Predicting the mechanism of removal of nonspecifically bound proteins in a surface acoustic wave biosensor: A fluid-solid interaction study

Biosensors typically operate in liquid media for measurement of biomarkers and suffer from fouling mechanisms such as nonspecific binding of protein molecules to the device surface. In the current work, using a novel numerical technique as well as experiments, we have identified that fluid motion induced by high intensity sound waves, such as those propagating in these sensors, can lead to the removal of the nonspecifically bound proteins, thereby eliminating sensor fouling. We present a computational and experimental study of the acoustic-streaming phenomenon induced biofouling elimination by surface acoustic waves (SAWs). The transient solutions generated from the developed coupled field fluid solid interaction (FSI) model were utilized to predict trends in acoustic-streaming velocity for various design parameters such as voltage intensity, device frequency, fluid viscosity and density. The model predictions were utilized to compute the various interaction forces involved and thereby identify the possible mechanisms for removal of nonspecifically-bound proteins. Our study indicates that the SAW body force overcomes the adhesive forces of the fouling proteins to the device surface and the fluid-induced drag and lift forces prevent its re-attachment. The streaming velocity fields computed using the finite-element models in conjunction with the proposed mechanism were used to identify the conditions leading to improved removal efficiency. Our research findings have significant implications in designing reusable and highly sensitive biosensors.