These are also known as elastic electronics and the underpinning technology involves depositing stretchable electronic components and the whole circuitry on substrates that are flexible and stretchable. Popular examples of these substrates are silicon and polyurethane.
How Are They Made?
Stretchable electronics are made from the same components used in the production of rigid printed circuit boards (PCBs). The only difference is that the substrate needs to be stretchable as opposed to being flexible or rigid. In addition, the preferred material for this sort of production is a polymer.
Now, one question you might be asking is, “How do rigid electrical components become stretchable?” The answer isn’t too farfetched.
When the rigid component has been deposited onto the substrate, the components are then subjected to a high level of mechanical strain whenever there is a flex on the substrate. This then means that the radius of the bend will also stretch in order to accommodate the interconnections and the other components.
You might have heard about elastronics. This is the new branch of stretchable electronics and there are several new applications. One of these is a cyber skin for robots that creates a pathway for sensors. There are also sponge-like electronics that are implantable and can be embedded in the nervous systems.
We shall discuss some other applications of these stretchable electronics in the subsequent paragraph.
Some Applications of Stretchable Electronics
Energy Storage Devices
There are common energy storage devices based on carbon-based materials and they are chosen because they have very high electrical conductivity and surface area. With adequate structural engineering to back it up, the material also makes the energy storage devices stretchable. One considerable shortcoming is the low energy density and specific capacitance and this can be improved if redox materials are incorporated.
In diagnostics, detecting anomalies, and even carrying out corrective surgeries, stretchable electronics are proving useful. For instance, there was a patch that has been developed by researchers from Seoul National University and MC10. This patch is able to detect the level of glucose in the human body via sweat and diabetes medicine (insulin or metformin) can be delivered on demand.
The patch comprises graphene colored with gold particles and it also contains sensors that identify the temperature, the pH level, the glucose level, and the humidity. MC10 is a flexible electronics company that originated from MIT.
Stretchable electronics are also used to create soft robots that can be used to carry out minimal intrusive surgeries in hospitals. This is especially important for surgeries relating to the brain. Remember that the brain is one of the most important parts of the body and every single millimeter is just as important. The structural make-up means that these robots are able to carry out more precise actions when compared to humans.
3D Stretchable Electronics
If you’ve been impressed so far, what is about to come is even more mind-blowing! A team of researchers at the University of California, San Diego came together to build a patch that is worn on the skin and that can be used to monitor vital signals from the body. The range of application varies from respiration to the movement of the body and even to the temperature. The operation is wireless and this patch can even be used to control the arm of a robot.
How big is this device? It resembles a coin.
There are four layers of interconnected stretchable flexible circuit boards and each layer is built on a silicone elastomer substrate. This substrate is patterned with an island-bridge design; a small, rigid electronic part and this can consist an antenna, a sensor, a Bluetooth chip, an accelerometer, a resistor, capacitor, and even an inductor.
Up until now, the major issue with wearable electronics is in creating electrical connections between the stacks as this is a very pressing requirement. These connections are known as vertical interconnect accesses (VIAs) and they are conductive holes that allow passage through the different layers on the circuit.
The issue before now was that this technique wasn’t applicable to stretchable elastomers. But then, the researchers on this project adopted lasers. The idea behind it was that the silicone elastomer was mixed with black organic dye so as to absorb energy from a laser beam. The circuits were then formed on each layer and stacked, hitting some specific points with a laser beam and this created the VIAs.
In the years to come, we can expect the concept of stretchable electronics to have burgeoned even more. With the level of focus and investment, the field is receiving, this should happen sooner rather than later.