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Nano/microstructures of compound semiconductors such as gallium arsenide (GaAs) demonstrate enormous potential for advanced photonic technologies as they provide realistic means for miniaturization of optoelectronic devices that feature better performance and low power consumption. However, intimately integrating them onto flexible substrates is challenging and restricts their use in the next generation of applications such as wearables and soft robotics. Herein, printed arrays of well-defined and laterally aligned semi-insulating (undoped) and doped GaAs microstructures are presented to develop high-performance flexible broadband photodetectors. The direct roll transfer printed GaAs microstructures-based photodetectors exhibit excellent performance under ultraviolet and near-infrared illumination, including ultrafast response (2.5 ms) and recovery (8 ms) times, high responsivity (>104 AW–1), detectivity (>1014 Jones), external quantum efficiency (>106), and photoconductive gain (>104) at low operating voltage of 1 V. The achieved performance is among the best reported for broadband photodetectors but with an added benefit of the developed devices having a flexible form factor. Further, the photodetectors show stable performance under mechanical bending (500 cycles) and twisting loading. The developed materials and manufacturing route can enable high-speed communications and computation via high-performance flexible electronics and optoelectronics and transform numerous emerging applications such as wearable systems and internet of things.

The advances in robotics are often inspired by biological systems, which have attained harmonised functionality and efficiency through billions of years of evolution. Motivated by the nature, this paper presents the realisation of sensorimotor correlation using printed synaptic transistor. While such a concept has drawn increasing attention recently, no report on the adopted technology details has been published. To this end, this paper specifically presents the technical elements for the practical realisation of the concept through printed synaptic transistor and the development of the conditioning printed circuit board (PCB) for operating the as-realised device. This work presents a possible roadmap for the future advancement towards e-Skin with neural-like processing capability through a heterogeneous integration of printed circuits on flexible PCBs.

The wearable and flexible sensors are enabling advances in next-generation technologies such as soft robotics, mobile healthcare, internet of things etc. In consequence, novel materials and manufacturing methods have received most of the attention so far. However, with the growing use of these technologies in real applications, other important areas such as mechanical reliability under repeated mechanical deformations also require greater consideration. A few studies covering this aspect have mainly focused on mechanical stress under simple bending conditions and ignored stress evolution under twisting (torsional) movements. The present work studies the influence of different parameters such as carrier substrate dimensions and its material and twisting angles on the stress distribution during torsional movements using finite element method. Following this, highly stretchable strain sensors are fabricated using nanocomposite of carbon nanotubes and Ecoflex™ and tested under various twisting angles. The soft strain sensor possesses excellent repeatable and robust torsional strain detection properties with >100% change in resistance at ±90° of twisting and has shown potential for wearable and robotics applications.

Flexible electronics with high-performance devices is crucial for transformative advances in several emerging and traditional applications. To address this need, herein we present p-type silicon (Si) nanoribbons (NR)-based high-performance field-effect transistors (FETs) developed using innovative Direct Roll Transfer Stamping (DRTS) process. First, ultrathin Si NRs (~70 nm) are obtained from silicon on insulator (SOI) wafers using conventional top-down method, and then DRTS method is employed to directly place the NRs onto flexible substrates at room temperature (RT). The NRFETs are then developed following RT fabrication process which include deposition of high-quality SiNx dielectric. The fabricated p-channel transistors demonstrate high linear mobility ~100±10 cm2/Vs, current on/off ratio >10^4, and low gate leakage (

Innovative methods to fabricate and integrate biodegradable high-grade electronics on green substrates are needed for the next generation of robust high-performance transient electronics. This is also needed to alleviate the growing problem of electronic waste (e-waste). Herein, the authors present the n-channel silicon (Si) nanoribbons-based high-performance transistors developed on biodegradable metal (magnesium) foils using the direct transfer printing method. The developed transistors present high effective mobility of >600 cm2 V−1 s−1, high on/off current ratio (Ion/off) of >104, negligible hysteresis, transconductance of 0.19 mS, and an on-current of 1.6 mA at a bias of 2 V. Further, the transistors show stable device performance under temperature stress (5–50 °C), gate-bias stress, continuous long-term transfer scans for 24 h (>3000 cycles), and aging test (up to 100 days) demonstrating the excellent potential for futuristic high-performance robust transient devices and circuits. Finally, the effect of transience on the electrical functioning of devices on Mg foils (at pH 8) and degradation of Mg foils at different pH values is studied by hydrolysis. The outcome from these experiments demonstrates the potential of direct transfer printing for high-performance transient electronics and also as the new avenue toward zero e-waste.

High-performance flexible electronics developed with resource efficient printing route will transform the way future electronics is manufactured and used to advance applications such as healthcare, Internet of Things, wearables, consumer electronics, etc. Herein, an innovative approach is presented that involves, for the first time, the in-tandem use of contact and transfer printing methods to realize high-quality electronic layers at selected locations on rigid (Si/SiO2), flexible (polyimide), and biodegradable (magnesium (Mg) foils). Superior grade quality of printed electronic layers is demonstrated by realizing transistors and printed UV photodetectors (PDs) employing high-resolution electrohydrodynamic printing. The all-printed PDs show extremely high performance for UV detection, with extraordinary high responsivity (>107A W−1) and specific detectivity (≈1017Jones) values at low UV intensity of 0.1 µW cm−2. Finally, the fabricated PDs on Mg foil are dissolved in deionized water at room temperature. Thus, in-tandem contact and transfer printing has potential for ecofriendly development of transient electronics. Further, the approach allows printing of wide range of nanomaterials and heterostructures or complex superlattice structures, which can open exciting new possibilities for high-performance electronics.

