Exceptional Points Enhanced Acoustic Sensing of Biological Cells

This award supports research that investigates the fundamentals understanding of a novel biosensing concept for high-sensitivity measurement of cell mechanical biomarkers. Biomarkers, or biological markers, are measurable indicators of a biological cell state or condition and can be closely associated with changes in functionality and health of cells. Thus, the ability to measure multiple cell mechanical properties as biomarkers will benefit biological research and clinical applications such as cancer studies, drug screening/discovery, and immunology. The acoustic sensing concept in this project relies on the detection of exceptional points, which are highly sensitive dynamic states that occur in non-Hermitian physical systems characterized by balanced gain and loss. The long-term research goal of the project is to employ the sensing scheme for measuring mechanical biomarkers of individual cells in high throughput for both fundamental studies and clinical applications. The research findings will also contribute to the PIs’ long-term education and outreach goals of motivating students toward science and engineering, by illustrating far reaching implications of engineering. The project activities will also specifically illustrate how engineers contribute to biomedicine through acoustic sensing and fundamental wave mechanics concepts. Results from this research will benefit the US health and society, impacting the fields of acoustic sensing, disease diagnosis, and cellular biology. The project will investigate fundamental research questions related to how biological cells with different mechanical properties (stiffness, density, compressibility and viscosity) interact with acoustic waves propagating along a substrate, how perturbations caused by the cell and by changes in its properties can break the dynamic equilibrium associated with exceptional points, and how the corresponding frequency splitting mechanism can quantify changes in the cell properties and thus form the basis for a novel acoustic biosensing technique. The project objectives will be accomplished through two research tasks: (1) investigation of cell-wave interaction and fundamental studies on exceptional point generation in acoustic substrates; and (2) experimental investigations, and proof-of-concept of exceptional point-based acoustic biosensing. This project will lead to advances in the understanding of the interaction between surface acoustic waves and a cell. The study of exceptional points generation in surface acoustic waves substrates with a cavity is a novel aspect of the work, which will explore the interaction of multiple wave modes with cavity-cell resonances, their coupling and hybridization. Analytical, numerical, and experimental studies will explore the sensitivity of exceptional points sensing of the cell’s physical properties, which will open new pathways for sensing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.