Inverse Leidenfrost drop manipulation using menisci

TL;DR

This paper explores the use of inverse Leidenfrost drops on evaporating liquid baths to probe, control, and manipulate droplets via menisci, with potential applications in contactless biological sample handling.

Contribution

It demonstrates how frictionless Leidenfrost drops can be used to measure interface shapes and manipulate droplets with designed menisci, advancing contactless droplet control techniques.

Findings

Leidenfrost drops can probe unknown interface shapes.

Menisci can direct and focus droplets.

Droplet manipulation has potential in cryopreservation.

Abstract

Drops deposited on an evaporating liquid bath can be maintained in an inverse Leidenfrost state by the vapor emanating from the bath, making them levitate and hover almost without friction. These perfectly non-wetting droplets create a depression in the liquid interface that sustains their weight, which generates repellent forces when they approach a meniscus rising against a wall. Here, we study this reflection in detail, and show that frictionless Leidenfrost drops are a simple and efficient tool to probe the shape of an unknown interface. We then use the menisci to control the motion of the otherwise elusive drops. We create waveguides to direct and accelerate them and use parabolic walls to reflect and focus them. This could be particularly beneficial in the scale up of droplet cryopreservation processes: capillary interactions can be used to transport, gather and collect vitrified biological samples in absence of contact and contamination.