Integrated Material Systems Lab - Research
Research
Energy Environ. Sci., 2016, 9, 2555-25621
The ionic redox transistor is a conducting polymer membrane in which ion transport is regulated by its redox state. In the case of our implementation, the magnitude of ionic current through the membrane is dependent on the reduced/oxidized state and allows for the membrane to be switched between ON/OFF state. Our results indicate that ionic current across the polymer in its reduced state is facilitated by the affinity of cations to immobile anionic dopant (DBS) and increases with concentration and applied transmembrane potential. The first generation of ionic redox transistor has a maximum conductance of 30μS/cm and a current gain of 60X as the polymer switches between oxidized (Vm>-200mV) and reduced state (Vm<-600mV), as shown in the figure below.
The demand for rechargeable electrochemical energy storage with high specific energy (SE) and specific power (SP) is driven by drivetrain power and energy requirements in ground transportation, unmanned aerial vehicles (UAVs), electrification of avionics, and miniaturization of consumer-electronic gadgets. Electric vehicles powered by Li-ion batteries are limited by short driving range, long recharge time and capacity fade to compete with fossil fuel-powered vehicles. Alternatives to Li-ion batteries such as supercapacitors and redox flow batteries with comparably high specific power and rapid recharge/refill have poor energy density due to self-discharge.
The scientific challenges in designing rechargeable batteries with high SE, SP and high MPMs can be understood from the mechanics of charge storage in electrode materials. It should be noted that the projected technology roadmap for rechargeable lithium-ion batteries lacks a practical solution to design batteries with high GED, SP and 100s of MPM (as shown in MPM plot). A true mass-market adoption of electric vehicles for transportation and aerial vehicles will require technologies that do not compromise on MPM.
Ongoing research in the lab address these issues by designing novel architectures for Lithium ion batteries, fundamental characterization experiments to study electrodes and looking at alternative battery chemistries.
Mechanoelectrochemistry
Mechanoelectrochemistry is the study of charge and mass transport, volumetric expansion and dynamic evolution of localized stress/strain. My group has pioneered recent advances in scanning electrochemical microscopy and shear force imaging (SECM+SF imaging) through structural models of nanoelectrodes and surface-tracking techniques. These developments now enable our group to be the first to study the evolution and dynamics of ion transport into and out of cathodes and anodes for batteries. This knowledge will be essential for building high performance Li-ion batteries for aerospace and automotive applications. The SECM+SF Imaging hardware and correlated fluorescent imaging platform (SECM+SF+FL) in my group as shown in the figure below is unique to our lab. This simultaneous electrochemical, topography and optical imaging is applicable for electroactive surfaces, cells and tissues and will allow my group to collaborate with other researchers in mechanical engineering, material science, chemistry, cellular and molecular biology and play a supportive role in new materials development.
Bioderived and Bioinspired Materials
Ionic smart materials that are fabricated with biological macromolecules are referred to as 'Biomolecular materials' (or) 'Bioderived materials'. Starting from Prof. Sundaresan's doctoral thesis on 'Biological Ion Transporters as Gating Devices for Chemomechanical and Chemoelectrical Energy Conversion', research on bimolecular materials has been one of our major thrusts and we continue to make significant contributions in this area. This research group's work in this area has led to Dr. Hao Zhang's doctoral thesis and Robert Northcutt's master's thesis at Virginia Commonwealth University.
Bioinspiration has 'seeded' innovative and simple solutions to complex engineering problems. Our group looks to biology at the nanoscale towards the development of engineering solutions and this page presents a glimpse of some of our projects that have this flavor.
Bioderived Ionic Transistors
A novel active material system is formed from integrating the ionic properties of a bio-derived membrane and a conjugated polymer into a thin-film hybrid membrane. This hybrid membrane is a laminate arrangement of bioderived membrane and a conjugated polymer and referred to as a Bioderived Ionic Transistor (BIT). We are investigating changes to the physical properties of a conjugated polymer membrane using proteins (channels, ions and pumps) in bio-derived membranes and developing techniques to fabricate this assembly into a thin-film device for sensing, controlled actuation and energy storage. The research objective of this program is the development of a hybrid membrane that can respond to low power electrical signal (nanowatt) or low concentration chemical trigger and perform electrochemical work using ambient chemical gradients.
References
R. Northcutt, and V.B. Sundaresan, Fabrication and characterization of an integrated ionic device from suspended polypyrrole and alamethicin-reconstituted lipid bilayer membranes. Smart Materials and Structures, 2012. 21(9): p. 094022.
H. Zhang, S. Salinas, and V.B. Sundaresan, Conducting polymer supported bilayer lipid membrane reconstituted with alamethicin. Smart Materials and Structures, 2011. 20(9): p. 094020.
Biotemplated Polypyrrole Membranes
Sundaresan and Salinas discovered the formation of nanostructured polypyrrole membranes during the electropolymerization of pyrrole with phospholipid vesicles. This novel, biologically inspired one-step electropolymerization process (or, biotemplating) produces a nanostructured polypyrrole (PPy) membrane using unilamellar phospholipid vesicles. Biotemplated electropolymerization of PPy doped with dodecylbenzenesulfonate (DBS) (above critical micellar concentration (cmc)) consists of 100mM pyrrole and 2.5 mg.ml-1 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) vesicles over gold-evaporated silicon-silicon nitride wafers. From SEM imaging, columnar structures measuring 4-5µm due to DBS- micelles along with ϕ1-1.5 µm sponge-like nodules due to DPhPC templating span the thickness of the biotemplated PPy(DBS) and increase the interfacial surface area between the PPy(DBS) membrane and electrolytic solution. Charge capacity of the PPy(DBS) membranes are quantified by cyclic voltammetry at various concentrations of NaCl and LiCl and normalized to the mass of the membrane. From cyclic voltammetry, biotemplated membranes have a 45% increased anodic current vs planar and the capacitance for a monovalent cation is 666.7 F.g-1 for a 2.5 mm2 projected area. Biotemplated membranes are more robust than the planar counterparts (100s of cycles vs 10s in high salt concentrations) and can be used for fabricating flexible electrodes and packed into tight geometries for designing novel power sources. Ongong research addresses the following research questions: role of the phospholipids in the final structure of the PPy(DBS) membranes, charge storage in PPy(DBS)-DPhPC matrix using scanning electrochemical microscopy, structure-function (charge storage) relation and design rules for battery and supercapacitor electrodes.
