Session: 04-23-01: Functional Soft Composites - Design, Mechanics, and Manufacturing

Paper Number: 150691

150691 - Metamaterial Adhesives for Programmable Adhesion Through Reverse Crack Propagation 

The integration of functional soft composite materials into larger systems can enable exciting advances in electronics, robotics, and multifunctional structures. However, typically integration approaches to create strong yet reversible adhesives needed for integration in these applications lack independent control of strength and release, require complex fabrication or only work in specific conditions. Here we introduce a metamaterial adhesive that enables strong and reversible adhesion with directional, spatially selective adhesive strength through programmed nonlinear cut architectures in adhesive films. The nonlinear cuts consist of open polygonal shapes that control how adhesive cracks propagate by trapping cracks and then forcing them to reverse direction for high adhesion and allow them to propagate forward normally for low adhesion. Through reverse crack propagation, we decouple high global peel angles into low local peel angles at the adhesive interface. This mechanism enhances adhesion strength up to 60× for strong adhesion relative to the same material without cuts, while also enabling easy release on the order of an unpatterned adhesive by peeling in the opposite direction. These characteristics allow for independent control of adhesion strength and release with reusability. Reverse crack propagation also tunes adhesion strength at any film location and uniquely enables the programming of adhesive strength in two directions simultaneously in a single region of a film. Metamaterial adhesives do not rely on specific chemistry or environmental conditions, microstructured surfaces, or active or patterned stiffness to tune adhesion, but utilize nonlinear cuts for highly systematic control of adhesive crack propagation and direction across a film. This enables their deployment in a diverse set of materials and applications, enabling robust integration of functional soft composite materials into larger systems.

We term these ‘metamaterial adhesives’ because the nonlinear cut architectures decouple global applied loads into a deterministic local adhesive response, leveraging insight from mechanical metamaterials, which decouple local and global mechanical properties. This functionality is intrinsic to the geometry and allows us to enhance properties and to enable unique adhesion behaviour in a wide range of adhesives, on diverse surfaces, and in dry and wet environments. This applicability to diverse materials allows metamaterial adhesives to leverage both material and geometric mechanisms to span a spectrum of unique adhesive properties, from strong and extremely reversible to extremely strong with reversibility, including adhesives with strengths over 3,000 N m⁻¹ (J m⁻²) that are also reusable and directional. These multifunctional metamaterial adhesives achieve highly systematic control of adhesive crack movement, and this property allows us to achieve an unconventional combination of strong adhesion and easy release, and to program adhesive strength in two directions simultaneously. This approach has applicability in numerous adhesives, while introducing a digital fabrication framework to automate design and rapidly manufacture adhesives in minutes with deterministic control of adhesive characteristics at any location across a film. We demonstrate these metamaterial adhesives as an effective strategy to incorporate functional soft composite materials into integrated systems for wearable devices, material handling, and packaging applications.

Presenting Author: Michael Bartlett Virginia Tech

Presenting Author Biography: Michael D. Bartlett is an Associate Professor and John R. Jones III Faculty Fellow of Mechanical Engineering at Virginia Tech. His research focuses on soft multifunctional materials for deformable electronics and soft robotics, adaptive materials, and switchable and intelligent adhesives. He received his BSE in Materials Science and Engineering from Michigan in 2008 and Ph.D. in Polymer Science and Engineering from UMass Amherst in 2013. After obtaining his Ph.D. he worked as a Senior Research Engineer in the Corporate Research Laboratory at 3M, as a Postdoctoral Fellow at Carnegie Mellon University, and was an Assistant Professor at Iowa State University before joining Virginia Tech in 2020. His research has resulted in publications, patents, media coverage, and awards including an NSF CAREER award, a DARPA Young Faculty Award (YFA) and Director’s Fellowship, a ONR Young Investigator (YIP) Award, a Senior Member of the National Academy of Inventors (NAI), the Early Career Scientist Award from the Adhesion Society, a 3M Non-Tenured Faculty Award, a ICTAS Junior Faculty Award, and an Outstanding Faculty Award (student nominated) among others. More at: www.bartlett.me.vt.edu

Authors:

Chanhong Lee Virginia Tech
Dohgyu Hwang Virginia Tech
Rong Long University of Colorado Boulder
Michael Bartlett Virginia Tech