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The feasibility of an underground LoRaWAN bushfire temperature sensing node from the point of view of survivability in a bushfire event is considered. Thermal penetration into the soil is modelled using a one-dimensional analytical formulation for a semi-infinite solid. A working prototype of the sensor unit was tested experimentally beneath a relatively small (400 mm × 400 mm base) timber fire. A buried LoRa radio (depth 100 mm) with a k-type thermocouple monitored the temperature from beneath the fire. The analysis demonstrates that under dry soil conditions, the time that the sensor node under the fire base can endure is proportional to the square of the depth of burial of the electronic components and inversely proportional to the thermal diffusivity of the soil. The original contribution of the work is in the practical demonstration of the durability of a LoRa sensing node beneath a fire front for bushfire sensing applications.

The development of a multimodal sensing platform with multiple layers for electronic skin (e-skin) sensing of temperature and pressure has attracted considerable interest to practical applications in soft robotics, human-machine interfaces, and wearable health monitoring. In this work, we demonstrated a new platform technology with multiple sandwiched layers of highly oriented carbon nanotube membrane and polyacrylonitrile for the integration of pressure and temperature sensory functionalities into a single platform that is thin, ultra-lightweight, flexible, and wearable. The key technology of in situ deposition of sensor platform on objects or in robot interface makes this a unique method for the development of e-skins for robotic applications, offering a new approach to wearable electronics and portable health care.

This letter reports on the impact of compressive pressure on the electrical properties of carbon nanotube (CNT) yarns fabricated by dry Web-spinning and heat-treatment processes. Under increasing applied compressive pressure in the radial direction of the yarn, the electrical resistance of CNT yarns gradually decreased by 2.8% at a threshold applied pressure of 60 kPa where the resistance change is saturated. The decrease of CNT resistance with increasing pressure is attributed to the increase in the volume fraction of CNT, resulting in the increase of the effective junctions between adjacent CNTs, and the reduction of the tunneling distance between single CNTs. CNT yarns embedded in elastomers show high potential as an advanced functional element for a wide range of mechanical sensing applications including flexible pressure and tactile sensing.

E-skin with physical sensing capability has attracted considerable interest towards practical applications in soft robotics, human–machine interfaces, and wearable health monitoring. However, the development of a multimodal sensing platform with multiple layers for e-skin sensing of temperature and pressure has faced challenges due to the typical use of bare or single sensing layers as well as the complication of integration of multifunctional sensing modules onto curved surfaces. Herein, we demonstrate a new platform technology with multiple sandwiched layers of highly oriented carbon nanotube (CNT) films and polyacrylonitrile (PAN) for integration of pressure and temperature sensory functionalities into a single platform that is thin, ultra-lightweight, flexible, and wearable. The key technology of in-situ deposition of sensor platform on objects or in robot interface makes this a unique method for the development of e-skins for robotic applications, offering a new approach to wearable electronics and portable health care.

We report the effect of stress or strain on the electronic characteristics of a normally off AlGaN/GaN high electron mobility transistor (HEMT) and demonstrate its role as a highly sensitive pressure sensor. We observe that the HEMT drain current exhibits a linear change of 2.5%/bar upon the application of pressure, which is translated to a strain sensitivity of 1250 ppm−1. This is the highest strain sensitivity ever reported on HEMTs and many other conventional strain sensing configurations. The relative change of drain current is largest when the gate bias is near-threshold and drain bias is slightly larger than the saturation bias. The electron sheet density and mobility changes in the AlGaN/GaN heterointerface under the applied pressure or mechanical strain are explained qualitatively. The spontaneous and piezoelectric-polarization-induced surface and interface charges in the AlGaN/GaN heterojunction can be used to develop very sensitive and robust pressure sensors. The results demonstrate a considerable potential of normally off AlGaN/GaN HEMTs for highly sensitive and reliable mechanical sensing applications with low energy consumption.

The development of electronic skin (e-skin) and soft tactile sensing has recently attracted great interest. Here we report for the first time on a novel ionic liquid (IL) based soft pressure sensor with multi-point touch detection capability using 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]+[BF4]−) as a highly conductive sensing medium. The sensing mechanism is attributed to the repopulation of charge cations and anions in aqueous solution under pressure. The sensor can detect two dimensional touching positions with a sensitivity of −0.28% kPa−1. Our sensor showed good stability and temperature independence thanks to the incompressibility of IL in the range of touch pressure and the appropriate signal measurement configuration. We successfully demonstrated the sensor's capability to detect multi-point human touch with different pressure levels. Our simple design with smart structures and ease of fabrication processes enable the development of a soft and low-cost sensor with multiple-point sensing capabilities on a single chip.

Design and implementation of sensing devices have been driven by the need for high sensitivity, low cost, and simple fabrication. Ionic liquids have some desirable properties for soft sensor design in terms of their volatility and conductivity. By applying low cost and simple fabrication methods, we present a multifunctional pressure and temperature sensor. Preliminary results show a sensitivity of 0.24 × 10−3 kPa−1 and −17,000 ppm/K for pressure and temperature respectively. Showing high promise for the presented ionic liquid in soft sensor design. Further investigation into the measuring method, structure, and working principle of the materials involved could provide a higher quality multimodal and multifunctional device.

Developing flexible pressure sensors is of high interest in soft skin and tactile sensing applications. Here we demonstrate a simple approach to fabricating a sensitive resistive pressure sensor using carbon nanotube (CNT) micro-yarns as a pressure sensing element which is constructed on a stretchable acrylic elastomer. The sensor showed a high sensitivity of −0.86 Ω/kPa and a fast response time of 100 ms. Different to the longitudinal piezoresistive effect of micro-yarns, the high pressure sensitivity of the sensor was achieved owing to the compressibility of the micro-yarn in the direction perpendicular to the yarn axis. The sensor was also able to monitor finger pressure in real-time, demonstrating its potential for tactile sensing applications.

This paper presents the design and development of a low cost and reliable maximal voluntary bite force sensor which can be manufactured in-house by using an acrylic laser cutting machine. The sensor has been designed for ease of fabrication, assembly, calibration, and safe use. The sensor is capable of use within an hour of commencing production, allowing for rapid prototyping/modifications and practical implementation. The measured data shows a good linear relationship between the applied force and the electrical resistance of the sensor. The output signal has low drift, excellent repeatability, and a large measurable range of 0 to 700 N. A high signal-to-noise response to human bite forces was observed, indicating the high potential of the proposed sensor for human bite force measurement.