Researchers at the University of California, Irvine have developed a Laplace pressure trap that can fuse droplets from different inlets and fuse droplets generated at different frequencies. The device traps and fuses droplets passively by balancing the driving hydrostatic pressure with increasing Laplace pressure imposed by the device’s design geometry.
Above are video frames showing the Laplace pressure trap and of a single droplet fusion event at the Laplace trap.
Currently, “active” devices are used to generate droplets fused from different inlets. The droplet generation rates need to be matched and their paths to the droplet fusion region need to be synchronized. This requires active detection mechanisms and the holding of droplets of interest indefinitely through the use of electrodes in order to synchronize the fusion of droplets. This active detection and synchronization requires electrical current which may not be suitable for biological assays and the preparation of biological samples for microfluidic analysis. These devices that use electricity to synchronize droplet fusion are also costly to fabricate.
This new Laplace pressure trap may be used to fuse droplets to perform chemical and biological assays. For example, droplets containing primers may be fused with droplets containing DNA for PCR analysis.
This new Laplace pressure trap is a passive device that fuses droplets and bypasses the problems of active electrical devices. Unlike active devices, this passive device is less costly to fabricate.
Prototypes have been developed and shown to have droplet fusion rates between 80-100%.