The field of soft robotics is growing at an exponential rate, and new discoveries in electrical engineering and material sciences are fueling this growth. Recently, a team of scientist from the National University of Singapore (NUS) have published a paper detailing a newly-discovered metallic material that could revolutionize the way flexible origami soft robots are constructed, as well as how they communicate and affect the environment around them.


Traditionally, soft robots are constructed from flexible materials such as paper, cloth, rubber, or plastic, but this limits their durability and function as well as the type of electronics packages they can carry. Typically these soft robots are fitted with rigid electronic components needed for sensing and wireless communication, but this also limits the motion of these robots. The team of researchers from NUS has demonstrated that very thin carbon-metal compositions can be created that are more durable, more flexible, and can feature built-in sensors, act as heating elements, and even deliver electrical signals, meaning they can also function as antennas to deliver wireless communications.


NUS Assistant Professor Chen Po-Yen (right) and doctoral student Yang Haitao (left) and their team created a new metallic material for soft and flexible robots. Image Credit: National University of Singapore.


The new material consisting of a mixture of metallic ions and common wood ash. For the purpose of demonstration, the team soaked a folded cellulose-based paper soft robot in a solution that contained graphene oxide, followed by a soak in a solution containing platinum metal ions. The platinum soaked paper origami soft robot was then fired in an oven filled with inert argon gas at 800c, and then refired in the air at 500c. The result was a folded soft robot that was made from a thin layer of metal just 90-micrometers thick.


This process is called called ‘graphene oxide-enabled templating synthesis’ and results in a sheet of material made up of about 70-percent platinum and 30-percent amorphous carbon (AKA common carbon ash). This new material is not only highly flexible but is stretchable as well and maintains durability fairly well when flexed numerous times. The team’s research showed that other metals such as gold and silver can be used to form similar materials as well. In addition to the flexible soft robot, the team also used cellulose paper cutouts int the shape of a phoenix as a symbol of the transition the original material goes through to form the new flexible metallic material. 


“We are inspired by the mythical creature. Just like the phoenix, it can be burnt to ash and reborn to become more powerful than before,” said Asst Prof Chen, from NUS Chemical and Biomolecular Engineering.


One application the team sees for this new material is the backbone of new soft robots. This material would allow for strain sensors to be built within the soft robot’s frame without adding any additional weight or extra electronic components. Wireless antennae could also be built directly into the soft robot’s body as well, further reducing the extra components needed to complete the robot. One of the most promising applications, however, is the material’s ability to heat up when an electrical current is passed through it. This could come in handy to de-ice soft robots that might one day navigate pipes to clear clogs or aid in search and rescue efforts in cold climates where the soft robot must be warmed to remain functional. One application I see personally is the ability to provide intense heat to very specific areas of the body via soft biomedical robots. As an example, soft robots could utilize this heating property to cauterize blood vessels that are causing internal bleeding. 


“We experimented with different electrically conductive materials to finally derive a unique combination that achieves optimal strain sensing and wireless communication capabilities. Our invention therefore expands the library of unconventional materials for the fabrication of advanced robots,” said Mr Yang Haitao, a doctoral student at NUS Chemical and Biomolecular Engineering and the first author of the study.


Moving forward, the team is going to focus on adding new functions and features to the metallic backbone, and hope to incorporate electrochemically active materials into the mix to serve as small energy storage devices, batteries if you will, that could help power soft robots that feature these new ultra-thin metallic flexible materials. The team hopes to find success using this method with other materials such as copper and nickel in an effort to lower cost and make mass production easier.