Highly Conductive, Stretchable, and Cell‐Adhesive Hydrogel by Nanoclay Doping

Abstract

Electrically conductive materials that mimic physical and biological properties of tissues are urgently required for seamless brain–machine interfaces. Here, a multinetwork hydrogel combining electrical conductivity of 26 S m−1, stretchability of 800%, and tissue‐like elastic modulus of 15 kPa with mimicry of the extracellular matrix is reported. Engineering this unique set of properties is enabled by a novel in‐scaffold polymerization approach. Colloidal hydrogels of the nanoclay Laponite are employed as supports for the assembly of secondary polymer networks. Laponite dramatically increases the conductivity of in‐scaffold polymerized poly(ethylene‐3,4‐diethoxy thiophene) in the absence of other dopants, while preserving excellent stretchability. The scaffold is coated with a layer containing adhesive peptide and polysaccharide dextran sulfate supporting the attachment, proliferation, and neuronal differentiation of human induced pluripotent stem cells directly on the surface of conductive hydrogels. Due to its compatibility with simple extrusion printing, this material promises to enable tissue‐mimetic neurostimulating electrodes.

Rapid prototyping of soft bioelectronic implants for use as neuromuscular interfaces

“…S10). Our printing method is amenable to the introduction of emerging materials such as hydrogels or conductive polymers that hold promise for decreasing electrode impedances and improving implant biointegration (29,30). With their simple construction, NeuroPrint electrodes eliminate the need for cleanroom processing and the development of design-specific masks and fabrication tools which are typically employed for the production of neural probes (31).…”

4D Printed Hydrogels: Fabrication, Materials, and Applications

“…For example, a number of hydrogels having high electrical conductivity and good mechanical strength have been reported. [ 34,120,121 ] The conductive and stretchable hydrogel has the potential for application as the matrix of electrical‐ and mechanical‐responsive hydrogel composites. On the other hand, the output signal for current 4D printed hydrogel devices is limited mainly to the mechanical and biological; the output signals of hydrogels in other areas are seldom employed for 4D printing.…”

Smart Bioinks as de novo Building Blocks to Bioengineer Living Tissues

“…For example, when polymer concentration is used to increase the matrix biomechanics, this also increases the concentration of cell-adhesive binding ligands, altering cell biochemistry. Similarly, some bioinks use the addition of fillers, such as nanocellulose [48] or nanoclay [49,50] to increase matrix mechanics. However, these changes directly affect the porosity and topographical structure of the network, thereby altering the local presentation of cell-adhesive binding ligands, which affects cell adhesion, migration, and proliferation potential.…”

“…For example, in cardiovascular and neural research it may be necessary to consider the electroconductivity of the chosen bioink. In line with this, electroconductive hydrogels with functional pendant groups have been synthesized, showing responsive electroactivity in physiological conditions [50,57]. These functionally smart hydrogels have been used as cardiac patches in preliminary in vivo studies, showing their compatibility with the rhythmogenic activity of the heart [58].…”