Antoine Barbot, Dominic Wales, Eric Yeatman, Guang-Zhong Yang
Delivery and sampling nanoliter volumes of liquid can benefit new invasive surgical procedures. However, the dead volume and difficulty in generating constant pressure flow limits the use of small tubes such as capillaries. This work demonstrates sub-millimeter microfluidic chips assembled directly on the tip of a bundle of two hydrophobic coated 100 µm capillaries to deliver nanoliter droplets in liquid environments. Droplets are created in a specially designed nanopipette and propelled by gas through the capillary to the microfluidic chip where a passive valve mechanism separates liquid from gas, allowing their delivery. By adjusting the driving pressure and microfluidic geometry, both partial and full delivery of 10 nanoliter droplets with 0.4 nanoliter maximum error, as well as sampling from the environment are demonstrated. This system will enable drug delivery and sampling with minimally invasive probes, facilitating continuous liquid biopsy for disease monitoring and in vivo drug screening.
Schematic illustration and microscopic images of the proposed micro-system for droplet delivery and sampling at a fiber tip. a) Illustrates the concept of a passive valve created at the liquid gas interface. b) Illustrates droplet delivery and sampling mechanisms at the tip of a two capillaries bundle linked together at the tip. A small opening to the environment acts as a passive valve that allows liquid exchange (either out for delivery or in for sampling) only when a droplet is present. c) Shows a Scanning Electron Microscope (SEM) image of the Two-Photon Polymerization (2PP) structure assembled at the tip of a capillary bundle to provide both connection between the two capillaries and with the outside through several holes acting as passive valve. d) A Video frame showing the transport and delivery of an ink droplet inside the environment.
Institute of Medical Robotics