While vehicle interiors might be an obvious target for emerging technologies based on printed/flexible electronics, there are also plenty of opportunities for vehicle exteriors. These range from transparent heaters to solar panels, and benefit from attributes as varied as transparency, conformality, low weight, and tunable absorption spectra.
EVs create requirement for transparent heaters
Cameras and LIDAR in autonomous vehicles or advanced driver assistance systems (ADAS) will always require a clear view of the road. This means ensuring that a transparent cover over the sensor is free of mist/frost is essential. While simple, this requirement is significantly more challenging in an electric vehicle since there is far less residual heat generated than with a conventional combustion engine. A similar argument applies to LED headlights – since they are much more efficient than halogen bulbs insufficient waste heat is generated to melt ice on the headlight covers.
The solution to this challenge is to develop transparent heaters. This can be achieved by embedding printed metal wiring via in-mold electronics (IME), or by using transparent conductors such as silver nanowires, carbon nanotubes (CNTs), or metal mesh. Over time these technologies are likely to fall in price, enabling them to be applied to windows as well, making scraping ice off car windows a thing of the past.
Connected cars require integrated antennas
Vehicles become more connected every year, necessitating multiple antennas to cover multiple frequency bands. One approach is to integrate these antennas into plastic body panels, which could be achieved using either in-mold electronics or by printing directly onto 3D surfaces.
Another non-metallic area of vehicles that can be utilized for antennas is windows. This approach would clearly require transparent conductors. Possible transparent conductor material choices, all of which can be printed, include silver nanowires, carbon nanotubes, fine metal mesh, and even very thin layers of particle free ink.
Hybrid SWIR for ADAS
ADAS and autonomous vehicles will require a continuous stream of information about their surroundings. Such data is likely to originate from multiple sources such as LIDAR, RADAR, and cameras to increase redundancies, an approach known as sensor fusion.
This demand for a range of sensors creates an opportunity for hybrid short-wave infra-red (SWIR) sensors, which require a layer of printed semiconducting material on top of a CMOS readout circuit. The printed layer can either be an organic semiconductor or quantum dots, with the aim in both cases of extending the spectral sensitivity beyond that of silicon into the SWIR region.
Imaging in the SWIR spectral region (1000-2000 nm) is especially desirable for vehicles since light scatters less at a longer wavelength, enabling objects to be identified at longer distances in fog or dust. The incumbent technology for SWIR image sensors is prohibitively expensive, so innovative technologies such as hybrid partially printed sensors are required.
Increase battery life with photovoltaics
While photovoltaics will never be able to power a car continuously over a long journey, they do enable around 30 km of distance to be added each day. This would remove the need to recharge for cares that are only used for short trips around cities, greatly increasing convenience. Furthermore, integrated photovoltaic panels can provide power for ancillaries such as air conditioning when the vehicle is parked without drawing the batteries.
At present, the few electric vehicles with integrated solar panels use silicon photovoltaics as that is the established technology with proven durability. However, emerging thin film photovoltaics such as those based on organic and even perovskite semiconductors are promising alternatives due to their low weight and conformality. The latter is important if solar panels are to one day coat the entire exterior surface of the car, as unlike rigid flat silicon panels, there would be no need to compromise on styling or aerodynamics.
Exterior displays for autonomous vehicles
As vehicles become increasingly autonomous, they will need to interact with pedestrians. After all, glance at the driver to check that they have seen you before stepping in front of a slow-moving car becomes impossible if the car is being ‘driven’ by a computer. One solution to this oncoming challenge is to incorporate a large display on the bonnet of the car that can relay information such as whether it is safe to step in front.
Low-cost printed/flexible displays are ideally suited to this purpose, as low weight, durability, and conformality (including in an accident) are all more important than resolution. Possible approaches include printed LEDs, and mounting LEDs on flexible substrates.
