Abstract
Gel-based flexible and wearable electronics, such as sensors and supercapacitors, have attracted much attention in the past two decades. Strong, flexible, tough, conductive, and durable (fatigue-resistant, anti-swelling, and anti-freezing etc.) gels that can endure in harsh environments without performance degradation are highly desirable. In this work, a strong, anti-freezing, and piezoresistive .24-(PVDF/PAAm) organohydrogel was fabricated via a simple one-pot thermal curing approach using acrylamide (AAm), polyvinylidene difluoride (PVDF), ammonium persulfate (APS), and N,N'- methylene bisacrylamide (MBAA), followed by sequential soaking in deionized water and 2.0 M Zn2+ (water: glycerol = 1:1) solution. The resulting .24-(PVDF/PAAm): 2.0 M Zn2+/glycerol : water (1:1) organohydrogel exhibited sustained mechanical properties after -20 ºC treatment for xx hours, with maximum tensile ultimate strength and strain of 203 kPa and ~100% (13 hours), respectively, and compressive strength of 153 kPa up to 50% stain, comparable to the unfrozen counterparts (164 kPa and ~100% for tensile and 185 kPa up to 50% strain compressive strength) (17 hours). The piezoresistive properties for the S3: .24-(PVDF/PAAm): 2.0 M Zn2+/glycerol: water (1:1) was demonstrated using a two probe approach and a four probe approach, allowing for the observation of the piezo-resistive properties. The 2-probe test employed on all 3 stages of the gel showed the conductivity increase as the final stage 3 organohydrogel was produced, and the 4-probe test method demonstrated the gels ability to be strained in both a compressive manner and coupled with finger bending to record the subsequent repeated resistance changes (kΩ) with successful return to baseline. Overall, these findings overwhelmingly support the claim that the fabrication process outlined below is capable of providing a strong and anti-freezing piezoresistive organohydrogel capable of being applied for sensing applications such as a strain gauge.