# Protein Biomaterials with Muscle-like Water-Driven Actuation

## TL;DR

Researchers developed protein-based actuators that mimic muscle movement using ethanol and water, enabling fast and reversible shape changes with potential applications in smart materials.

## Contribution

A novel class of protein-based actuators that enable muscle-like, water-driven motion through ethanol-induced fibril formation in BSA hydrogels.

## Key findings

- Ethanol-induced fibril formation in BSA hydrogels enables reversible shape changes and mechanical stiffening.
- Intermediate ethanol concentrations (40–80%) promote shape retention, while high concentrations (80–99%) allow full recovery upon rehydration.
- Rehydration triggers stochastic motion and rotational speeds up to 471 deg·s–1 in protein-based propeller motors.

## Abstract

Unlike muscles, man-made
shape-morphing biomaterials take much
longer times to perform their actuation. Here we report a novel class
of protein-based actuators that mimic muscle contraction through ethanol-induced
fibril formation in bovine serum albumin (BSA) hydrogels, enabling
reversible shape changes and fast, water-driven motion. These structural
changes result in mechanical stiffening, enabling programmable and
reversible shape changes, which take place over minutes to hours.
At intermediate ethanol concentrations (40–80%), fibril formation
dominates and contributes to shape retention, while at high ethanol
concentrations (80–99%), aggregation outpaces fibrillation,
allowing full recovery of the original shape upon rehydration. Furthermore,
upon reinsertion into water, ethanol retention triggers stochastic
pulsating motion in cylindrical samples and spins on the a protein-based
propeller motor (rotational speeds up to 471 deg·s–1), a process driven by a surface tension gradient. These findings
address the challenge of achieving rapid, reversible motion in biomaterials,
resembling that of muscles, with promising applications in smart biomaterials,
microactuators, and bioresponsive systems.