A Hydro-Expansive and Degradable Biomaterial Enabling Shape Recovery of Film-Based Devices in Biofluids

Area of Science:

• Biomaterials Science
• Soft Robotics
• Medical Device Engineering

Background:

• Hygroscopic actuation is crucial for implantable devices, but challenging in soft bio-materials due to lost intermolecular interactions.
• Existing soft materials rapidly lose mechanical integrity upon water absorption, limiting their use in wet environments.

Purpose of the Study:

• To develop a chitosan-based bio-composite with sustained hygroscopic actuation for soft, implantable devices.
• To enable self-flattening capabilities for thin-film devices used in minimally invasive procedures.

Main Methods:

• Development of a chitosan bio-composite leveraging synergistic effects of hydrogen bonding, plasticization, and nano-confinement.
• Characterization of the material's stable tensile force during volume expansion in body fluids.
• In vivo demonstration using a rolled triboelectric nanogenerator (TENG) for intracardiac implantation.

Main Results:

• The chitosan bio-composite maintains strong intermolecular repulsive forces during water absorption, providing stable tensile force.
• The material successfully enabled a thin-film device to self-flatten from a tubular shape.
• An implanted TENG device recovered its shape and energy harvesting function within the heart ventricle.

Conclusions:

• The developed chitosan bio-composite offers robust hygroscopic actuation for soft materials.
• This material facilitates the minimally invasive implantation of flexible, functional devices.
• The findings support the use of such materials in advanced biomedical applications, including self-powered implantable sensors.