A hydrogel that can naturally stretch and self-heal while adhering to the body, enabling new designs for medical adhesives.
Hydrogels are naturally biocompatible materials that could revolutionize diverse medical technologies ranging from artificial muscles to wearable electronics. Their simple non-toxic composition along with their non-rigid structure allows the material to easily conform to the human body. Hydrogels, however, could have poor stretchability, weak adhesion (especially when wet), and limited self-healing mechanisms. This prevents their use in spaces like the cranial cavity, where electronic signals could be administered to treat seizures.
The researchers created a hydrogel mix that takes advantage of dynamic covalent bonding to provide extreme stretchability, strong adhesion in air and water, and robust self-healing. This material only uses well-known and easily available polymer components which are naturally biocompatible. The team can even adjust the material’s electric and thermal conductivity by introducing components like MXene, graphene sheets, and carbon nanotubes, enabling electronic applications.
First, polyvinyl alcohol is dissolved in a buffer solution. Then, boronic acid and optional chitosan is added, resulting in a thick hydrogel. Additives like dyes or conductive MXene sheets can be added for extra functionality such as increased electric conductivity. The dynamic boronic ester bonds enable bond exchanges which promote high strength and fast healing at defect sites. The bonds in chitosan allow quick adhesion in air and water alike.
- Stretchable up to 310 times original length.
- Chitosan enables strong adhesion in air or water.
- Self-healing within 5 seconds.
- Maybe imbued with MXenes or carbon nanotubes to achieve conductivity around 30 μS/cm.
- Maybe encapsulated with drugs or dyes.
- Non-toxic composition.
- Requires simple mixing of inexpensive ingredients, leading to low manufacturing costs.
- Stage of Development:
- Proof of Concept
The hydrogel comprises polyvinyl alcohol dynamically crosslinked with boronic acid (left), with additional chitosan to provide extra strength and wet adhesion (right). A typical recipe has a 15:1 weight ratio of PVA to BA with around 2 wt% chitosan. This provides extreme stretchability, natural adhesion in both air and water, and nearly instant self-healing.
Driscoll, N. et al. Curr Opin Biotechnol, 2021 December 72: 76.
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