Picoliter Droplet Dispenser with Integrated Impedance Detector for Single-cell Printing

We present the fabrication and first experimental results of a microfluidic droplet dispenser with electrical impedance detection of single cells. The microdispenser features microchannels, two sets of parallel facing electrode pairs and an on-demand droplet generator. It has been fabricated by sandwiching dry film photopolymer (TMMF) between silicon and Pyrex substrates. The channels and dosage chamber are patterned in TMMF, the platinum electrodes are on the fluid-contacting sides of the silicon and Pyrex substrates. The presented fabrication is achievable at full-wafer level, offering low temperature (75 °C) silicon to glass bonding using adhesive TMMF. Experimental characterization for the electrical impedance detection using single micro beads (10 m diameter) suspended in standard saline (PBS) has shown that the sensor is capable to detect single particles as they pass the electrode pairs. Real-time data processing is able to detect particles, calculate their velocities and issue a trigger to dispense the detected particle encapsulated in a microdroplet successfully.