Flexible wearable electronics have made remarkable strides in healthcare monitoring and human-machine interaction, yet one stubborn obstacle remains: the cold. When temperatures drop, conventional hydrogel sensors tend to freeze, lose elasticity, and shed ionic conductivity, rendering them useless in winter environments or refrigerated settings. A team reporting in the Journal of Bioresources and Bioproducts believes it has found a way around the problem by returning to one of nature's most abundant building blocks-cellulose.
The researchers dissolved cotton pulp cellulose in a binary molten salt hydrate composed of zinc chloride and lithium bromide, maintaining a total salt-to-water molar ratio of 1:3. Within ten minutes, the blend broke down the rigid crystalline structure of cellulose. Molecular simulations revealed that the small, highly charged lithium ions penetrated the crystalline regions and disrupted hydrogen bonds, while zinc ions formed stable hydration shells around the liberated chains, preventing the hydrolytic damage that pure zinc salts typically cause. The dissolved cellulose was then cast into hydrogels and rinsed, yielding a transparent, flexible material designated HZ0.3L0.7-C3.
The numbers are striking. The optimized hydrogel posted an ionic conductivity of 4.48 S/m and withstood compressive stress up to 2.48 MPa. Differential scanning calorimetry scans from -80°C to 20°C showed no exothermic peaks associated with water crystallization, meaning the salts bind water so aggressively that ice formation is effectively shut out. Even after the sensor sat at -25°C for 168 hours, it continued to deliver clear, repeatable electrical signals during finger bending and fingertip pressing.
Beyond raw performance, the hydrogel exhibits pronounced shear-thinning behavior, allowing it to flow through a 3D printer nozzle and then hold its shape. The team successfully printed intricate structures such as five-pointed stars and maple leaves. For practical wearables, the researchers coated the hydrogel with polydopamine to improve skin compatibility without sacrificing conductivity. Mounted on fingers, wrists, elbows, or throats, the sandwich-structured sensor responded in about 100 milliseconds and recovered in 300 milliseconds, maintaining stable output over 500 compression cycles at 30 percent strain. The device was also integrated into a data-glove system that mapped hand motions onto a robotic model in real time.
By marrying renewable cellulose with a carefully tuned salt chemistry, the work offers a credible path toward cold-resilient, customizable sensors that do not force engineers to choose between performance and sustainability.
See the article:
DOI
https://doi.org/10.1016/j.jobab.2026.100285
Original Source URL
https://www.sciencedirect.com/science/article/pii/S2369969826000575
Journal
Journal of Bioresources and Bioproducts
