Monitoring Finger Research Articles

A Review of Wearable Optical Fiber Sensors for Rehabilitation Monitoring.

As the global aging population increases, the demand for rehabilitation of elderly hand conditions has attracted increased attention in the field of wearable sensors. Owing to their distinctive anti-electromagnetic interference properties, high sensitivity, and excellent biocompatibility, optical fiber sensors exhibit substantial potential for applications in monitoring finger movements, physiological parameters, and tactile responses during rehabilitation. This review provides a brief introduction to the principles and technologies of various fiber sensors, including the Fiber Bragg Grating sensor, self-luminescent stretchable optical fiber sensor, and optic fiber Fabry-Perot sensor. In addition, specific applications are discussed within the rehabilitation field. Furthermore, challenges inherent to current optical fiber sensing technology, such as enhancing the sensitivity and flexibility of the sensors, reducing their cost, and refining system integration, are also addressed. Due to technological developments and greater efforts by researchers, it is likely that wearable optical fiber sensors will become commercially available and extensively utilized for rehabilitation.

3D Printed Carbon Nanotubes Reinforced Polydimethylsiloxane Flexible Sensors for Tactile Sensing

Technology is constantly evolving, and chronic health issues are on the rise. It is essential to have affordable and easy access to remote biomedical measurements. This makes flexible sensors a more attractive choice owing to their high sensitivity and flexibility along with low cost and ease of use. As an additional advantage, 3D printing has become increasingly popular in areas such as biomedicine, environment, and industry. This study demonstrates 3D-printed flexible sensors for tactile sensing. A biocompatible silicone elastomer such as polydimethylsiloxane (PDMS) with low elastic modulus and high stretchability makes an excellent wearable sensor material. Incorporating CNTs at varying concentrations (0.5, 1, 2)wt% enhances the sensor’s mechanical strength, conductivity, and responsiveness to mechanical strain. In addition to enhancing the thermal stability of the composite by 44%, multi-walled carbon nanotubes (MWCNTs) also enhanced the breaking strength by 57% with a 2 wt% CNT loading. Moreover, the contact angle values improved by 15%, making it a biomedical-grade hydrophobic surface. The electrical characteristics of these sensors reveal excellent strain sensitivity, making them perfect for monitoring finger movements and biomedical measurements. Overall, 2 wt% CNT-PDMS sensors exhibit optimal performance, paving the way for advanced tactile sensing in biomedical and industrial settings.

Novel flexible capacitive pressure sensor with a wide detection range enabled by carboxyl iron particle-paraffin wax/silicone composite

The emergence of flexible capacitive pressure sensors has prominently accelerated the development of flexible electronics. However, most capacitive pressure sensors reported so far have limited detection ranges, which greatly restricts their application scenarios. In this work, a novel flexible capacitive pressure sensor with a wide detection range was produced by employing the carboxyl iron particle-paraffin wax (CIP-PW)/silicone composite as the dielectric layer. Due to the introduction of phase-changing PW and magnetic CIPs, the resultant CIP-PW/silicone composite exhibits magnetism and temperature-controllable mechanical properties, which therefore provides the capacitive pressure sensor with a tunable effective detection range in the frequency range of 0.1–5 Hz. To be specific, the sensor could achieve an effective detection range of 0.2–350 kPa, much wider than other capacitive sensors reported. This merit is further demonstrated by monitoring finger and arm movements as well as walking status. In addition to the physical contact sensing, the sensor exhibits a contactless sensing capacity, and could be used to monitor finger movements without direct contact. In virtue of the wide detection range and bimodal sensing capacity, the current capacitive pressure sensor shows greatly promising in the fields of wearable devices, e-skin, robotics and so on.

