Thin-film flexible robots

In plain language

Most robots are built from rigid parts and bulky motors, which makes them too large for narrow gaps or delicate surfaces. A thin-film robot is made from flexible circuit films less than a millimetre thick. Its main parts are an actuator that can move in two directions and four electrostatic pads that hold the robot to a surface using electrical attraction.

The paper describes the robot's motion as inchworm-like: the adhesive feet are controlled independently of the actuator, so the robot can hold and release its footing in steps and advance. In laboratory tests it moved over flat, curved and vertical test surfaces, and it scanned a 7 mm-high gap in a demonstration. The robot is still a prototype: it is wired to external high-voltage supplies and control hardware, so it cannot yet work untethered.

Technical explanation

The actuator uses two electrode sets that drive motion along the X and Y axes, and four electrostatic adhesive pads hold the robot to the surface. The authors report a maximum actuator output force of 1.07 N. Actuation displacement tests ran at 450 V zero-to-peak, and the maximum force test ran at 600 V zero-to-peak. Adhesion tests on insulating materials ran at up to ±1400 V. Actuator-level tests gave 21.7 μm bidirectional repeatability, 23.1 μm mean positioning accuracy and a maximum speed of 290 mm/s at a 240 Hz driving frequency. These are actuator figures, not the speed of the robot on a surface.

On an aluminium plate at 80 Hz, the robot travelled at 27.6 mm/s in a straight line and 39.0 mm/s through a 45° turn. At 50 Hz it tracked a trajectory with a maximum absolute error of 0.26 mm and an RMSE of 0.124 mm. Adhesion depends strongly on the surface: the measured force on dusty aluminium was 0.339 N, against 3.84 N for brushed aluminium at ±450 V, and porous polyurethane gave the lowest force measured, 0.031 N at ±1400 V.

The authors also report an 80 g payload (4.06 times the robot's mass) and survival of a 3 kg impact in five trials. Demonstrations included scanning a narrow gap, grinding a curved aluminium workpiece with 1000-grit paper, where surface roughness fell from Ra 0.81 μm to 0.46 μm over 10 minutes at 30 Hz, and a microscale electrical-discharge machining (EDM) test. In that test a 0.05 mm tungsten needle machined a 3 × 3 array of nine points on aluminium at ±1000 V and 1 Hz.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Limitations and open problems

• The prototype is tethered to external high-voltage amplifiers, controller hardware, relays and a power supply. The authors list an onboard high-voltage amplifier, microcontroller, communication unit and power supply as future work (Wang et al., 2026). The adhesion tests used up to ±1400 V, so high-voltage safety and insulation are central engineering issues.
• Adhesion depends on the surface. Force fell on dusty, porous and fibrous materials, on rougher surfaces, and on tighter concave curves (from 5.35 N at a 1000 mm radius to 1.32 N at 50 mm). Real structures may be dirty, coated or irregular, and the study tested only the materials it lists.
• Trajectory accuracy falls on sharp turns, and the system is open-loop. In actuator trajectory tests at 2, 10 and 30 Hz the paper reports an RMSE rising above 0.154 mm. The authors also link part of the tracking error to voltage switching by relays, which takes about 50 ms per switch.
• The demonstrations are short laboratory tasks on test workpieces. The paper does not report field trials, routine maintenance on aircraft or ships, or repeatable industrial machining.
• Long-term durability and environmental robustness are not established. The paper reports more than 10,000 cycles at a 20 mm stroke and 20 Hz, but this is not evidence of field service life.

Possible future uses

Timeline

1. Apr 2020A comprehensive review of electroadhesion technologies for robotics is published in IEEE Transactions on Robotics (volume 36, issue 2). Electroadhesion is the adhesion principle the robot's feet rely on. Sources: [2]
2. 21 Oct 2025The manuscript describing the thin flexible robot is received by Nature Communications. Sources: [1]
3. 5 Jun 2026The manuscript is accepted after peer review. Sources: [1]
4. 23 Jun 2026The peer-reviewed paper is published, reporting a 970 μm-thick, 19.7 g electrostatic film robot demonstrated on laboratory surfaces, in a narrow-gap scan, in curved-surface grinding and in microscale EDM. Sources: [1]

Futures this could help bring about

How far away?

Robots as thin as paper

Engineering prototypes · 3 of 6 steps done

Glossary

Electrostatic actuator

A device that creates movement using forces between electrically charged or energised elements.

Electrostatic adhesion (electroadhesion)

A way to hold a pad against a surface using electrical forces, which can be switched on and off.

Electrical-discharge machining (EDM)

Material removal using controlled electrical sparks between an electrode and a conductive workpiece.

Inchworm locomotion

Movement in which a robot alternately anchors one part of its body and extends or contracts another, like an inchworm.

Sources

1. peer reviewed paper
   A thin robot made of flexible electronics for in-situ machining and inspection of large structures
   Huacen Wang, Yujin Dai, Ting Wang et al.. Nature Communications, 23 Jun 2026. DOI: 10.1038/s41467-026-74548-1. Accessed 21 Oct 2026.
2. review article
   Electroadhesion Technologies for Robotics: A Comprehensive Review
   Jianglong Guo, Jinsong Leng, Jonathan Rossiter. IEEE Transactions on Robotics, Apr 2020. DOI: 10.1109/tro.2019.2956869. Accessed 21 Oct 2026.
3. review article
   Soft electroadhesion systems for soft robotics
   Peiwen Huang, Yangyang Xin, Pooi See Lee. npj Robotics, 3 Sept 2025. DOI: 10.1038/s44182-025-00046-z. Accessed 21 Oct 2026.

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