Finger Joints Research Articles

A rotary transformer cross-subject model for continuous estimation of finger joints kinematics and a transfer learning approach for new subjects.

Surface Electromyographic (sEMG) signals are widely utilized for estimating finger kinematics continuously in human-machine interfaces (HMI), and deep learning approaches are crucial in constructing the models. At present, most models are extracted on specific subjects and do not have cross-subject generalizability. Considering the erratic nature of sEMG signals, a model trained on a specific subject cannot be directly applied to other subjects. Therefore, in this study, we proposed a cross-subject model based on the Rotary Transformer (RoFormer) to extract features of multiple subjects for continuous estimation kinematics and extend it to new subjects by adversarial transfer learning (ATL) approach. We utilized the new subject's training data and an ATL approach to calibrate the cross-subject model. To improve the performance of the classic transformer network, we compare the impact of different position embeddings on model performance, including learnable absolute position embedding, Sinusoidal absolute position embedding, and Rotary Position Embedding (RoPE), and eventually selected RoPE. We conducted experiments on 10 randomly selected subjects from the NinaproDB2 dataset, using Pearson correlation coefficient (CC), normalized root mean square error (NRMSE), and coefficient of determination (R2) as performance metrics. The proposed model was compared with four other models including LSTM, TCN, Transformer, and CNN-Attention. The results demonstrated that both in cross-subject and subject-specific cases the performance of RoFormer was significantly better than the other four models. Additionally, the ATL approach improves the generalization performance of the cross-subject model better than the fine-tuning (FT) transfer learning approach. The findings indicate that the proposed RoFormer-based method with an ATL approach has the potential for practical applications in robot hand control and other HMI settings. The model's superior performance suggests its suitability for continuous estimation of finger kinematics across different subjects, addressing the limitations of subject-specific models.

Contribution of Soft Tissue Passive Forces in Thumb Carpometacarpal Joint Distraction.

Thumb carpometacarpal joint space changes when the surrounding soft tissues including the capsule, ligaments, and tendons are stretched or pulled away. When at rest, joint forces originate from passive contraction of muscles and the involvement of joint capsule and ligaments. Previous biomechanical models of hand and finger joints have mostly focused on the assessment of joint properties when muscles were active. This study aims to present an experimental-numerical biomechanical model of thumb carpometacarpal joint to explore the contribution of tendons, ligaments, and other soft tissues in the passive forces during distraction. Five fresh cadaveric specimens were tested using a distractor device to measure the applied forces upon gradual distraction of the intact joint. The subsequent step involved inserting a minuscule sensor into the joint capsule through a small incision, while preserving the integrity of tendons and ligaments, in order to accurately measure the fundamental intra-articular forces. A numerical model was also used to calculate the passive forces of tendons and ligaments. Before the separation of bones, the forces exerted by tendons and ligaments were relatively small compared to the capsule force, which accounted for approximately 92% of the total applied force. Contribution of tendons and ligaments, however, increased by further distraction. The passive force contribution by tendons at 2-mm distraction was determined less than 11%, whereas it reached up to 74% for the ligaments. The present study demonstrated that the ligament-capsule complex plays significant contribution in passive forces of thumb carpometacarpal joint during distraction.

A soft wearable exoglove for rehabilitation assistance: a novel application of knitted shape-memory alloy as a flexible actuator

We developed the knitted shape-memory alloy (SMA) as a flexible actuator and applied it to a soft wearable exoglove for rehabilitation assistance. Based on user needs and anthropometric data, we custom-designed the exoglove for three hemiplegic patients using the knitted-SMA actuator and evaluated its bending performance, gripping force and wearability under the four simulation conditions (S1–S4). To address the specific needs, both SMA plain- and double-knit modules were applied to the exoglove based on the patients’ finger joint range of motion (ROMs). The joint ROMs of all fingers increased by 13.71% and the skin temperature increased by 2.21 °C after actuating the glove (p = 0.006). The gripping force increased as much as 55.01%, when compared to the baseline. All patients were able to don and doff the developed glove independently, and positively evaluated their subjective satisfaction and thermal perception. The findings suggested the potential of the knitted SMA for the future development of soft wearable robots.

