Reversible Tuning between Isotropic and Anisotropic Sliding by One-Direction Mechanical Stretching on Microgrooved Slippery Surfaces

Abstract

Dynamically responsive liquid-infused interfacial materials have broad technological implications in manipulating droplet motions. However, present works are mainly about reversible tuning of the isotropic slippery surface; the reversible switching between isotropic and anisotropic sliding has not been deeply explored. Here, we report a kind of liquid-infused elastic-grooved surface (LIEGS) by femtosecond laser ablation and realize reversible switching between isotropic and anisotropic sliding by one-direction mechanical stretching. Under mechanical stretching and strain release, droplet motion can be reversibly switched between the sliding and pinned states along the perpendicular direction to the grooves, whereas the droplet keeps sliding along the parallel direction to the grooves. The mechanism of reversible switching mainly contributes to the decrease of film thickness during the stretching process in which the film thickness decreases from 13 to 4 μm with the increase of the strain from 0 to 60%. Finally, we demonstrate the realtime flexible control over a droplet sliding/pinned on the strain-changing LIEGS.

A Review of Smart Lubricant-Infused Surfaces for Droplet Manipulation

“…This increases friction against wind [61]. Isotropic directional droplet transportation can be realized by creating a groove structure similar to other responsive LIS [51].…”

“…Targeting this active direction, Yang et al summarized developments of wettability-tunable LISs induced by external stimuli and their applications in fog collection, oil-water separation, complex-flow distribution, droplets' delivery in 2019 [37]. However, with the fast advancement of smart LISs, many important and successive works on improvements of responsive LISs and other nonconventional LISs were developed for droplet manipulation [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55], but these studies are not reported by Yang' work. This review is an overview of the recent progress in smart LIS for droplet manipulation induced by external stimuli, as presented in Figure 1. We first give a summary of some unique properties and fundamentals of droplets on LIS.…”

High‐Performance Unidirectional Manipulation of Microdroplets by Horizontal Vibration on Femtosecond Laser‐Induced Slant Microwall Arrays

“…Slant Microstructure fabrication: The PDMS film was ablated by line-byline [33][34][35] using femtosecond laser oblique scanning, and the processing area was 15 × 7 mm 2 . The laser beam (pulse width: 100fs; repetition rate: 1 kHz; central wavelength: 800 nm) from a one-box regenerative amplified Ti: sapphire femtosecond laser system (Solstice Ace, Spectra-Physics, USA) was utilized for ablation (Discussion S2.5, Supporting Information).…”

Bioinspired Surfaces With Switchable Wettability

“…Smart surfaces have attracted considerable interests because the surface chemistry and surface roughness play an important role in controlling surface wettability (Fang et al, 2010 ; Xu et al, 2013 ; Huang et al, 2017 ; Wei et al, 2017 ). Nowadays, the rapid development of responsive materials has enabled surface chemistry and surface roughness change to switch surface wettability through external stimuli (Xin et al, 2016 ; Wu et al, 2017 ; You et al, 2018 ; Salter and Booth, 2019 ; Zhang et al, 2019c ; Fu et al, 2020 ; Zou et al, 2020 ). Due to the reversible dynamic control capability, tremendous effects have been devoted to developing driving techniques (Yin et al, 2018 ; Liu et al, 2020 ; You et al, 2020 ) such as temperature, light, electric/magnetic fields, chemicals, and mechanical motion (Han et al, 2015a , b , 2016 ; Yong et al, 2015 ).…”