# Polymer Casting and Water Immersion-Based Large-Area Graphene Transfer for Flexible Electronics Fabrication

## TL;DR

This paper introduces a new method to transfer large-area graphene onto flexible biodegradable substrates for implantable electronics, showing it is efficient and functional for tissue regeneration.

## Contribution

A novel low-temperature, high-efficiency graphene transfer method combining laser engraving, polymer casting, and water immersion for flexible electronics.

## Key findings

- Graphene sheets transferred with ∼100% efficiency and high conductivity (∼40 Ω/sq) on biodegradable substrates.
- Two functional flexible devices were fabricated and tested for cell/tissue regeneration potential.
- Successful ex vivo implantation and suturing demonstrated on rat cadavers.

## Abstract

This study focuses
on developing an efficient large-area graphene
transfer method that combines high-throughput and precise laser engraving,
simple polymer casting, and water immersion to fabricate conductive
graphene and biodegradable polymer-based implantable flexible electronic
devices. The low-temperature treatment of graphene sheets on a glass
substrate reduced graphene sheet roughness and increased hydrophobicity,
enabling facile and high-efficiency (∼100%) large-area graphene
transfer to a flexible polymer substrate. This method also benefited
from differences in the work of adhesion at the graphene sheet/glass
substrate and the graphene sheet/flexible polymer substrate interfaces.
The transferred graphene sheets showed stability, structural integrity,
and high conductivity (∼40 Ω/sq sheet resistance) under
in vitro and in vivo mimicking conditions. The low-temperature-treated
and laser-engraved conductive graphene patterns, transferred on a
flexible and biodegradable polymer substrate, demonstrated in vitro
cytocompatibility on different cells. Two flexible electronic devices
(1a graphene coil-integrated electrode cuff and 2an
interdigitated graphene cuff-integrated piezoelectric device) were
fabricated using the developed method, and both demonstrated functionality
and proof of concept by generating output voltages that can enhance
cell/tissue regeneration. In addition, the ease of handling, ex vivo
implantation, and feasibility of suturing were demonstrated by performing
implantation surgeries on the pudendal nerve in cadaveric rats. Overall,
this promising large-area graphene transfer method can be used to
fabricate biodegradable, implantable devices that can serve as interfaces
to stimulate cells and tissues for regeneration and repair.