Soft machines are a promising design paradigm for human-centric devices
and systems required to interact gently with their environment
. To enable soft machines to respond intelligently to their ...surroundings, compliant sensory feedback mechanisms are needed. Specifically, soft alternatives to strain gauges-with high resolution at low strain (less than 5 per cent)-could unlock promising new capabilities in soft systems. However, currently available sensing mechanisms typically possess either high strain sensitivity or high mechanical resilience, but not both. The scarcity of resilient and compliant ultra-sensitive sensing mechanisms has confined their operation to laboratory settings, inhibiting their widespread deployment. Here we present a versatile and compliant transduction mechanism for high-sensitivity strain detection with high mechanical resilience, based on strain-mediated contact in anisotropically resistive structures (SCARS). The mechanism relies upon changes in Ohmic contact between stiff, micro-structured, anisotropically conductive meanders encapsulated by stretchable films. The mechanism achieves high sensitivity, with gauge factors greater than 85,000, while being adaptable for use with high-strength conductors, thus producing sensors resilient to adverse loading conditions. The sensing mechanism also exhibits high linearity, as well as insensitivity to bending and twisting deformations-features that are important for soft device applications. To demonstrate the potential impact of our technology, we construct a sensor-integrated, lightweight, textile-based arm sleeve that can recognize gestures without encumbering the hand. We demonstrate predictive tracking and classification of discrete gestures and continuous hand motions via detection of small muscle movements in the arm. The sleeve demonstration shows the potential of the SCARS technology for the development of unobtrusive, wearable biomechanical feedback systems and human-computer interfaces.
The position of the centre of gravity of the human body has been measured in a wide range of conditions, but in many cases a high degree of accuracy was not possible because of the crude nature of ...the equipment ... Each cantilever has strain gauges attached to it, giving...
Recent years have witnessed the booming development of flexible strain sensors. To date, it is still a great challenge to fabricate strain sensors with both large workable strain range and high ...sensitivity. Cotton is an abundant supplied natural material composed of cellulose fibers and has been widely used for textiles and clothing. In this work, the fabrication of highly sensitive wearable strain sensors based on commercial plain weave cotton fabric, which is the most popular fabric for clothes, is demonstrated through a low‐cost and scalable process. The strain sensors based on carbonized cotton fabric exhibit fascinating performance, including large workable strain range (>140%), superior sensitivity (gauge factor of 25 in strain of 0%–80% and that of 64 in strain of 80%–140%), inconspicuous drift, and long‐term stability, simultaneously offering advantages of low cost and simplicity in device fabrication and versatility in applications. Notably, the strain sensor can detect a subtle strain of as low as 0.02%. Based on its superior performance, its applications in monitoring both vigorous and subtle human motions are demonstrated, showing its tremendous potential for applications in wearable electronics and intelligent robots.
Based on carbonized plain weave cotton fabric, a wearable strain sensor with high sensitivity and large workable strain range (up to 140%) is fabricated through a cost‐effective, scalable, and green process. Its working mechanism is investigated and its application in detection of both subtle and large deformation of the human body is demonstrated, promising great potential in wearable electronics.
In this paper, a direct writing method for gallium‐indium alloys is presented. The relationships between nozzle inner diameter, standoff distance, flow rate, and the resulting trace geometry are ...demonstrated. The interaction between the gallium oxide layer and the substrate is critically important in understanding the printing behavior of the liquid metal. The difference between receding and advancing contact angles demonstrates that the adhesion of the oxide layer to the substrate surface is stronger than the wetting of the surface by the gallium‐indium alloy. This further demonstrates why free‐standing structures such as the traces described herein can be realized. In addition to the basic characterization of the direct writing process, a design algorithm that is generalizable to a range of trace geometries is developed. This method is applied to the fabrication of an elastomer‐encapsulated strain gauge that displays an approximately linear behavior through 50% strain with a gauge factor of 1.5.
A novel method for directly writing liquid gallium‐indium alloy is presented. In addition to the basic characterization of the direct writing process, a design algorithm for process stability is also developed. The method is employed to fabricate a strain gauge exhibiting an approximately linear behavior through strains of 50% with a gauge factor of 1.5.
