Bioinspired Microstructured Adhesives with Facile and Fast Switchability for Part Manipulation in Dry and Wet Conditions

Abstract

The rapid growth in the miniaturized mechanical and electronic devices industry has created the need for temporary attachment systems that can carry out pick‐and‐place and transfer printing tasks for fragile and tiny parts. Current systems are limited by a fundamental trade‐off between adhesive strength and state‐changing trigger force, which causes the need for a rapidly switchable adhesive. In this study, an elastomeric microstructure is presented combining a trapezoidal‐prism‐shaped (TPS) and a mushroom‐shaped microstructure, which overcomes the trade‐off with the help of the TPS structure. The optimal design exhibits a strong adhesive strength of 87.8 kPa and a negligible detachment strength of <0.07 kPa with a low trigger shear stress of 10.7 kPa on smooth glass surfaces. The large tip‐to‐stem ratio (50 to 20 µm) enhances the suction effect, allowing the microstructure to maintain its adhesive performance even in wet conditions. Pick‐and‐place manipulation tasks of a single and an array of ultralight parts from micrometer to millimeter scales are performed to demonstrate the capability of handling fragile and tiny parts. Moreover, it demonstrates the ability to transfer parts across water and air interfaces. This proposed microstructure offers a facile solution for manipulating microscale fragile parts in dry and wet conditions.

Soft Microstructure Arrays: A Multifunctional Microsystem for Mass Transport, Energy Transformation, and Surface Manipulation

“…63 Later models introduced trapezoidal-prism structures between the mushroom tip and stem, allowing rapid adhesive detachment and negligible peel strength (less than 0.07 kPa) on smooth surfaces. 190…”

“…This involved vertically aligned, smaller mushroom-shaped micropillar SMA on the outermost side of the initial array, conferring super-repellency and enhancing adhesion in wet environments . Later models introduced trapezoidal-prism structures between the mushroom tip and stem, allowing rapid adhesive detachment and negligible peel strength (less than 0.07 kPa) on smooth surfaces …”

Gecko-Inspired Controllable Adhesive: Structure, Fabrication, and Application

“…Besides designing tilted and controllable adhesive with tip features, some researchers have also designed adhesives with non-aligned features. For example, dividing the mushroom-shaped tip into upper and lower surfaces as shown in Figure 9 h–j [ 82 ], adding a trapezoidal structure at the bottom of the mushroom-shaped tip [ 83 ], and fabricating tilted triangular prismatic microstructures with a rectangular tip [ 84 ] have achieved controllable adhesion strength.…”

“…Copyright 2016, American Chemical Society). (i) Mushroom-like structures containing TPS in the stem (reprinted with permission from Ref [83]…”

Femtosecond Laser Direct Writing of Gecko-Inspired Switchable Adhesion Interfaces on a Flexible Substrate

“…Despite employing magnetic silicone to fabricate gecko-inspired adhesives that can achieve rapid response [39], shrinking them down to the microscale causes sharp declines in deformability and switching ability, as both magnetic force and torque decrease with the second to the fourth power of size [40][41][42]. Another method to accelerate the detachment process relies on mechanical deformation, such as sliding [43], twisting [44], and buckling [45], of the adhesion microstructures under overload. This method can achieve an ultra-high switching ratio, but the overload force is usually significantly higher than the force of preload, implying that releasing objects on soft substrates or in the air without sufficient support are impossible.…”