With this project, we built an experimental setup combining microwave sensing technology with optical microscopy for independent verification. By building different versions of sensitive microwave resonators integrated with microfluidic channels, we measured the geometric and electrical properties of single cells and microparticles.
In our efforts, we had to solve several technical problems, such as the uncertainty caused by the vertical position of a cell inside the channel. By using a system of multiple electrodes and particle velocity measurements, we were able to extract the particle's height inside the channel. With this improvement, we were able to distinguish between microplastic and microglass particles in the 20-micron size range. We also showed that our technique can detect the internal compositional changes induced by a chemical used to fix cells.
To make accurate measurements of cells and microparticles, we also developed three-dimensional microscopic structures integrated with our sensors. These structures generate a uniform electric field in the sensing region, so that the vertical position of an analyte particle does not degrade the measurement results. We have built such 3D micro-electrodes based on either liquid or solid sensing structures.
We have also extended microwave measurement technology from single cells to nanoparticles and viruses, by forming sensors around a nanopore. In our search for obtaining sensitive devices, we have also uncovered a novel mechanism for liquid flow rate sensing. This mechanism is based on the periodic pulsations, induced by a constant fluid flow, of a nanoscale membrane integrated with the microfluidic channel. We have also explored how the microwave sensing technology can be used for detecting viruses in air.
Our results were published in many different journal papers, and presented in many conferences. We also received patent protection for the flow-rate sensor technology, and applied for a patent for material-sensing technology developed in this project.
