Transparency Of Hydrogels Research Articles

Simple synthesis of cellulose hydrogels based on the direct dissolution of cellulose in tetrabutylphosphonium hydroxide followed by crosslinking

AbstractCellulose‐based hydrogels are valuable sustainable materials with significant potential applications in biomedical fields such as cell therapy, hemostasis, wound healing, tissue transplantation, regeneration technology, and drug delivery carrier to cells. In contrast to previous studies, the standard synthesis procedure needs high temperature, low cellulose concentration, and many additives. Here cellulose‐based hydrogels with a high cellulose concentration are produced at room temperature. The one‐pot preparation of chemical hydrogels involves the dissolution of cellulose in tetrabutylphosphonium hydroxide followed by epichlorohydrin crosslinking. The effects of the wide range of microcrystalline cellulose concentrations and the crosslinker ratio on swelling properties and crosslink density under different conditions are investigated. The hydrogels are characterized using Fourier transform infrared spectroscopy and X‐ray diffraction. The morphology of hydrogels is examined through scanning electron microscope. The transparency of hydrogel is determined by ultraviolet–visible (UV–vis) spectrophotometer.

A Multimodal Hydrogel Soft-Robotic Sensor for Multi-Functional Perception.

Soft robots, with their unique and outstanding capabilities of environmental conformation, natural sealing against elements, as well as being insensitive to magnetic/electrical effects, are ideal candidates for extreme environment applications. However, sensing for soft robots in such harsh conditions would still be challenging, especially under large temperature change and complex, large deformations. Existing soft sensing approaches using liquid-metal medium compromise between large deformation and environmental robustness, limiting their real-world applicability. In this work, we propose a multimodal solid-state soft sensor using hydrogel and silicone. By exploiting the conductance and transparency of hydrogel, we could deploy both optical and resistive sensing in one sensing component. This novel combination enables us to benefit from the in-situ measurement discrepancies between the optical and electrical signal, to extract multifunctional measurements. Following this approach, prototype solid-state soft sensors were designed and fabricated, a dedicated neural network was built to extract the sensory information. Stretching and twisting were measured using the same sensor even at large deformations. In addition, exploiting the distinctive responses against temperature change, we could estimate environmental temperatures simultaneously. Results are promising for the proposed solid-state multimodal approach of soft sensors for multifunctional perception under extreme conditions.

Tunable random laser in flexible hydrogel

Abstract We have demonstrated a low threshold and tunable flexible random laser (RL) in dye-doped poly ethylene glycol diacrylate (PEG-DA) hydrogel, which was prepared by crosslinking polymerization using PEG-DA monomer and photoinitiator. The random lasering is attributed to the light scattering from the porous structure of hydrogels, and the wavelength of random lasing can be tuned by ~3.2 nm in the temperature range from 30 °C to 70 °C. Under the continuous increasing and decreasing temperature cycle, the random lasing tunable phenomenon can still be observed, which proves that this flexible material can be used as a new temperature sensor. In addition, we also explored the application of flexible laser in phototherapy. Considering the good elasticity and transparency of hydrogels, this thermo-responsive property will be of great significance to the biomedical applications of flexible material.

Transparent and conductive amino acid-tackified hydrogels as wearable strain sensors

Currently, flexible and conductive hydrogels have become promising materials for wearable strain sensors. However, adhering to skin seamlessly without any adhesive tape or bandage still remains a challenge. Moreover, the transparency of hydrogel was highly desired for satisfying the diverse requirement of electronic devices. Here, an adhesive polyacrylamide hydrogel driven by amino acids was designed by using lysine. The lysine-mediated hydrogel exhibited excellent adhesive behavior for diverse material substrates (e.g., metal, stainless steel, plastic, glass, rubber, silica rubber) and even for skin. The maximum peeling strength of hydrogel on aluminium could achieve 202.2 N/m, which exceeded that of PAAm hydrogel with 36.4 N/m. Intriguingly, by introducing lithium chloride into the system, the adhesive hydrogel exhibited high conductivity (0.0736 S/cm), transparency (92%) and freezing-resistant property (−31.8 °C). Moreover, the hydrogel-based strain sensor could be sensitive to both large activities (e.g., joint bending) and tiny motions (e.g., swallowing, speaking and breathing). This work provided an inspiration for the design of novel adhesive and conductive hydrogels as flexible strain sensors.