Traditional robots, such as those used in industry, can precisely repeat automated procedures and lift heavy objects. Yet, they are too stiff and heavy for delicate work and human connection. Soft robotics research focuses on developing robots built of supple, organic materials and adaptable technical components. Material scientists at Kiel University have recently created a unique soft conductive material.
Unlike ordinary soft conductors, it has remarkably stable electrical characteristics even when deformed. This is caused by the material’s unique structure and a thin, insulating layer made of nano-scale particles. The study’s findings were published in Advanced Functional Materials’ most recent article.
Even when deformed, electrical resistance remains constant
Unlike traditional robots, humans and animals can perform fluid and precise motions and adapt them to their environment. Soft robotics, which takes its cues from nature, uses carbon-based elastic, organic materials rather than traditional, rigid metals. Soft robots also require flexible electrical cables for their sensors and actuators to communicate with one another.
“Conventional metal conductors are effective at carrying electricity but are too rigid for flexible components. They alter their electrical resistance when deformed, which impacts their employment in soft robotics,” Dr. Fabian Schütt, the chair of functional nanomaterials at Kiel University, is the leader of the junior research group multiscale materials engineering.
In contrast, the material’s resistance, which Schütt and colleagues at Kiel University’s Institute of Materials Science created, holds steady as it is distorted. Igor Barg, a Ph.D. researcher at the Chair for Multicomponent Materials and the article’s primary author, claims that even after 2000 cycles at 50% compression, the initial mechanical and electrical properties are preserved over long-term cycling.
They developed a material made of tiny wires that resembles a dark sponge by integrating many specialties under Kiel University’s Priority Research Area KiNSIS (Kiel Nano, Surface and Interface Science). An electrically conductive polymer’s microtubes are linked together to form the wires. The tiny network structure makes the material incredibly light and highly elastic.
A nanoscopic insulating sheet shields the material’s electrical properties.
“Stretchable, sponge-like conductors have been the subject of years of research. But, the so-called piezoresistive effect means that as soon as they are distorted, their resistance also alters, “explains Barg. The team covered their material with a non-conductive, nanoscopic thin coating of polytetrafluorethylene to prevent this effect (PTFE).
You can consider it to be a standard power cord, explains Barg. The layer stops the wires from making new electrically conductive routes when compressed by keeping them from directly touching one another. As a result, even with significant deformations, the resistance is constant. The insulation also strengthens the wires’ mechanical durability and shields the electrical components from outside influences like dampness.
This highly porous framework construction requires a unique coating method. The Chair for Multicomponent Materials’ Functional CVD Polymers junior research group is led by Dr. Stefan Schröder, who also works with the newly-initiated chemical vapor deposition (iCVD).
This allows for the conformal coating of materials with complicated structures and surfaces: A chemical reaction is triggered by mixing several gases in a reactor, and the material to be coated starts to develop a thin polymer coating. The wires continue to be elastic, and the material’s overall weight barely changes because the coating is only a few nanometers thick, according to Schröder.
It is also possible to use these applications in medical technology.
The framework structures in this example, which can be up to several cubic centimetres in size, “demonstrate very well how we can use a nanoscale coating to change the attributes of our framework structures and even generate whole new functionalities,” adds Schütt.
Future commercial applications, such as those in the energy storage or medical technology, may be made practical by integrating our technologies, says Schröder. They currently aim to explore these possibilities in other collaborative research projects.
