Photoacoustic detection of free-flowing particles using optofluidic microresonators

We introduce an integrated photoacoustic (PA) sensing platform designed for rapid, label-free characterization of microbial populations in synthetic biology contexts. By combining whispering-gallery-mode (WGM) optical microresonators with microfluidic handling, the system achieves high sensitivity in microliter-scale samples. WGM resonators amplify light-matter interactions through ultra-high optical quality factors, while PA signals capture complementary optical, thermal, and mechanical information from particles and cells. To streamline analysis, a deep learning model interprets the collected PA spectra, enabling accurate identification of particle or cell types and their concentrations without manual intervention. This approach provides fast, objective classification and demonstrates a versatile tool for precision monitoring of bioprocesses, offering potential applications in high-throughput synthetic biology and environmental sensing.