Laser-induced morphology-switchable slanted shape memory microcones for maneuvering liquid droplets and dry adhesion

Abstract

Slanted micro-/nano-structures play pivotal roles in a diversity of fields, including water-proof engineering and fogdrop collection. In light of recent advances in fabricating slanted microstructures by using photolithography or reactive ion etching techniques, however, a complex, environmentally unfavorable, and tedious fabrication process makes them far from practical in application. Herein, we present a viable strategy to prepare a slanted shape memory microcone array (SSMMA) by combining the femtosecond laser oblique microfabrication and replica-mold method. Thanks to its fast temperature-responsive feature, SSMMA enables the transition of adhesion forces to effectively control the sliding of droplet on the surface. The underlying principle of the adjustable migration behavior of droplet is that SSMMA switches between the slanted and collapsed states. Moreover, we systematically studied the influence of the microcone spacing/height together with the microcone bending angle on the wetting performance of water droplet. More significantly, the resulted SSMMA analogous to a “machine hand” is experimentally demonstrated to be competent for the grab and transfer of fragile and smooth objects (e.g., coverslip) with a maximum adhesion force of ∼19.404 mN. The current study opens up an avenue for rapidly fabricating functional slanted microstructures for practical usage.

Ultra‐Robust Joule‐Heated Superhydrophobic Smart Window: Dually‐Switching Droplets Adhesion and Transparency via In Situ Electric‐Actuated Reconfigurable Shape‐Memory Shutters

“…The results manifest that the WSAs were inclined to decrease to the valley at d = 0.5 mm and then unfold an increasing tendency (d > 0.5 mm), where we verify that the EA-RSMS with d = 0.5 mm is a turning point of its surface dwelt droplet converting from Cassie state to Wenzel state (Figure 4c). Moreover, the experimental measurements (a home-made apparatus) [20] coupled with theoretical calculations of adhesive force (F a ≈ F gravity × sinθ s ) [12] uncovered that a minimum hysteresis force was obtained at d = 0.5 mm (Figure S7, Supporting Information), which agrees well with our experimental result. On this basis, by repeating Joule-heating/pressing operation, we carry out the fatigue test of EA-RSMS with d = 0.5 mm.…”

Bioinspired Robust Mechanical Properties for Advanced Materials

“…In another instance, a gecko foot-inspired slanted shape memory microcone array (SSMMA) with tunable adhesion forces was developed (Figure 15D). [133] The adhesion/deadhesion reversibility of this bioinspired adhesive is achieved by altering the orientation and the contact areas of the microarrays as the responses to the changes in temperature and pressure. Under applied pressure, the SSMMA presented exclusive adhesion properties as a result of increased contact area between the collapsed microcones.…”

Multiple-Droplet Selective Manipulation Enabled by Laser-Textured Hydrophobic Magnetism-Responsive Slanted Micropillar Arrays with an Ultrafast Reconfiguration Rate

“…The obtained micropillar surface was covered with some rough structures that can be seen from the magnified SEM image, which is determined by the topography of the inner surface of the PTFE template. 39 Additionally, thanks to the magnetic response property of the CIP, the θ of MSMA can be reversibly tuned between 0°to 90°u nder the action of the magnetic field (Figure 1d). We investigate the dependence of the water contact angle on the various bending angles, and the typical micropillar array with a space of ∼300 μm and height of ∼380 μm was selected for testing.…”