Textiles enhanced with thin-film flexible sensors are well-suited for unobtrusive monitoring of skin parameters due to the sensors' high conformability. These sensors can be damaged if they are attached to the surface of the textile, also affecting the textiles' aesthetics and feel. We investigate the effect of embedding flexible temperature sensors within textile yarns, which adds a layer of protection to the sensor. Industrial yarn manufacturing techniques including knit braiding, braiding, and double covering were utilised to identify an appropriate incorporation technique. The thermal time constants recorded by all three sensing yarns was <10 s. Simultaneously, effective sensitivity only decreased by a maximum of 14% compared to the uncovered sensor. This is due to the sensor being positioned within the yarn instead of being in direct contact with the measured surface. These sensor yarns were not affected by bending and produced repeatable measurements. The double covering method was observed to have the least impact on the sensors' performance due to the yarn's smaller dimensions. Finally, a sensing yarn was incorporated in an armband and used to measure changes in skin temperature. The demonstrated textile integration techniques for flexible sensors using industrial yarn manufacturing processes enable large-scale smart textile fabrication.

The detailed measurement and characterization of strain induced performance variations in flexible InGaZnO thinfilm transistors (TFTs) resulted in a Spice TFT model able to simulate tensile and compressive bending. This model was used to evaluate a new concept, namely the active compensation of strain induced performance variations in pixel driving circuits for bendable active matrix arrays. The designed circuits can compensate the mobility and threshold voltage shifts in IGZO TFTs induced by bending. In a single TFT, a drain current of 1 mA varies by 83 µA per percent of mechanical strain. The most effective compensation circuit design, comprising one additional TFT and two resistors, reduces the driving current variation to 1.1 µA per percent of strain. The compensation circuit requires no additional control signals, and increases the power consumption by only 235 µW (corresponds to 4.7 %). Finally, switching operation is possible for frequencies up to 200 kHz. This opens a way towards the fabrication of flexible displays with constant brightness even when bent.

containing silver, [11] metallic nanowires, [12] indium-gallium alloys, [13] or carbon nanotubes. [14] In addition, inks containing semiconductors such as zinc oxide [15] or poly-3-octylthiophene [16] have been developed. These materials have been used for the development of electrocardiogram sensors, [17] antennas, [18] displays, [19] and transistors. [20][21][22] Nevertheless, the complex synthesis required to produce such inks limits their widespread use. Graphite, on the other hand, is an abundant and cheap material, and lead pencils have been used to write on paper since the 16th century. [23] More importantly, due to the bulk structure of graphite, which consists of disorganized clusters of stacked graphene sheets connected by Van der Wall bonds, graphite is an electrically conductive material. Hence, commercially available pencils can be used to fabricate pencil-written electronic components, circuits, and sensors. [24][25][26][27][28] In this work, the complexity and functionality of hand-written electronics is moved to a new level through the development of a complete pressure sensor system which also features the first hand-written Schottky diode on paper. The presented system is based on a pen and pencil-written half-wave rectifier, as well as a low-pass filter and percolation force-sensitive resistor. It also includes an off-the-shelf operational amplifier biased using hand-written passive components. The amplifier acts as a sensor conditioning circuit and improves the signal-to-noise ratio of the device. The realization of the system relied on a detailed characterization of the discrete components to evaluate and define the fabrication parameters.Pencils containing different graphite-to-clay ratios allow for the fabrication of thin-film resistors with varied sheet resistances. Changing resistance values is easily achieved by either removing or adding graphite layers to or from the existing structures, making the prototyping process faster. Graphitepaper-graphite parallel plate capacitors demonstrate capacitance values as high as 141 pF cm −2 ; this is three times larger than similar existing paper capacitors. [29] Larger capacitances can only be reached utilizing high-k solutions such as sulfuric acid. [30] Hand-written Schottky diodes on paper exhibiting rectification ratios of 1:8 were also fabricated and studied. All handwritten devices are used to realize circuits including rectifiers and filters for frequencies up to 13.56 MHz. Finally, all presented devices and circuits were tested under tensile and compressive stress. Bending radii down to 100 µm (corresponding -written fabrication techniques offer new ways of developing customizable, biodegradable, and low-cost electronic systems. In this work, a new level of complexity is demonstrated for hand-written electronics by fabricating passive components, circuits, and a sensor system on paper. The system comprises a pencil-written graphite force-sensitive resistor, a pencil-drawn RC filter, a pen-written half-wave rectifier, and a commercial front...

