A synopsis of selected research projects being carried out by researchers in Integrated Material Systems Lab is provided below. A list of archived research projects and relevant publications that resulted from the work is provided in Archives.
|Smart Composites||Energy Storage||Bioderived Materials|
Integration of smart materials into an engineered system in various actuation, sensing and energy harvesting applications presents engineering challenges that should be addressed via system level models. Synopsis of ongoing research in our lab towards developing a smart material system is presented here.
This research program focuses on the development of a new additive manufacturing technique for rapid prototyping of seamless multifunctional composites with an ionomers matrix and nanophase smart materials. This technique is built around thermal sintering of nanophase structural ionomers (polymers) and smart materials in which the matrix is constructed with nanoscale precision in three-dimensions and simultaneously cured to obtain composites with intrinsic actuation and sensing properties. For this reason, the principal investigators refer to this technique as ‘Simulcure’ and the resulting multifunctional composites as ‘Simulcure composites’. The technique offers the unique advantage of requiring a single manufacturing step to produce structural composites with smart materials at intrinsic locations that cannot be achieved using contemporary fabrication techniques.
Mechanoluminescence (ML) is a property of inorganic and organic materials that describes the emission of light due from the application of force. Inorganic crystals (mostly phosphors) and certain organic macromolecules exhibit elastico-ML and are a natural fit for structural health monitoring (SHM) of composite structures. Composites with particulate ML crystals enable the visualization of stress distribution over a plane and over contoured surfaces in a spatially continuous manner. Imaging ML composites with affordable high-resolution imaging methods further enables the creation of high-resolution validation method for computational methods. Besides model validation, we are pursuing various approaches to investigate the application of ML phosphors in structural and cosmetic applications.
Ionic Smart Materials utilize ionic interactions at various lengthscales to demonstrate multi-domain coupling, charge storage and energy conversion. The multi-domain interactions in these materials and material systems is the genesis for a new discipline called
mechanoelectrochemistry. The term ‘mechanoelectrochemistry’ is thus defined as the study of elastic and plastic deformation of materials during reversible reduction and oxidation processes. Ongoing research projects under this topic focuses on studying fundamental electrochemical processes and associated mechanical deformation in ionic Smart Materials. The focus of our research on mechanoelectrochemistry of faradaic materials is summarized in the figure alongside.
Mechanoelectrochemistry of PPy(DBS) for Charge Storage
This research project investigates nanostructured morphology-dependent charge storage and coupled mechanical strain of polypyrrole membranes doped with dodecylbenzenesulfonate (PPy(DBS)). Nanoscale features introduced in PPy(DBS) using phospholipid vesicles as soft-templates create a uniform and long-range order to the polymer morphology, and lead to higher specific capacitance. It is widely stated that nanostructured architecture offer reduced mechanical loading at higher charge capacities, but metrics and methods to precisely quantify coupled localized strains do not exist. Towards this goal, we demonstrate the use of scanning electrochemical microscope with shear force imaging hardware (SECM-SF) to precisely measure charge storage function and volumetric strain simultaneously, and define two metrics – filling efficiency and chemomechanical coupling coefficient to compare nanostructured morphologies and thicknesses. At smaller membrane thickness (smaller charge densities), the planar and vesicle-templated membranes have comparable mechanoelectrochemical response. For membranes with larger thickness (0.4 to 0.8 C.cm², a 15% increase in charge is associated with ~50% reduction in extensional strain for vesicle-templated membranes. These results allow for the formulation of rules to design nanostructured PPy(DBS)-based actuators and energy storage devices.
V. Venugopal* and V.B. Sundaresan, “A Chemo-Mechanical Constitutive Model for Conducting Polymers”, Proceedings of 2013 ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Bioinspired Smart Materials and Structures Symposium, Sep 16-18, 2013, Snowbird, UT.
Metal-air batteries are the most dense electrochemical power sources and are anticipated to play an important role in electrification of transportation. A typical metal-air battery consists of two electrodes: a metallic negative electrode (anode and typically made of lithium, sodium, potassium, zinc) and porous positive electrode (cathode and made of carbonaceous materials). During discharging, oxygen in air diffuses into the positive electrode to react with metal ions and generates electrical current. During charging, an electrical current supplied to the battery reverses the electrochemical reactions that occurred during discharging and releases oxygen back into the atmosphere. The inefficiencies in the reaction between oxygen and metal ions in the cathode lead to performance deterioration in metal-air batteries. In order to address the inefficiencies in the reaction between metal ions and oxygen, we are investigating novel design for cathodes that will lead to metal-air batteries with high-energy density and high-power density.
The fundamental limitation of potassium-air batteries is the crossover of molecular oxygen from the cathode to potassium anode. This leads to the formation of potassium superoxide on the anode surface and reduces the availability of metal that can participate in energy storage. Hence, the objective of this research is to investigate the feasibility of a composite cathode formed from conducting polymers and carbonaceous support materials that will regulate the oxygen reduction reaction in the cathode and prevent the diffusion of molecular oxygen to the anode. The proposed concept for a composite cathode is based on a mechanistic understanding of charge storage in conducting polymers that allows for precise estimation of mechanical stress, diffusion of gases and electrochemical reduction reactions during faradaic processes. This research will quantify chemomechanical coefficients that relate volumetric stress generated in conducting polymers and its application for increasing the energy density and specific power of potassium-air batteries.
Biomolecules are nature’s machines that have evolved over the course of hundred’s of years through systemic changes to ecosystem (climate, atmosphere, hydrology). The evolutionary changes driven by the need to survive has led to plant biomolecules to have diverse functionality from reduction of carbondioxide, methane to other forms of carbon, fixation of nitrogen, and high temperature biochemical processes. Tailoring synthetic macromolecules with the diverse portfolio poses insurmountable challenges and novel hybrid constructs between biomolecules and electroactive scaffolds have emerged. To address a few of these challenges, we are investigating various material architectures to incorporate biomolecules in polypyrrole doped with dodecylbenzenesulfonate (PPy(DBS)) and create functional devices for the conversion of carbon dioxide into precursors for high-value chemicals.