Photocontrol of fluid slugs in liquid crystal polymer microactuators

Abstract

The manipulation of small amounts of liquids has applications ranging from biomedical devices to liquid transfer. Direct light-driven manipulation of liquids, especially when triggered by light-induced capillary forces, is of particular interest because light can provide contactless spatial and temporal control. However, existing light-driven technologies suffer from an inherent limitation in that liquid motion is strongly resisted by the effect of contact-line pinning. Here we report a strategy to manipulate fluid slugs by photo-induced asymmetric deformation of tubular microactuators, which induces capillary forces for liquid propulsion. Microactuators with various shapes (straight, 'Y'-shaped, serpentine and helical) are fabricated from a mechanically robust linear liquid crystal polymer. These microactuators are able to exert photocontrol of a wide diversity of liquids over a long distance with controllable velocity and direction, and hence to mix multiphase liquids, to combine liquids and even to make liquids run uphill. We anticipate that this photodeformable microactuator will find use in micro-reactors, in laboratory-on-a-chip settings and in micro-optomechanical systems.

Surfaces Inspired by the Nepenthes Peristome for Unidirectional Liquid Transport

“…[6] Without energy input, these biological surfaces can harness the movement of water through their unique structural features and chemical composition, [11][12][13] which gives inspiration for designing and fabricating functional surfaces and materials with wide applications in fields including antifogging and fog-collection, [14][15][16] microfluidic devices, [17][18][19][20][21] lubrication, [22,23] and liquid transport. [24][25][26][27] One-dimensional materials for unidirectional liquid transport, inspired by spider silk and cactus spines, have attracted major research interest in the last few years.…”

External‐Field‐Induced Gradient Wetting for Controllable Liquid Transport: From Movement on the Surface to Penetration into the Surface

“…Recently, Yu and co-workers reported a new strategy to manipulate transportation of a liquid slug using photoinduced asymmetric deformation of a tubular microactuator www.advmat.de www.advancedsciencenews.com ( Figure 3b). [53] Inspired by the lamellar structure of an artery wall, they designed a linear liquid-crystal polymer and fabricated a tubular microactuator. Asymmetric deformation of the tubular microactuators occurred because of reorientation of azobenzene mesogens under light irradiation, accompanied by a decrease in the wall thickness and an increase in the crosssectional area.…”

“…Reproduced with permission. [53] Copyright 2016, Nature Publishing Group. c) Directional liquid motion on PNIPAAm-coated anisotropic gold nanoarrays by light illumination.…”

Stimuli‐Directed Dynamic Reconfiguration in Self‐Organized Helical Superstructures Enabled by Chemical Kinetics of Chiral Molecular Motors

“…Photoinduced molecular isomerization in azobenzene derivatives has been extensively utilized to modulate the magnitude of order parameter in liquid‐crystalline system, resulting in the perturbation of molecular alignment and even phase transition, thus opening the door for optical‐pattern devices,22, 23, 24, 25, 26 microstructure photolithography,27, 28, 29 surface‐active topographies,30, 31, 32 and shape‐deformation actuators 33, 34, 35, 36, 37. Although the kinetic evolution of azo‐based LCs can be expedited by the anchoring memory effect in polymer‐stabilized mixture38, 39 or the push–pull effect in glassy elastomer,37, 40, 41 the inherently accelerative isomerization motion is still desirable, causing a variety of attractions to improve the essential action of isomerization compound with particular structures 42, 43, 44…”