TY - JOUR
T1 - Resonance impedance sensing of human blood cells
AU - Zheng, Siyang
AU - Nandra, Mandheerej S.
AU - Shih, Chi Yuan
AU - Li, Wei
AU - Tai, Yu Chong
N1 - Funding Information:
Yu-Chong Tai received his BS degree from National Taiwan University, and the MS and PhD degrees in electrical engineering from the University of California at Berkeley. After Berkeley, he joined the faculty of electrical engineering at the California Institute of Technology and built the Caltech MEMS Lab. Not long ago, he joined the Bioengineering department and he is currently a professor of electrical engineering and bioengineering at Caltech. His current research interests include flexible MEMS, bioMEMS, MEMS for retinal implants, parylene-based integrated microfluidics, neuroprobes/neurochips, HPLC-based labs-on-a-chip. He has received several awards such as the IBM fellowship, the Best Thesis Award, the Presidential Young Investigator (PYI) Award and the David and Lucile Packard Fellowship. He co-chaired the 2002 IEEE MEMS Conference in Las Vegas. He is currently a subject editor of the Journal of Microelectromechanical Systems.
Funding Information:
This work is supported by the National Space Biomedical Research Institute through NASA NCC 9-58. The authors would like to thank other members of the Caltech Micromachining Laboratory for their valuable assistance.
PY - 2008/7
Y1 - 2008/7
N2 - A challenging problem in alternating current (AC) impedance sensing of particles (e.g., blood cells in plasma) with micro electrodes is that with the shrinking of electrode surface area the electrode double layer capacitance decreases. This double-layer capacitor dominates the system impedance in low frequency range, while the parallel stray capacitor dominates the system impedance in high frequency range. Hence the sensitivity for particle sensing for micro impedance sensors decreases over a wide frequency range. In this paper, we propose an approach to solve the problem. The idea is to use resonant sensing by connecting an external parallel inductor to the system. At the resonant frequency, the capacitive components in the system are nullified by the inductor, leaving the channel impedance (including the particle impedance) to be a major component in the system impedance. We then successfully demonstrate this idea by sensing 5 μm polystyrene beads. More important, this technique is extended to sensing blood cells in diluted human whole blood and leukocyte-rich plasma. The sensitivity can be improved by two orders of magnitude over more than three decades in frequency domain. The measured signal peak height histogram at low frequency matches well with known volume distribution of erythrocytes and leukocytes.
AB - A challenging problem in alternating current (AC) impedance sensing of particles (e.g., blood cells in plasma) with micro electrodes is that with the shrinking of electrode surface area the electrode double layer capacitance decreases. This double-layer capacitor dominates the system impedance in low frequency range, while the parallel stray capacitor dominates the system impedance in high frequency range. Hence the sensitivity for particle sensing for micro impedance sensors decreases over a wide frequency range. In this paper, we propose an approach to solve the problem. The idea is to use resonant sensing by connecting an external parallel inductor to the system. At the resonant frequency, the capacitive components in the system are nullified by the inductor, leaving the channel impedance (including the particle impedance) to be a major component in the system impedance. We then successfully demonstrate this idea by sensing 5 μm polystyrene beads. More important, this technique is extended to sensing blood cells in diluted human whole blood and leukocyte-rich plasma. The sensitivity can be improved by two orders of magnitude over more than three decades in frequency domain. The measured signal peak height histogram at low frequency matches well with known volume distribution of erythrocytes and leukocytes.
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U2 - 10.1016/j.sna.2007.10.047
DO - 10.1016/j.sna.2007.10.047
M3 - Article
AN - SCOPUS:44849130411
SN - 0924-4247
VL - 145-146
SP - 29
EP - 36
JO - Sensors and Actuators, A: Physical
JF - Sensors and Actuators, A: Physical
IS - 1-2
ER -