Abstract
Wearable electronic devices are evolving from current rigid configurations to flexible and ultimately stretchable structures. These emerging systems require soft circuits for connecting the various working units of the overall system. This paper presents fabrication of soft circuits by electrohydrodynamic (EHD) inkjet-printing technique. Multi-nozzle EHD printing head is employed for rapid fabrication of electric circuits on a wide set of materials, including glass substrate (rigid), flexible polyethylene terephthalate (PET) films, and stretchable thermoplastic polyurethane (TPU) films. To avoid the effects of substrate materials on the jettability, the proposed multi-nozzle head is equipped with integrated individual counter electrodes (electrodes are placed above the printing substrate). High-resolution circuits (50 ± 5 µm) with high electrical conductivity (0.6 Ω □−1) on soft substrate materials validate our well-controlled multi-nozzle EHD printing approach. The produced circuits showed excellent flexibility (bending radius ≈ 5 mm radius), high stretchability (strain ≈ 100%), and long-term mechanical stability (500 cycles at 30% strain). The concept is further demonstrated with a soft strain sensor based on a multi-nozzle EHD-printed circuit, employed for monitoring the human motion (finger bending), indicating the potential applications of these circuits in soft wearable electronic devices.Graphic
Highlights
Inkjet printing, as an additive manufacturing technology, empowers fast prototyping of complex components for numerus applications, including electronics [1, 2]
Many inkjet printers established with diverse actuation mechanisms such as piezoelectric, thermal, and aerosol are extensively employed in the electronics manufacturing
To make the EHD inkjet-printing technology commercially competitive for the additive manufacturing industry, we present an EHD inkjet-printing approach that employs a printing head comprising of five nozzles with integrated counter electrodes to simultaneously print on a variety of substrate materials without modifying the experimental parameters
Summary
As an additive manufacturing technology, empowers fast prototyping of complex components for numerus applications, including electronics [1, 2]. It offers several unique advantages for the fabrication of electronics as compared to conventional electronic fabrication techniques that employ several expensive and time-consuming steps such as lithographic patterning, chemical or physical vapor deposition of functional materials, and dry/wet etching to realize the device structures [1, 3]. The aforesaid printers are commercialized, yet, because of several inherent challenges of low resolution, head blockage, and overheating of functional inks, a novel inkjet-printing technique established on EHD atomization is an important research subject for numerous researchers in academia and industry [8,9,10]. Despite all the advantages offered and initial success of EHD printing in fine patterning, its low throughput is an important limitation
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