Projects

Design Rules for Electrical Transport in Colloidal Systems for Soft Robotic Sensors

Team Members: Matthew Brucks & Alina Arslanova

Approach: Quantitatively describing the electrical transport in suspensions with conductive particles will allow us to build a framework that can allow us to design new rate-of-strain sensors that exhibit a reversible electrical response. By synthesizing model conductive particles, we can investigate the mechanism of charge transport in colloidal systems using a simultaneous rheological and impedance spectroscopy technique. From this, we can build constitutive relationships that will govern suspension formulation for sensor development.

Related Publications:

Lin, H.; Majji, M. V.; Cho, N.; Zeeman, J. R.; Swan, J. W.; Richards, J. J. Quantifying the Hydrodynamic Contribution to Electrical Transport in Non-Brownian Suspensions. Proc. Natl. Acad. Sci. U. S. A. 2022, 119 (29), 1–7.

Brucks, M. D.; Arslanova, A.; Smith, C. B.; Richards, J. J. Electroless Deposition of Silver onto Silica Nanoparticles to Produce Lipophilic Core-Shell Nanoparticles. J. Colloid Interface Sci. 2023, 646, 663–670.

Improving the Performance of Carbon Suspensions as Electrically Conductive Flow Electrodes

Team Members: Paolo Ramos and Lucas Pham

Motivation: Carbon black is ubiquitous as an additive in electrochemically active slurries for emergent energy storage and capacitive desalination systems. When suspended, these conductive particles agglomerate, creating a charge-carrying microstructure that facilitates electron transport. Many of the rheological properties of carbon black suspensions originate from the breakup and formation of these agglomerates when subjected to flow. It has also been proposed that flow-induced microstructural change causes a varied response to the suspension charge transport capabilities. How the carbon black microstructure evolves thus directly impacts the mechanical (e.g., viscosity, solidification) and electrical (e.g., conductivity, capacitance) performance of slurries. Significant work, however, has focused on improved macroscopic behavior without quantitative investigation of the role of the microstructure. Furthermore, studies of the electrical properties are often measured without a well-defined control over the suspension mechanical history. There is a need to fundamentally understand the link between suspension composition and flow behavior on the conductivity, viscosity, and capacitance of carbon slurries.

Approach: This project aims to develop a quantitative insight towards the development of carbon black slurries with optimal performance. We achieve this by pursuing three fronts, all using simultaneous rheological and electrical characterization. First, we will engineer colloidal stability in carbon suspensions by tuning the nanoscale interaction of the colloidal particles. We functionalize the surface of carbon black to enhance electrostatic and/or steric repulsion and measure the resulting macroscopic properties. Second, we will investigate the mechanism for charge transport. We develop a framework that links changes in the microstructure to trends in the conductivity. Finally, we will analyze the hydrodynamic effects on the continuous storage and release of electrical energy. We seek to probe the electrochemical state of charge of carbon slurries with a changing salt environment while under flow speeds.

Related Publications:

P.Z. Ramos, C.C. Call, L.V. Simitz, J.J. Richards, Evaluating the Rheo-electric Performance of Aqueous Suspensions of Oxidized Carbon Black, J. Colloid. Interface. Sci., 634 (2023), pp. 379-387. 10.1016/j.jcis.2022.12.017

J.J. Richards, P.Z. Ramos, Q. Liu, A review of the shear rheology of carbon black suspensions, Front. Phys., 11 (2023). 10.3389/fphy.2023.1245847

Processing-Structure-Property Relationships of Lithium-Ion Battery Electrodes

Team Members: Borges Liu and Yoshita Gupta

Approach: The main question in this project is what structural features of the porous electrode are responsible for high-performance lithium-ion batteries and what processing conditions are necessary to achieve these structural features. To address this question, we combine rheology, dielectric spectroscopy, and neutron scattering measurements to correlate the microstructure to rheological and electrical response.

Related Publications:

Liu Q, Richards JJ. (2023) Rheo-Electric Measurements of Carbon Black Suspensions Containing Polyvinylidene Difluoride in N-Methyl-2-Pyrrolidone.Journal of Rheology. https://doi.org/10.1122/8.0000615

Richards JJ., Ramos P^†, and Liu Q^†. (2023) A review of the shear rheology of carbon black suspensions. Frontiers in Physics. https://doi.org/10.3389/fphy.2023.1245847

Mapping Rheological and Morphological Responses of Stimuli-responsive Systems

Team Members: Kush Patel

Motivation: Current formulations of many paints and coatings require high amounts of volatile organic compounds (VOCs) to achieve desired properties. Due to growing global concern over the negative environmental and health effects of VOCs such as smog, cancer, and asthma, the EPA seeks to impose tighter restrictions on allowable levels of VOCs in such products. This work is in collaboration with PPG Industries who, anticipating enhanced regulations of VOCs, aim to develop waterborne resins consisting of water-stable core-shell polymeric particles. The architecture of these engineered resins has been designed to respond to various stimuli – including salt concentration, pH, and solvent conditions – to achieve similar rheological properties as traditional solvent-borne resins including a low high-shear viscosity for ease of application and a high low-shear viscosity for quality appearance. While the rheology of traditional solvent-borne resins can be easily predicted by the molecular weight and total weight fraction of the polymer, several factors contribute to the rheology of these novel formulations. Our research therefore seeks to develop a framework for understanding the link between the rheology of these materials and their microstructure.

Approach: We utilize rheological techniques to measure the response of the PPG resins to various stimuli (pH, salt, solvent, etc.). Theory on colloidal suspension rheology and polymer rheology help guide analysis and provide microstructural insight on the origin of the response. This is coupled with small angle X-ray scattering (at Argonne National Laboratory), small angle neutron scattering (at Oak Ridge National Laboratory), and dynamic light scattering to directly probe the microstructure.

Colloidal Silica Coated with Mixed Ionic/Electronic Conducting Layers for Stimulus-responsive Composites

Team Members: Xi Wan

Approach: To realize such structures, we have developed a synthesis technique to manufacture silica nanoparticles with electrostatically adsorbed PEDOT:PSS. By controlling the molecular weight of PSS and the ratio of EDOT to PSS monomer, we use combined methods of electron microscopy, light scattering, and spectroscopy to characterize these surface layers and show that their properties determine the optical characteristics of their assemblies, demonstrating their potential of being an electrically responsive CPCs.

Our approach combines the expertise of our lab and other collaborators. It mainly consists of three Objectives:

1. Synthesis of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate(PEDOT:PSS) layer on Silica Particles;
2. Driven Assembly of Nanoparticles into Colloidal Crystals;
3. Characterizing and controlling photonic reconfiguration through electrochemical doping/dedoping via ion injection.

Related Publications:

Richards, Jeffrey J., Austin D. Scherbarth, Norman J. Wagner, and Paul D. Butler. “Mixed ionic/electronic conducting surface layers adsorbed on colloidal silica for flow battery applications.” ACS applied materials & interfaces 8, no. 36 (2016): 24089-24096.