Gelatin Biogel–Liquid Metal Composite Transient Circuits for Recyclable Flexible Electronics

AbstractTransient electronics with degradability or dissolvability on demand possess remarkable characteristics for wearable, bioelectronic, and implanted electronic devices. While synthetic materials have made significant progress in degradability and stretchability, they suffer from intrinsic limitations, including low degradation rates, poor mechanical compliance, and high production cost, which restrict the growth of transient electronic devices. Herein, a versatile fabrication strategy is presented for transient electronics that combine a resilient biopolymer substrate (gelatin biogels) with liquid metal (Galinstan). The circuits made from gelatin biogel‐based and liquid metal are mechanically resilient and durable, exhibiting good compliance with irregular and deformable surfaces, and thus can withstand long‐term exposure to dynamic deformation (about 60 000 cycles at a strain of 50%). More importantly, gelatin biogels are naturally derived and endowed with thermally reversible gelling, which enables on‐demand rapid dissolution and recycling of the materials. As a proof‐of‐concept, transient circuit‐based capacitive sensors, which can be degraded within 20 s, are fabricated for monitoring finger touching, morse code generation, and electrical touchpad. Such a strategy provides a guideline for designing transient electronics with a combination of biopolymer gels and liquid metal, and this approach is anticipated to find applications in human–machine interfaces and wearable devices.

Electrochemical self-powered strain sensor for static and dynamic strain detections

The self-powered strain sensors based on piezoelectric and triboelectric principles have been widely reported in flexible electronics, but they cannot achieve static strain detection. Inspired by electrochemical reactions, we propose and construct an electrochemical self-powered strain sensor for static and dynamic strain detections. Specifically, the sensor is composed of Cu/Al electrodes, elastic core-spun yarn coated with LiCl-carbon nanotubes (CNTs), and latex tube encapsulation. Among them, Cu and Al electrodes are used for electrochemical reactions; Elastic core-spun yarn endows the sensor with excellent tensile performance; LiCl provides conductive ions in electrochemical reactions; CNTs with good conductivity not only reduce the resistance between Cu and Al electrodes, but also facilitate good resistance strain effect; Latex tube encapsulation inhibits the evaporation of water molecules in the electrolyte. The strain sensing performance of the sensor is evaluated based on the current response. The results show that the sensor has wide strain detection range (2–100 %) and good repeatability (1000 times). By analyzing the strain voltage and current responses, as well as the morphology characterization of the sensor, the strain response mechanism of the sensor has been clarified, which is controlled by electrochemical reactions and resistance strain effect. The static strain monitoring function of the sensor is verified by monitoring finger bending. Combined with machine learning, the sensor can be used for respiratory behavior recognition. This work fundamentally contributes to developing self-powered strain sensor with static and dynamic strain detections.

Facile fabrication of flexible and adhesive micro-supercapacitor tapes from conducting polymer solution for self-powered wearable sensing system

Flexible micro-supercapacitor (MSC) with in-plane electrodes has attracted significant attention as microscale energy storage device. Especially, flexible MSCs with adhesion properties are of great interest for wearable electronics. Here, we demonstrate a facile and cost-effective mask-assisted drop-casting method to fabricate adhesive MSC on medical tape using dimethyl sulfoxide (DMSO) doped poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) aqueous solution. The fabricated MSC with poly (vinyl alcohol)/H3PO4 gel electrolyte exhibits an areal specific capacitance of 10.96 mF cm−2 at a current density of 0.1 mA cm−2 with excellent mechanical flexibility. The MSC can be attached on various substrates due to the stickiness of the medical tape. For practical application, the MSC can be coupled with a solar cell to achieve a stand-alone power supply system for a flex senor in monitoring finger movements. Therefore, we believe that the mask-assisted drop-casting method paves a new way to develop flexible and adhesive MSCs for self-powered integrated wearable electronics.

Structurally hierarchical flex-sensor of MWCNTs/TPU composite via mesh mould-based selective laser sintering (SLS) and ultrasonic cavitation-enabled treatment (UCT)

• Structurally hierarchical MWCNTs/TPU flexible strain sensors were designed. • Selective laser sintering (SLS) with inverted-mould grooving produced sensors. • Ultrasonic cavitation-enabled treatment (UCT) fabricated a grass-like structure. • Sensor hierarchical structure-determined sensing mechanisms were dissected. • The sensor exhibited detecting surface curvatures and monitoring finger action. The piezoresistive performances of conductive polymer composites (CPCs) largely depend on the material composition and fabrication process. A structurally hierarchical flexible strain sensor of a multi-walled carbon nanotubes (MWCNTs)/thermoplastic polyurethane (TPU) CPC was prepared via a simple hybrid fabrication path including selective laser sintering (SLS) 3D printing, inverted-mould grooving, and ultrasonic cavitation-enabled treatment (UCT). The influences of SLS process parameters, mesh-molded groove geometry, and material ratio on the sensor properties were studied. The sensing mechanisms were discussed. Some application demonstrations of the prepared sensors were exhibited. The hierarchically structural design and fabrication path facilitate the development of more versatile flex-sensors.

