Japanese electronics company Murata is looking for partners to come up with IoT applications for a transparent and bendable conductive film.

The material combines transparency, flexibility, conductivity and safety. Furthermore, it realises high workability to draw circuit patterns and other elements easily with diverse methods.

Murata wants partners to discuss ideas using this material regardless of business or industry.

“Given the characteristics of the new material we are developing, I feel it will be possible to apply it to a wide range of applications beyond just electronic components,” said Koyanagi, who helped develop this material. “For example, I feel it will be possible to apply it to automobiles, industrial machinery, medical and health-care devices, and also entertainment and sports.”

Without giving details of the composition and structure of the material, Murata says it has broadly two strong points: it enhances the functions and performance in applications; and it produces usage benefits to companies that develop and produce products to which this material is applied.

As its name suggests, the transparent and bendable conductive film combines conductivity while being transparent. It also has the strong point of not losing those characteristics even when it is bent.

Sheet resistance is lower by approximately two digits compared with the ink of graphene composite materials with a similar level of light transmittance. Compared with a material coated on polyethylene terephthalate (PET) film (a material with relatively bendy characteristics among numerous ITO-based materials), it can achieve characteristics at the same level or only slightly below that. Moreover, the film is in the initial stage of development.

“Its current characteristics have room for further improvement in the future,” said Koyanagi.

Furthermore, it does not lose its characteristics even if bent. Even if it is repeatedly bent so it leaves a clear crease after applying it to a substrate, its resistance value does not change.

Furthermore, it is safe, with low skin sensitisation, and it has no effect if it comes into contact with a living body. It does not cause metal allergies and does not act as an endocrine disruptor that has various adverse effects on living bodies. Therefore, it is expected to have compatibility in applying it to biometric information sensing, wearable devices, disposable devices and other applications.

“It is easy to apply this new material to various applications because it has a high level of compatibility with the coating and processing used in diverse existing processing systems,” said Naruse, who is developing technologies that produce an easy-to-use form such as ink based on the film material.

The film is a hydrophilic material. Accordingly, it can be easily and uniformly dispersed in solvents. Therefore, it is possible to produce inks according to the processing method and to use existing coating and printing techniques to form films with stable characteristics. Specifically, it is possible to draw patterns under normal temperatures and pressures with inkjet printers, stamp and screen printing, spray coating, pen drawing, and other methods. It should also be possible to open up unknown applications by developing never-before-seen coating systems and optimising the ink.

The ability to draw patterns using such diverse processing methods is a strong point that will support expansion of applications. For example, it is possible to draw wiring with fine line widths of several hundred microns by using an inkjet printer. Using such processing methods allows patterns to be drawn as desired without a removal process such as masks or etching. In addition, it is possible to draw just the parts that function as conducting wire.

Therefore, it also realises the effective use of materials and a reduction in the environmental burden.

On the other hand, adopting a method of coating with a spray means it should even be possible to cover substrates with three-dimensional curved surfaces by using the same method as that of coating the body of an automobile. That enables the formation of conductive film on the surface of large and complex objects. Furthermore, it is also possible to add electrical functions to the surface of tools and devices for which the shape itself has meaning.

Another advantage is that post-processing after the pattern formation is simple. It is necessary to add a firing process at 150 to 200˚C for Ag ink that is one of the conventional materials to form transparent conductive film. This is to ensure conductivity by connecting fine Ag particles to each other after drawing the pattern. This film can demonstrate conductivity just by drying water at 50 to 100˚C. Therefore, it is possible to form it on substrates vulnerable to heat damage. It can even be used with natural drying, though this takes time.

The film that has all these points in a material made from micro-ceramics at the nanometre level with the property to carry electricity. The shape of these micro-ceramics is flat. Accordingly, due to the microscopic size and shape of these ceramics, this material exhibits characteristics halfway between metal and ceramics to obtain transparency and conductivity. Its workability is also due to this size and shape. The film after coating and drying the ink in which this material is dispersed enters a state in which the entire pattern drawn is energised because the micro-ceramics lie on top of each other.

Murata says it can be made with its existing production technologies. No rare metals or earths are used.

In addition, there is room for further adjustments to improve the material’s characteristics and to enhance its suitability for applications by optimising the composition, structure and size of the micro-ceramics.