What is active wetting?

TL;DR

This paper reviews and classifies wetting phenomena, introduces the concept of active wetting, and discusses its definition and distinctions from passive wetting in various physical and biological systems.

Contribution

It provides a coarse classification of wetting phenomena and proposes a tentative definition of active wetting, highlighting differences from passive wetting.

Findings

Active wetting encompasses various phenomena in biological and physical systems.

A classification scheme distinguishes passive and active wetting behaviors.

The paper discusses criteria and caveats for defining active wetting.

Abstract

In recent years the term \textit{active wetting} has gained some traction in works describing, analyzing and modeling a wide variety of wetting phenomena, for instance, in the contexts of biomolecular condensates, of cell layers or cell aggregates, and of active Brownian particles. The present perspective proposes a coarse classification of wetting phenomena including a tentative definition of active wetting. First, different categories of static and dynamic wetting of passive liquids are briefly discussed, in particular, distinguishing equilibrium wetting, relaxational wetting, driven wetting, and reactive wetting. Second, an overview is given of the various phenomena recently described as active wetting. We conclude by discussing a possible definition of active wetting together with a number of caveats one might want to keep in mind when using such classifications.