is still a lack of truly personalized treatments since cancer tumors are not fully understood, especially between different cancer patients. 3D models known as patient derived tumor organoids (PDTOs) have been gaining traction as in vitro models to mimic a patient’s tumor outside of their body. Grown from the patients' cells into cell clusters (spheroids) or organoids (mini parts of the tumor tissue), these models can serve as precise avenues for personalized drug discovery or studying tumor complexity. However, there are still limitations to these 3D models due to conventional fabrication methods. In order to achieve personalized care, the models being tested on should be consistent through each batch, reliable, and affordable. Traditionally, organoid development from cells aggregating in hanging droplets or rotating in flasks for maintained cell-aggregate suspension, can cause batch-to-batch inconsistencies (lack of uniformity between samples), low throughput, and often require high volume of reagents. To recreate a 3D suspension for cells in a more native environment, hydrogels have become popular biocompatible scaffolds capable of sustaining cell growth. Hydrogels themselves have been widely studied for ideal cell environments, yet common methods of cell encapsulation into these hydrogels (e.g. manually pipetting) do not address the mentioned limitations, but rather introduce inconsistencies. Droplet microfluidics (DM), with the inclusion of hydrogels, has become a technology that has assisted in organoid fabrication, addressing conventional limitations. DM can create uniform aqueous droplets at high frequencies through controlled emulsion, using microchannels. These uniform droplets allow for controlled cell encapsulation with minimal reagent usage, thus addressing the drawbacks of traditional organoid formation and cell encapsulation techniques. Yet, the downside to using DM for cell encapsulation (whether it is multi- or single- cell encapsulation) is the high initial concentration of cells used at the inlet reservoir (millions), compared to the typical sample size obtained from patient biopsies (thousands). To still leverage the advantages of DM, thoughts of encapsulating pre-formed cell clusters or spheroids (instead of forming them with the DM devices) can aim to lower the number of initial cells used, and aid in growing spheroids into organoids. Thus, the proposal of this thesis was to employ DM and defined hydrogels to encapsulate pre-formed spheroids into their own microenvironment, for the goal of supporting the growth of primary cancer patient cells into PDTOs in a robust and uniform iv manner. This thesis intends to give a better understanding of the need of using DM for pre-formed spheroid encapsulation, and the ways to achieve a robust system for this purpose. The first chapter of this thesis provides a deeper background of the motivation to the overarching goal and a further breakdown of the project tasks. Specifically, projects were designed around two aims: (1) optimizing portions of the system and (2) validating the system. In addition to this background information, more context is given through a literature review found in Chapter 2. This literature review further justifies the rationale of the work by providing more insight into each component. After outlining protocols used in each project (Chapter 3), the optimization work began, starting with finding the best way to form spheroids that would enter the DM device (Chapter 4). It was important that the mechanism of forming these spheroids was also robust and uniform to maintain the advantage over conventional spheroid fabrication techniques. A well-established micropattern technology known as the AggreWellTM was implemented due to its capabilities of forming uniform spheroids in a high throughput manner with a low quantity of cells. Using PDMS replicas of the AggreWellTM (referred to as PDMS AWs) caused for adjustments to typical protocols followed when using the original AggrewellTM. Parameters such as surface treatment, cell culture conditions, and collection methods, were studied to find the most appropriate outcome of spheroids for the intended application. Continuing in the avenue of optimization, the other portion of Chapter 4 focused on exploring DM devices and fabrication techniques. After comparing parameters such as mold fabrication through 3D printing and soft lithography, chip design and geometry (T-junction versus double flow focusing (DFF)), and system tubing size, the selected chip design was a DFF junction, similar to one used in previous work of single cell encapsulation. The other factors ensured that uniform droplet formation and single pre-formed spheroid encapsulation could be achieved, in part of making the system robust. Using the decisions made in the optimization work, validation of hydrogel selection, encapsulation efficiency, and spheroid viability were assessed in the main chapter (Chapter 5). This thesis work aimed to demonstrate the capabilities of the DFF DM device with the use of stratified flow. A hydrodynamic focusing stream of either Gelatin Methacrylate (GelMA) or sodium alginate hydrogel precursors helped to gather spheroids into their own droplets. Depending on the flow conditions, the width of the flow focusing stream varied, affecting the encapsulation efficiency. Along with focusing width, the concentration of spheroids at the inlet reservoir also affected the encapsulation efficiency. This study was able to show spheroid encapsulation with a range of spheroid quantities; from 1000 to 7000 total spheroids in 500 μL of hydrogel precursor. Lastly, the spheroid laden hydrogel droplets were crosslinked and assessed for stability in cell culture conditions over time. With this, the spheroid viability was also tested to ensure the overall system was not too harsh on them. As most spheroids showed a high viability, this was enough to satisfy the proposed objective and conclude that this system has potential to be further explored. In conclusion, the overall system showed success in robustly encapsulating pre-formed spheroids, in hopes of being applied to patient derived samples for uniform growth into relevant 3D models. As this work is preliminary, Chapter 6 outlines recommendations and suggestions to future work, to guide this project towards the overarching goal.
