A plastic robotic arm powered by visible light that contains no electronic parts has been developed by Chinese scientists.

The rapid development of robots in the past 50 years has greatly changed our lives in industry, agriculture, and many related areas. So far, most robotic devices used as micromachines and muscle-like actuators require electric energy sources and metal components such as wires and electrodes which can make them low in flexibility, easy to corrode and not very biocompatible.

Now Yanlei Yu and colleagues at Fudan University in Shanghai have made a plastic robotic arm capable of picking up and moving small objects without any physical or electrical contact. All of the device's power comes from the visible light source which activates contractions in the robotic arm and no metal parts are used.

The active parts of the device are made from double-layered strips of two different polymeric materials, one is a special cross-linked liquid crystalline polymer (CLCP) and the other is an inactive polyethene. The CLCP is a special kind of electro-active polymer (EAP) - often referred to as 'artificial muscles'. On irradiation with blue light, the CLCP material contracts against the static half of the bi-layer, made of inactive polyethene, causing a bending motion. The bend is fully reversible allowing the arm to flex in the middle like an elbow and to grip at the end like a hand. The device also has an active 'wrist' that bends under irradiation.

Yu's microrobot can lift objects weighing ten times the combined mass of the active hand, wrist and elbow polymer parts and the force-per-unit-area generated (300kPa) compares to that produced by muscles in the human body (320kPa). As light energy is safe, abundant, renewable, and clean, Yu sees it as an ideal potential substitute for electrical power. 'Our research focuses on how to convert the light energy directly into 'real mechanical work,' she says.

Yu, believes that this type of robot could be used in micromanufacturing. Robots that pick and place microelectonic components are currently widely used on assembly lines and Yu envisages a future for light driven robots in similar roles. 'Maybe one day when the sun rising up, light-driven microrobots will work regularly doing picking and placing jobs in industry or in our daily life,' she says.

'[This work] presents unique significant advances in both materials design, using visible light activation instead of UV, and device design with unique bimorph structures,' comments Patrick Mather, an expert in functional polymeric materials at the Syracuse Biomaterials Institute. 'Indeed, the field of smart polymers is transforming from studies of composition variation to more device-based research and this will certainly lead to such applications as the robotic platform envisioned by Yu,' he adds.

James Hodge 

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