Design, Engineering Analysis, and Fabrication of a Prototype Electromechanical Finger Fixator Control System

This paper investigates a new external fixator system for treating finger contractures. This innovative system is electric and user-friendly, providing precise readings of the angles of diseased finger joints. Accurate measurements of the angles of the diseased finger joints can assist therapists and patients during rehabilitation procedures. The fixator consists of ten parts assembled using polyether-ether-ketone (PEEK) for the plastic components and stainless steel for the metal components. The design model was engineered, drawn, and analyzed using SolidWorks Computer-Aided Design software. The verification process utilizes finite element analysis to demonstrate that the maximum stress was lower than the yield strength of the chosen materials. As a result, the new device design is robust and stable enough to withstand the anticipated loading conditions of human fingers. Subsequently, a prototype was fabricated using advanced additive manufacturing technology, specifically fused deposition modeling (FDM). The proposed fixator is simple to control, reliable, easy to use, and reproducible. It enables device users to exercise their finger joints throughout the day without requiring the assistance of specialists.

A Web-based Survey Research on Clinical Practice Patterns of Korean Medicine Treatment for Degenerative arthritis of hip and finger joints

Objectives: This study aimed to understand the current status of clinical practice patterns of Korean medicine in the treatment of degenerative arthritis of the hip and finger joints using web-based survey.Methods: An e-mail questionnaire survey was conducted with the Korean Medicine Doctor(K.M.D) registered in the Korean Medicine Association. The survey data were analyzed using Microsoft Excel.Results: Although the response rate of the survey was low, the characteristics of the respondents generally reflected the characteristics of the study population. A total of 35.2% of the respondents had heard of the guidelines; however, they did not use them for medical treatment. The reason as answered by 32.8% of the respondents was “not enough treatment time to check the manual and apply it.” More than half (78.80%) answered that they were treating patients with both degenerative hip and finger arthritis; however, the average monthly number of first-time patients was ≤5. A total of 379 (60.9%) respondents answered that “acupuncture is very important,” which was the only one that exceeded the majority compared to other treatments. As a result of the safety investigation, “Acupuncture, herbal medicine, cupping” were considered high in safety, while “Pharmacopuncture and Bee venom acupuncture” were considered low in safety.Conclusions: This survey helped to determine the current clinical practice patterns of Korean medicine treatments, further providing basic data for CPGs for degenerative arthritis of the hip and finger joints.

Estimation of radiographic joint space of the trapeziometacarpal joint with computed tomographic validation.

Joint space width (JSW) is a common metric used to evaluate joint structure on plain radiographs. For the hand, quantitative techniques are available for evaluation of the JSW of finger joints; however, such techniques have been difficult to establish for the trapeziometacarpal (TMC) joint. This study aimed to develop a validated method for measuring the radiographic joint space of the healthy TMC joint. Computed tomographic scans were taken of 15 cadaveric hands. The location of a JSW analysis region on the articular surface of the first metacarpal was established in 3D space and standardized in a 2D projection. The standardized region was applied to simulated radiographic images. A correction factor was defined as the ratio of the CT-based and radiograph-based joint space measurements. Leave-one-out validation was used to correct the radiograph-based measurements. A t-test was used to evaluate the difference between CT-based and corrected radiograph-based measurements (). The CT-based and radiograph-based measurements of JSW were and , respectively. The correction factor for radiograph-based joint space was . Before correction, the difference between the CT-based and radiograph-based joint space was 1.43mm [95% CI: ; ]. After correction, the difference was [95% CI: ; ]. Corrected measurements of radiographic TMC JSW agreed well with CT-measured JSW. With in-vivo validation, the developed methodology has potential for automated and accurate radiographic measurement of TMC JSW.

Reverse dorsolateral proximal phalangeal island flap: Long-term results

ObjectivesThis study aims to present long-term follow-up results of the reverse dorsolateral proximal phalangeal island flap designed for reconstruction of large fingertip and pulp defects. MethodsWe examined 18 patients who underwent reverse dorsolateral proximal phalangeal island flap surgery to address ≥2.5 cm fingertip and pulp defects. Mean follow-up was 84.4 months. Sensitivity assessments were conducted using the Semmes–Weinstein monofilament and 2-point discrimination tests. Additionally, we evaluated finger joint active range of motion, complications and cold intolerance. ResultsMild venous congestion was observed in 5 flaps. Significant differences were observed in 2-point discrimination and Semmes-Weinstein monofilament tests between the injured and contralateral sides, specifically in the flaps, the dorsal side of the middle phalanx, and the donor site. The flap's mean static 2-point discrimination was 8.3 mm. Restricted distal interphalangeal joint extension was observed in 2 cases. Total active motion with the flap was good or excellent in the injured fingers, but with a significant difference between injured and contralateral fingers. Additionally, 42% of the injured fingers exhibited hook nail deformity, and 2 patients reported cold intolerance. Despite these issues, most patients has high scores for the appearance and satisfaction aspects of the Michigan Hand Outcomes Questionnaire. ConclusionIn moderate or larger fingertip defects, the reverse dorsolateral proximal phalangeal island flap serves as an alternative for reconstructing both fingertip and pulp issues. However, this option involves sacrificing some sensation in the dorsum of the middle phalangeal finger and the donor area. Level of evidenceIV, therapeutic study.