In Vitro Modelling of Fuchs Endothelial Dystrophy for Corneal Endothelial Cell Apoptosis and Characterization of Human Descemets Membrane
(University of Waterloo, 2024-04-18) Myagmartsend, Enkhbat
The corneal endothelium is a terminally differentiated tissue that is typically considered non-proliferative in vivo. Corneal endothelial dystrophies, including Fuchs' endothelial dystrophy (FED), are a significant cause of dysfunction, ultimately leading to corneal edema. Corneal transplantation is a well-established and effective treatment for corneal endothelial dysfunction. This condition is particularly prominent post-cataract surgery, which increases the risk of corneal transplant failure. However, the global shortage of human donor corneas has prompted ongoing research into alternative treatment approaches. Utilizing engineering solutions to model Fuch’s endothelial dystrophy and investigating the mechanical properties of Descemet’s membrane (DM) are pivotal for advancing our understanding and improving treatment options. This research had two aims to advance our understanding of FED. The first aim was to investigate how human corneal endothelial cells (HCEC-B4G12) respond to synthetic guttata (S-guttata) pillars, with a specific emphasis on cell apoptosis, gene expression, and cytoskeletal changes. Subsequent examination of B4G12 cell responses to these pillars revealed induction of early and late apoptosis, with significantly higher rates observed on 20×20×20 (20 μm diameter, 20 μm spacing, and 20 μm height) and 40×80×20 (40 μm diameter, 80 μm spacing 20 μm, and height) pillars compared to unpatterned tissue culture polystyrene (TCPS) controls, respectively. Flow cytometry analysis confirmed enhanced early apoptosis on day 2, particularly on the 20×20 ×20 pillars. The α1 type V collagen (Col5A1) coating, which was shown to be highly expressed on large guttata in FED patients’ DM, on S-guttata enhanced the cell apoptosis level on the larger 40×80×20 pillars. Moreover, the results demonstrated cytoskeletal stress induction in B4G12 cells in contact with S-guttata pillars, as evidenced by the increased alpha smooth muscle actin (α-SMA) and phosphorylated-myosin light chain 2 (pMLCK) expression levels, suggesting a potential mechanism underlying the observed apoptotic response. The RT-qPCR results revealed differential modulation of oxidative stress-related gene expression in B4G12 cells on S-guttata pillars, with upregulation of NQO1 and SOD2 on 40 μm pillars and downregulation of SOD2 on 20×20×20 pillars. The second aim was to characterize and develop a method to measure the mechanical properties of human DM across distinct regions, including the central (CE), peripheral (PE), and transition zone (TZ). Variations in the thickness were observed, with TZ being the thickest region, followed by CE and PE. Furthermore, the stiffness analysis revealed that the TZ exhibited the lowest stiffness compared to the CE and PE regions. Our developed approach can be used to noninvasively measure DM thickness, and these findings will contribute to advancing our knowledge of corneal endothelial dystrophy and have the potential to improve current therapies, ultimately benefiting clinical outcomes and patient well-being.
