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.
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.
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.