Dynamic Size-Tracking of Single Cells Using Microfluidics-Integrated Microwave Sensors

Cellular size is one of the most important biophysical indicators of the state of a cell. Cellular size can be used as a sensory signal for determining cellular growth and decay trends and can facilitate the testing of novel drugs on cancerous cells. While size measurements have traditionally been performed using optical microscopy and quantitative phase imaging, there is still ample space for sensors with higher resolution and throughput, as well as lower cost. In this respect, microwave resonators have been suggested for detecting single cells in a label-free manner; however, little has been done to systematically compare the microwave signal output induced by single cells to the cellular size obtained by optical microscopy. Here and for the first time, we demonstrate that the cellular size measurements conducted by microscopy and a microfluidics-integrated microwave sensor indeed correlate, at the single cell level. We further study in real-time the changes in size of single cells that are dynamically trapped around the sensing region and chemically induced to shrink. The strong correlation between the electronic and optical size results indicates that microwave sensors can be used for detecting and sizing single cells in real time.