Upcycling Plastic Waste to Activated Carbon for Waste Water Treatment Applications
(University of Waterloo, 2024-04-09) Blanchard, Rachel Jessica
Plastic waste disposal continues to be a widespread issue, as plastic products are discarded at high rates and do not biodegrade in the environment. Although a portion of this waste is recycled, the limitations of conventional recycling methods have prompted the need to investigate alternative disposal methods. This thesis highlights the upcycling plastic waste through carbonization and activation to produce adsorbent material for wastewater treatment applications. This conversion method involves heat treatment at high temperature under an inert atmosphere with the addition of an activating agent to produce activated carbon (AC), a carbonaceous material of high surface area. This process can yield high value material with excellent adsorption properties and can be applied to a variety of plastics including thermosets, which are notoriously difficult to recycle. The first section of this thesis focused on the synthesis of AC from poly(ethylene terephthalate) (PET) bottle waste and its application as an adsorbent for dye contaminated water. A product of high surface area (1124 m²/g) was produced through KOH chemical activation and exhibited a high adsorption capacity (335 mg/g) for cationic methylene blue (MB) dye. The adsorption capabilities were investigated through detailed analysis of the MB adsorption mechanism in addition to the effects of solution pH and dye charge characteristic. The second section of this thesis focused on the synthesis of AC from epoxy thermoset plastic for the adsorption of nano-plastic pollution. A high surface area AC (1705 m²/g) was obtained through KOH activation after investigation of other potassium-based activators. It was found to adsorb PET nano-plastics through multilayer physical adsorption with a substantial monolayer capacity of 325 mg/g and maximum recovery of 94%. These studies confirmed the successful conversion of a thermoplastic and thermoset into AC material with high potential for adsorption of aqueous pollutants.
CO2 Conversion to Syngas and Hydrocarbons over Transition Metal-Based Catalysts Synthesized via Reverse Microemulsion Method
(University of Waterloo, 2024-03-28) Yu, Yue
This thesis offers a comprehensive exploration into the development, exploration, and practical implications of various catalysts, with a particular focus on their performance and critical roles in the efficient and sustainable conversion of CO2 through thermo-catalytic processes. In particular, this thesis focused on the exploration of potential catalysts for CO2 conversion and hydrogenation processes including various catalyst systems such as Co-Mo carbides and oxides, Fe/Al2O3, and CeO2-based materials. The study combines experimental and theoretical approaches to discover new insights and avenues for catalysis development. In the study of Cobalt-Molybdenum oxide and carbide catalysts for the reverse water gas shift (RWGS) reaction, the studies conducted in this thesis identified promising activity at specific conditions but also highlighted the need for further improvements in carburization and synthesis processes. The investigation into Al2O3-supported iron catalysts for CO2 hydrogenation reveals that the RME Fe/Al2O3 catalysts, prepared through the RME method, exhibit superior performance, particularly in terms of CO2 conversion rate and selectivity towards C2+ hydrocarbons. This finding underscores the importance of synthesis methods and reaction conditions in catalytic performance. Moreover, the study conducted on CeO2-based catalysts for RWGS showed that Cu/CeO2 and Fe/CeO2 catalysts synthesized by reverse microemulsion method are favored in CO2 reduction to CO, maintaining high selectivity to CO across a broad temperature range. This is attributed to the effective doping with transition metals like Cu and Fe, which enhances CO2 adsorption on CeO2 surfaces, also underscoring the significant role of oxygen vacancies generated by doping in CO2 adsorption and activation. These insights paved the way for a more nuanced understanding of the factors influencing adsorption and subsequent catalytic activity. These findings contribute significantly to the field of catalysis, providing a robust foundation for developing more efficient and resilient catalysts for RWGS reactions and CO2 conversion. The novel integration of experimental and computational methods in this thesis offers a comprehensive understanding of the catalytic processes, setting new benchmarks for catalyst design and advancing sustainable energy initiatives. This thesis integrates theoretical research with practical application, providing insights and guidelines that hold substantial promise for the future of environmental sustainability and efficient, selective CO2 conversion processes.
