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Novel Multiplexed Coulter Counters for High Throughput Parallel Analysis of Microparticles

2011, Doctor of Philosophy, University of Akron, Mechanical Engineering.

Coulter counters are well established analytical instruments for counting and sizing micro and nano scale particles. One long-standing drawback of microfabricated Coulter counter type devices is their low throughput because they scan each individual
particle passing through a fluidic channel where the channel size is comparable to the particle size. To overcome the low detection throughput, in this research, novel Coulter counters that use parallel sensing channels to achieve high throughput detection of
microparticles are designed and tested. The sensor uses multiplexed detection to measure a combined signal from all channels using a single pair of electrodes for a microfabricated multichannel sensor. The detection uses frequency division multiplexing based on amplitude modulation of applied AC excitation signals at unique frequencies. The design, fabrication and testing of single and four channel sensors are presented. The
single channel devices were used to demonstrate the feasibility of using the amplitude modulation method to detect microscale particles. Numerical analysis based on an electrical equivalent circuit and experimental results confirmed the amplitude modulation
concept for the single channel sensor at selected frequencies for 30 µm polystyrene and Juniper pollen particles.


A four channel sensor was microfabricated and tested using 30μm polystyrene particles to demonstrate improvement in detection throughput. Four unique and known modulation frequencies were applied to each channel using their central electrodes. A combined response for the sensor was collected at one major electrode and demodulated to obtain the signals for each individual channel. The testing results indicated that using the multiplexing technique, detection throughput of the sensor was improved by 300% in
contrast to a single channel sensor. No false positives due to crosstalk among channels were observed. It is possible to extend the design concept to a large number of channels,thereby increasing the throughput significantly. In addition, for both the single and four channel devices, AC modulation allowed accurate measurement of particle sizes by eliminating the polarization effect typically seen on the electrode-electrolyte interfaces of
many microfabricated devices.


Finally, an eight channel microfabricated device using a novel and improved electrode placement was used to demonstrate improvement in throughput over the four channel sensor. The electrode placement uses electrodes connected to ground and placed in between the sensing electrodes to isolate adjacent channels. The use of isolation electrodes allows placement of the sensing electrodes outside the microchannel. This design eliminates the need for using a central electrode and fabrication of a masking layer used in the four channel design to prevent cross-talk between channels. Testing of Juniper pollen particles using DC excitation demonstrated that particles in each channel can be detected without cross talk. The design concept can be extended to frequency division multiplexing of submicron and nanoscale channels where fabrication of a central electrode can be problematic.

Jiang Zhe, PhD (Advisor)
182 p.

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Jagtiani, A. (2011). Novel Multiplexed Coulter Counters for High Throughput Parallel Analysis of Microparticles. (Electronic Thesis or Dissertation). Retrieved from https://etd.ohiolink.edu/

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Jagtiani, Ashish. "Novel Multiplexed Coulter Counters for High Throughput Parallel Analysis of Microparticles." Electronic Thesis or Dissertation. University of Akron, 2011. OhioLINK Electronic Theses and Dissertations Center. 24 Nov 2017.

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Jagtiani, Ashish "Novel Multiplexed Coulter Counters for High Throughput Parallel Analysis of Microparticles." Electronic Thesis or Dissertation. University of Akron, 2011. https://etd.ohiolink.edu/

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