(315e) Generating Single Cell Samples As Droplets Using a DVD Pickup Based Optical-Tweezer in a Microfluidic Platform

Single cell detection, handling and isolation are vital for the generation of samples for single cell-based diagnostics and purifying rare cells such as stem cells, circulating tumor cells, and cells for genetic testing. Commercial instruments available for single-cell deposition into 96 well plates are often bulky and expensive. Micro-fluidic platforms have addressed these issues but have often had the limitation in sample delivery as the generated samples are often inaccessible or become contaminated as you try to extract them. There is a need for a microfluidic chip that can deliver the generated samples off the chip in the form of droplets that can be collected and used readily. We have developed a compact (scale of a handheld device) and inexpensive platform to generate single cell samples as individual droplets. Our device is powered by a gravity driven microfluidic chip coupled with an optical trapping DVD optical pickup. Our device exploits the laminar nature of flow in microfluidics to deterministically guide cells to separate exits with an optical trap. Directional vaults in the microfluidic channel roof move sorted cells away from slow streamlines close to the wall into faster streamlines at the channel center. This reduces cell residence time in the device and improves the throughput of the device manifold. Holes were drilled in the glass substrate for the fluid to leave the device. Selective hydrophobic treatment of the underside of glass slides causes samples to form droplets. Consistency of droplet generation is crucial for the performance of the continuous flow chip that delivers single-cell samples as droplets. We have designed a device where droplets are generated at regular intervals and have a tight distribution around 53.72 µl ± 0.07µl. This small deviation gives us the confidence that a particle sorted at a regular interval upstream will end up in a new droplet every time. However, falling droplets cause significant pressure fluctuations upstream. Compliance reservoirs were added upstream of the droplet outlet to absorb/dampen pressure waves from falling droplets and shield the sorting section. The compliance reservoirs dampen the large fluctuations effectively. We believe we have a compact sorting and delivery module that can be added downstream of many common detection mechanisms based on viscoelasticity, electrical impedance, size or florescence.