A Journey into Jamming: Phase Transitions and Edge-to-Edge Heterostructures in Langmuir Blodgett Films of Exfoliated Two-Dimensional Materials
(University of Waterloo, 2024-03-21) Storwick, Thomas
Two-dimensional (2D) materials hold significant promise as new electronic materials, and could enable high mobility devices, and flexible electronics. In particular, graphene and few-layer molybdenum disulfide have been the subject of significant study as new and exciting materials. Hindering the application of 2D materials is the lack of easy, scalable methods for deposition single layers of 2D materials. Top-down chemical methods like CVD can deposit large area high quality films, but remain highly destructive techniques, requiring high temperatures, harmful and caustic reagents, and high vacuum. Recent research in Langmuir Blodgett techniques have enabled large area coatings, continuous roll-to-roll coating, and expanded the repertoire of materials that can be coated. With this research has come renewed interest in the mechanics and dynamics of 2D materials coatings on the air-water interface. In this work, we expand this knowledge by undertaking a comprehensive study of 2D particle jamming on the air-water interface. Furthermore, we employ this understanding to demonstrate, for the first time, edge-to-edge heterostructure films assembled on the air-water interface. To address the challenges of in-situ characterization of a growing film, we designed a method for non-destructive, in situ film monitoring using video-kymography, in addition to traditional Langmuir film characterization techniques such as surface pressure and compression isotherms. In our findings we identify two modes of 2D material film growth on the air-water interface, an unjammed, or flowing growth mode, that is typically seen in Langmuir films of 2D materials, and a jammed growth mode, where material is condensed into a solid film by the deposition process. The key parameters that determine which mode the deposition will proceed were then identified. Within the jammed growth mode, we identify 3 phases of jammed film growth: gaseous, liquid, and solid. We then show that both the spreading dynamics of the chosen material “ink”, and the constant adding of material itself is required to progress through these stages and propose a mechanism for how a Langmuir film of 2D material can jam. Using these findings, edge-to-edge heterostructure films of reduced graphene oxide and molybdenum disulfide were assembled on the air-water interface. Critical to the assembly of these films was the ability to deposit material in the jammed growth mode, and identify when the film was in the solid phase. This serves as a proof of concept for greater and more complex multi-material films on the air-water interface.
Design and development of nanocomposites by carbon-based 2D materials for piezoresistive sensing application
(University of Waterloo, 2024-02-08) Rahimidarestani, Yasaman
In the realm of wearable electronic devices, considerable attention has been directed toward flexible compressive piezoresistive sensors, given their potential applications in real-time human health monitoring and gesture recognition for robotics. Development of such sensors using electrically conductive polymer nanocomposites (E-CPnC) holds great promise due to their remarkable characteristics such as lightweightness and cost effectiveness. Despite notable advancements in this field, the fabrication techniques for compressive polymer-based piezoresistive sensors still tend to rely on complex and multi-step processes. This highlights the urgent need for developing facile and cost-effective manufacturing methods to propel advancements in the electronic industry. In this research we address the growing demand for facile and cost-effective manufacturing methods in the development of compressive piezoresistive sensors for wearable electronic devices. This study introduces a novel one-pot soft-templating method for fabricating PDMS-based conductive compressive sensors, benefiting the unique physical properties of cyclohexane. By controlling temperature and pressure conditions, a microcellular structure was prepared through the solvent's crystals sublimation, effectively serving as a soft template. Graphene, chosen for its conductive properties, was dispersed in varying proportions of cyclohexane, with the addition of PDMS and its curing agent. The solution freeze-dried, and the rapid evaporation of cyclohexane solid crystals within the structure coupled with the crosslinking of PDMS facilitated the creation of pores. Consequently, diverse microcellular structures with varying levels of porosity were successfully fabricated. For investigating the morphology of the resulting microcellular nanocomposites scanning electron microscopy (SEM) was used. The electrical conductivity, dielectric properties, and sensitivity of the nanocomposites could be analyzed through electrochemical impedance spectroscopy (EIS) and EIS coupled with universal testing machine (UTM). The mechanical performance, considering the stress-strain curves, mechanical strength, Young’s modules and the fatigue testing were analyzed by UTM. The fabricated sensors exhibit remarkable electrical conductivity, mechanical strength and sensitivity that can be achieved through the optimization of graphene concentration in the microcellular structure. Optimization of solvent concentration led to the attainment of varied pore sizes and void fractions. When 0.43 vol% graphene was introduced, the microcellular nanocomposite displayed an electrical conductivity of 2.5×10-2 S/m and a mechanical strength of 780 kPa at 85% compression strain. This remarkable compressibility was attributed to the robust 3D interconnected structure featuring a high void fraction of 82%. With an increase in graphene concentration to 0.87 vol%, the electrical conductivity rose to 35×10-2 S/m, and the compressive strength reached 1500 kPa at 70% strain, accompanied by a void fraction of 64.8%. Moreover, the electromechanical performance analysis reveals two linear resistance responses along the compressive strain range, demonstrating the versatility of the sensors in capturing different levels of compression. For instance, the foam loaded with 0.43 vol% exhibited a notable change in resistivity up to 10% strain, resulting in a high gauge factor of 0.5 kPa-1. From 10 to 85% strain, the foam displayed a second linear detection region with a gauge factor of 1.2 MPa-1. The compressive sensors demonstrated a rapid response time of 20 ms and exceptional cyclic stability of 500 cycles, owing to their resilient 3D interconnected structure, indicating their suitability for mid and high-pressure (10 kPa- 1 MPa) sensing applications, as well as real-time monitoring of human joint movements.
