In order to develop highly reproducible, highly selective, and miniaturized sensitive electrical DNA sensing platform, it is important to develop and study sensor-biological interface that is compatible with microfabrication processing and also provide the requisite sensitivity and stability when exposed to biological environments. Recent developments in Carbon-MicroElectroMechanical Systems and Carbon-NanoElectroMechanical Systems have led to simple fabrication techniques that result in novel micro/nano-scale carbon structures with high-aspect-ratio and high surface area. The research objective of this award is to advance fundamental research in the use of pyrolyzed carbon as a bio-sensing electrode material by testing and engineering various types of carbon electrodes with high surface areas and different arrangements, developing methods of increasing the surface immobilization efficiency of bio molecules, engineering techniques for bio molecules immobilization on polymer/carbon interfaces, and further understanding fundamental chemical and electrochemical phenomena occurring at or near bio/carbon or bio/polymer/carbon interfaces.
If successful, the results of this research will provide an opportunity to create next generation highly sensitive and highly selective inexpensive portable biosensors. This research will broaden the participation of women and minority students in science and engineering, and also foster interdisciplinary interactions with students (especially Hispanic minority students). The research results will be broadly disseminated to enhance scientific and technological understanding through presentation at conferences and publication in journals. In this project, we will effect graduate and undergraduate education and try to raise the awareness in state-of-arts MEMS device and biotechnology for elementary and high school students in local area. Newly developed technique will be highlighted in graduate courses.
Carbon microelectromechanical systems (C-MEMS) technique is a promising solution for developing miniaturized biosensors because biologically modified pyrolyzed photoresist carbon surfaces exhibit extraordinary chemical stability and excellent sensitivity in recent biomolecular recognition studies. Our goal in this project is mainly focused on investigating different strategies to develop functionalized high surface area bio-carbon interface for electrochemical and biosensing applications. We have focused our research efforts on (1) synthesizing 3D carbon microelectrode arrays with controllable surface area and porosity; (2) development of conformal coating method for integration of carbon nanomaterials (CNTs and graphene) on microelectrodes; (3) development, investigation and comparison of various surface functionalization methods for pyrolyzed photoresist carbon surface, i.e., direct amination approach, Oxygen RIE treatment, Diazonium grafting, Vacuum UV-treatment, UV/Ozone treatment, and Electrochemical activation; (4) verifying and quantifying functional groups on carbon surface, (5) verifying the attachment of biomolecules (such as DNA and protein) on the functionalized electrode surface; and (6) building and testing three different type of biosensors, i.e., DNA sensor, H2O2 sensor, and protein sensor, based on C-MEMS/NEMS electrode arrays. During this project, high aspect ratio three-dimensional carbon microarrays were fabricated via C-MEMS technique, which is based on pyrolyzing patterned photoresist polymers. Using F127 as porogen, treatment with oxygen reactive ion etching, and integrating of nanomaterials (such as: carbon nanotubes and graphene) are demonstrated as effective methods for further increasing surface areas of the electrode arrays. The amperometric response of conformally coated graphene on carbon micropillar arrays exhibited higher electrochemical activity and improved charge transfer and a linear response towards H2O2 detection. Furthermore, carbon nanostructures were successfully developed based on pyrolyzing photo-nanoimprint lithography patterned organic resist polymer. In order to develop and study the surface functionalization, covalently attachment of bioreceptors on the carbon surface was conducted by various surface modification techniques. The types of carbon–oxygen groups formed on the surface and their coverage were compared. Finally, DNA sensors and protein sensors were developed and evaluated. For example, a label-free detection strategy using signaling aptamer/protein binding complex for platelet-derived growth factor oncoprotein detection on functionalized three-dimensional carbon microarrays platform was demonstrated. The sensor showed near linear relationship between the relative fluorescence difference and protein concentration even in the sub-nanomolar range with an excellent detection limitation. Our educational activities are mainly focused on (1) K-12: aiming to promote science and engineering at early stage. (2) undergraduate students: providing research opportunity and professional training, and (3) women and minority students: promoting the participation and advancement of women and minorities in science and engineering careers. This research has broadened the participation of women and minority students in science and engineering, and also foster interdisciplinary interactions with students at all levels and from various backgrounds.
