Soft Artificial Muscles

The development of bioinspired materials that mimic animal muscles is a key step in the advancement of several scientific fields, including robotics and medicine.

Muscles exhibit a unique combination of softness, mechanical resistance, adaptability and the ability to undergo large anisotropic deformations, which is so far unmatched in artificial materials.

This action will develop a novel class of nanocomposite materials that mimic natural muscles by combining stimuli-responsive hydrogels (SRH) and colloidal liquid crystals (CLC). SRHs consist of a network of stimuli-responsive polymer chains and a high fraction of water.

By changing the solubility of the polymer with stimuli such as temperature and light it is possible to control the amount of water in the network, thereby producing large volumetric variations.

SRHs are soft and shape-compliant actuating materials like muscles, but they generally exhibit poor mechanical resistance and the volumetric expansion has no preferential direction.

These limitations will be overcome by attaching the stimuli-responsive polymer chains to anisotropic colloidal particles and assembling these building blocks in a uniaxially oriented manner like CLCs.

The resulting nanocomposites will be soft, yet strong, capable of actuation-like conventional SRHs, and their expansion/contraction will be directional, thanks to the preferred orientation of the colloidal particles.

The proposed platform will rely on rod-like cellulose nanocrystals (CNCs) that will be decorated with cross-linkable poly-N-isopropylacrylamide chains bearing photoresponsive spiropyran units (poly-spiropyrans, PSPs).

CNCs are inexpensive, biocompatible and can be easily extracted from renewable resources, while PSPs are known to form photoresponsive hydrogels.

The combination of these elements and integration into uniaxially oriented structures will afford a novel class of soft actuators that will bring significant advancement to fields like robotics and medicine.