A new soft robotic hand made of liquid crystals and graphene may be able to support operations in the future. Because the robotic hand is made of organic materials, it can be used safely in operations.
The robot hand was developed by researchers at Eindhoven University of Technology (TU/e) led by PhD student Laura van Hazendonk, Zafeiris Khalil (as part of his master's research), Michael Debije and Heiner Friedrich. Soft robots are not new. However, many current soft robots contain metals. This makes applications in aquatic environments - such as the human body - limited.
Researchers have succeeded in developing a soft robot made of graphene and liquid crystals, which are both organic materials. According to TU/e, this offers possibilities for the safe use of the robot hand during operations.
Robots increasingly widely used
The use of robots in operations is not new. For example, surgical robots assist in hospitals during operations, enabling minimally invasive surgery, among other things. The researchers also point to the wide use of robots for other applications, ranging from factories to domestic environments.
"Society has become dependent on robots and we are inventing new ways to use them," says Laura van Hazendonk, PhD researcher in the Faculty of Chemical Engineering and Chemistry. "But for new ways to use them, we need to think about different types of materials with which they can be made."
This specifically involves liquids, gels and elastic materials. In all cases, these materials are easily deformable. "Usually robots are made of metals, which are rigid and hard. But in certain applications, hard robots limit performance," says Van Hazendonk. "The solution is to think soft."
Soft robotics
Soft robotics - also known as soft robotics - are robots made of materials that can deform in certain situations, while their behaviour resembles that of traditional 'hard' robots.
Van Hazeldonk points to the possibilities within surgery, where she believes the impact of soft robots could be great. "For a surgeon, many operations can be complex and delicate and therefore require specific dexterity. Sometimes that is just not possible and then they resort to robots. But rigid robots cannot easily reach some areas either. That's where soft robots can make a difference. Our goal is to provide the potential new helping hand for, for example, clamping and suturing devices used during operations," Van Hazeldonk explains.
Combination of graphene and liquid crystals
The researchers combined graphene with a liquid crystal, which is a similarly deformable material. From this combination, they manufactured a soft robotic hand with four controllable and deformable 'fingers'.
A liquid crystal can behave as a liquid or solid depending on how it is disrupted. If the material flows, it behaves like a liquid. In special situations, the molecules can arrange themselves and create a regular pattern or structure. Similar to a crystal you would see under a high-powered microscope in a solid material. "The ability of liquid crystal materials to behave like this is perfect when it comes to making soft robots," Van Hazeldonk said.
Liquid-crystal network actuators
From the combination of graphene and liquid crystals, researchers have created an actuator. Actuators are responsible for controlling and regulating movement in robotic systems. Whereas a regular actuator is powered by electricity, air or a liquid, this is different with the newly developed liquid-crystal network (LCN) actuators. The actuators deform thanks to the effect of heat on graphene-based heating elements or spores in the fingers of the gripper.
"When electric current runs through the black graphene tracks, the tracks get hot and then the heat from the tracks changes the molecular structure of the fingers from liquid crystal and some molecules go from ordered to disordered. This leads to bending of the fingers," says Van Hazendonk. "Once the electric current is switched off, the heat is lost and the gripper returns to its original state."
Not without challenge
This is not without its challenges. "We had to make sure they reached the right temperature to change the liquid crystal layer, and that this could be done with a safe electrical voltage," he says. Initially, the graphene elements did not reach the right temperatures at safe voltages, or they would overheat and burn the device," says Heiner Friedrich, associate professor at TU/e's Faculty of Chemical Engineering and Chemistry. "This problem and many other important challenges were solved by Zafeiris Khalil during his research for his MSc thesis."
The researchers' actuator operates smoothly at electrical voltages of less than 15 volts. The grippers can lift small objects weighing 70 to 100 milligrams. Among other things, the researchers see opportunities in medical applications such as surgery, where the robotic hand can provide precise and minuscule movements of small tools, implants or biological tissue.
Useful and tangible application
Van Hazeldonk: "I love how our work combines a useful and tangible application. The gripping device is based on fundamental technologies, but the actuator itself could form the basis for a range of future robots for biomedical or surgical applications."
The researchers' research is published in Applied Materials & Interfaces and can be found here.
Author: Wouter Hoeffnagel
Photo: fernando zhiminaicela via Pixabay
