The result is a fully soft system that can sense, respond, and adapt in real time.
Many designs still rely on rigid electronics or pneumatic systems, which limit flexibility. While hydrogels like PNIPAM offer a softer alternative, they’ve typically required slow and energy-intensive heating methods, such as immersion in heated environments. This new approach addresses both limitations at once.
How the System Works
The team developed three types of double-network granular hydrogels (DNGHs), each with a specific role: sensing, actuation, and heating. These materials were created by first forming bulk hydrogels, breaking them into microgels, and then reassembling them into printable inks that could be cast or 3D printed into complex structures.
For sensing and heating, the researchers used a combination of PAMPS microgels and the conductive polymer PEDOT:PSS, with zinc chloride added to the heater to enhance conductivity. The actuator layer was built using PNIPAM, which contracts when heated.
A key advantage of this design is that everything is integrated into the material itself. When a small voltage (5V) is applied, the embedded heater generates localized heat, triggering the actuator to bend without warming the surrounding environment. Just one centimeter away, temperatures remain close to room level.
Performance Highlights
Testing showed that the material maintains its softness while delivering strong performance. The actuator achieved bending angles of up to 150° in bilayer structures, significantly outperforming conventional hydrogel systems. It also responded faster, cutting actuation time by more than half.
The heating system proved equally effective. By combining zinc ions with PEDOT:PSS, the material achieved both ionic and electronic conductivity, allowing it to reach temperatures above 52 °C, the threshold needed to activate PNIPAM. Importantly, this heating remains highly localized, improving efficiency and safety.
The system is also well-suited to manufacturing. Its shear-thinning properties allow it to flow during 3D printing and quickly regain structure afterward, enabling a full gripper to be produced in about 15 minutes. Adjusting parameters like infill density and thickness allows engineers to fine-tune speed and range of motion, with some designs achieving a full 180° bend.
To showcase its capabilities, the team integrated the gripper with a robotic arm and demonstrated closed-loop control using built-in piezoresistive sensors. These sensors detect strain with high sensitivity and provide continuous feedback, allowing the system to adjust its movements in real time.
In a fruit-sorting test, the gripper successfully distinguished objects by size. It could gently pick up strawberries while releasing larger fruits, demonstrating selective handling rather than simple gripping. Despite weighing just 35 grams, the device lifted up to 110 grams while consuming only 2 watts of power.
Conclusion
By combining sensing, actuation, and control within a single material, this work moves soft robotics closer to fully autonomous systems that don’t rely on rigid components. The ability to handle delicate objects efficiently and adaptively could be particularly useful in areas like food processing, agriculture, and biomedical applications.
Just as importantly, the approach shows how material design itself can take on roles traditionally handled by separate hardware and electronics, simplifying systems while improving performance.
Journal Reference
Georgopoulou et al. (2026). Programmable somatosensory soft robots. Npj Flexible Electronics. DOI:10.1038/s41528-026-00558-0. https://www.nature.com/articles/s41528-026-00558-0
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