10:30 AM - 10:45 AM
[4-1015-C-02] Efficient Filtering of Live Escherichia coli by Using 60 GHz CMOS Sensor
Keywords:Bacteria separation, 60 GHz CMOS sensor, Dielectrophoresis, E. coli
The separation and extraction of bacteria are essential for food safety evaluation and infection diagnosis by a blood test. In particular, the quick selection of live and dead bacteria can contribute to developing efficient and high precision bacterial testing. To realize this, we have been developing a near-field array CMOS sensor with a 60 GHz oscillator. 1488 oscillators are arranged in 3 mm square, and when the sample exists on the surface, the distribution of the electric field on the sensor surface changes and the resonance frequency also changes. We succeeded in mounting the circuit of dielectrophoresis (DEP) in each oscillator by CMOS integration technology. In this presentation, we report the investigation of the optimization of applied voltage and frequency to this DEP circuit in order to distinguish live and dead bacteria.
The cultured E. coli suspension was centrifuged twice to replace the medium and distilled water. This E. coli suspension was used as a measurement sample of viable bacteria. Also, 5 ml of this suspension was placed in an autoclave for 1 hour to make dead bacteria. And the oscillation frequency of two samples of live and dead bacteria was measured every 6 seconds for 300 seconds. In the measurement, the sample was flowed at 5 μL / min with a syringe pump (YWC). In addition, DEP was set to a voltage of 5 V and a frequency of 10, 100, and 1000 kHz. DEP was turned off from 0 to 60 seconds, DEP was turned on from 60 to 240 seconds, and DEP was turned off from 240 to 300 seconds. The experiment was conducted while confirming the presence of E. coli on the CMOS sensor with a microscope.
The oscillation frequency at 240 seconds minus the oscillation frequency at 300 seconds was taken as the frequency shift. At DEP 10 kHz, it is thought that no live bacteria or dead bacteria were affected by the negative DEP force and bacteria did not accumulate on the oscillator. At DEP 100 kHz, a positive force of DEP acts on the live bacteria, and the live bacteria are accumulated on the oscillator, and the shift of the live bacteria is considered to be 0.015 GHz. It is thought that bacteria did not accumulate on the oscillator because negative DEP force was exerted on dead bacteria. At DEP 1000 kHz, it is thought that positive DEP force acts on both live and dead bacteria, and bacteria accumulate on the oscillator. From this experiment, the possibility of distinction between live and dead bacteria of E. coli was shown at DEP 100 kHz.
The cultured E. coli suspension was centrifuged twice to replace the medium and distilled water. This E. coli suspension was used as a measurement sample of viable bacteria. Also, 5 ml of this suspension was placed in an autoclave for 1 hour to make dead bacteria. And the oscillation frequency of two samples of live and dead bacteria was measured every 6 seconds for 300 seconds. In the measurement, the sample was flowed at 5 μL / min with a syringe pump (YWC). In addition, DEP was set to a voltage of 5 V and a frequency of 10, 100, and 1000 kHz. DEP was turned off from 0 to 60 seconds, DEP was turned on from 60 to 240 seconds, and DEP was turned off from 240 to 300 seconds. The experiment was conducted while confirming the presence of E. coli on the CMOS sensor with a microscope.
The oscillation frequency at 240 seconds minus the oscillation frequency at 300 seconds was taken as the frequency shift. At DEP 10 kHz, it is thought that no live bacteria or dead bacteria were affected by the negative DEP force and bacteria did not accumulate on the oscillator. At DEP 100 kHz, a positive force of DEP acts on the live bacteria, and the live bacteria are accumulated on the oscillator, and the shift of the live bacteria is considered to be 0.015 GHz. It is thought that bacteria did not accumulate on the oscillator because negative DEP force was exerted on dead bacteria. At DEP 1000 kHz, it is thought that positive DEP force acts on both live and dead bacteria, and bacteria accumulate on the oscillator. From this experiment, the possibility of distinction between live and dead bacteria of E. coli was shown at DEP 100 kHz.