Dynamically tunable interfacial dry adhesion plays a significant role in numerous biological functions and industrial applications. Among various strategies, pneumatics-activated adhesive devices draw much attention due to their distinct advantages such as fast speed, reliable performance, large adhesion tunability and easily accessible materials. To understand and predict adhesion strength of pneumatics-activated adhesives, it is necessary to examine their interfacial mechanics that is nonlinearly coupled with the large deformation of the devices under pressure. However, previous studies have only focused on axisymmetric cases in which the outline of the contact area is circular, whereas the tunable adherence of non-circular contact controlled by pneumatics remains elusive. In this work, through a combination of experiments and simulations, we study the effect of non-circular contact geometry on tunable dry adhesion of pressure-activated soft hollow pillars. Specifically, elliptical, square, and rectangular contact shapes are considered and their effects on tunable adhesion of the soft hollow pillars are compared to that of circular contact geometry thoroughly. The results show that soft hollow pillars with elliptical, square, and rectangular contact surfaces demonstrate rich interfacial delamination behaviors that depend on the contact outline geometry and internal pressure. Among all contact geometries, elliptical contact has the highest adhesion tunability yet requires lowest activating pressure owing to the non-uniform curvature distribution of the contact outline. However, when the eccentricity increases, the elliptical contact has reduced tunability of adhesion caused by the contact of opposing sides of the sidewall upon buckling. For square and rectangular contacts, they have the lowest adhesion tunability and need higher activating pressure than those of circular and elliptical contact since the 90-degree edges of the sidewall prohibit buckling instability. Our findings greatly broaden the design space of pneumatics-activated adhesive devices by adding the contact geometry of the soft hollow pillars as a new design parameter, which can provide valuable guidance for tunable adhesive design for various applications in manufacturing and robotics.

中文翻译：

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具有非圆形接触的弹性体软空心柱的气动可调粘附力

动态可调的界面干粘附力在众多生物功能和工业应用中发挥着重要作用。在各种策略中，气动粘合装置因其速度快、性能可靠、粘合可调性大和易于获取材料等独特优势而备受关注。为了了解和预测气动粘合剂的粘合强度，有必要检查其与设备在压力下的大变形非线性耦合的界面力学。然而，以前的研究仅关注接触区域轮廓为圆形的轴对称情况，而气动控制的非圆形接触的可调粘附性仍然难以捉摸。在这项工作中，通过实验和模拟相结合，我们研究了非圆形接触几何形状对压力激活软空心柱的可调干粘附力的影响。具体来说，考虑了椭圆形、正方形和矩形接触形状，并将它们对软空心柱可调粘附力的影响与圆形接触几何形状进行了彻底比较。结果表明，具有椭圆形、正方形和矩形接触表面的软空心柱表现出丰富的界面分层行为，该行为取决于接触轮廓几何形状和内部压力。在所有接触几何形状中，椭圆形接触具有最高的粘附可调性，但由于接触轮廓的曲率分布不均匀，因此需要最低的激活压力。然而，当偏心率增加时，椭圆形接触会降低由侧壁相对侧在屈曲时的接触引起的粘附的可调性。对于方形和矩形接触，它们具有最低的粘附可调性，并且需要比圆形和椭圆形接触更高的激活压力，因为侧壁的 90 度边缘抑制了屈曲不稳定。我们的研究结果通过添加软空心柱的接触几何形状作为新的设计参数，极大地拓宽了气动激活粘合装置的设计空间，这可以为制造和机器人技术中各种应用的可调粘合设计提供有价值的指导。