Efficacy and Safety of High Density LED Irradiation Therapy for Patients With Hand Osteoarthritis: A Single-Center Clinical Study.

To assess the safety and effectiveness of high-density light-emitting diode (LED) irradiation therapy in patients with hand osteoarthritis (OA) and compare the pre- and post-intervention symptoms. Twenty-three patients with hand OA underwent eight sessions of high-density LED irradiation therapy directed at the five most painful areas in the finger joints. Each session lasted for 18 minutes; and the sessions were conducted twice a week, for 4 weeks. We evaluated the degree of pain using the visual analogue scale, ring size, and passive range of motion (flexion+extension) for two most painful joints from the baseline to post-therapy (weeks 4 and 6). High-density LED irradiation therapy significantly reduced the pain posttreatment compared with that observed at the baseline (p<0.001). Although improvements were observed in ring size and joint range of motion at 4 and 6 weeks, they were not statistically significant (p>0.05). No adverse events were observed. We examined the safety and effectiveness of high-density LED irradiation therapy in reducing pain and hand swelling and improving joint mobility in patients with hand OA. These results suggest that high-density LED irradiation therapy has the potential to be an important strategy for managing hand OA.

Enhancing the Versatility and Performance of Soft Robotic Grippers, Hands, and Crawling Robots Through Three-Dimensional-Printed Multifunctional Buckling Joints.

Soft robotic grippers and hands offer adaptability, lightweight construction, and enhanced safety in human-robot interactions. In this study, we introduce vacuum-actuated soft robotic finger joints to overcome their limitations in stiffness, response, and load-carrying capability. Our design-optimized through parametric design and three-dimensional (3D) printing-achieves high stiffness using vacuum pressure and a buckling mechanism for large bending angles (>90°) and rapid response times (0.24 s). We develop a theoretical model and nonlinear finite-element simulations to validate the experimental results and provide valuable insights into the underlying mechanics and visualization of the deformation and stress field. We showcase versatile applications of the buckling joints: a three-finger gripper with a large lifting ratio (∼96), a five-finger robotic hand capable of replicating human gestures and adeptly grasping objects of various characteristics in static and dynamic scenarios, and a planar-crawling robot carrying loads 30 times its weight at 0.89 body length per second (BL/s). In addition, a jellyfish-inspired robot crawls in circular pipes at 0.47 BL/s. By enhancing soft robotic grippers' functionality and performance, our study expands their applications and paves the way for innovation through 3D-printed multifunctional buckling joints.

Bilateral reconstruction of palmar soft tissues defects of the hands after thermal injury

Introduction Thermal injury to the palmar surface of the hand is usually complicated by flexion desmogenic contracture of the finger joints. This condition is more complicated with significant wound areas and depths of soft tissue destruction. Conventional surgical methods and soft tissue reconstructions may fail to provide full restoration of the hand function.The objective was to present the optimal treatment strategy for patients with scar flexion contractures of the fingers after thermal injury to the palmar surface of both hands using a pediatric case report.Material and methods A child aged 2 years and 4 months underwent surgical treatment to include excision of scars, skin grafting of both hands with a vascularized fasciocutaneous flap raised with the radial artery.Result The patient could regain all types of hand grip on both sides 12 years after surgical treatment. Both hands were aesthetically acceptable.Discussion Treatment of patients with thermal injury and substantial soft tissue damage is a complex disease process. Conservative treatment and surgical procedures using non-vascularized skin flaps are normally used for the condition. These approaches are associated with cicatricial and arthrogenic flexion contracture of the finger joints. The radical treatment includes thorough wound debridement and early flap coverage and wound closure using a flap with an axial-pattern blood supply, free flaps and reverse-flow flaps. The surgical approach helps to avoid flexion contracture of the fingers initiating early restoration of professional, social stereotypes and stereotypes in everyday life.Conclusion The clinical observation has shown the possibility of one-stage organ-preserving surgical treatment using flaps with an axial blood supply.

