Search

In order to develop and evaluate the extent to which itching affects a person's daily life, it is useful to develop automated means to recognise the action of scratching. We present an investigation of sensors and algorithms to realise a wearable scratch detection device. We collected a dataset, where each user wore 4 inertial measurement unit (IMU) sensors and one electric potential sensor (EPS). Data were collected from nine users, where each user followed a 40-min protocol, which involved scratching different parts of head, shoulder, and leg, as well as other activities such as walking, drinking water, brushing teeth, and typing to a computer. The dataset contained 813 scratching instances and 5 h 15 min of recorded data. We investigated the trade-offs between the number of devices worn (comfort) and accuracy. We trained the k-NN and random forest algorithms by using between 1 and 5 features per channel. We concluded that a scratch could be detected with 80.7% accuracy by using the random forest algorithm on hand coordinates, which required four devices. However, an f1 score of 70% could be achieved with k-NN with IMU and EPS data, which only required one device. Moreover, the fusion of IMU data with EPS data improved the accuracy and reduced the deviation between the folds. This expanded the state-of-the-art method by opening up new trade-offs between accuracy and comfort for future research

Textiles enhanced with thin-film flexible sensors are well-suited for unobtrusive monitoring of skin parameters due to the sensors&rsquo, high conformability. These sensors can be damaged if they are attached to the surface of the textile, also affecting the textiles&rsquo, 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 &lt, 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&rsquo, performance due to the yarn&rsquo, 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.

Safety requirements and physical constraints often prohibit contacting high voltage terminals. This limits the options for monitoring and maintaining high voltage machinery and power distribution grids. We present a non-contact AC (alternating current) voltage and frequency measurement system with 600 mm of operation range to overcome this issue. The method relies on measuring the electric potential of an AC voltage source using a single capacitive electrometer. Simultaneously, the distance from the AC source is measured using time-of-flight sensors. By combining the data from both sensors, AC voltages can be measured accurately without the need for any galvanic contact. The system is packaged in a handheld battery powered form factor. Measurements of voltages between 25 VRMS and 250 VRMS and distances from 25 mm to 600 mm demonstrated accuracy within 4%. Furthermore, frequencies between 5 Hz to 500 Hz were measured with 10 mHz of resolution. The presented technique can be used as a test and measurement instrument where the source terminals are inaccessible or as a wearable safety device in high-voltage environments.

In this talk, we show how acoustic metamaterials can be used to build the acoustic equivalent of optical devices. We demonstrate two key devices: (1) an acoustic prism, used to send the different notes in a melody towards different directions, and (2) an auto-zoom lens, used to send sound to a moving target. We conclude, discussing potential applications and limitations.

In this paper, Low Earth Orbit radiation, temperature and magnetic field conditions are mimicked to investigate the suitability of flexible Indium Gallium Zinc Oxide transistors for lightweight space wearables. Such wearable devices could be incorporated into spacesuits as unobtrusive radiation detectors or physiological monitors. Due to the harsh environment to which these space wearables would be exposed, they have to be able to withstand high radiation doses, low temperatures and magnetic fields. For this reason, the impacts of high energetic electron irradiation with fluences up to 1E12 e−/cm2, low operating temperatures down to 78K and magnetic fields up to 11mT are investigated. This simulates 278 h in Low Earth Orbit. 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 +0.38V and -5.95 cm2 V−1 s−1 for the same parameters. These values are larger than the ones obtained from non irradiated reference samples. In addition, 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 irradiate, 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.

The detailed measurement and characterization of strain-induced performance variations in flexible InGaZnO thin-film transistors (IGZO 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 1mA varies by $83~\mu \text{A}$ per percent of mechanical strain. The most effective compensation circuit design, comprising one additional TFT and two resistors, reduces the driving current variation to $1.1~\mu \text{A}$ per percent of strain. The compensation circuit requires no additional control signals and increases the power consumption by only $235~\mu \text{W}$ (corresponds to 4.7%). Finally, switching operation is possible for frequencies up to 200 kHz. This opens a way toward the fabrication of flexible displays with constant brightness even when bent.

Electric potential sensors (EPS) are classified as capacitive sensors with the ability to measure small variations in electric potential or electric field remotely and accurately. Here we show how a low cost single chip version of EPS can be integrated into a wearable device such as smart watch to provide relevant information about habitual movements specifically, hair touching and scratching as well as leg movement. This new modality could be used in consumer care product research such as studying the quality of shampoos and to study restless leg syndrome remotely without the need of wearing additional sensors. In both scenarios, a single sensor was worn on the wrist, similar to a smart watch, with the sensing electrode pointing away from the body (i.e. no skin contact).

Hand-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 sensorsystem 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-end voltage amplifier. The sensor system exhibits a linear response for pressures up to 1.2 kPa, and a sensitivity of 51 mV kPa-1 . Furthermore, the electrical and mechanical performance of the single components and circuits is studied. Diodes fabricated through pen-written deposition of silver and nickel contacts on amorphous Indium-Gallium-Zinc-Oxide coated paper show rectification ratios up to 1:8. Tensile and compressive bending measurements applied to all pencil-written components for radii down to 0.1 mm indicate minor influence of strain. Similar results are obtained for circuits created from these individual components. Diodes and half-wave rectifiers show a stable behavior when bent to a radius of 5 mm. The presented techniques can enable the development of flexible and eco-friendly wearables and sensors for consumer and healthcare applications, and are an effective way for school-pupils to explore the world of electronics.