Dynamically Actuated Liquid‐Infused Poroelastic Film with Precise Control over Droplet Dynamics

Abstract

Traditional dynamic adaptive materials rely on an atomic/molecular mechanism of phase transition to induce macroscopic switch of properties, but only a small number of these materials and a limited responsive repertoire are available. Here, liquid as the adaptive component is utilized to realize responsive functions. Paired with a porous matrix that can be put in motion by an actuated dielectric elastomer film, the uncontrolled global flow of liquid is broken down to well-defined reconfigurable localized flow within the pores and conforms to the network deformation. A detailed theoretical and experimental study of such a dynamically actuated liquid-infused poroelastic film is discussed. This system demonstrates its ability to generate tunable surface wettability that can precisely control droplet dynamics from complete pinning, to fast sliding, and even more complex motions such as droplet oscillation, jetting, and mixing. This system also allows for repeated and seamless switch among these different droplet manipulations. These are desired properties in many applications such as reflective display, lab-on-a-chip, optical device, dynamic measurements, energy harvesting, and others.has led to unprecedented capabilities such as autonomous actuation and sensing, [1,2] controlled release, [3] self-healing, [4] self-regulation, [5] self-reporting, [6] self-cleaning, [7] antifouling, [8] tunable optical properties, [9,10] and others. Such conventional materials with adaptive responses often rely on compounds with specific chemical properties that undergo various phase transitions at the atomic/molecular scale to enable macroscopic dynamic behavior in the form of piezoelectric, pyroelectric, electrochromic, shape memory effects, and so on. [11][12][13][14][15] The limited availability of the solids that undergo such atomic/ molecular transitions is a major constraint. Our quest for new dynamic adaptive materials has to go beyond the search for specific materials formulations and to adopt a bioinspired strategy of designing a hybrid materials system comprising a combination of multiple components responding to various stimuli with coupled energy transduction mechanisms across the system. [16][17][18] Moreover, different from traditional engineering materials that rely on carving, extruding, rolling, weaving, and molding of solids, Nature's tool box goes far beyond just a solid. Instead, Nature seamlessly and ubiquitously mixes and matches different solids and Droplet Dynamics

External Stimuli Responsive Liquid‐Infused Surfaces Switching between Slippery and Nonslippery States: Fabrications and Applications

“…Recently, inspired by responsive skin, Hu and co-workers developed a multilayer structural substrate with shape dynamic changing under voltage. [65] Different from our research, the electrostatic attraction existed between the conducting layers of the substrate instead of between repellent droplet and substrate. Electric field E-LIS was applied electric field directly on the surface, with high voltage.…”

“…b) Schematic illustration and demonstration of droplet's mobility on electric field E‐LIS. Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

“…These microreactors demonstrated advantages including rapid, precise and remote manipulation, high droplets transfer efficiency, without constraining on path geometries of droplets. For example, Hu and co‐workers developed an electrically E‐LIS based on dielectric elastomer film . Actuated voltage with 147 Hz frequency and 12 kV, the morphology of the substrate changed simultaneously.…”

“…a) On an electrical field E‐LIS, two repellent droplets on the top of surface showed dynamic oscillation and mixing. Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

“…Reproduced with permission. [65] Copyright 2018, Wiley-VCH. c) An electrothermal E-LIS based on shape-memory graphene sponge.…”