Highly sensitive flexible strain sensor based on GSB-enhanced three-dimensional graphene composite

High-sensitive flexible strain sensor is a key device for artificial intelligence and wearable electronics. Specifically, the aim of this work is to investigate the design of graphene-SiO2 balls enhanced (GSB-enhanced) three-dimensional (3D) graphene foam (GSBF) electrode structure, which is combined with flexible material polydimethylsiloxane (PDMS) for a highly sensitive strain sensor. The GSBF/PDMS strain sensor presents excellent performances: stretching ratio of 50%, response time of less than 128 ms and high sensitivity (the strain coefficient GF = 103, in variation range of 0–13% strain), due to its unique mechanical and conductive properties. Moreover, a high stability of more than 300 loading-unloading cycles is achieved without dramatic resistance increment. Our sensors could be used in several wearable applications including monitoring finger movement, the pulse ratio, the strain of the knee joint in patellar reflex and the movements of elbow, wrist, sole etc. Our research illustrates the potential abilities in the fields of robotic systems, healthcare and flexible electronics applications with less cost and more accessible.

P230 Feasibility study of mobile phone photography as a possible outcome measure of systemic sclerosis-related digital ulcers

Abstract Background/Aims Digital ulcers cause pain and disability in patients with systemic sclerosis (SSc). They are often used as outcome measures in clinical trials; however, trials have been hampered by a lack of reliable outcome measures of healing. Photographic monitoring of digital ulcers using smartphones could overcome this difficulty. Our objective was to assess the feasibility of patients collecting mobile-phone images of their digital ‘lesions’ as a first step in a programme of research to develop a smartphone-based outcome measure. Methods An imaging protocol was developed with input from a patient representative group. Patients with SSc-related digital lesions were recruited and instructed to photograph one or more finger lesions each day over 30 days using their smartphone, at the same time each day. Instructions on how to take the photographs were given either face-to-face or remotely. An adhesive dot, placed adjacent to the lesion(s), provided a 1cm reference scale to help extract accurate measurements. Images were uploaded by each patient to a secure Dropbox folder. Image quality was assessed using six criteria: blurriness, shadow, uniform lighting, dot location, dot angle, and central positioning of the lesion. After image collection, patients were asked to complete a feedback questionnaire, with most questions on a scale of 1 (very easy) to 10 (very difficult). Results Twelve patients (10 female, age 37 to 72 years, disease duration 1 to 27 years) returned 331 photographs of 19 lesions (maximum three lesions per patient). Each patient sent a median of 30 photographs (IQR 14 to 33), with a median of 15 photographs per lesion (IQR 2 to 31). Of the 331 photographs, 24 were ‘duplicates’ taken on the same day, meaning that there were 263 ‘missing’ photographs (i.e., 570 photographs would have been taken if 19 lesions had been photographed every day). Image quality results included the following: 255 (77%) of photographs were sufficiently in focus; 268 (81%) had some shadow; lighting was even in 55 (17%); dot location was acceptable in 231 (70%); dot angle was ideal in 107 (32%); the lesion was centred in 254 (77%). Patient feedback showed 9/10 responses would be willing to record images at least 1-3 times per week, and the overall patient experience taking photographs was good, with a median rating of 3 (IQR 3 to 4). Conclusion Capturing photographs of digital lesions with a smartphone was feasible for most patients. They were able to take photographs in focus and with lesions central in the image. Support will be required to improve lighting, shadow, and dot positioning while minimising discomfort. These encouraging results will inform the next research phase to develop a smartphone app for monitoring finger lesions. Disclosure A.K. Davison: None. H. Patrick: None. P. New: None. G. Dinsdale: None. V.P. Taxiarchi: None. W.G. Dixon: None. A. Vail: None. A.K. Murray: None. M. Dickinson: None. C. Taylor: None. A.L. Herrick: None.