One of the most valuable contributions robotics can offer is support to daily human activities, yet rigid robots often fail to comply with safety regulations in the proximity of humans. Soft robotics takes inspiration from living organisms' ability to adapt to their environment using flexible structures. These systems have to generate mechanical forces and simultaneously sense their environment. We developed a soft gripper with integrated sensing microstructures by monolithically 3D printing the structure. The rubber gripper mimics the versatile sensing and actuation abilities of living organisms. This is done using stereolithographic printing technology, rubber material, and resistive, pressure sensitive EGaIn microchannels. Printed microscale pressure sensing cavities are filled with liquid metal and act as resistive pressure sensors. They imitate human haptic perception and provide a sensitivity of 0.5% kPa −1 . Simultaneously, a soft-robotic actuator design, which is derived from pneumatic networks, delivers a force of 2.5 N with 16 kPa of actuating pressure and an average efficiency of 0.56 mW kPa −1 . Monolithically 3D printed systems promise numerous advantages since the compliance matching between multi-modal capillary sensing networks and actuators enables scale production of smart soft manipulators. Potential applications include collaborative manufacturing and medical support systems such as exoskeletons.

In this paper, low earth orbit radiation (LEO), temperature, and magnetic field conditions are mimicked to investigate the suitability of flexible InGaZnO transistors for lightweight space wearables. More specifically, the impacts of high energetic electron irradiation with fluences up to 10 12 e − /cm 2 , low operating temperatures down to 78 K and magnetic fields up to 11 mT are investigated. This simulates 278 h in LEO. The threshold voltage and mobility of transistors that were exposed to e − irradiation are found to shift by +(0.09 ± 0.05) V and −(0.6 ± 0.5) cm 2 V −1 s −1 . Subsequent low temperature exposure resulted in additional shifts of +0.38 V and −5.95 cm 2 V −1 s −1 for the same parameters. These values are larger than the ones obtained from non-irradiated reference samples. Conversely, the performance of the devices was observed not to be significantly affected by the magnetic fields. Finally, a Cascode amplifier presenting a voltage gain of 10.3 dB and a cutoff frequency of 1.2 kHz is demonstrated after the sample had been irradiated, cooled down, and exposed to the magnetic fields. If these notions are considered during the systems design, these devices can be used to unobtrusively integrate sensor systems into space suits.INDEX TERMS Flexible electronics, space applications, amorphous oxides, wearables, thin film transistors.

The growing usage and consumption of electronics-integrated items into the daily routine has raised concerns on the disposal and proper recycling of these components. Here, a fully sustainable and green technology for the fabrication of different electronics on fruit-waste derived paper substrate, is reported. The process relies on the carbonization of the topmost surface of different cellulose-based substrates, derived from apple-, kiwi-, and grape-based processes, by a CO 2 laser. By optimizing the lasing parameters, electronic devices, such as capacitors, biosensors, and electrodes for food monitoring as well as heart and respiration activity analysis, are realized. Biocompatibility tests on fruit-based cellulose reveal no shortcoming for onskin applications. The employment of such natural and plastic-free substrate allows twofold strategies for electronics recycling. As a first approach, device dissolution is achieved at room temperature within 40 days, revealing transient behavior in natural solution and leaving no harmful residuals. Alternatively, the cellulose-based electronics is reintroduced in nature, as possible support for plant seeding and growth or even soil amendment. These results demonstrate the realization of green, low-cost and circular electronics, with possible applications in smart agriculture and the Internet-of-Thing, with no waste creation and zero or even positive impact on the ecosystem.

A biocompatible inexpensive strain sensor constituting of an elastomer filled with natural coconut oil (CNO) and carbon black (CB) is presented here. Strain sensors are widely utilized for applications in human activity recognition, health monitoring, and soft robotics. Given that these sensors are envisioned to be present in a plethora of fields, it is important that they are low cost, reliable, biocompatible, and eco‐friendly. This work demonstrates that CNO can be used to create conductive percolation network in elastomers, without the necessity for harmful chemicals or expensive machinery. The sensor has a gauge factor of 0.77 ± 0.01, and the sensing material has a porous morphology filled with an oily suspension formed of CNO and CB. Results indicate that the liquid filled porous structure can improve the reliability of these resistive strain sensors in comparison to sensors fabricated utilizing commonly used non‐polar solvents such as heptane. Consequently, the sensor demonstrates a hysteresis of only 2.41% at 200% strain over 250 stretch/release cycles. Finally, to demonstrate the potential of this fabrication technique, a functionalized glove is developed and used to detect wrist motion. These easily manufacturable and cost‐effective sensors enable wearable on‐skin ergonomic intervention systems with minimal impact on the environment.

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