The research in my group is focused on fundamental and exploratory projects in colloids, microfluidics and nanoscience. The major thrust is the controlled on-chip assembly of colloidal particles into advanced materials and microscopic functional structures. Our research could underlie future technologies for fabrication of chemical and biological sensors, photonic devices, microscale materials synthesis, bioelectronic interfacing, and rapid fabrication of nanostructured coatings and materials. Three primary research areas are outlined below.
Electrically Functional Microdevices by Interfacing Colloidal Assemblies with Electronic Chips
One of the major challenges in nanoscience is the development of rapid and controllable techniques for nanoparticle assembly. One effective tool for directed assembly is the AC field-induced mobility and interactions of particles, which is called dielectrophoresis (DEP). Our group has pioneered a few areas of DEP on-chip assembly and its use in microfluidics and biosensing. We have explored the potential and demonstrated the formation of electrically functional microdevices by interfacing colloidal assemblies with on-chip electronic circuits. Microscopic electronically readable biosensors have been assembled in situ from latex particles by combining dielectrophoresis with tuning of the colloidal forces. We have also revealed a new phenomenon of dielectrophoretic assembly of conductive microwires from suspensions of metallic nanoparticles. These unique structures are promising for wet electronic and bioelectronic circuits. My group has demonstrated techniques for electric field assembly of colloidal crystals and developed new types of chips for electric field manipulation of freely suspended microdroplets and for collection of live cells. More recently we demonstrated how external AC fields can be used to power self-propelling semiconductor devices, which act as prototypes of autonomous micromachines and microrobots. Presently, we are also studying the application of on-chip dielectrophoretic techniques in the co-assembly of live cells and particles into on-chip biodevices and larger scale biomaterials.
Microstructured and Photonic Materials Based on Colloidal Crystals and/or Biocolloids
We have been the first to use colloidal crystals as templates for the preparation of “inverse opals”, which by now are one of the most studied photonic materials. We used this method to obtain a new type of material – nanostructured porous gold. These metallic nanostructures have unique optical and photonic properties and hold promise for advanced applications in electro-optics, microelectronics, or catalysis. We now synthesize these materials in the form of thin films, and study their use in high-performance flow chemical sensors based on surface enhanced Raman spectroscopy. Functionalization of these materials can make them useful in integrated on-chip devices for biological and biochemical detection.
Environmentally-Friendly Nanomaterials and Nanostructures
We are studying the potential of liquid CO2 as a medium for the assembly of colloidal crystals and related nanostructured and photonic materials. This work can find application in processes for fabrication of nanofunctional materials that are both oriented to high technologies and environmentally benign. We specifically look for nanostructures and devices that make sense in terms of cost of fabrication and better performance than alternative technologies. Another industry-oriented project is the development and evaluation of new environmentally friendly processes for the synthesis of nano- and microparticles from hydrophobically modified cellulose and other naturally derived products. These nanoparticles will have minimal environmental impact as they are made from benign biodegradable material. They could revolutionize the ways emulsions and foams are formulated and fabricated in industry.
Focus Areas - Colloidal Nanoscience and Nanoengineering. Microfluidics, Biosensors and On-chip Devices. Colloidal Interactions. Self-assembly and Directed Assembly of Nano- and Microstructures with Photonic, Optical, Biological and Electrical Functionality. Hydrogel Photovoltaics and Biomimetic Soft Matter Circuits. Self-propelling Particles. Soft Robotics and Microrobotics.