Electrical Stability and Piezoresistive Sensing Performance of High Strain-Range Ultra-Stretchable CNT-Embedded Sensors.

Highly flexible and stretchable sensors are becoming increasingly widespread due to their versatile applicability in human/robot monitoring sensors. Conductive polymeric composites have been regarded as potential candidates for such sensors, and carbon nanotubes (CNTs) are widely used to fabricate such composites. In the present study, CNT-embedded high flexible sensors were fabricated using a facile three-roll milling method, which mitigates the drawbacks of the conventional fabrication methods. CNTs content varied between 0.5 and 4.0 wt.%, and the percolation threshold range was obtained via conductivity/resistivity values of the fabricated sensors. Following this, the electrical stability of the sensors was examined against the various DC and AC signals. Furthermore, the fabricated sensors were stretched up to 500% strain, and their sensitivity against varying strain amplitudes was investigated in terms of the change in resistance and gauge factors. Lastly, the fabricated sensors were applied to human fingers for monitoring finger bending and releasing motions to validate their potential applications. The experimental results indicated that these sensors have a percolation threshold of around 2% CNTs content, and the sensors fabricated with 2 to 4% CNTs content showed measurable resistance changes against the applied strain amplitudes of 50–500%. Among these sensors, the sensor with 2% CNTs content showed the highest sensitivity in the studied strain range, exhibiting a resistance change and gauge factor of about 90% and 1.79 against 50% strain amplitude and about 18,500% and 37.07 against 500% strain amplitude, respectively. All these sensors also showed high sensitivity for finger motion detection, showing a resistance change of between 22 and 69%.

Nacre-inspired tunable strain sensor with synergistic interfacial interaction for sign language interpretation

A highly sensitive and stretchable strain sensor is urgently required in wearable applications. Nevertheless, high sensitivity requiring a significant structural variation even at a subtle deformation and large stretchability related to morphological integrity under a large strain are considered as two contradictory performance indicators of strain sensors. It remains a huge challenge to synchronously acquire high sensitivity and wide detection range. Herein, we prepare a strain sensor with nacre-mimetic structure through spaying Ti-O-C covalent bonding crosslinked MXene/reduced graphene oxide (rGO) (MGO) solution among the multilayer thermoplastic polyurethane (TPU) electrospun mat. The special nacre-mimetic structure and the synergistic motion of different nanosheets endow the MGO/TPU strain sensor (MGTSS) with high sensitivity (GF of 879 within 100% strain, GF of 17782 for a strain of 100%−160%, and 84326 for a strain of 160%−200%), ultra-low detection limit (0.05% strain), large detection range (up to 200% strain), short response time (70 ms) and a favorable sensing stability and durability (5000 stretching/releasing cycles). Moreover, the nacre-mimetic strain sensor can be used for sign language interpretation through monitoring finger gestures, showing great promise for applications in next-generation of wearable flexible electronics devices.

Validation of a modular and wearable system for tracking fingers movements

<p class="Abstract">Supervising manual operations performed by workers in industrial environments is crucial in a smart factory. Indeed, the production of products with superior quality, at higher throughput rates and reduced costs with the support of the Industry 4.0 enabling technologies is based on the strict control of all the resources inside the factory, including workers. This paper shows a protocol for validating a new wearable system for tracking finger movements. The wearable system consists of two measuring modules worn on the thumb and on the index measuring flexion and extension of the proximal interphalangeal (PIP) joint by a stretch sensor and rotation of the proximal phalanx (PP) by an inertial measurement unit. An optical system is used to validate the system by capturing specific finger movements. Four movements that simulate typical tasks and gestures, such as grasp and pinch, were performed to validate the proposed system. The maximum root-mean-square error is 3.7 deg for the roll angle of PP. The resistance changes of the stretch sensors with respect to flexion and extension of PIP joint is 0.47 Ohm/deg. The results are useful for the data interpretation when the system is adopted for monitoring finger movements and gestures.</p>

Nanomesh pressure sensor for monitoring finger manipulation without sensory interference.

