ORIGAMI Project yields novel touch wheel from high-precision 3D forming

 

A pioneering touch slider enabled by multiple layers of printed electronics and combined with innovative heating, thermoforming and injection moulding technologies, was developed in the publicly-funded Innovations with Organic 3D Electronics (ORIGAMI) project, which brings together various German and Japanese technology companies and institutes. The demonstrator is equipped with 14 LEDs, has a drawing depth of 10mm, and a touch functionality. This engineering feat enables the fast sheet-to-sheet production of injection-moulded 3D electronic devices, reducing the necessary productions steps and overall weight of the finished devices. This achievement in printed electronics is expected to find its way to automotive interiors, white goods, large electronic appliances, and medical equipment, among others.

The ORIGAMI project is funded by the German Federal Ministry of Education and Research and coordinated by Organic Electronics Saxony (OES). Dr Jonas Jung, project leader at OES, said: “This exciting demonstrator is a great result of the ORIGAMI project, showing the innovative strength of the longstanding German-Japanese collaboration. By utilising novel production technologies the demonstrator showcases new application possibilities for printed electronics.”

Heraeus produced Clevios conductive polymer pastes, which are PEDOT:PSS-based formulations for screen printing. They are used to print transparent conductive electrodes, used in many devices and new technology applications such as capacitive touch sensors. They can be thermoformed into three dimensional shapes and are flexible, transparent and highly conductive. Within the ORIGAMI project, Heraeus could further optimise the Clevios paste to enable stretching the transparent electrodes by more than 100%.

Fujikura Kasei provided two DOTITE inks – an electrically conductive ink and an electrically insulating ink – which are used to screen-print thermoformable multi-layer conductive traces on polycarbonate. They are designed for a high degree of deformation when thermoformed with minimal loss of conductivity. They are also able to withstand the injection moulding process, allowing them to be used to create exciting in-mould, printed electronic devices.

TES Frontdesign printed the touch sensor foils and equipped the LEDs. The challenge they faced was to print with the new developed silver and isolation inks onto a stretchable foil. TES Frontdesign developed, together with the Fraunhofer Institutes and adSphere, different sensor and connection line designs to use the stretchable properties of the inks for the sensor foils. An additional challenge was the gluing of the LEDs. The touch foils have touch sensor areas in a form of a ring. TES Frontdesign developed hard- and software to show the functionality of the touch sensor areas on the computer screen.

Fraunhofer IVV developed the geometry of the demonstrator. Care was taken that no critical elongation maxima are existing. Furthermore, it was up to now not possible to form parts when the electrical components are mounted around the forming area. A new technology has been developed for this purpose, which allows components to be taken into account during forming. For successful forming, material characterisations were also conducted in order to use the optimum materials and forming parameters for the forming process. Nevertheless, harsh process conditions of thermoforming and subsequent injection overmoulding require reliable mounting technologies with sufficient bond strength.

Fraunhofer IZM developed fully in-line compatible SMT processes based on thermoplastic substrates, printing and adhesive bonding. Accelerated ageing tests of overmoulded test coupons, including a variety of different circuit materials and components (stretchable Ag-paste, conductive polymers, 0201-, 0402-, 0603-, 1206-, VSOP8-components) have validated reliable functionality within the chosen test environments (thermal cycling, thermal storage, temperature humidity).

To demonstrate new technologies and to present the new product and design options, Adenso implemented a demonstrator system with which these technologies were included in a roll-to-roll process. This enables the production of 3D electronics in a cost-effective process suitable for the masses. Through an extensive series of tests, Adenso has optimised the process in such a way that functional models with a moulding depth of up to 14mm could be produced.

adSphere has redefined input devices: By reshaping directly from the substrate, operating elements can be made gap-free, hygienic and watertight. This replaces the conventional processes in which operating elements often consist of many individual components. Thanks to the capacitive touch surfaces and the slider elements, many functions can be combined into just one part in the future. The new input devices are therefore ideally suited for applications in medical technology, in the field of white goods or the automotive industry.

Accomplast, a plastics processor, used its technology for the overmoulding. Sub-assemblies are now replaced by direct integration into individual plastic components through overmoulding. The challenge was to achieve resistance of the printed electronics to the temperatures, pressures and sometimes abrasive effects of the plastic flowing into the printed structures and the applied electronic components. Narrow process windows in the injection process were indispensable. Due to the close cooperation between the producers of printed electronics and Accomplast as a plastics processor, the now-available demonstrators could be produced as representative results.

Caption: Thermoforming and printed electronics are combined in the production of the novel touch wheel (photo: adSphere)