Stretchable inkjet-printed electronics on mechanically compliant island-bridge architectures covalently bonded to elastomeric substrates

Herein, we present an approach that allows versatile combination of inkjet-printed electronics and stretchable substrates. For this, we created a hybrid platform made out of stretchable Ecoflex covalently bonded via silane monolayers to flexible polyethylene terephthalate islands interconnected by bridges. The islands served as platforms where conductive lines, capacitive sensors and electrochromic devices (ECDs) were fabricated by inkjet printing. The robustness of the approach is highlighted by the minor influence of strain on the conductivity of printed Ag electrodes, which changed the resistance only by 1.3% at an applied strain of 50%. Furthermore, we demonstrated capacitor sensors capable of responding to strain changing their capacitance from 0.2 to 1.6 pF. To further show the applicability of the approach for multilayer/multimaterial optoelectronic elements, we processed ECDs capable of displaying information on the stretchable platform. Thus, we demonstrate how this digital and additive concept can be applied for the scalable integration of printed optoelectronic devices onto stretchable systems without relying on lithographic processes

Biodegradable inkjet-printed electrochromic display for sustainable short-lifecycle electronics

The fabrication of electronics on the basis of biofriendly materials aims to counterbalance the negative trends conveyed by the short life-cycle of electronics. Furthermore, these materials open the possibility to develop optoelectronic technologies which will be in contact with the human body. In this work, we present an electrochromic display fabricated by resource- and energy-efficient digital printing techniques. The biodegradation of the device is certified under the ISO 14855 standard. The display comprises of a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) electrochromic layer, a gelatin-based electrolyte and Au electrodes deposited on a cellulose di-acetate substrate. We investigate the impact of various naturally sourced ionic species on the ionic conductivity of the electrolyte and the figures of merit of the display. The printed devices show an electrochromic contrast of 32 ± 4% and switching times of 3.0 ± 1.4 s, comparable to the spincoated reference devices. The utilization of inkjet printing enables the fabrication of different device designs with individually addressable pixels. The display can be worn innocuously on the skin without loss of performance thanks to the self-adhesion properties of the gelatin hydrogel. The present work highlights the use of industrial relevant technology for the fabrication of truly ecofriendly optoelectronic systems

Color‐Selective Printed Organic Photodiodes for Filterless Multichannel Visible Light Communication

Future lightweight, flexible, and wearable electronics will employ visible-lightcommunication schemes to interact within indoor environments. Organic photodiodes are particularly well suited for such technologies as they enable chemically tailored optoelectronic performance and fabrication by printing techniques on thin and flexible substrates. However, previous methods have failed to address versatile functionality regarding wavelength selectivity without increasing fabrication complexity. This work introduces a general solution for printing wavelength-selective bulk-heterojunction photodetectors through engineering of the ink formulation. Nonfullerene acceptors are incorporated in a transparent polymer donor matrix to narrow and tune the response in the visible range without optical filters or light-management techniques. This approach effectively decouples the optical response from the viscoelastic ink properties, simplifying process development. A thorough morphological and spectroscopic investigation finds excellent charge-carrier dynamics enabling state-of-the-art responsivities >10² mA W⁻¹ and cutoff frequencies >1.5 MHz. Finally, the color selectivity and high performance are demonstrated in a filterless visible-light-communication system capable of demultiplexing intermixed optical signals

Active matrix-based pressure sensor system with a 4 × 16 printed decoder designed with a flexible hybrid organic process design kit

The innovative field of printed sensor with a demand for high accuracy, sensitivity and durability has enabled a wide application area in sensing, healthcare etc. A large-area printed sensor system on a flexible foil substrate emplying p-type organic field-effect transistors (OFETs) is presented. Thereby, the OFET is fabricated through a hybrid manufacturing process, including photolithographically structured source- and drain-electrodes, ink-jet printed organic semiconductor, and spin-coated dielectric. Moreover, a dedicated device model, derived from the variable range hopping model, is developed and integrated together with process related design rules, materials properties and geometric information into a comprehensive process design kit (FH_OPDK). The FH_OPDK is integrated in a commercial electronic design automation tool and is used to design and perform post-layout simulations on logic gates, such as INV, NAND2, and NOR2 as well as circuitry such as ring oscillators and a 4 × 16 digital decoder. Several circuit topologies have been tested and evaluated in a detailed model-hardware correlation analysis. Finally we have optimized logic gates and the decoder in a PMOS only, pseudo CMOS design style. To demonstrate the feasibility of the full sensor system in hardware a 16 × 16 active matrix pressure sensor on a flexible substrate integrated with a 4 × 16 binary decoder was fabricated and tested. We have integrated our flexible hybrid sensor system with a PCB board and a microcontroller to demonstrate the hardware readout platform capable of detecting the weight of objects and visualizing a digital map of applied forces