References
R. Northcutt and V.B. Sundaresan, Phospholipid Vesicles as Soft Templates for Electropolymerization of Nanostructured Polypyrrole Membranes with Long Range Order. Journal of Materials Chemistry A, 2014 (DOI: 10.1039/C4TA02352H)
R. Northcutt and V.B. Sundaresan, "Characterization of Electrochemical Capacity of Biotemplated Conducting Polymer Membrane", 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.
S. Salinas and V.B. Sundaresan, "Integrated Bioderived-Conducting Polymer Membrane Nanostructures for Energy Conversion and Storage", Proceedings of 2012 ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Bioinspired Smart Materials and Structures Symposium, Sep 19-21, 2012, Stone Mountain, GA.
Surface Synthetic Jet Actuators
Synthetic Jet Actuators (SJA) generates the jet of air via momentum transfer from high frequency oscillation in the piezoelectric diaphragm10. Acoustic waves generated in the chamber excite air entrained in the orifice and forces the formation of an oscillatory outflow near the orifice. This outflow is observed to be associated with the formation of a vortex ring that weakens with the oscillations of the air in the orifice and switches to inflow. This inflow brings air from around the shed vortex ring and is subsequently ejected outwards in successive cycles. The velocity of synthetic jet produced in a SJA is dependent on the geometry of the chamber, material properties of the oscillating diaphragm and shape of the chamber. Sundaresan and Gilmore have shown that a conical chamber for a SJA generates a higher jet velocity than SJA with cylindrical chambers and presents interesting applications in vector delivery, flow control, etc., Recent conference publications have demonstrated the results presented in the figure.
Self-sensing Magnetoelectric Surgical Tools
Magnetoelectric materials are self-sensing materials and are highly suitable for designing actuators that can be used in closed-loop. The research work focuses on developing magnetoelectric cantilever that can be used as an ablation tool in minimally invasive surgery (shown in figure below), as a damper in vibration isolation and as an adaptive mirror in optics. The magnetoelectric material is fabricated from combining a magnetostrictive material such as Galfenol and a piezoelectric material such as lead zirconate titanate (PZT). Current work is targeted towards developing the magnetoelectric cantilever into a smart ablation tool. It is common knowledge that a cantilever can be used as cutting tool in minimally surgery. But a cantilever-cutting tool riding on a catheter will have the tendency to drift due to force generated in the cutting action and hence pose danger to the patient. The novelty in this research is the addition of a second segment to the cantilevered end of the tool that will dynamically stabilize the cutting end of the tool. In order to realize the technical objective, a dynamic model for the magnetoelectric material is developed using variational principles and the principle of virtual work. A control algorithm such as linear-quadratic-regulator will be applied to the dynamic model for precise operation.
References
V.B. Sundaresan, J. Atulasimha, J. Clarke, 2010, US 8,602,034 B2; Awarded Date: Dec 10, 2013, Magnetoelectric Surgical Tools for Minimally Invasive Surgery.
DASH Ecosystem for Electric Vehicles
Mobile devices offer a unique opportunity for integration with daily life functions on a unified platform. In spite of market penetration, mobile devices have not made any impact on interfacing with the driving functions of an automobile. The primary challenge for this deficiency is the lack of unifying hardware/software platforms and barriers that exists between popular ecosystems. In order to address these issues, this work proposes a unifying platform that has the potential to combine internet connectivity, reconfigurable and personalized user interface and interaction with the automobile. This futuristic paradigm for automobiles is demonstrated using an Android tablet and interface hardware, where the tablet serves as the input device for primary or secondary vehicle functions and the interface hardware could be added on to existing dashboard controller. The interface hardware is based on a real-time board with multicore architecture and can serve as the bridge between the connected world and local ecosystem in an automobile. This research presents novel open source, open architecture for commanding vehicle functions from a mobile device over wired and wireless local area network (WLAN, also called as WiFi). We anticipate incorporating system level security functions, software integrity functions, various V2V, V2I, V2X constructs through a mobile device and our current implementations are centered around Google's Android platform. Our seminal work in this field was presented in the International Conference on Connected Vehicles (Electric Vehicle symposium, session P06-4) at Las Vegas on 5th December, 2013 by Pedro Daniel Urbina Coronado (http://edas.info/p15085). Our continuing work in this area places an upgradeable software running in a mobile device as a hub for regulating various driving and miscellaneous functions in a car.
'DASH' Ecosystem stands for Driving Assistance Software Hardware Ecosystem and is a collection of software and hardware that will allow mobile devices to control driving and miscellaneous functions in an electric vehicle.
The first implementation of this ecosystem is based on a Parallax Propeller-based board for connecting Android devices to the in-car network and was designed by Prof. Sundaresan and Pedro Urbina Coronado (visiting scholar in Sundaresan Research Group) between Jan-2013 and Dec-2013. This work was presented as a technical presentation at the IEEE International Conference on Interconnected Vehicles & Expo (ICCVE-2013) on 5th December 2013.
This project has been discontinued since the announcement of Android Auto and Apple CarPlay in early 2014.