The ability to display virtual objects midair that can be seen without special headwear is an attractive proposition for the virtual reality systems of the near future. Volumetric display technologies have demonstrated this concept, allowing users to view virtual objects with real dimensions in 3D space while enabling some forms of interaction. Developments have been witnessed in haptic feedback technologies which are used to deliver a sensation of touch in the digital world. As virtual environments find more applications in today's world, haptic feedback devices have potential to integrate with virtual reality systems and contribute to a more immersive and interactive user experience. Herein, an air-based haptic feedback device, named Aerohaptics, is presented, which delivers mid-air tactile feedback while the user is manipulating virtual objects within a pseudo-holographic display. The developed system constitutes a cost-effective approach with relatively low complexity and various potential applications as no wearable or handheld peripherals are required. The delivered haptic feedback can be accurately directed at specific locations on the user's hand and its intensity can be controlled to suit various interaction scenarios. Through experiments, localized feedback on the user's fingertips as well as varying feedback force according to the user's hand movement is demonstrated.

Stimulus-responsive soft structures, with biological organs like intrinsic sensing, are needed to enable controlled movements and hence bring the transformative advances in soft robotics. Herein, bioinspired inchworm- and earthworm-like soft structures with intrinsic strain sensing achieved by seamless embedding of a graphite-paste-based sensor material are presented. The developed strain sensor exhibits a record stretchability (900%) and sensitivity (of 103 up to ≈200 and of the order of 105 at around 700% linear strain). With tiny permanent magnets incorporated at the ends of these soft structures, the sensory-feedback-based controlled movements of magnetically driven inchworm- and earthworm-like soft robots are also demonstrated. The presented results potentially boost the prospects of self-sensing in soft robots and advance the field toward cognitive soft robotics.

As a result of the novel Coronavirus disease (COVID-19) outbreak, a surge is witnessed in the demand for mechanical ventilators needed for treating affected patients. With the rapidly virus spreading around the globe, the shortage of ventilators becomes a global challenge and numerus efforts are followed. While industry mobilizes toward producing medical grade equipment, a number of low-cost and less complex emergency ventilators have been developed, mainly through academic and open-source channels, with a hope to meet any temporary needs gap until medical grade ventilator provision becomes sufficient. Herein, the design and implementation of one such emergency ventilator called GlasVent is presented, which an automated version of manual resuscitator device, commonly known as big valve mask or artificial manual breathing unit bag and widely used prior to initiating the mechanical ventilation. GlasVent uses 3D printed mechanical parts, widely available materials and off-the-shelf electronic and sensing devices which can be fast assembled. Furthermore, it requires minimal training and can be operated manually by hands or legs, thus meeting the emergency requirements even in the low-resource settings or regions with less developed healthcare systems. Post-COVID-19, such ventilators can potentially find use in clinical care of a wider variety of patients with injury, pulmonary noncommunicable diseases, and severe asthma etc.

Flexible multifunctional sensors on skin or wearables are considered highly suitable for next-generation noninvasive health care devices. In this regard, the field-effect transistor (FET)-based chemical sensors such as ion-sensitive FETs (ISFETs) are attractive as, with the ultrathin complementary metal oxide semiconductor technology, they can enable a flexible or bendable sensor system. However, the bending-related stress or strain could change the output of devices on ultrathin chips (UTCs), and this has been argued as a major challenge hindering the advancement and use of this technology in applications such as wearables. This may not be always true, as with drift-free ISFETs, we show that bending could also enhance the performance of UTCs. Through fine control of bending radius in the micrometer scale, the mechanically flexible RuO2-based ISFETs on UTCs (44.76 μm thickness) are shown to reproducibly enhance the performance even after 1000 bending cycles. The 1.3 orders of magnitude improved stability (the drift rate changed from −557 nA/min to −28 ± 0.16 nA/min) is observed over a time period of 417.3 s (∼7 min) at fixed biasing and temperature conditions and under different pH conditions. Finally, a compact macromodel is developed to capture the bending-induced improvements in flexible ISFETs. The performance enhancement by controlled bending of devices could generally benefit the rapidly growing field of flexible electronics.

Herein, the design and implementation of a transparent 3D touch‐enabled surface for richer user interaction with midair 3D virtual objects in a touch‐interactive pseudo‐holographic display are presented. Frustrated total internal reflection (FTIR)‐based touch sensing is used in combination with a four‐sided pyramidal pseudo‐holographic projection. The developed system allows gesture‐based control and smooth touch interaction through facile and inexpensive hardware and open‐source software tools. A software application is also developed as the interface between the touch/gesture‐sensing system and the optical display. By bringing the virtual and real world closer through touch‐based interaction, the presented system will enrich user experience and enable advances in areas such as education, entertainment, gaming, retail, and museums where holograms are currently used.