A Transparent Poly(vinyl alcohol) Ion‐Conducting Organohydrogel for Skin‐Based Strain‐Sensing Applications

Abstract

The increasing demand for cost‐efficient and user‐friendly wearable electronic devices has led to the development of stretchable electronics that are both cost‐effective and capable of maintaining sustained adhesion and electrical performance under duress. This study reports on a novel physically crosslinked poly(vinyl alcohol) (PVA)‐based hydrogel that serves as a transparent, strain‐sensing skin adhesive for motion monitoring. By incorporating Zn2+ into the ice‐templated PVA gel, a densified amorphous structure is observed through optical and scanning electron microscopy, and it is found that the material can stretch up to 800% strain according to tensile tests. Fabrication in a binary glycerol:water solvent results in electrical resistance in the kΩ range, a gauge factor of 0.84, and ionic conductivity on the scale of 10−4 S cm−1, making it a potentially low‐cost candidate for a stretchable electronic material. This study characterizes the relationship between improved electrical performance and polymer–polymer interactions through spectroscopic techniques, which play a role in the transport of ionic species through the material.

Rapid Self-Healing Hydrogel with Ultralow Electrical Hysteresis for Wearable Sensing

“…This shift to lower wavenumbers implies a blue shift in the characteristic absorption spectrum and signifies the formation of stronger hydrogen bonds between PVA and glycerol . This result suggests a substantial interaction between the primary alcohol groups in glycerol and the alcohol groups in PVA, thereby reinforcing intermolecular interactions Figure d shows the X-ray diffraction (XRD) patterns of the hydrogel and the control group.…”

“…The influence of glycerol on the hydrogel structure was further evidenced by the appearance of additional peaks at 1043 cm –1 (Figure S4). It is important to highlight that PVA contains relatively few primary alcohol groups, whereas glycerol primarily consists of primary alcohols . The observed shifts in the C–C–O peak, characteristic of primary alcohols, provide a means to track the hydrogen bonding within the hydrogel.…”

“…This phenomenon can be attributed to glycerol's exceptional hydrogen bonding capabilities and its plasticizing effect, which impedes the formation of ice crystals and enhances the flexibility of the hydrogel. 49 As a result, the PVA polymer chains adopt a closer arrangement, ultimately leading to a denser structural configuration. 50 The swelling ratio of the control group and hydrogel was measured to investigate the influence of glycerol on the structure of hydrogels, and the results are shown in Figure 2b.…”

“…53 It is important to highlight that PVA contains relatively few primary alcohol groups, whereas glycerol primarily consists of primary alcohols. 49 The observed shifts in the C−C−O peak, characteristic of primary alcohols, provide a means to track the hydrogen bonding within the hydrogel. In particular, the control group exhibited a shoulder peak at 1054 cm −1 , while the hydrogel displayed a more prominent peak at 1043 cm −1 .…”

“…54 This result suggests a substantial interaction between the primary alcohol groups in glycerol and the alcohol groups in PVA, thereby reinforcing intermolecular interactions. 49 Figure 2d shows the X-ray diffraction (XRD) patterns of the hydrogel and the control group. Notably, differences emerged in the full width at half maximum (fwhm) of the peaks after the introduction of glycerol.…”