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Exit indium tin oxide! Here come carbon nano buds By Julien Happich Finnish startup Canatu Oy believes it is onto something big with its carbon NanoBuds (CNBs), a hybrid nanomaterial combining the conductive properties of carbon nanotubes (CNTs) and the chemical reactivity of fullerenes (hollow carbon molecules). Officially launched in 2004 as a spin-off from the Helsinki University of Technology, the company’s real breakthrough is its proprietary NanoBud manufacturing and Direct Dry Printing process (DDP), all done in one-step. The unique process performed at ambient temperature and pressure from raw gas materials enables the direct synthesis and patterned deposition of NanoBud films, a few nanometres thin, on any substrate material such as the PET or glass. In 2008, the company received its first seed funding to further develop the material and process, identifying many potential applications in electronics where the NanoBud films could offer better conductivity than indium tin oxide (ITO) while being thinner and truly flexible (beyond the limits of all other materials currently used in the manufacture of flexible displays). “A lot of laboratories offer carbon nanotubes, but typically, their results are not so homogeneous, with large fractions of impurities that must be removed through additional processes”, told us Canatu’s CEO, Risto Vuohelainen. “Then special inks are made from these CNTs to dispense them as an ITO alternative, but the films obtained are not so uniform and not suitable for displays”, he added. “We are able to tune the thickness of the layer we deposit to achieve resistance levels from a few Ohms to several kOhms. In fact our electrically conductive films could also find use in flexible batteries or in supercapacitors, but since 2012, we’ve decided to focus our commercialization efforts towards the capacitive touch-screen industry where our solution could be 20 to 30% cheaper than ITO”. Another claim the company makes is that the NanoBud films have a refractive index of 1.55, closely matching that of both PET and glass, which means less optical reflectivity and better picture contrast when implemented in touchscreens. To reduce unwanted glare, the use of ITO typically requires additional refractive index matching layers which also reduce light output. Canutu is in business to manufacture coated PET and glass sheets flexible electronics in volume, for touchscreen manufacturers to process (patterning the electrodes through laser removal). The electrodes are then connected to off-the-shelve capacitive touch driver ICs the same way they would with ITO. Earlier this month, the company revealed Santa Clara-based TouchTurns as its official partner for producing CNB film based touch sensors, with high-volume manufacturing facilities in China. Now the company is exploiting the mechanical properties of these films further by announcing its CNB In-Mold Film for transparent touch on 3D surfaces. “Because the deposited NanoBuds form a random network on the surface of the substrate, they can easily be stretched in any direction” explained Vuohelainen. “In fact, the nanotubes are not chemically bonded, they can slide and form new connections through Van der Waals interactions, so there are no breakpoints” he added. This makes the film stretchable up to 120% and suitable for back-moulding using standard industrial processes such as Film Insert Molding (FIM). The only tricky part then is to design the capacitive-touch electrodes on the flat sheet before the 3D moulding, to take into consideration the deformations that they will undergo so as to obtain the right touch patterns in 3D. The NanoBud films could find applications in automobile centre consoles and dashboards, in home appliance control panels, remote controls, smartwatches and flexible displays. The company is engaging with several OEM manufacturers and expects the first devices using its technology to hit the consumer market next year, 3D formed touchinterfaces towards the end of 2015. Canatu says some of its partners are working on flexible touch-displays which could hit the market early 2016. www.electronics-eetimes.com Electronic Engineering Times Europe December 2014 19


EETE DEC 2014
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