Tiny robot harvests battery power via skin on its feet

Researchers have developed a paper-thin foot membrane that lets crawling microrobots harvest electricity directly from the ground beneath them, ditching heavy onboard batteries by turning metal and silicon surfaces into an active power source.Tiny microrobots could slip through rubble to locate earthquake survivors or inspect the tightest crevices of nuclear reactors, but their biggest hurdle remains remarkably mundane: power. Conventional commercial batteries are simply too bulky, with a 1.7-gram robot burning out after roughly two minutes unless a battery accounts for an impractical 94% of its total weight.Researchers at Fudan University in China have bypassed onboard storage entirely by turning the ground beneath the machine into a power supply.In a study published in National Science Review, the team demonstrated a soft, paper-thin membrane attached to a robot's footpad that generates electricity on the fly as it treads across active surfaces like aluminum, zinc, or silicon. The system effectively turns every step into an instantaneous electrochemical generator. An electrochemical polymer membrane enables the continuous operation of the microrobots.Science China Press The mechanism relies on a polymer gel sheet measuring just 135 µm (0.0053 in) thick – roughly the diameter of a human hair – chemically grown directly onto the robot's feet. When the foot contacts a compatible surface, it behaves like an open-air battery. The metal floor donates electrons while the membrane pulls oxygen and moisture from the surrounding air to complete the circuit. Power flows immediately on contact and cuts out the second the limb lifts.In laboratory trials, a 3D-printed crawler measuring 6.7 × 5.7 cm (2.6 × 2.2 in) trotted for 150 days intermittently, clocking over 10,000 steps without voltage dips. It eventually crossed the one-million-step mark while consuming only about 2 g of aluminum. The sticky gel membrane even allowed the robot to scale inclined metal sheets, it withstood temperatures from -20 to 80 °C (-4 to 176 °F), and it successfully powered an onboard LED and Bluetooth transmitter.The concept is not without real-world constraints. The footpad cannot extract energy from chemically inert surfaces such as plastic, glass, soil, or organic tissue, prompting the team to add a small onboard supercapacitor to buffer power across dead zones. Crucially, exposure to atmospheric carbon dioxide and continuous corrosion gradually degrades the internal electrolyte, requiring researchers to manually replenish potassium hydroxide to keep it running.The breakthrough arrives amid a broader push toward multifunctional synthetic skins. Roboticists around the world are turning outer coatings into sensory networks, ranging from Stanford University's self-healing layered skins that autonomously stitch back together after cuts, along with Cambridge and UCL's pain-sensing flexible hydrogels, to humanoids like Generative Bionics' Gene.01, which senses touch and thermal proximity to work safely alongside humans. At the University of Tokyo, researchers have even grown living human skin over robotic digits to wrinkle naturally and mend wounds with collagen.By upgrading synthetic skin from a passive sensor into an energy harvester, the Fudan team offers a clever alternative to deadweight batteries. If researchers can automate electrolyte maintenance, miniature explorers might finally cut their umbilical cords for good – quietly crawling through ventilation shafts, substations, and nuclear reactors to gather critical diagnostic data right at the source.Source: Science China Press via EurekaAlert