Numerical characterization and optimization of the acoustic device for heterogeneous immunoassays

In the context of the COVID-19 epidemic, enhancing the transport of analyte to a sensor surface is crucial for rapid detection of biomolecules, since common conditions including low diffusion coefficients cause inordinately long detection times. SAW-based method owns low propagation loss, low power consumption, and ease of integration. However, the microstreaming effect is not stable and predictable using the bubble-induced acoustofluidic mixers. There is a strong need for developing efficient and robust acoustic devices for enhancing immunoassays. We herein take advantage of dual SAW streaming flow to enhance a continuous and non-invasive mixing of the target molecule with the immobilized antibody region. Acoustic streaming flow is utilized to stir the flow field in the micro-chamber, accelerate the transport of analyte to the functionalized surface and simultaneously minimize the localized target depletion. Using simulations, an optimized design of the proposed microfluidic chip is proposed based on the immunoassay enhancement by investigating the influences of the position of the reaction surface, the chamber height, the excitation frequency, the applied voltage, the antibody concentration, and the reaction rate on the binding performance. To the best of authors' knowledge, it is the first investigation of enhancing immunoassays in SAW-based devices by optimizing the key parameters using simulations. As a result, the sensor target interaction can be enhanced and the nonspecific molecules can be simultaneously displaced from the reaction surface. The current Acoustic streaming flow assisted immunoassay technology can also be extended to other proteins, DNA and cell analysis.