Discrete Femtolitre Pipetting with 3D Printed Axisymmetrical Phaseguides

Abstract

AbstractThe capacity to precisely pipette femtoliter volumes of liquid enables many applications, for example, to functionalize a nanoscale surface and manipulate fluids inside a single‐cell. A pressure‐controlled pipetting method is the most preferred, since it enables the widest range of working liquids. However, precisely controlling femtoliter volumes by pressure is challenging. In this work, a new concept is proposed that makes use of axisymmetrical phaseguides inside a microfluidic channel to pipette liquid in discrete steps of known volume. An analytical model for the design of the femtopipettes is developed and verified experimentally. Femtopipettes are fabricated using a multi‐scale 3D printing strategy integrating a digital light processing printed part and a two‐photon‐polymerization printed part. Three different variants are designed and fabricated with pipetting resolutions of 10 picoliters, 180 femtoliters and 50 femtoliters. As a demonstration, controlled amounts of a water‐glycerol mixture were first aspirated and then dispensed into a mineral oil droplet.