Development of Cobalt-Free Cathodes for Lithium-Ion Batteries
(University of Waterloo, 2024-01-22) Or, Tyler
Lithium-ion batteries (LIBs) are the dominant energy story technology for mobile devices and plug-in electric vehicles due to their unmatched combination of energy density, power output, and cycle stability. A coveted goal in their development is the expansion of energy density, which is currently bottlenecked by the charge storage capacity of the cathode material. Moreover, the ramp-up and projected growth of LIB production raises concerns over the availability and cost of raw resources, particularly on the reliance of cobalt in the cathode material. To suit these requirements, layered structure LiNixMnyCozO2 (NMC, x + y + z = 1) class materials are the most commercially relevant, with ongoing efforts to increase the Ni to Co ratio. Although Ni-rich NMC cathodes (x ≥ 0.8) can achieve higher energy densities, their applicability is limited due to the poor cycle life and safety. Thus, it is critical to develop strategies to address these problems. In general, the performance of electrode materials can be modified by 1) altering the particle morphology, 2) applying a surface coating, 3) applying a transition metal dopant, and 4) modifying the electrolyte composition to suppress deleterious electrode-electrolyte side reactions, all of which were explored in this work. The electrochemical performance of single crystal LiNi0.83Mn0.06Co0.11O2 (SC-NMC811) electrodes was enhanced by coatings applied with atomic layer deposition (ALD). The performance of various coating materials (Al2O3, alucone, TiO2, and titanicone) was thoroughly compared and their mechanisms were analyzed. As the coating was applied on the fabricated electrode, it was observed to be localized on the electrode surface. Thus, it was concluded that the ALD-applied coatings primarily act by accelerating the decomposition of LiPF6, coating the cathode with fluoride and phosphate species that passivate its surface. The coatings were most effective at improving cycle stability at low currents, where capacity degradation is dominated by active material loss from HF corrosion. At elevated currents, kinetic factors dictate capacity degradation, which minimized the impact of the ALD-applied coatings. Preliminary investigation was also conducted on the relationship between coatings and electrolyte additives, which share many mechanisms. In subsequent work, Zr and Ce-based coatings were formed on SC-NMC811 particles by sintering. Consequently, doping within the particle bulk can also occur. The coating thickness and extent of doping were optimized in order to delineate the various improvement mechanisms. Doping was found to improve cycle stability at elevated currents, likely due to its improvement of Li+ diffusion kinetics and suppression of lattice volume evolution. However, the thickness of the coating should be minimized, particularly when cycling at elevated currents, due to the rapid build-up of surface impedance. Finally, SC-NMC811 was cycled with a passivating high concentration LiFSI-based electrolyte, with its cycle stability further enhanced by incorporating coatings. Under this unconventional electrolyte system, the passivation mechanism of the coatings was proposed.
