Injectable and moldable hydrogels for use in sensitive and wide range strain sensing applications

Abstract

Recently, the use of hybrid double network (DN) hydrogels has become prominent due to their enhanced mechanical properties, which has opened the door for new applications of these soft materials. Only a few of these gels have demonstrated both injectable and moldable capabilities. In this work, we report the mechanical properties, gauge factor (GF) values and demonstrate both the injectability and moldability of a gelatin/polyacrylamide DN hydrogel. We optimized several parameters, such as, gelatin to polyacrylamide ratio, reactant concentrations and metal ion concentration, to produce a gelatin/polyacrylamide hydrogel with superior mechanical properties. The highest water content gel was capable of withstanding strains of 5000% before failure. These gels were facilely injected into molds where they effectively changed shape and maintained similar properties prior to remolding. When 20 mM calcium was doped into a similar gel, a tensile strength of 1.71 MPa was achieved. Aside from improving the mechanical properties of the gels, both Ca2+ and Mg2+ also improved their conductivity, so they were tested for use as strain sensors. The sensitivity of the hydrogel strain sensors were measured using the GF. For the 20 mM Ca2+ hydrogel, these GF values ranged from 1.63 to 6.85 for strains of 100% to 2100% respectively. Additionally, the sensors showed good stability over continuous cyclic stretching, demonstrating their long term reliability for strain sensing.

Highly stretchable gelatin‐polyacrylamide hydrogel for potential transdermal drug release

“…This hydrogel was already reported (ref. [15]). Briefly, it can be prepared as follows: 0.4 g acrylamide, 0.05 g gelatin were dissolved in 5 mL distilled water in a vial.…”

“…[ 14 ] Recently, we developed a highly stretchable and tough hydrogel that is made of PAAm and gelatin. [ 15 ] The gelatin/PAAm hybrid hydrogel can stretch up to 5000% before failure and a tensile strength of 0.3 MPa. The gel demonstrated a full recovery of the gel morphology a broad dynamic range of 0‐3000% and the gel are stable over continuous stretching cycles, demonstrating their good reliability in a patch for transdermal drug delivery application.…”

Characterisation of Rapid In Situ Forming Gelipin Hydrogel for Future Use in Irregular Deep Cutaneous Wound Healing

“…The three-minute selection for the polymerisation time was selected in the current study to ensure the clinician/surgeon has enough time to apply them on skin wounds before polymerisation. The polymerisation process occurred due to the helix-coil transition mechanism, which has been reported by Pattinelli et al [ 38 ] and Qiao et al [ 39 ]. In addition, the proposed crosslinking mechanism of action ( Scheme 1 ), that occurred between Gel and GNP, was stipulated and concluded with some modifications from previous articles that were published by Erdagi et al [ 40 ], Wang et al [ 41 ], Muzzarelli et al [ 42 ] and Liu et al [ 43 ], which explored the GNP abilities as a natural crosslinker.…”

Recent Progress in Natural Biopolymers Conductive Hydrogels for Flexible Wearable Sensors and Energy Devices: Materials, Structures, and Performance

“…Recently, owing to the excellent biocompatibility and moderate gelation condition of gelatin, a number of researchers have developed low-power, sensitive, artificial wearable sensors based on gelatin by mimicking the functions of mechanoreceptors in human skin. , For example, Qin et al demonstrated a highly stretchable device from a composite of gelatin and deep eutectic solvent (DES) hydrogels, improving the long-term use of hydrogel-based devices (Figure a–c). The DES hydrogel containing 22 wt % gelatin showed high stretchability (∼300% fracture strain) and the ionic conductivity up to 2.5 mS cm –1 at room temperature.…”