Mechanical and electrochemical characterization of CNT/PDMS composited soft and stretchable electrodes fabricated by an efficient solution-based fabrication method

This work reports a comparative study on the preparation and characterization of a novel carbon nanotube (CNT) based stretchable electrode aiming at developing wearable electrical biosensors. Polydimethylsiloxane (PDMS) was chosen as the elastomeric substrate for electrodes due to its promising biocompatibility, remarkable mechanical properties and ease of use. A new structure of the electrode composited by three layers has been proposed which showed significant improvement in electrochemical and mechanical properties. A simple solution-based fabrication method was employed to make CNT (active material) coated PDMS/CNT composite thin film which was integrated with a pre-cured PDMS film substrate. The electrochemical activity of the electrodes composed by single-wall carbon nanotube (SWCNT) and multi-wall carbon nanotube (MWCNT) was studied and compared by cyclic-voltammetry test. Two electrodes with surface concentration of 0.5 mg/cm2 SWCNT and 0.75 mg/cm2 MWCNT showed optimized electrochemical redox signals of K3[Fe(CN)6] in PBS buffer solution at pH 7.4. The resistance changes of the stretchable electrodes at different stretch levels were characterized using uniaxial stretcher machine. The result showed that in the specific surface concentration of 0.5 mg/cm2 SWCNT and thickness of 500 μm, the electrode can maintain its surface resistance as low as 50 Ω/cm up to 300% stretch. The novel CNT/PDMS composed stretchable electrode has great potential for the development of flexible soft bioelectronics such as wearable biosensors.