Stretchable electronics has attracted much interest recently because of its potential applications in the area of wearable electronics and healthcare. Highly elastic polydimethyl siloxane (PDMS) has been for decades a widely used material in prototyping purposes. It enables the realization of a variety of mechanical and optical functions besides being a substrate for other processes or applications. As a substrate, PDMS enables high stretchability and easy integration of other parts made of PDMS. In this work, we demonstrated a high-volume production of stretchable electrical interconnections on PDMS substrates. We used roll-to-roll (R2R) rotary screen printing that has been conventionally applied in high-throughput fabrication of electronics on flexible, but not stretchable, substrates. We demonstrated silver interconnects whose conductivity remains sufficient for signal transmission, for example, in sensor structures under repeated 20% strain over 100 cycles. We also demonstrated R2R compatible PDMS encapsulation of electrical interconnections that increased the strain repetition durability by a factor of 2.

Freedom of design that was introduced as organic photovoltaic (OPV) modules were fabricated by printing. As proof-of-concept, we show OPV leaf fabrication in A5 size using gravure and rotary screen printing processes for the main active layers of the OPV structure. These printing methods allow direct printing of any kind of arbitrary, two-dimensional shapes including patterning of the electric contacts thus post-patterning stages are not needed. Fabrication of custom-shaped OPV modules requires detailed information about the technical boundaries set by the manufacturing process and materials which in turn influence the layout design and R2R upscaling. In this paper, we show custom-shaped OPV modules, patterned directly in a shape of a tree leaf with an overall size of 110 cm2 and an active area of 50 cm2 providing a power conversion efficiency of 2.0% and maximum power of 98 mW.

Novel continuous and mass customizable lightemitting diode (LED) lighting foil system, capable to produce adequate lighting levels for general lighting, was designed, processed, and characterized. Lighting element substrate was processed by roll-to-roll (R2R) printing using silver ink and automatic bonding of LEDs and current regulators on polyethylene terephthalate (PET) substrate using isotropic conductive adhesive (ICA). Demonstrator consisting of two basic lighting elements contained 98 LEDs and produced 860 lm when running with 25 mA operational current through the LEDs when using total electrical driving power of 8.4 W. Measured power conversion efficiency of the demonstrator was 31 % and efficacy 102 lm/W. Element produced 460 lx illumination level measured by an illumination level meter at element's central axis at distance of 1 m. At a distance of 2 m, illumination level was 110 lx, respectively. Temperature measurements with T3Ster thermal characterization instrument showed that when driving LED with maximum nominal driving current of 100 mA, LED junction temperature was about 120°C, when lighting element was in air in room temperature. Accelerated environmental stress tests consisting of 500 cycles from −40 … +80°C in aging oven and 1000 h in +60°C/95 % RH climate chamber were performed to test samples without any failures. In addition, over 700 bending cycles using 20 mm bending radius were performed to test samples without any failures, so bonding of LEDs were shown reliable according to these tests. Achieved results proved that thin, flexible, and large area high luminous flux lighting elements and systems can be processed based on plastic foil manufactured using R2R silver ink printing and R2R automatic bonding of LEDs and regulator components using ICA on that foil.

No abstract

No abstract