Mechanically Soft and Conductive Hydrogel : Aligned Polyaniline-Carbon Nanotubes Hybrids for Cell Growth

Abstract

Traditional neural interfaces using metallic electrodes have many problems such as high impedance, mechanical mismatch. These problems result in unstable electrical stimulation of tissue such as cell damage and foreign body response. To resolve these problems, Blending hydrogels with conductive polymers or carbon nanotubes (CNTs) have been studied due to low impedance. However, the mechanical properties of these conductive hydrogels are still not ideal, as they are quite stiff. The considerable researches have been reported for development of the electrode interfacing material with an elastic modulus close to nature tissue. In this study, an electrically conductive hydrogels composed of aligned polyaniline (PANI) coated CNTs were fabricated for use as biomaterials. By adjusting the intensity of the electrical stimulus to deliver partially accurate electric signal, PANI were coated on synthesized aligned CNTs. And both the number of the CNTs and thickness of the PANI-CNTs were respectively controlled. The conductivity using a two-point probe station was respectively measured. Also randomly distributed PANI-CNTs/PAAm hydrogel was compared to confirm high conductivity of aligned PANI-CNTs/PAAm hydrogel. Young’s modulus of the aligned PANI-CNTs/PAAm hydrogel using AFM was measured to confirm stiffness of conductive hydrogel compared with native tissue. The device interfaces which can minimize the limitations of the gap between the electrode and tissue have been developed. The soft and conductive hydrogel was proven to be biocompatible using Live/Dead assay, which is available as biomaterials.