Tunable Dry Adhesion of Soft Hollow Pillars through Sidewall Buckling under Low Pressure

Abstract

Controlling adhesion on demand is essential for many manufacturing and assembly processes such as microtransfer printing. Among various strategies, pneumatics‐controlled switchable adhesion is efficient and robust but currently still suffers from challenges in miniaturization and high energy cost. In this paper, a novel way to achieve tunable adhesion using low pressure by inducing sidewall buckling in soft hollow pillars (SHPs) is introduced. It is shown that the dry adhesion of these SHPs can be changed by more than two orders of magnitude (up to 151×) using low activating pressure (≈−10 or ≈20 kPa). Large enough negative pressure triggers sidewall buckling while positive pressure induces sidewall bulging, both of which can significantly change stress distribution at the bottom surface to facilitate crack initiation and reduce adhesion therein. It is shown that a single SHP can be activated by a micropump to manipulate various lightweight objects with different curvatures and surface textures. Here, it is also demonstrated that an array of SHPs can realize selective pick‐and‐place of an array of objects. These demonstrations illustrate the robustness, simplicity, and versatility of these SHPs with highly tunable dry adhesion.

Sensing-triggered stiffness-tunable smart adhesives

“…In addition, the proposed tunable-stiffness strategy can achieve the fast response time compared to the approaches with light and thermal control ( 5 , 36 , 48 ), even reaching the level of pneumatic control. Moreover, the tunable-stiffness regulation method based on magnetic field may have a simper structural configuration compared to the pneumatic control method, which usually requires additional fluid channel design to provide pressure for a controllable pick-and-place system ( 9 , 49 , 50 , 51 ). The upper limit for grasping objects was determined by the high adhesion, while the lower limit for releasing objects was determined by the low adhesion.…”

Preload‐Induced Switchable Adhesion

“…By characterizing MAs' performances, the results of our work were evaluated alongside those of previous studies [ 5,9,18,24,34–36 ] in terms of switching efficiency, switching time, maximum adhesion, durability, and cleanability (Figure 6c). The switching efficiency was proposed by Julia Purtov et al.…”

“…By characterizing MAs' performances, the results of our work were evaluated alongside those of previous studies [5,9,18,24,[34][35][36] in terms of switching efficiency, switching time, maximum adhesion, durability, and cleanability (Figure 6c). The switching efficiency was proposed by Julia Purtov et al [24] the switching time refers to the time required to transition from high adhesion to low adhesion, and cleanability refers to the degree of difficulty in cleaning the adhesive after contamination.…”

“…Therefore, research in this field is focused primarily on developing simple, efficient, and convenient switchable adhesive systems. [3,4] Common methods for achieving switchable adhesion involve controlling various stimuli, such as temperature, [5][6][7] light, [8][9][10] electric fields, [11][12][13] magnetic properties, [14][15][16] pneumatics, [17,18] DOI: 10.1002/smll.202305091 and mechanical forces. [19][20][21] Li et al [7] developed a novel low-molecular-weight supramolecular adhesive P1 and achieved switchable adhesion by exploiting the rapid solidification of P1 upon cooling.…”

“…Therefore, research in this field is focused primarily on developing simple, efficient, and convenient switchable adhesive systems. [ 3,4 ] Common methods for achieving switchable adhesion involve controlling various stimuli, such as temperature, [ 5–7 ] light, [ 8–10 ] electric fields, [ 11–13 ] magnetic properties, [ 14–16 ] pneumatics, [ 17,18 ] and mechanical forces. [ 19–21 ] Li et al.…”