Researchers have developed a nature-inspired magnetic soft millirobot capable of locomotion and real-time environmental sensing. As detailed in Nature, the robot uses a micro conical leg matrix and triboelectric-enhanced sensors fabricated through high-speed jet printing and magnetic alignment. Equipped with machine learning, it adapts to different terrains and tracks its own physical state without relying on magnetic surfaces.
Study: Magnetic soft millirobot with simultaneous locomotion and sensing capability. Image Credit: P. Fromentin/Shutterstock.com
Background
Soft robots take cues from biological organisms to achieve flexibility and adaptability, making them promising for tasks like surgical procedures or structural inspections. Magnetic actuation allows for contactless, precise control, but most existing designs struggle with unreliable leg structures and a lack of integrated sensing, limiting their effectiveness in complex, real-world environments.
This study addresses both issues by introducing an inchworm-inspired millirobot that combines robust motion with embedded sensing. Using a precise jet-printing and magnetization method, the researchers created a uniform microconical matrix for enhanced locomotion and integrated triboelectric sensors. The design supports two-way movement, load carrying, and navigation through tight spaces, while producing electrical signals that feed into a machine learning model for surface recognition.
Fabrication and Characterization
The robot is built from a composite ink containing nanoscale ferroferric oxide, microscale NdFeB particles, PTFE nanoparticles, and silicone rubber, blended through planetary mixing. This ink is jet-printed onto a PVC substrate in hemispherical droplets, then magnetically shaped into a microconical matrix.
Two magnetized layers are joined using silicone rubber, with silver and indium tin oxide electrodes added for sensing. The movement layer features microcones spaced at 1300 µm and 1280 µm in height, mimicking legs, while the sensing layer uses a denser configuration (500 µm spacing, 700 µm height) to boost triboelectric output.
Printing conditions included 100 V pulses, 250 kPa backpressure, and 120 Hz frequency at room temperature (25 °C). The structure was analyzed via SEM, microscopy, and profilometry, while rheology, viscosity, and electrical output were measured using contact-separation and bending modes.
For terrain classification, a temporal perceiver network processed time-series voltage signals via FFT and multi-scale convolution. Data from five surface types—sandpaper, wood, plastic, and paper—was used to train and test the system with 80:20 data splits and a 25-point sliding window.
Key Findings
The resulting robot moves bidirectionally at speeds up to 1.4 mm/second under a 100 mT magnetic field and supports loads up to five times its weight. Its triboelectric sensor outputs 7.92 V during contact and 2.4 V when bent, maintaining performance across 12,000 cycles.
A major advancement is the robot’s ability to simultaneously move and sense its environment. The integrated system identifies terrain types with 96.7 % accuracy using a machine learning model. It also navigates tight spaces as narrow as 3 mm while tracking internal deformation through voltage changes, from 0.3 V to 0.15 V.
The use of magnetically shaped microcones allows for rapid customization and prototyping. By merging actuation and sensing, the researchers have developed a scalable approach for soft robots designed for constrained, unstructured environments.
Conclusion
This study introduces a soft, magnetic millirobot that combines movement and sensing in a compact, scalable form. Its design enables it to crawl in both directions, carry loads, and recognize terrain through triboelectric signals—all while navigating gaps as small as 3 mm. The microconical matrix serves a dual purpose as both legs and sensors, streamlining the system’s functionality.
Looking ahead, future work will aim to incorporate wireless communication, enhance three-dimensional control, and improve durability for practical use in areas like pipeline inspection or environmental monitoring.
Journal Reference
Zeng, W., Ding, X., Jin, Y., Liu, B., Zeng, R., Gong, F., Lou, Y., Jiang, L., & Li, H. (2025). Magnetic soft millirobot with simultaneous locomotion and sensing capability. Npj Flexible Electronics, 9(1). DOI:10.1038/s41528-025-00437-0. https://www.nature.com/articles/s41528-025-00437-0
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