Piezoresistive and electrical properties of a catecholic amino acid-polyacrylamide single-walled carbon nanotube hydrogel hybrid network

We have developed a functional hydrogel combining the advantages of single-walled carbon nanotube (SWCNT) hydrogels and 3,4-dihydroxy-l-phenylalanine (l-DOPA) that would be expected to lead to a material with elevated piezoresistive ability. SWCNT hydrogel precursors were thus embedded into the catecholic amino acid 3,4-dihydroxy-l-phenylalanine-polyacrylamide (l-DOPA-PAM) hydrogel to form a l-DOPA-PAM-SWCNT hydrogel hybrid network. This hybrid network as formed was soft but became a hard gel at room temperature. An advantage of this material design is the prevention of overoxidation of l-DOPA to maintain enough free catechol groups to endow the desired properties. Several characterization techniques, including optical microscopy, field-emission scanning electron microscopy, Raman spectroscopy, and dynamic mechanical analysis, were utilized to characterize the l-DOPA-PAM-SWCNT hydrogel hybrid network. The negative piezoresistive effect and electrical properties of the l-DOPA-PAM hydrogel and the l-DOPA-PAM-SWCNT hydrogel hybrid network were measured under different pressures and at different times after the application of pressure started, demonstrating the potential for pressure-sensing applications.<p></p>