Liquid metals are attractive for flexible electronics because they conduct electricity while remaining deformable. Yet when liquid-metal particles are incorporated into polymer networks, their surfaces can be unstable. Droplets may collide and coalesce, producing irregular conductive pathways and compromising the material’s mechanical and electrical performance. The Fuzhou University team, led by Yan Yu and Sheng-Hong Zhong, tackled this problem with gelatin, a natural biomolecule widely used in food, medicine and biomaterials. Instead of relying on conventional synthetic stabilizers, the researchers used gelatin to form a protective molecular layer around liquid-metal particles before embedding them in a hydrogel.

The stabilization mechanism is based on coordination bonding at the metal-particle surface. Liquid-metal droplets naturally develop a thin oxide layer when exposed to air. Functional groups in gelatin, particularly amino and carboxyl groups, interact strongly with this oxide coating. The resulting molecular associations create a gelatin-rich shell that helps keep individual liquid-metal particles separated and uniformly distributed. This arrangement prevents uncontrolled coalescence while preserving contact between neighboring particles, allowing the droplets to form a continuous and deformable conductive network throughout the hydrogel.

The gelatin performs another important chemical function during fabrication. According to the researchers, it helps initiate the polymerization of acrylic acid without the traditional chemical initiators normally required to start the reaction. In this process, acrylic acid molecules link together to form the polymer framework, while gelatin-coated liquid-metal particles become integrated into the developing network. Eliminating harsh initiators simplifies preparation and may improve the material’s environmental and biological compatibility. The researchers describe the method as rapid, scalable and more sustainable than approaches that require multiple synthetic additives or complicated processing steps.

The resulting material, known as a Gelatin-Mediated Hydrogel, or GMH, combines the water-rich softness of a hydrogel with the conductivity and deformability of liquid metal. It can be stretched beyond 700 percent of its original length and recover its shape without a major loss of function. Such resilience is essential for electronic skin, where a sensor must follow bending joints, moving muscles and repeatedly flexing fingers. Because the liquid-metal particles remain distributed throughout the polymer matrix, mechanical deformation changes the conductive pathways in a measurable way. This produces electrical signals that can be correlated with strain, pressure and motion.

In one demonstration, the researchers attached the hydrogel to a finger and used it to record electrical changes produced while writing the 26 letters of the English alphabet. Each movement generated a distinctive signal pattern as the hydrogel stretched and relaxed. The data were then analyzed using a convolutional neural network, a type of deep-learning model commonly used for image and pattern recognition. The system identified handwritten letters in real time with an accuracy of 93.3 percent. The result turns a soft sensor into more than a passive detector: it becomes an interface capable of converting body movement into machine-readable information.

This combination of flexible sensing and artificial intelligence could have wide implications for wearable technology. Conventional keyboards and touchscreens require rigid surfaces or deliberate finger contact, while a hydrogel sensor can gather information directly from natural movement. Similar systems could support gesture recognition, rehabilitation monitoring, sign-language interfaces or controls for wearable and robotic devices. The researchers’ demonstration remains a laboratory proof of concept, but its use of a simple biomolecule and a deformable conductive network highlights how materials science and machine learning can be integrated into lightweight human-machine interfaces.

The GMH also demonstrated a method for converting solar or near-infrared light into electricity. Liquid metal acts as an efficient photothermal component: it absorbs incoming light and rapidly converts part of that energy into heat. When the hydrogel was exposed to near-infrared illumination, its temperature increased. Coupling the material to a thermoelectric module allowed the temperature difference to be converted into an electrical voltage of approximately 16 millivolts. That output is modest, but the principle could support low-power sensors or help extend the operating time of wearable systems by reducing dependence on conventional batteries.

The researchers say the work establishes a versatile platform for multifunctional hydrogel electronics, but practical deployment will require further development. Future studies will need to examine long-term stability, performance under repeated environmental exposure, large-scale manufacturing and integration with complete power-management circuits. Even so, the material offers an unusually broad combination of properties: liquid-metal conductivity, hydrogel softness, gelatin-mediated stabilization, AI-compatible sensing and photothermal energy conversion. By using a common natural biomolecule to control an otherwise difficult-to-handle electronic material, the Fuzhou University team has brought flexible “electronic skin” a step closer to becoming adaptive, intelligent and partially self-powered.

Subject of Research: Gelatin-stabilized liquid-metal conductive hydrogels for flexible sensing, AI-assisted handwriting recognition and photothermal energy harvesting.