Monitoring of finger manipulation without disturbing the inherent functionalities is critical to understand the sense of natural touch. However, worn or attached sensors affect the natural feeling of the skin. We developed nanomesh pressure sensors that can monitor finger pressure without detectable effects on human sensation. The effect of the sensor on human sensation was quantitatively investigated, and the sensor-applied finger exhibits comparable grip forces with those of the bare finger, even though the attachment of a 2-micrometer-thick polymeric film results in a 14% increase in the grip force after adjusting for friction. Simultaneously, the sensor exhibits an extreme mechanical durability against cyclic shearing and friction greater than hundreds of kilopascals.

Freestanding silver/polypyrrole composite film for multifunctional sensor with biomimetic micropattern for physiological signals monitoring

Flexible electronic sensors, which can perceive and respond to mechanical stimuli, are essential components of wearable electronics. Here, the utilization of biomimetic microstructures from natural lotus leaves and freestanding polypyrrole/silver (PPy/Ag) hybrid films are demonstrated to design and fabricate multifunctional sensors. The sensors consist of sandwich structure, including the surface of the designed polydimethylsiloxane (PDMS) films with biomimetic micropattern and the interlayer of the conductive PPy/Ag film (PDMS/PPy/Ag/PDMS). It is discovered that the polypyrrole and silver nanoparticles (PPy/AgNPs) aggregated and the freestanding PPy/Ag hybrid film formed at the air/water interface under ultraviolet (UV) irradiation. The PPy/Ag film exhibits well electrical conductivity, which could be used for fabricating the sensors to detect pressures, stretching and bending forces. The sensors based on the micropatterned PDMS substrate show well strain gauge factor (≈21 for 18 ~ 20 strain) and pressure sensitivity (≈0.58 kPa−1 in 300 ~ 400 Pa) due to the effective contact areas. The sensors attract considerable attention for their application in monitoring finger pressure, respiration, acoustic vibrations, and real-time pulse wave at the current detection range from 0 to 60 mA. The results indicate that the PPy/Ag-based sensors with high sensitivity have promising potential for the future applications in wearable electronics and human-machine devices.

Transition metal pincer complex based self-healable, stretchable and transparent triboelecctric nanogenerator

As a promising energy converter, triboelectric nanogenerator (TENG) demonstrates unparalleled advantages. However, its performance is extremely affected by wear, tear and damage of the functional materials during triboelectrification. In this work, by incorporating tridentate pincer ligand moieties into a linear polydimethylsiloxane (PDMS) chain, the Zn-Pdca-PDMS elastomer for triboelectric layer was synthesized with excellent viscoelastic behaviors, super-stretchability (>5200%), self-healing ability and transparency. As a newly developed strategy, the strength of metal-ligand complex could be tuned efficiently by changing molar ratio of metal ions and ligands and three kinds of anions (CF3SO3−, BF4−, ClO4−) to adapt the desirable material performances. Subsequently, a stretchable, self-healable and transparent Zn-Pdca-PDMS based TENG (ZPP-TENG) was fabricated. With the molar ratio of Zn2+ to Pdca-PDMS ligand of 2:1, it exhibits the best output performance of 145 V, 6.7 nC cm−2 and 0.74 μA cm−2, respectively. The self-healable ZPP-TENG was employed as energy harvester to light up LEDs and charge a capacitor to driven electronic watch effectively. Even after several cutting-healing cycles, the output performance of the ZPP-TENG still maintain consistent. Finally, it was demonstrate to be employed a self-powered sensor for monitoring finger movement and pulse wave with excellent repeatability and stability.

Micro-patterned graphene-based sensing skins for human physiological monitoring

Ultrathin, flexible, conformal, and skin-like electronic transducers are emerging as promising candidates for noninvasive and nonintrusive human health monitoring. In this work, a wearable sensing membrane is developed by patterning a graphene-based solution onto ultrathin medical tape, which can then be attached to the skin for monitoring human physiological parameters and physical activity. Here, the sensor is validated for monitoring finger bending/movements and for recognizing hand motion patterns, thereby demonstrating its future potential for evaluating athletic performance, physical therapy, and designing next-generation human-machine interfaces. Furthermore, this study also quantifies the sensor’s ability to monitor eye blinking and radial pulse in real-time, which can find broader applications for the healthcare sector. Overall, the printed graphene-based sensing skin is highly conformable, flexible, lightweight, nonintrusive, mechanically robust, and is characterized by high strain sensitivity.

