A MODULAR DISPENSING SYSTEM FOR LEAKAGE-FREE PICOLITER DROPLET RELEASE IN LIQUID ENVIRONMENTS

We present a new tool that can be positioned accurately next to any individual cell for the precisely controlled transfer of individual picoliter (pL) droplets in the range of 150-950 pL (CV < 3.5%) in liquid environment while avoiding any leakage. This is achieved by a low-cost, disposable and biocompatible cap that is placed on top of any pL-dispenser and generates a phase-gap between dispensing agent and target liquid when the dispenser is dipped into the latter thus avoiding diffusive transport. We developed two different working modes: (i) the standard mode enables an instant injection (<< 1 ms) of the droplet into the liquid environment and (ii) the focus mode further increases the spatial resolution from 100 µm to 50 µm. For the phase-gap we have proven an excellent long-term stability of more than 30 hours against capillary priming and a maximum volume ejection rate of up to 137 nL/s without flooding.