Hot fingers: robotic hand moves with liquid crystals and graphene
Actuators based on liquid crystals and graphene move a soft robotic hand. The hand could be used in medicine.
The robot fingers move through heat-excited liquid crystals.
(Image: Laura van Hazendonk)
A team of scientists at Eindhoven University of Technology has developed a soft robotic hand based on liquid crystals and graphene. According to the researchers, the hand could be used in medicine, for example.
Hard robots are not particularly suitable for surgical procedures because they cannot easily reach all parts of the human body. Soft robots can do this and work more gently for the patient, but they often cannot be controlled and deformed precisely enough.
The researchers from Eindhoven therefore looked for a solution to the problem and built a soft robotic hand. As they describe in the study "Hot Fingers: Individually Addressable Graphene-Heater Actuated Liquid Crystal Grippers", which was published in ACS Applied Materials & Interfaces, the actuators of the robotic hand they developed essentially consist of liquid crystals and graphene. Both are organic materials, which makes them safe to use during operations on humans.
Heating liquid crystals
The researchers make use of the special properties of liquid crystals. Depending on how they are excited, they can behave like a liquid or a solid. The molecules can be arranged in the liquid in such a way that a regular pattern or structure is created so that the liquid crystal material becomes solid. The scientists used these abilities to build a soft robotic hand with four movable fingers.
The liquid crystal network (LNC) actuators required for this work with graphene-based heating elements to initiate the deformation process. The conductive graphene is used to produce conductive paths through which electricity is sent. This emits heat so that some of the molecules in a liquid crystal finger can be changed from an ordered to a disordered structure. In practice, this causes a finger to deform. If the current is switched off and the finger cools down again, the finger returns to its original state.
According to the scientists, the heating elements turned out to be the biggest problem to be solved. This is because the current supply had to be regulated very precisely in order to be able to change the liquid crystal layer. It was important to use voltages that were safe for humans and the actuators. Otherwise, the actuators could have overheated and burned.
Robotic hand for very light objects
The actuator developed by the researchers works with less than 15 volts. The robotic hand equipped with it is able to lift objects with a mass of between 70 and 100 milligrams. This may not seem like much at first glance, but it is often sufficient for medical applications in which tiny tools are used, small implants are moved or small amounts of biological tissue are removed.
The researchers see the result of their scientific work more as an inspiration to use similar LNC actuators for biomedical and surgical applications. They are now planning to create a fully 3D-printed robot in which the liquid crystal layer is printed directly into it. In the current robotic hand, the scientists still had to cast the layer into a mold. The graphene layer was produced using a printing process. The scientists have already shown that printing liquid crystals is possible in principle, but still need to develop a process to implement this in a fully printed robot.
(olb)