A spray-on antenna is a conductive material that can be sprayed onto nearly any surface to create a thin, lightweight and flexible antenna. Antennas are a key component used in devices that can communicate with one another by emitting and receiving radio signals. In certain circumstances, having an antenna made from rigid materials will limit what electronics could be built into it, which is where spray-on antennas come in. Being able to spray an antenna on a flexible substrate widens the applications of electronic devices.
The concept works using a material called MXenes, which is a chemically stable, strong and conductive material. It's a very thin material that can transmit and direct radio waves. The material can then be applied in a spray-on method similar to the use of an aerosol spray can, and can be used to enable smaller IoT devices, industrial or medical sensors, mobile devices, wearables and other subtle communications devices.
How it works
Spray-on antennas were created by researchers at Drexel University and are composed of a metallic compound call MXene. MXene is a water-soluble compound made of titanium carbide that is very conductive. The material is made of metals with carbon or nitrogen atoms that, in all, are a few atoms thick. Other than titanium, various metals can be used to create spray-on antennas, including molybdenum, vanadium and niobium.
Initially made in a powdered form, MXene is dissolved in water to form an ink or paint-like material which can then be sprayed onto a surface, creating a spray-on antenna in whatever shape is needed. The resulting antenna excels at transmitting and directing radio waves in small layers.
When mentioning antenna thickness, the malleable and nearly imperceptible spray-on material achieves optimum performance near 8-micron thickness, but can be made as thin as 10 nanometers. This is thin enough to be mostly transparent. Successful applications have included wireless communications in water filtration, energy storage devices, structural reinforcement and chemical sensing.
Even though the MXene material was discovered in 2011, its use in wearable devices has been discussed recently.
Having such thin materials, these antennas can be used in smaller, lighter and flexible devices for a variety of uses. Although it's thin and flexible enough to be applied to skin, not enough testing has been done to determine if it is safe and free of consequences, and not many applications of this instance have been explored.
Spray-on antennas and IoT
Spray-on antennas could be very useful for the internet of things (IoT). IoT will commonly use radio-frequency (RF) antennas to communicate with other nearby devices. Having an antenna that can be sprayed onto a surface, which usually wouldn't be possible, could massively improve data-collecting possibilities. For example, a spray-on antenna could be attached to a data center wall to act as a large antenna, or the same technology could be sprayed on to clothes for electronic wearables that can wirelessly communicate with each other. The spray-on antenna is so thin that it would be practically transparent, would add very little weight and would be hard to notice. Antennas could be attached to a number of objects to create a more interconnected environment and network.
Antennas typically come in one of four forms: isotropic, dipole, monopole and array antennas. Isotropic antennas are hypothetical antennas that emit equal signal powers in every direction. Dipole antennas are the more typical and look like a television antenna, consisting of two balanced poles or wires. Monopole antennas consist of a single conductor, commonly a single metal rod. Antenna arrays consist of multiple simple antennas that work together as one.
Normally, conventional antennas require a special shape and nanomaterials such as carbon nanotubes. However, after long periods of research and development, traditional antennas still have trouble in specific areas. For example, nanotube antennas have more of a challenge in being applied and maintaining shape. However, science advances. The spray-on material is more resilient and outperforms nanotechnology, which is popular but more difficult to produce.
Printable antennas are created by using an ink made from conductive materials placed in an inkjet printer. Inkjet printing allows multiple thin conductive layers to be printed with a relatively low edge roughness. The performance of the antenna depends on the thickness and accuracy of the printed areas. Comparatively, it is much faster and easier to create an antenna by simply spraying one onto a surface. In addition, the materials used in printing antennas -- graphene and silver -- are 50 and 300 times less effective at preserving radio wave transmissions respectively compared to MXene.
Spray-on antennas can rival many different types of antennas that are found in modern devices like wireless routers. Their mobile energy efficiency is also up to 10 times more than in current fabrication methods.