The touch of a butterfly can be felt even by a robot that using artificial skin. The sensitive skin used in robotics is a synthetic substitute for human skin used to feel the pressure exercised on a surface or the temperature.
Since in the 1970s when the first synthetic skin was revealed at MIT by John F. Burke, the sensitive layer went through many processes of improvements reaching a level of sensitivity closer to human skin.
Using elastic layers the sensitive sensors can take any shapes and are very thin. Most of these examples of artificial sensitive sensors use carbon, silicon, and a lot of innovation to create a real substitute for human skin.
A robot dressed in a suit of artificial skin is closer than ever by people. I like the idea to use this sensitive technology for both industrial and social robots. Used in industry the robots become more friendly and can work together with humans without suffering injury on both sides. Just using this artificial skin for service robots can understand the benefits. To defense the robot from dust, rain and other actions that could prejudice the structure built from metal and silicon and to a friendly human-robot interaction, the artificial skin plays an important role in the development of robots.
In this article, I reviewed the latest artificial skin innovations which can be used or already used in robotics.
01. Artificial Skin With Carbon Nanotubes
This is not the first time when the properties of carbon nanotubes were used to create wonderful things and this time for robots. Researchers from the Department of Energy Berkeley Lab designs the first artificial skin made from semiconductor-enriched carbon nanotubes. The technology can be used to create flexible and thin artificial skin at large-scale and with a lower price.
The arranged hexagonal patterns of graphene was the solution of researchers. A carbon nanotube is flexible and at the same time has strong properties. A great challenge for researchers was to purify the carbon nanotubes until a value of 99 percent. To purify the carbon nanotubes was necessary since the transistors has to be a good conductor of electricity.
The final product is a matrix of transistors built using a sheet of polyamide, silicon, and aluminium oxide. The prototype used in the test was a 24-square-centimeter sensor and the result can be seen in the picture attached. Using plastic to build electronics open the roads to use in future 3D printers to build artificial skin.
At a resolution of 96 pixels, the robot can feel for small to large objects.
02. Artificial Skin for Industrial Robots
Using artificial skin inside industry can create a friendly environment for humans along robots. Researchers from Robotics Laboratory at Laval University designs artificial skin used in the industry to maximize the human-robot cooperation. The technology interprets the touch as a command from a human and send to the robot brain a signal to respond to requests. This is a simple way to reduce the accidents in factories where humans works shoulder to shoulder with robots.
The artificial skin has a sensitivity to pressure, is flexible, and has a lower price.
03. Touch-sensitive Plastic Skin
The researchers use almost any material to produce new and innovative technologies. Researchers from Stanford build the first material used as skin that is self-repairing at ambient temperature. This technology can open new roads for electronics that resist to damage and repair themselves.
Inspired by human skin and its properties, the researchers create a good environment for robots to feel precisely and efficiency what they touch or when are touched. The skin has the role to feel and send information about pressure and temperature to the brain from where new commands are coming.
In the same material the chemist and researchers pack two features: the artificial skin feels even the weakest pressure forces and restore the initial form when the material is cut.
Every technology has its weaknesses. The touch-sensitive plastic skin cannot work at high temperatures, or subjected to a cut, the material can have a modified structure. One of the most important property of an artificial skin must be the electrical conductivity. Unfortunately, this properties is not widespread in this artificial skin, but was improved using tiny particles of nickel. The nickel increases the material conductivity and also allow the artificial skin to be flexible.
About the self-repairing property of the material, researchers explain the case when the material is supposed to a cut. The bonds between molecules can be easily broken, but supposed to a temperature with a value of room temperature, the bonds can restore the structure of material closer to the initial structure. One interesting feature is that the material can be cut for infinite times in the same place.
When a pressure is applied on material surface, the distance between nickel particles is changing and at the same time the electrical resistance changes its value. Using the value of electrical resistance can be easily found the value of pressure and tension in the artificial skin.
This material has a great potential for commercial use in the robotics field with improvements to material thickness.
04. Most Sensitive Electronic Skin
At what would be good an artificial skin if it cannot feel the touch? The researchers from Seoul National University develops the most sensitive artificial skin that can feel a drop of water. In addition to the fact that the artificial skin is very sensitive, it can be produced at a lower price allowing an extensive use in the robotics field.
The nature is the most advanced source of inspiration for researchers. This time they develop a sensitive skin after a deep study of the microscopic cilia found in the human body in different places including ears, intestines and kidneys. The result is one of the most sensitive artificial layers with a very fine level of detection. To give you an idea the material can detect a human pulse.
Even it has a simple design, the sensitive skin incorporates the nanotechnology. Using nanotechnology the researchers creates on a polyurethane acrylate a forest of microscopic strain gauges with 100 nanometers in diameter. The final product is created using two polyurethane acrylate layers that are coated using silicone polymer polydimethylsiloxane (PDMS). Between these two polyurethane acrylate layers the nano-fibers are mesh, rub or bend when a pressure is added. In this case, the value of current in the skin is changed and can be detected the area when the electrical resistance is changed.
Back to the polymer nano-fibers, these are so tiny that has a diameter of 60 times lower than a human hair.
In tests the skin responds very well and keep the sensitivity for many cycles. Since it is very sensitive, durable, and has a low cost of production, this artificial skin is one of the best technologies that can be used in robotics to create the sense of touch for robots.
05. Smart Fingertips
The technology called Smart Fingertips was developed in the labs of the University of Illinois at Urbana-Champaign and is designed to detect the temperature, the pressure on surfaces, and other characteristics.
The layer created from a polymer material called Polyimide is very thin, flexible, and can be added to robotic hands. The touch sensor changes its electrical current when pressure is applied to the surface of the sensor.
Built from gold conductive lines, the sensor is embedded in a flexible polymer layer. The sensor is smart, and this is because it can be used to feel and in the same time to create sensations of feelings. Feeling things is not the single features of this sensor. It can be improved with other type of sensors to detect vibrations or motion.
Used in robotics, the artificial skin can be designed to fit in any part of a robot.
06. Transparent Artificial Skin
The concept of smartphones was taken by a team of researchers from Stanford and creates a transparent touch sensor that is resistant to repeated deformation. Again, the nanotechnology was used to create a sensitive layer called artificial skin.
On a layer of silicone was added a large number of carbon nano-tubes with the ability to stretch in any direction. The sensor was designed using two conductive layers. When a pressure is exerted on the sensor layer or layers, the distance between two parallel plates is changed and the capacitance of the sensor is changed. Measuring the capacitance of the sensor and then applied a formula, the exercised pressure on that surface can be measured.
The sensitivity of the sensor is not on the highest peaks and the next phase is to be increased to feel the lowest pressures on the surface.