Xanthan gum toughen ionically conductive hydrogels for flexible and artificial epidermis sensors with multifunctionality and self-healability

Conductive hydrogels that possess hydrophobic interaction have gained much attention in fields like strain sensors, soft robotics, tissue engineering, human-machine interaction, and biomedical sensors due to their excellent stretchability and effective energy dissipation mechanism. However, their use is limited due to poor mechanical performance, low sensing ability, lack of response time, and deficiency of self-healing capability. To overcome these limitations, acrylamide-co-butylacrylate/xanthan gum-based hydrophobically associated conductive hydrogels were designed. Amphiphilic sodium dodecyl sulfate was employed both as a cross-linker and a micelle-forming agent, while LiCl make the hydrogel as an ionic conductive material. The obtained hydrogels show fracture stress and fracture strain of 661kPa and 1100% respectively. The measured conductivity was 0.21Sm−1 and the strain sensing of the designed hydrogel reached up to 800%. Similarly, the designed hydrogels show remarkable sensitivity (Gauge factor = 28.8 at an applied strain of 800%) which is useful in the detection of a wide range of human motions. Finger, wrist, elbow, and knee joint movement can be easily detected with these hydrogels. Furthermore, the hydrogel can detect speaking, facial expressions, and pressure sensing. The designed hydrogels showed an excellent response and recovery time of 0.15 s and 0.13 s respectively. During multiple stretching and un-stretching cycles for 140 s, the designed hydrogels show continuous linear response without any current drop or fracture. Therefore the as-fabricated hydrogel presents a novel opportunity for its application in various fields such as flexible conductive material, strain sensors, human motion detection devices, and tissue engineering.

Evaluation of the results of salvage surgical treatment of distal phalanx injuries and substantiation of the algorithm of finger salvage treatment

Introduction The rates of hand injuries in the structure of total of injuries range from 30 to 50 % in recent decades. The improvement of approaches to the choice of optimal options for treatment of injuries of the distal phalanges of fingers that ensure the preservation of anatomical integrity and function of fingers remains relevant.The purpose of the work was a comparative analysis of the clinical efficacy of various methods for surgical treatment of trauma to the distal phalanx of fingers.Methods Forty-seven patients (18 men and 29 women, mean age 34.2 ± 13.3 years) with injuries to the distal phalanges of the fingers were examined and treated. The patients were divided into 2 groups. Group 1 (comparison) was 25 patients. Conventional approaches to the formation of finger stumps were used by shortening the bone part of the phalanx, forming two opposite flaps and applying several interrupted sutures; group 2 (main group) were 22 patients treated according to the surgical tactics developed by us. The proposed tactics of reconstructive plasty of the defects in the nail phalanges of three joint fingers involves the formation of a stump of the nail phalanx with a visual effect of elongation of the phalanx due to local or cross-plasty with dermo-fascial flaps. Comparison of treatment results in the groups of patients was performed 1, 3, 6, 12 months after reconstruction operations.Results It was established that the use of the developed surgical treatment of the injury to the distal phalanx of the fingers results in less severity (compared to the use of standard methods) of pain on days 10-21 after surgery (by 44.8-54.3 %), lower levels of the Quick DASH indicators after 3-12 months, decrease in Vancouver scoring of skin scar severity changes after 6-12 months, higher patient satisfaction with the functional result of treatment. Based on the results obtained, a diagnostic and treatment algorithm for providing medical care to hand injuries has been proposed.Discussion The results of the study indicate the effectiveness of the developed method of plastic surgery of fingertip defects of nail phalanges in the three joint fingers by moving the palmar-lateral and dorsal-lateral blood-supplied flaps from the fingers of the same name and neighboring fingers without shortening the bone stumps of the nail phalanges while achieving an esthetic result by visual lengthening of the fingertip phalanx. Based on the results obtained, a diagnostic and treatment algorithm for providing medical care to patients with finger injuries has been proposed.Conclusion The proven method improves the results of reconstructive surgical interventions in the treatment of fingertip defects the of tnail phalanx in three joint fingers.

