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Metal dendrites are usually something chemists try to avoid. Best known for causing short circuits and safety hazards in lithium and zinc batteries, these needle-like metallic structures are typically treated as a problem to be solved rather than a feature to be celebrated. But a team of researchers led by Dr Si Yu Zheng, Zhejiang University of Technology, China, and involving researchers across China and Australia, has now turned this reputation on its head, that dendrites can be grown deliberately inside hydrogels to create soft materials with an unusual combination of high toughness and high electrical conductivity.  

Conductive hydrogels are widely used in soft electronics, wearable health monitors and soft robotics, yet their design has long been constrained by a fundamental trade-off. Electronic fillers such as graphene or metal particles can boost conductivity but often make the gel brittle, while ionic conductors disperse well but offer lower conductivities and may leach out over time.  

Instead of adding solid particles, the team began by soaking their hydrogels in a solution of stannous ions, where the ions distribute uniformly throughout the network. Applying a voltage then converts the absorbed ions into metallic tin dendrites, which grow inside the gel in intricate, tree-like patterns. A final water dialysis step removes excess ions and causes the gel to contract slightly, pulling the dendrites closer together and forming continuous electrical pathways. 

The resulting materials substantially outperform typical hydrogels. The tin-reinforced network reaches conductivities of around 12.5 S m^-1, alongside a fracture energy exceeding 1300 J m^-2 and a fatigue threshold nearly an order of magnitude higher than the unmodified gel. The researchers attribute this to the dendrites’ microscopic architecture. 

Design of the dendrite composite gel. The zwitterionic pVB gel absorbs Sn²⁺ ions from SnCl₂ solution based on the strong anti-polyelectrolyte effect. Sn electrodes are then attached to both ends of pVB gel to covert Sn²⁺ ions to Sn dendrites in situ via an electrochemical reaction. To eliminate excess Sn²⁺ ions, the dendrite composite gel is dialyzed in water. The dense and branched Sn dendrites establish efficient conductive pathways in the gel, resulting in high conductivity. The interactions between the dendrites and pVB chains enable the transfer of stress and dissipation of energy during loading. 

The method also proves unexpectedly versatile. Because the process relies on ion uptake rather than doping with dispersed particles, it works across a wide range of gel chemistries. A zwitterionic polymer known as pVB performed particularly well, absorbing high concentrations of Sn²⁺ and enabling rapid dendrite formation.  

To demonstrate practical use, the team fabricated simple but effective wearable strain sensors, which showed large, reversible resistance changes during bending. They also produced soft bioelectrodes that recorded clear ECG signals, performing at least as well as commercial conductive gel electrodes.  

By reframing dendrite growth as a structural advantage rather than a defect, the study outlines a new strategy for designing robust, conductive soft materials. The authors suggest that other metals could be explored next, opening the way to a broader family of dendrite-reinforced hydrogels tailored for flexible electronics and biomedical interfaces.  

Towards real-world impact  

Beyond the laboratory, the work points to technologies that could make a tangible difference to people’s lives. Hydrogels that are both highly conductive and mechanically robust are essential for future medical monitoring systems, soft prosthetics and long-term wearable devices that remain comfortable and reliable. The authors suggest that dendrite-reinforced gels could lead to more durable, more accurate physiological sensors that patients can wear for days or weeks without irritation or performance loss.

The materials may also help advance soft robotics and assistive devices, where flexible but resilient conductors are needed to create responsive, human-friendly systems. Their ease of fabrication – relying on ion-soaking and simple electrochemical growth –could lower manufacturing barriers, making advanced soft-electronic components more accessible.  

Related research 

B Tang et al, Mater. Horiz., 2025, 12, 4229-4237. DOI:

X Rong et al, Mater. Horiz., 2024, 11, 2420-2427. DOI:    

Z Ren et al, Mater. Horiz., 2024, 11, 5600-5613. DOI:

L Zhou et al, Mater. Horiz., 2024, 11, 3856-3866. DOI: