4D-printed multifunctional hydrogels as flexible strain sensors and nerve conduits

fCNT loading. Owing to their good combination of electrical conductivity and mechanical properties, the (three-dimensional) 3D-printed gels were successfully applied as strain sensors to sense subtle human motions, such as finger and elbow bending. Bilayered hydrogels prepared through four-dimensional (4D) printing exhibited programmable shape changes owing to differential swelling post-printing to yield nerve guidance conduits (NGCs) of intricate and tissue-adaptable designs, such as single and multichannel and bifurcated designs, based on accurate prediction by finite element analysis. The proliferation of neural cells was enhanced on the fCNT-gel compared to the neat gel. Sutureless deployment and enhanced peripheral nerve regeneration were established for the fCNT-gel in a rat sciatic nerve injury model. Overall, this work presents the fabrication of 4D-printed multifunctional conductive hydrogels, which can find diverse applications ranging from implantable nerve conduits to strain sensing.