Aligned carbon nanotube-based flexible gel substrates for engineering bio-hybrid tissue actuators.

Muscle-based biohybrid actuators have generated significant interest as the future of biorobotics but so far they move without having much control over their actuation behavior. Integration of microelectrodes into the backbone of these systems may enable guidance during their motion and allow precise control over these actuators with specific activation patterns. Here, we addressed this challenge by developing aligned CNT forest microelectrode arrays and incorporated them into scaffolds for stimulating the cells. Aligned CNTs were successfully embedded into flexible and biocompatible hydrogel exhibiting excellent anisotropic electrical conductivity. Bioactuators were then engineered by culturing cardiomyocytes on the CNT microelectrode-integrated hydrogel constructs. The resulting cardiac tissue showed homogeneous cell organization with improved cell-to-cell coupling and maturation, which was directly related to the contractile force of muscle tissue. This centimeter-scale bioactuator has excellent mechanical integrity, embedded microelectrodes and is capable of spontaneous actuation behavior. Furthermore, we demonstrated that a biohybrid machine can be controlled by an external electrical field provided by the integrated CNT microelectrode arrays. In addition, due to the anisotropic electrical conductivity of the electrodes provided from aligned CNTs, significantly different excitation thresholds were observed in different configurations such as the ones in parallel vs. perpendicular direction to the CNT alignment.

Fabrication of three-dimensional carbon nanotube and metal oxide hybrid mesoporous architectures.

Three-dimensional (3D) vertically aligned carbon nanotube (CNT) patterns were utilized as templates for fabricating mesoporous hybrid architectures composed of CNTs and various crystalline metal oxide (MO; M = Co, Zn, Mn) nanoparticles by a microwave-assisted chemical approach. Post-synthesis thermal treatment of the CNT/MO patterns culminated in structural reorganization, depending on the treatment conditions. In air, CNTs were removed by oxidation. The remaining MO architectures preserved the shape and alignment of the original 3D CNT patterns, but with different porosity characteristics and improved MO crystallinity. Elastocapillary condensation and bending were demonstrated to be useful tools for further architecture alternation. The mesoporous nature of the CNT/MO hybrids and the MO materials were confirmed by N2-BET measurements. CNT/Co3O4 aligned strips were used as an example to demonstrate the potential application of the CNT/MO architectures as electrode materials for supercapacitive storage. Galvanostatic measurements showed that the CNT/Co3O4 strips were stable up to 1000 charge-discharge cycles at a current density of 377 µA/cm(2) with a specific capacitance as high as 123.94 F/g.