Article Title: Gelatin-Stabilized Liquid Metal for Conductive Hydrogels with Multifunctional Sensing Applications and Energy Harvesting

News Publication Date: 23-Jun-2026

Web References: https://doi.org/10.26599/NR.2026.94908692; Nano Research

References: Nano Research, DOI: 10.26599/NR.2026.94908692

Image Credits: Nano Research, Tsinghua University Press

Keywords

Liquid metal; gelatin; conductive hydrogel; electronic skin; wearable sensors; artificial intelligence; handwriting recognition; photothermal conversion; thermoelectric energy harvesting; flexible electronics

Central to this groundbreaking research are Alexandra Rutz, an assistant professor of biomedical engineering, along with Anna Goestenkors, a fifth-year doctoral student in Rutz’s lab. Together, they have created an array of novel granular hydrogels composed of microparticles. These microparticles, capable of being injected into the body or spread over tissues, can serve multiple purposes, including the encapsulation of cells and the monitoring and stimulation of biological activity. Their findings were recently published in the reputable nanoscience journal, Small, on October 8, marking a significant step forward in this field.

The microparticles in question are spherical hydrogels derived from a conducting polymer known as PEDOT:PSS. When tightly packed, these materials exhibit properties akin to wet sand or paste. This unique structure allows the hydrogels to maintain solidity while incorporating micropores. Furthermore, they can be 3D printed or manipulated into various shapes without losing their structural integrity. When dispersed in liquid, the particles can revert to individual microparticles, showcasing their dynamic nature.

Rutz emphasizes the innovative potential of these granular hydrogels, stating that they have not been extensively studied for bioengineering applications. By borrowing techniques from tissue engineering, the team strives to enable these electrically conductive materials to emulate the properties found within the human body. This ability to mimic biological characteristics while utilizing the functional advantages of the materials opens up new avenues for medical applications and interventions.

One of the most intriguing attributes of this material is its porosity at the microscopic scale, which has profound implications for biological interactions. The spaces between closely packed particles create a porous structure that can facilitate bioactivity on a cellular level. According to Goestenkors, the particles exhibit a degree of movement relative to each other. When a force is applied, the material behaves like a liquid, allowing it to be injected or extruded with ease. Once the force is removed, the particles re-establish connections, reverting to a more solid, paste-like consistency. This inherent adaptability underscores the material’s suitability for biomedical applications, where flexibility is paramount.

In a testament to their practical applications, Rutz and Goestenkors conducted an experiment utilizing locusts. Collaborating with Barani Raman, a professor at McKelvey Engineering and co-director of the Center for Cyborg and BioRobotic Research, they applied small clumps of the granular hydrogel on the tips of locust antennae, regions rich in olfactory receptor neurons. This innovative setup allowed the researchers to measure local field potentials corresponding to odors detected by the locusts, showcasing the hydrogels’ responsive capabilities within living systems.

Imagining the future, Rutz envisions conducting further research with these customizable 3D printed electrodes. The potential for these electrodes to conform to diverse anatomical surfaces and encapsulate biological tissues presents exciting opportunities in tissue engineering and regenerating therapies. This bioelectronic technology could fundamentally reshape how medical diagnostics and treatments are conducted. From prosthetics to neural interfaces, the implications of conducting granular hydrogels extend well into future healthcare innovations.

Additionally, Rutz and Goestenkors are taking tangible steps to protect their intellectual property. They have filed for a U.S. patent that encompasses the fabrication and applications of conducting polymer microparticles along with granular hydrogels. Collaborating with Washington University’s Office of Technology Management, they are navigating the commercialization process, aiming to bring their findings to practical use in medicine and health technology.

The ability of the research team to leverage advances in material science and biomedical engineering collectively demonstrates a forward-thinking vision. It illustrates not only the potential for significant advancements in the field but also the importance of interdisciplinary collaboration in achieving such breakthroughs. The flexibility and capability of granular hydrogels may pave the way for next-generation bioelectronics that more seamlessly integrate with biological systems.

As the development of these bioelectronic hydrogels progresses, the research opens a dialogue about the future of medical technology. Key questions arise about how these new materials can be utilized in various biomedical applications, from real-time monitoring of physiological changes to more effective therapeutic interventions. This research not only represents a synthesis of engineering and biology but also highlights the transformative potential of emerging materials in improving healthcare outcomes.

In conclusion, the development of granular hydrogels by the Washington University research team signifies a pivotal step toward more adaptable and responsive biomedical devices. With capabilities that allow for injectable applications and the emulation of biological structures, this technology can revolutionize monitoring and therapeutic practices in medicine. Continued exploration in this area will undoubtedly uncover even more applications, making a meaningful impact on our approach to health and wellness.

Subject of Research: Bioelectronic hydrogels and their applications in biomedical engineering.
Article Title: Innovative Bioelectronic Hydrogels Set to Revolutionize Biomedical Engineering
News Publication Date: October 8, 2023
Web References: https://engineering.washu.edu/news/2025/Extrudable-hydrogels-act-as-bioelectronic-conductors.html
References: Goestenkors AP, et al. PEDOT:PSS Microparticles for Extrudable and Bioencapsulating Conducting Granular Hydrogel Bioelectronics. Small, Oct. 8, 2025. DOI:
Image Credits: N/A

Keywords

Bioengineering, Biomedical Engineering, Chemical Engineering, Materials Engineering.