A sensor is a device that measures a chemical or physical event and produces a corresponding signal that can be read by an observer or an instrument. Broadly, sensors can be divided into physical (e.g., temperature, pressure, magnetic field) and chemical (e.g., NOx, H2S) sensing devices. The driving forces for advancement in sensing technology include reducing cost, reducing size, improving performance, and realizing autonomous self-powering devices and new functionalities. Our research in this area is currently focused on chemical, biochemical and biomedical sensing, with applications including environmental and health monitoring, air and water quality assessment, industrial process monitoring, search & rescue operations, and security.
Microheater-Based Platform for Environmental, Process, and Health Monitoring
The widespread use of chemical sensors can give access to new streams of information to both industries and consumers. However, many existing chemical sensors, especially ones that require heated sensing materials, are bulky or have a large power consumption that prevent the use of portable power sources like batteries. The goal of this project is to develop small, low-power chemical sensors with competitive performance and reliability. Our approach is based on a microheater platform that requires only 10 mW to reach 350 °C. We have successfully sensed hydrogen and propane using novel catalyst materials of Pt nanoparticles-functionalized graphene aerogels and Pt nanoparticle-functionalized boron-nitride aerogels. We have also demonstrated sensitive detection of toxic air pollutants such as carbon monoxide, nitrogen dioxide, and formaldehyde using two-dimensional transition metal dichalcogenides. Long-range goals include the development of novel catalyst materials (e.g., MOFs) for enhanced selectivity, improved catalyst integration with the microheater platform, and investigation of materials issues for long-term reliability.
Electrochemical Sensors Based on Wearable Carbon Textiles
Nowadays, electrochemical sensors play an important role in wide range of potential applications, especially in point-of-care applications for real-time human physiology monitoring. Considerable efforts have been devoted not only to improve their sensitivity, response time, stability, and biocompatibility, but also to develop new materials which enable the researchers to create smarter multifunctional devices. In this regard, flexible textiles such as carbon-fiber sheet integrated electrodes are the promising materials due to their high conductivity, low cost, biocompatibility, and stability even in the harsh environment conditions. We are developing flexible carbon-based textiles incorporating electroactive species as the electrode for electrochemical sensor and biosensor applications.
Silicon Carbide Sensors for Harsh Environment Applications
Silicon carbide (SiC) is an attractive material for high-temperature applications, as well as for use in chemically and mechanically harsh environments (such as abrasive, erosive, corrosive, and biological media). SiC is biocompatible, durable, possesses low-friction characteristics, and is second only to diamond in wear resistance. SiC is also a wide band-gap semiconductor of great interest in high-power, high-temperature, and high-radiation applications. For these reasons, we are developing novel designs, material synthesis, and processing strategies for SiC-based microsensors. In particular, we are developing chemical sensors for high temperature applications and implantable devices for biomedical applications.
Nanoplasmonics for Sensing Applications
Controlling and concentrating infrared radiation has significant potential to impact infrared sensors, thermal imaging devices, and heat conversion systems. Nanofabricated plasmonic gratings offer the dual advantage of low-loss transmission and compression of long wavelength IR radiation. This localization effect enhances spatial resolution and offers high-intensity fields at scales much smaller than the IR wavelengths in free space. We are exploring the applicability of plasmonic gratings as sensors for 1) detecting infrared signatures of molecules, 2) imaging, including bio-imaging, and 3) concentrating thermal infrared radiation for energy harvesting.
Recently Completed Projects
The extraordinary electrical properties of graphene make it an excellent candidate for next generation electrochemical sensors for gas or liquid sensing. Our efforts focused on the growth and modification of graphene sheets with metal nanoparticles through electroless deposition, and their transfer onto different transducers (e.g., screen printed electrodes and interdigitated electrodes) to achieve various characteristics depending on the final desired applications. Further modification of the metal nanoparticle with biomarkers and biomolecules for more specific recognition was also explored. Selective detection of a number of analytes, ranging from glucose to hydrogen peroxide to PDDE, was demonstrated.