Research

Bioelectronic devices help patients around the world to participate in a normal life by replacing lost body functions. The metal-based electronics used in these devices nowadays show great physicochemical mismatch compared to living matter. The materials are inorganic, rigid and dry. The biological tissue they are interfacing is organic, soft and hydrated. This mismatch leads to massive limitations in the long-term use of modern bioelectronic devices.

Using conductive hydrogels, we are able to recapitulate the physicochemical properties of living tissue combined with high electrical conductivity in one material system. Hydrogels are hydrated polymers that can be tuned in their mechanical properties to be as soft as the tissues they are interfacing. By combining charged colloidal particles (laponite), a covalent polymer hydrogel (polyacrylamide) and the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT), we are able to synthesize highly conductive, organic and soft interpenetrating polymer networks.

The negative charges of the laponite particles embedded in the polyacrylamide matrix act as a dopant for the conductive polymer. This leads to a massively increased conductivity compared to undoped hydrogels. In addition, the electrostatic interaction of the particles strengthens the polymer network and makes it highly elastic. This makes the materials stable over multiple stretch cycles with only minimal reduction in conductivity during stretch.

Another advantage of polymers over metals is the possibility of chemically functionalizing them with different molecules. Using a chemically defined, artificial biomatrix, it is possible to transform the materials from bioinert to highly cell-adhesive. This offers the possibility to optimize the materials depending on the specific application and the tissue type which they will interface. In the example shown the material were made adhesive for stem cells and neurons.

In perspective, we plan to develop materials that address not only the physicochemical mismatch but also the challenge of the functional mismatch between purely electrical signaling in metals and interconnected signaling (biomolecular and electronic) in living tissues. Using this approach, we expect to revolutionize bioelectronic and biomedical devices and further bridge the gap between living matter and electronics.

Methods and Expertise

• Conductive polymer hydrogel composite fabrication
• Electrical hydrogel characterization (electrical impedance spectroscopy, cyclic voltammetry, chronoamperometry)
• Microfabrication (lithography, soft lithography, microfluidics, 3D printing)
• Molecule binding and release studies
• Organic electrochemical transistors