Digital Microfluidics With Pressure-Based Actuation

One of the key issues in biosensors is the time it takes for biomolecules in a solution to reach and bind to the sensor surface (particularly in low-concentration analytes). We present a novel flow scheme without microfluidic channels for label-free biosensors to decrease the delivery time of biomolecules. Through designing the biosensor in such a way that it becomes a membrane with holes, we can apply a droplet on it and push or pull it through the membrane by means of a pressure difference. Contrary to traditional microfluidics for, e.g., flow cells where the analyte flows over the sensor, the flow is now directed through the sensor. We have implemented this scheme in silicon-on-insulator biosensors and have demonstrated in a first proof-of-principle experiment, an improvement in delivery time of at least a factor of three.