Batch Fabrication of Customizable Silicone‐Textile Composite Capacitive Strain Sensors for Human Motion Tracking

This paper presents design and batch manufacturing of a highly stretchable textile‐silicone capacitive sensor to be used in human articulation detection, soft robotics, and exoskeletons. The proposed sensor is made of conductive knit fabric as electrode and silicone elastomer as dielectric. The batch manufacturing technology enables production of large sensor mat and arbitrary shaping of sensors, which is precisely achieved via laser cutting of the sensor mat. Individual capacitive sensors exhibit high linearity, low hysteresis, and a gauge factor of 1.23. Compliant, low‐profile, and robust electrical connections are established by fusing filaments of micro coaxial cable to conductive fabric electrodes of the sensor with thermoplastic film. The capacitive sensors are integrated on a reconstructed glove for monitoring finger motions.

Design and Evaluation of a 3-D Printed Optical Sensor for Monitoring Finger Flexion

The development of techniques for monitoring finger movement is becoming increasingly important in areas, such as robotics, virtual reality, and rehabilitation. To date, various techniques have been proposed for tracking hand movements, but the majority suffer from poor accuracy and repeatability. Inspired by the articulated structure of finger joints, we propose a novel 3-D printed optical sensor with a compact hinged configuration for tracking finger flexion. This sensor exploits Malus’ law using the attenuation of light transmitted through crossed polarizers. The sensor consists of a single LED, two pieces of linear polarizing film, and a photodetector that detects the changes in polarized light intensity proportional to the angle of finger flexion. This paper presents the characterization of the proposed optical sensor and compares it with a commonly used commercial bend sensor. Results show that the bend sensor exhibits hysteresis error, low sensitivity at small angles, and significant temporal drift. In contrast, the optical sensor is more accurate (±0.5°) in the measuring range from 0° to 90°, and exhibits high repeatability and stability, as well as a fast dynamic response. Overall, the optical sensor outperforms the commercial bend sensor, and shows excellent potential for monitoring hand movements in real time.

LOVETT Scaling with Flex Sensor and MYO Armband for Monitoring Finger Muscles Therapy of Post-Stroke People

LOVETT scale is a common parameter used by the doctor or therapist to determine the muscle strength of the patient’s hands, especially patients with post-stroke. As a result of previous work of our group, a sensory glove for monitoring finger muscle therapy for post-stroke people with the name of Electronic Therapy Gloves (ETG) was proposed. With the flex sensor that embedded to the gloves we can measure the LOVETT scale of the post-stroke people. This sensory glove can help the patient doing their rehabilitation fast so that they don’t have to go to the hospital every week to check up their progress. In this work, we combine the data of sensory glove and the MYO armband for LOVETT scaling that has never been done before. The output of the Electronic Therapy Gloves can be optimized by 25%. All the LOVETT grade can be identify by the gloves, then it can help the doctor monitor the patient’s rehabilitation just by looking the patient’s record data with ETG.Keyword: LOVETT scale, flex sensor, MYO armband, post-stroke, rehabilitation.

Elastomeric Electronic Skin for Prosthetic Tactile Sensation

This report demonstrates a wearable elastomer‐based electronic skin including resistive sensors for monitoring finger articulation and capacitive tactile pressure sensors that register distributed pressure along the entire length of the finger. Pressure sensitivity in the order of 0.001 to 0.01 kPa−1 for pressures from 5 to 405 kPa, which includes much of the range of human physiological sensing, is achieved by implementing soft, compressible silicone foam as the dielectric and stretchable thin‐metal films. Integrating these sensors in a textile glove allows the decoupling of the strain and pressure cross‐sensitivity of the tactile sensors, enabling precise grasp analysis. The sensorized glove is implemented in a human‐in‐the‐loop system for controlling the grasp of objects, a critical step toward hand prosthesis with integrated sensing capabilities.