| AVS 65th International Symposium & Exhibition | |
| MEMS and NEMS Group | Wednesday Sessions |
| Session MN+2D+AN+NS-WeA |
| Session: | IoT Session: MEMS for IoT: Chemical and Biological Sensing |
| Presenter: | Selim Hanay, Bilkent University, Turkey |
| Authors: | S. Hanay, Bilkent University, Turkey H. Aydogmus, Bilkent University, Turkey A. Secme, Bilkent University, Turkey H.S. Pisheh, Bilkent University, Turkey M. Kelleci, Bilkent University, Turkey U. Hatipoğlu, Bilkent University, Turkey |
| Correspondent: | Click to Email |
In this study, a facile microwave sensor is designed and fabricated to detect transient cells one by one and extract their morphological and electrical properties in real time, without labeling. Multiple modes can be measured by multiplexing the electronic frequencies to obtain multiple analytic parameters at the same time. Our simple fabrication technique obviates the need to complex fabrication process.
A microwave sensor, in the form of a microstrip line resonator, is constructed by fixing copper tape at the back and the front side of a 1-mm thick glass slide. The backside is covered entirely with the tape to form a ground plane; on the front side, a copper tape was thinned within a few mm, extended across the slide and terminated with SMA feed through. On the front side, just below the copper tape, five capillary tubes are placed to transport the cells into the active sensing region. Microwave signals are transmitted through the two SMA ports at the end of the glass slide, perpendicular to the flow. The resonator is formed by electrically shorting the input/output ports. An initial characterization of the device is done by using spectrum analyzer so that its first and second order mode frequencies are obtained.
A digital phase-locked loops (PLL) measurement system with PI controller was constructed to track the resonance frequencies of the first two modes simultaneously in real-time. The PLL system tracks the two modes of the microstrip line resonator to sense the frequency shifts originating from the passage of the cells in the capillary.
As a proof of concept, initial PLL measurements were done with DI water. As water flows through the tube, frequency shifts around 100 kHz were observed in both modes. Later on, wildtype Skbr3 breast cancer cells were flown through the same capillary. Frequency shifts in both modes were the responses of the resonator to the passage of the Skbr3 cells beneath microstrip-line. The ratio between the first and second mode frequency shifts can be used determine the location of each cell by two-mode theory. The analyzed data indicates almost a constant slope, verifying the positional response of the sensors. Moreover, the size distribution of the cells is cumulated around a contour line for constant size as expected.
Earlier, we had detected single cells and distinguished different oncogenic cell lines using a PDMS based device. With this work, single-cell detection and sizing are accomplished with a device paradigm that does not require any lithography, metal deposition under vacuum or precise alignment of electrodes.
We acknowledge funding from European Research Council (ERC) Starting Grant (REM, 758769).