# Adhesion of Self-Complementary, Sinusoidal Surfaces Fabricated Using Two-Photon Polymerization

## TL;DR

Researchers developed a method to control adhesion between 3D-printed surfaces using temperature and mechanical compression, achieving high adhesive strength for microscale applications.

## Contribution

A novel approach to switchable adhesion using self-complementary metasurfaces fabricated with two-photon polymerization.

## Key findings

- Adhesive strength between printed surfaces exceeded 3 MPa when tested with pull-off stress.
- Heating surfaces above 60°C reduced adhesion, while compression and cooling increased it.
- Tailoring complementary surfaces could enable microscale disassembly for component recovery.

## Abstract

Microscale, pick-and-place
assembly is a non-lithographic assembly
method poised to impact diverse fields including flexible electronics,
microfluidics and robotics. However, a major technological challenge
is the need to deterministically control adhesion between parts. Here,
switchable adhesion involving 3D-printed, self-complementary surfaces
is demonstrated. Mechanical properties of metasurfaces pressed against
flat, rigid substrates are modeled using finite element methods. A
series of flat slabs and metastructured slabs with 2D sinusoidal surfaces
are printed using two-photon polymerization (2PP) of a shape-memory
resin. The surface frequency of featured slabs was varied between
3.3̅ mm–1 and 26.6̅ mm–1 with similar amplitudes. Adhesion between printed metasurfaces and
glass and between printed, self-complementary metasurfaces is studied
above and below the cured resin’s glass transition temperature
(∼45 °C). Simple heating of adhering surfaces to above
60 °C lowers adhesion, and compression of surfaces while above
the glass transition temperature followed by cooling to room temperature
elevates adhesion. The nominal adhesive strength between printed,
self-complementary surfaces, as determined by the maximum observable
pull-off stress, exceeds 3 MPa. Further tailoring complementary surfaces
for adhesion control may facilitate microscale disassembly for recovery
of components or precious metals.