ECE Seminar with Pingshan Wang

4:00 pm on Monday, March 18, 2013
Photonics Center, 8 Saint Mary’s St., Room 339
Highly Sensitive and Tunable RF Sensors: Label-Free Detection and Analysis of Single Cells and Particles in Liquid

With Pingshan Wang
Department of Electrical and Computer Engineering
Clemson University

Faculty Host: Enrico Bellotti

Refreshments will be served outside Room 339 at 3:45 p.m.

Abstract: Lab-on-chip (LOC), i.e. micro-total-analysis-systems (μTAS), is a technology driver in the More than Moore (MtM) domain. A difficult challenge in LOC development is label-free detection and analysis of single cells, particles and molecules at high speed. Different approaches, including optical, electrical, magnetic, and mechanical methods, have been aggressively explored to address the problem. Substantial progress has been achieved. Yet, critical scientific and technical road-blocks remain. A key bottleneck is the lack of specificity and sensitivity of current label-free sensing techniques.

In this talk, I will present some of our efforts in tackling the problem. We develop high frequency LOC (HiFi-LOC) techniques, i.e. microwave μTAS (μ2TAS), which are based on our novel RF sensors that can achieve an effective quality factor, Q (=f0/Δf3dB), up to ~3106. The Q is a few orders of magnitude higher than that of previously reported microwave resonators. It is also comparable with the Q value of the super sensitive optical micro-resonators that can detect and count single viruses and nanoparticles. Furthermore, our RF sensors are tunable from ~20 MHz to ~38 GHz. Such a combination of high sensitivity and broadband operation has never been achieved before. The broadband capability is expected to yield significantly more information about the properties of material-under-test (MUT), as well as facilitate label-free detection and analysis of MUT.

Our specific efforts that are related to the proposed RF sensors include the following. First, we demonstrated the interference-based operating principle of the sensors at ~6 GHz, measured methanol-water and ethanol-water mixtures, and proved that the sensors were much more sensitive than other microwave sensors. Secondly, we achieved clear sensing and identification of individual viable and nonviable yeast cells in de-ionized (DI) water at ~5 GHz in a label-free manner. Single latex particles with diameters between 1 and 5 μm in DI water were also measured. An algorithm was developed to obtain the dielectric property values of those single particles and cells. Thirdly, such sensors were developed and used to characterize high-frequency dynamics of single magnetic nanowires. Recently, we showed that the RF sensors are promising for the development of miniaturized electron paramagnetic resonance (EPR) spectrometers as well as portable devices for rapid diagnostic tests of malaria.

Compared with optical techniques, our RF method facilitates immediate integration with other electronic capabilities. The inherently stronger interactions between RF probing-fields and MUT could offer higher sensitivity. When compared with DC/low frequency methods, which dominate current electrical LOC efforts overwhelmingly, our approach avoids electrode-polarization effects. Furthermore, the operating frequency of the proposed RF sensors can be scaled for terahertz operations. The sensor electrodes can be scaled to achieve nanometer spatial resolutions. Thus, the RF sensors are expected to play a key role in our efforts on HiFi-LOC development for label-free detection and analysis of single cells, particles and molecules.

About the Speaker: Dr. Pingshan Wang obtained his Ph.D. degree in Electrical and Computer Engineering from Cornell University in 2004. He joined the Department of Electrical and Computer Engineering, Clemson University, in 2006, after serving for two years at the Southern Illinois University Carbondale. Dr. Wang and his group are currently working on high-frequency lab-on-chip (HiFi-LOC)/microwave micro-total-analysis-systems (μ2TAS) techniques, for which they develop high-frequency and high-voltage CMOS circuits, radio-frequency (RF) sensors, and RF nanotechnologies mainly aimed for chemical and biomedical applications.