Sustainable Droplet Manipulation on Ultrafast Lubricant Self‐Mediating Photothermal Slippery Surfaces

Abstract

Designing intelligent slippery surfaces for droplet manipulation is critical for many applications from drug delivery to bio‐analysis, while is of great challenging in sustainability for inescapable wastage of lubricant layer. Herein, an ultrafast lubricant self‐mediating (self‐replenishing/‐absorbing) photothermal slippery surface is designed that achieves sustainable transport of droplet under the irradiation of near infrared light (NIL) even if the lubricant layer is wiped clean completely, as well as at other man‐made extreme conditions. The ultrafast lubricant self‐mediating performance is caused by synergistic effects of interconnection of porous structure and photothermal expansion of the material. When lubricant on surface is lost, photothermal expansion of material can quickly squeeze the lubricant inside the base to flow into and out of the interconnected porous structure to generate a fresh lubricant layer. Attractively, when the NIL is turned off, the rebuilt lubricant layer can be swiftly self‐absorbed into the porous to inhibit unnecessary wastage. Moreover, an arbitrary split of droplet in desired configurations can be achieved by controlling the NIL irradiating route. This sustainable droplet manipulation induced by ultrafast lubricant self‐mediating can be extensively applied in microfluidics and micro‐reactor settings.

An electrothermal platform for active droplet manipulation

“…[6][7][8] To serve this purpose, static approaches that integrates asymmetric surface textures have been devised to passively alter the dimension, direction, and velocity of droplet transport on designated functional surfaces. [9][10][11][12][13][14] Furthermore, surfaces incorporating stimulus-responsive elements that respond to electrical, [15][16][17][18] magnetic, 19-21 thermal [22][23][24] and acoustic [25][26][27] stimuli are endowed with intelligent functionalities to manipulate the mobility of residing droplets by reversible structural restructuring and chemical reactions. Most notably, electrowetting-on-dielectric (EWOD), 28,29 electro-dewetting 15,30 or opto-electrowetting 31,32 systems can transport discrete droplets by exploiting interactions between the solution and elec-tried surfaces.…”

Curvature Adjustable Liquid Transport on Anisotropic Microstructured Elastic Film

“…Inspired by the liquid directional transport of biological surfaces, both active and passive artificial surfaces capable of directional liquid transportation have been developed. − The bionic liquid directional transport surface simulates the excellent form and composition of biological surfaces and shows the superior characteristic of liquid directional transport. − Moreover, liquid transport can be controlled by adjusting feature structures or surface energy under external stimuli, e.g. , temperature, − light, , electric, magnetism, , stretch, − etc . Among them, surface curvature is easy to operate, environmentally friendly, and promising for manipulating liquids. − Despite many studies that have been conducted on surface wettability control, there are still challenges to achieving real-time transformation of liquid transport with switchable direction on the material surface.…”

“…15−18 The bionic liquid directional transport surface simulates the excellent form and composition of biological surfaces and shows the superior characteristic of liquid directional transport. 19−24 Moreover, liquid transport can be controlled by adjusting feature structures or surface energy under external stimuli, e.g., temperature, 25−27 light, 28,29 electric, 30 magnetism, 31,32 stretch, 33−37 etc. Among them, surface curvature is easy to operate, environmentally friendly, and promising for manipulating liquids.…”

Light Fueled High-Throughput Binary Droplet Splitting and Transport on High-Energy Substrate

“…8,11 However, the generated microdroplets are tightly anchored on the highly adhesive or hydrophilic regions, confining its applicability to in situ analysis and detection only. Active droplet splitting techniques leverage electricity, 9,12 magnets, 13,14 acoustics, 15 and light 16,17 to split droplets and some of them could also enable transport of the generated microdroplet. However, most of them can divide a droplet into two microdroplets in a single operation, making it difficult to achieve a high-throughput implementation.…”

“…For example, the droplet can be split by impacting it on patterned superhydrophobic–hydrophilic surfaces or patterned adhesive surfaces, with which the droplet could be fragmented into a preset number of microdroplets and deposited with a designated arrangement for simultaneous arrayed reactions. , However, the generated microdroplets are tightly anchored on the highly adhesive or hydrophilic regions, confining its applicability to in situ analysis and detection only. Active droplet splitting techniques leverage electricity, , magnets, , acoustics, and light , to split droplets and some of them could also enable transport of the generated microdroplet. However, most of them can divide a droplet into two microdroplets in a single operation, making it difficult to achieve a high-throughput implementation.…”