Within the scope of the High-Luminosity LHC project, the collaboration between CERN and U.S. LARP is developing new low- Formula Omitted quadrupoles using the Nb3Sn superconducting technology for the ...upgrade of the LHC interaction regions. The magnet support structure of the first short model was designed, and two units were fabricated and tested at CERN and at LBNL. The structure provides the preload to the collar-coil subassembly by an arrangement of outer aluminum shells pretensioned with water-pressurized bladders. For the mechanical qualification of the structure and the assembly procedure, superconducting coils were replaced with solid aluminum "dummy coils," and the structure was preloaded at room temperature and then cooled-down to 77 K. The mechanical behavior of the magnet structure was monitored with the use of strain gauges installed on the aluminum shells, the dummy coils, and the axial preload system. This paper reports on the outcome of the assembly and the cooldown tests with dummy coils, which were performed at CERN and at LBNL, and presents the strain gauge measurements compared with the 3-D finite-element model predictions.
Capacitive sensors of mechanical strain Ignakhin, V S; Sekirin, I V; Shilovskiy, N A
IOP conference series. Materials Science and Engineering,
06/2021, Letnik:
1155, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
The paper reviews recent research and applications of both laboratory prototypes and commercially fabricated capacitance gauges of mechanical strain. Basic operational principles as well as ...advantageous points of each type of sensors are considered. The prospective areas of applications of the capacitive gauges are briefly considered. The properties of other strain gauges are briefly discussed and compared with those of the capacitive sensors.
In this paper we present an experimental demonstration and a theoretical study on mechanical tuning of whispering gallery modes (WGMs) of double-tailed silica microspheres. The mechanical tuning is ...performed by applying tensile stress on double-tailed microspheres with a variety of diameters. The dependence of the tuning sensitivity on some geometrical considerations of the double-tailed microsphere is studied and demonstrated experimentally for the first time to the best of our knowledge. The tuning sensitivity is calculated for various microspheres using a simplified analytical model, and the calculation are compared with the measured values. The comparison shows good agreement between the calculated and measured values. As shown in the paper, the sensitivity increases with increasing the radius ratio of the fiber tails and that of the microspheres; the <inline-formula><tex-math notation="LaTeX">{R_f}/{R_s}</tex-math></inline-formula> ratio. A strain-gauge based on a double-tailed microsphere with a sensitivity of 0.33 pm/µϵ is demonstrated, with a detection limit of ∼ 0.02 μ ϵ.
A non‐classical organic strain gauge as a voltage signal sensor is reported, using an inverter‐type thin‐film transistor (TFT) circuit, which is able to sensitively measure a large quantity of ...elastic strain (up to ≈2.48%), which approaches an almost folding state. Novel heptazole‐based organic TFTs are chosen to be incorporated in this gauge circuit; organic solid heptazole has small domain size in general. While large crystal domain‐pentacene TFTs seldom show sufficient current variation upon mechanical bending for tensile strain, these heptazole TFTs demonstrate a significant variation for the same strain condition as applied to pentacene devices. In addition, the pentacene channel does not recover to its original electric state after bending but heptazole channels are very elastic and reversible, even after going through serious bending. More interesting is that the heptazole TFTs show only a little variation of signal current under horizontal direction strain, while they make a significant amount of current decrease under vertical direction strain. Utilizing the anisotropic response to the tensile bending strain, an ultrasensitive voltage output strain gauge composed of a horizontally and vertically oriented TFT couple is demonstrated.
An ultrasensitive organic strain gauge as an inverter‐type thin‐film transistor (TFT) circuit, which uses heptazole‐based organic TFTs, is reported. On a plastic substrate, this non‐classical organic strain gauge sensitively measures 2.48% tensile strain by bending, which leads to a minimum radius of 1 mm. Both strain sensitivity and sensing speed of our strain gauge are good enough to be used as a muscle motion sensor attached on a human arm.
•First study on cold expansion of rail-end-bolt holes with strain gauges and 2D-DIC.•Two experimental methods to validate FE simulation of cold expansion of rail holes.•Strain-time histories acquired ...along radial paths during the entire CE process.•FE model validation by experimental comparison with maximum and residual strains.
This paper provides experimental validation of a FE model simulating the cold-expansion of rail-end-bolt holes. Three rail holes were used for the experiments and, contrary to literature, hoop and radial strains were measured along different radial paths during the entire process using both electrical strain gauges and 2D-Digital Image Correlation. Residual and maximum strains predicted with the FE model agree well with measurements obtained with both experimental techniques, providing good confidence in the use of the proposed model to predict the effective stresses acting around the holes and to develop a LEFM-based model for crack growth simulation at cold-expanded holes.
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