Improved Dynamic Latent Variable Modeling for Process Monitoring, Fault Diagnosis and Anomaly Detection
(University of Waterloo, 2024-01-04) Zhang, Haitian
Due to the rapid advancement of modern industrial processes, a considerable number of measured variables enhance the complexity of systems, progressively leading to the development of multivariate statistical analysis (MSA) methods to exploit valuable information from the collected data for predictive modeling, fault detection and diagnosis, such as partial least squares (PLS), canonical correlation analysis (CCA) and their extensions. However, these methods suffer from some issues, involving the irrelevant information extracted by PLS, and CCA’s inability to exploit quality information. Latent variable regression (LVR) was designed to address these issues, but it has not been fully and systematically studied. A concurrent kernel LVR (CKLVR) with a regularization term is designed for collinear and nonlinear data to construct a full decomposition of the original nonlinear data space, and to provide comprehensive information of the systems. Further, dynamics are inevitable in practical industrial processes, and thus a dynamic auto-regressive LVR (DALVR) is also proposed based on regularized LVR to capture dynamic variations in both process and quality data. The comprehensive monitoring framework and fault diagnosis and causal analysis scheme based on DALVR are developed. Their superiority can be demonstrated with case studies, involving the Tennessee Eastman process, Dow’s refining process and three-phase flow facility process. In addition to MSA approaches, autoencoder (AE) technology is extensively used in complicated processes to handle the expanding dimensionality caused by the increasing complexity of industrial applications. Apart from modeling and fault diagnosis, anomaly detection draws great attention as well to maintain the performance, avoid economic losses, and ensure safety during the industrial processes. In view of advantages in dimensionality reduction and feature retention, autoencoder (AE) technology is widely applied for anomaly detection monitoring. Considering both high dimensionality and dynamic relations between elements in the hidden layer, an improved autoencoder with dynamic hidden layer (DHL-AE) is proposed and applied for anomaly detection monitoring. Two case studies including Tennessee Eastman process and Wind data are used to show the effectiveness of the proposed algorithm.
Fabrication of Transparent Nanocellulose Paper from Plant Sources for Energy Devices
(University of Waterloo, 2024-01-04) Sen, Rajeswari
Over the past decades, electronic waste has accumulated and has increased by 21% in the last five years. Recently, a UN report founded that the world dumped a gross record of 53.6 million tonnes of e-waste across last year. In the past, electronics had limitations due to their size constraint but with technological growth, electronics have now become a prominent part of the waste stream. Plastic substrates such as polyethylene (PET) and polycarbonate (PC) has been used pervasively in electronic devices. But due to their low co-efficient of thermal expansion (CTE), low recyclability and immense levels of pollution, a new state-of-art technology the cellulose nanopaper (CNP) has shown immense potential to replace plastic as a substrate in optoelectronics. Bio-derived decomposable electronics have exhibited great prospective to reduce the environmental footprint and avoid the surplus amounts of plastic based waste. This project reports about a nanopaper fabricated from self-assembled network structure from nanoscale building blocks known as cellulose nanofibers (CNF). Nanofibers from two distinct sources were tested – (a) Cannabis sativa - Hemp (b) Softwood – Pine. Hemp CNFs provided by IND Hemp, United States in association with Tangho Green Inc., Canada was prepared via alkaline and acid hydrolysis along with high compression grinding and a cellulose purity of 97% was obtained. Pine CNFs were purchased from Forestry Department of University of Maine, USA had a >98% purity spectrum. A comprehensive study of CNP’sstructure-property relationship has been established under different processing conditions such as temperature of drying and CNF grammage, through characterization analyses. Two main nanopaper fabrication techniques of Solution Casting and Vacuum Filtration were studied in detail. Secondary objective comprised of optimizing optical properties of CNPs by adding polymers like Poly (vinyl alcohol) (PVA) and Polymethyl methacrylate (PMMA). Both PVA and PMMA showed considerable compatibility with CNF as a way of making them transparent. The project was rounded off by incorporating Silver Nanowires (AgNWs) which was chosen as a conductive nano-filler due to its well-expressed aspect ratio. AgNWs showed high conductivity with increasing its loading density (mg/cm2 ) or grammage. The films showed a resistivity as low as 9.45 ohm.µm with higher grammage of nanowire added. The results showed that nanocellulose changed their nature from insulator to conductor after addition of conductive materials. Moreover, iv the highest conductivity around 1.05 kS/cm was obtained with maximum amounts of nanowire deposited. This work solely presents a trend for the application of this conductive nanopaper in foldable or flexible electronics such as solar cells, OLEDS, electrodes or electronic skin for electrophysiological monitoring.

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