Microfluidic platform using focused ultrasound passing through hydrophobic meshes towards automatic biological experiment

Laboratory automation is critical in improving productivity and data quality. Droplet-based microfluidic systems offer a solution that enables parallel handling of small samples with high reconfigurability and scalability. The most common technique is electrowetting-on-dielectric (EWOD), which manipulates droplets by exploiting the imbalance of wetting. However, this method is often limited by biofouling. In our previous study, we proposed a novel microfluidic platform using focused ultrasound passing through a hydrophobic mesh, which reduces the contact area and thus the hydrophobic interactions and electrostatic attractions of biomolecules. Our platform demonstrates the manipulation of protein-rich droplets at concentrations up to 1 mg/ml without the need for any additives. This is a significant improvement over existing EWOD methods which are limited to handling samples with protein concentrations as low as 0.005 mg/ml without additives. Here, we further investigate the influence of protein concentration, pH, and buffers using fluorescence microscopy to determine the effect on the system. Our platform also provides basic functions such as moving, merging, and splitting, as well as superior jumping capabilities. With reduced biofouling and the ability to directly transfer droplets to adjacent devices and multi-step processes, our platform opens up new possibilities for the automation of biology.