Enabling & Support
11/05/2026
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The inchworm may not be the first thing that springs to mind when you think of planetary explorers, but a recent ESA Discovery activity led by the University of Gothenburg looked to one of nature’s most elegant crawlers for a new approach to soft robot locomotion.
A robot exploring another planet needs to traverse unpredictable, uneven terrain, withstand extreme temperatures and radiation, and do all of this with minimal power and without maintenance. Conventional rigid robots – like those deployed on Mars – have a fixed number of joints and degrees of freedom, limiting their ability to squeeze through narrow gaps or adapt to irregular surfaces. Soft robots, by contrast, are flexible and compliant, making them far better suited to unstructured terrain. The challenge has always been how to make them move with precision.
Muscles without motors
The Gothenburg team built their robot around a dielectric elastomer actuator (DEA) – a type of artificial muscle consisting of a thin, flexible polymer sandwiched between two compliant electrodes, which contracts and extends radially when a voltage is applied. DEAs are promising because they mimic the behaviour of biological muscle: they can deform significantly, respond quickly, and store and release energy efficiently. In this case, the team used a rolled version of the actuator (an RDEA) to drive the robot’s inchworm-like motion – contracting and extending axially to inch forward.
A key requirement for any robot destined for planetary exploration is that it can operate reliably in a harsh radiation environment. The compliant electrodes used in the actuator are made from single-walled carbon nanotubes (SWCNTs) – a cylindrical nanomaterial formed from a rolled sheet of graphene. Experiments and simulations have shown that SWCNTs have fault-tolerant properties that allow them to withstand mechanical damage and provide partial shielding against Martian radiation, specifically alpha and proton particles simulated at 10 MeV energy. This fault-tolerant behaviour could significantly extend the operational lifespan of a robot deployed on Mars or the Moon. The design also operates at relatively low voltages, reducing power consumption and minimising the risk of failure – both critical considerations when a robot is millions of kilometres from the nearest repair technician.
“The core challenge we were trying to solve was achieving multidirectionality in soft robots without the need for complex electronics or multiple actuators,” explains Dr Hari Prakash Thanabalan of the University of Gothenburg, the project’s lead researcher. “The inchworm became a model due to its simple yet effective design – its locomotion is controlled mainly by contraction and extension of its body, which makes it a well-suited source of inspiration for a robot that needs to adapt to the surface on which it moves.”
“Biomimicry is increasingly central to advanced space concepts, and this activity is a good example,” says Ugo Lafont, Space Materials & Technology Specialist and ESA lead on the project. “The key enabling technology is the rolled dielectric elastomer actuator – a cylindrical artificial muscle that continues to function even when partially cut or punctured. This fault-tolerant behaviour is essential for any device destined for the harsh conditions of space.”
An unexpected discovery
Inchworm-inspired soft robot
While testing the robot’s locomotion on 3D-printed substrates, the team made an unplanned finding that has opened up a promising new line of research. The substrates had groove patterns 3D printed into their surface, and the team noticed that the robot’s legs were hooking onto the grooves as it moved – causing it to align itself with the groove direction.
“Initially we tested the robot on groove angles that were perpendicular to the direction of motion,” says Dr Thanabalan. “We realised that the robot was ‘hooking’ its front legs onto the grooves on the surface. This led us to experiment with increasing the groove angles – and the robot started aligning itself with the groove direction as it locomoted. It was our Eureka moment!”
By systematically varying the groove angle from 0° to 5°, 15°, and 30°, the team demonstrated that passive surface interaction alone – without any additional actuators or electronics – could steer the robot precisely. The steeper the groove, the more strongly the robot reorients itself. The robot was also tested across sequences of substrates with different groove angles, successfully navigating left turns, right turns, and combinations of both – demonstrating true multidirectional locomotion from a single actuator.
The grooved substrates are, of course, a controlled laboratory environment, and passive steering alone would not be sufficient on the unpredictable terrain of another planet. But the finding demonstrates an important principle: that surface interaction can substitute for complex onboard control systems, pointing towards robots that are simpler, lighter, and more resilient.
The road ahead
The next steps for the research follow both strands of the activity’s findings. On the locomotion side, the team plans to improve the robot’s robustness to thermal cycling and radiation exposure, and to integrate sensors that would allow it to respond more intelligently to its environment without significantly increasing its complexity. On the steering side, the longer-term goal is to combine the groove-guided principle with onboard sensors and feedback systems, allowing the robot to navigate natural, unstructured terrain.
Ultimately, the team hopes to test the robot on terrain that mimics the surface of other planets – including the Mars Yard at ESA’s ESTEC facility in the Netherlands – as a first step towards validating its performance under realistic exploration conditions.
“As the design matures, incorporating multiple actuators into an optimised configuration could enable not only locomotion but also controlled steering, independent of the terrain’s texture,” says Ugo Lafont.
The ‘Soft Annelid-Inspired Robot with Peristaltic Gait using Low Voltage Fault-Tolerant Artificial Muscles for Planetary Exploration‘ activity was submitted through ESA’s Open Space Innovation Platform and funded by the Discovery element of ESA’s Basic Activities.
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