Bioinspired micropillar array with micropit for robust and strong adhesion

• FCM has an adhesion strength of 1.2 MPa under a loading force of 5 mN, which is 3.7 times of the micropillars with a flat punch top. • FCM is quite robust that the structure and the adhesion performance are very well maintained even after1000 cycles of adhesion tests. • The structure of FCM is quite simple that it could be easily fabricated and replicated. Robust and strong adhesion is highly required for reversible adhesions. Inspired by gecko setae and octopus sucker, micropillar array with frustum of conical micropits (FCM) was fabricated by direct laser writing lithography. With an optimized micropit in FCM, the adhesion strength of 1.2 MPa is achieved under a loading force of 5 mN, which is 3.7 and 2.1 times the micropillars with flat punch top and circular conical micropit, respectively. Under a loading force larger than 3 mN, compliant contacts are formed between FCM micropillars and the counterpart surface, which results in a uniformly distributed stress at the separating interface, an instantaneous detachment of multiple FCM micropillars, and therefore a strong adhesion. Moreover, the adhesion of FCM is quite robust that 1000 cycles of attaching and detaching have no influence on the adhesion performance. The work here not only provides a bioinspired structure for strong and robust adhesion but also consolidates the concept of combining features from different biological systems to create new functional materials.