Scleromyxedema

Scleromyxedema or generalized diffuse lichen myxoedematosus is arare mucinosis that is associated with monoclonal gammopathy and which frequently affects multiple extracutaneous organ systems. The pathogenesis of scleromyxedema has not been fully elucidated, but includes stimulation of glycosaminoglycan synthesis. The clinical course of scleromyxedema is chronic and often progressive, leading to severe morbidity and even death. The characteristic skin findings encompass multiple waxy papules often on indurated plaques, while thickening of skin leads to conspicuous folds on glabella and dorsal aspects of finger joints. Microscopical manifestations are dermal deposits of glycosaminoglycans between collagen bundles in reticular dermis, increased numbers of fibroblasts and fibrosis as well as loss of elastic fibers. Progressive skin involvement results in decreased mobility of the mouth and joints and even contractures. Extracutaneous manifestations occur in the musculoskeletal or cardiovascular system, in the gastrointestinal or respiratory tract, in the kidneys or in the central and peripheral nervous system. There are no in-label or evidence-based treatments available for scleromyxedema, but by expert consensus high-dose immunoglobulins are considered as treatment of choice, followed in case of insufficient efficacy by systemic glucocorticosteroids and then lenalidomide or thalidomide. In severe and refractory cases, autologous hematopoietic stem cell transplantation has been performed. Long-term maintenance treatment is usually required to prevent recurrences. Close interdisciplinary follow-up is recommended.

Giant cell tumour of tendon sheath (GCTTS) – 2 Most common tumour of hand after ganglion cyst

Probably one of the most common benign neoplasm in the human hand, the Giant Cell Tumour of Tendon Sheath (GCTTS) has been studied by many authors over the years as a popular tumour. There have been studies on the etilogical factors, however, limited attention has been given to etiology, prognostic factors, and recurrence rate. Because there are several factors that predispose to recurrence, it is imperative that medical practitioners ensure complete excision of the tumour, including removal of residual satellite nodules. This study is a focus on 0.5cm swelling over dorsal part of the interphalangeal joint of middle finger of the right hand of a 55-year old female that was initially unilobulated, which eventually increased to 3cm and was bilobed over 6 months. With meticulous dissection and the use of magnification loupe to obtain a low recurrence rate, thereby emphasising the key role of surgery as the first prognostic factor of GCTTS.

Semi‐Solid Stretchable Carbon Nanotubes Inkpad for Hand‐Based Haptic Interaction

AbstractDexterity and perceptual abilities of the hand are crucial in virtual reality (VR) interactions. This necessitates haptic gloves capable of accurately measuring finger movements and ensuring comfort, a challenging combination that demands both high sensitivity and stretchability. A flexible sensor fabricated from semi‐solid material CNTs‐Inkpad composed of carbon nanotubes (CNTs) mixed with silica gel is proposed and its real‐time response can be achieved by controlling the ratio. Its semi‐solid form harnesses CNTs' high conductivity and sensitivity, avoiding structural cracking in solid CNTs during extensive stretching, thus the semi‐solid form can adapt to various hand gestures. This mechanism enables the CNTs‐Inkpad to function as strain sensors with high gauge factors (GF = 16.99) and high extensibility (350%). By integrating ten CNTs‐Inkpad sensors and five vibrators, a thin and lightweight haptic glove is developed with high sensitivity and stretchability. The glove enables collaborative measurement of all finger joints required for typical gestures in VR interactions, suitable for motion detection and haptic feedback.

Associations of inflammatory and metabolic biomarkers with incident erosive hand osteoarthritis in the osteoarthritis initiative cohort

Erosive hand osteoarthritis (eHOA) is a subtype of hand osteoarthritis (OA) that develops in finger joints with pre-existing OA and is differentiated by clinical characteristics (hand pain/disability, inflammation, and erosions) that suggest inflammatory or metabolic processes. This was a longitudinal nested case-cohort design among Osteoarthritis Initiative participants who had hand radiographs at baseline and 48-months, and biospecimens collected at baseline. We classified incident radiographic eHOA in individuals with ≥1 joint with Kellgren-Lawrence ≥2 and a central erosion present at 48-months but not at baseline. We used a random representative sample (n=1282) for comparison. We measured serum biomarkers of inflammation, insulin resistance and dysglycemia, and adipokines using immunoassays and enzymatic colorimetric procedures, blinded to case status. Eighty-six participants developed incident radiographic eHOA. In the multivariate analyses adjusted for age, gender, race, smoking, and body mass index, and after adjustment for multiple analyses, incident radiographic eHOA was associated with elevated levels of interleukin-7 (risk ratio (RR) per SD=1.30 [95% confidence interval (CI) 1.09, 1.55] p trend 0.01). This exploratory study suggests an association of elevated interleukin-7, an inflammatory cytokine, with incident eHOA, while other cytokines or biomarkers of metabolic inflammation were not associated. Interleukin-7 may mediate inflammation and tissue damage in susceptible osteoarthritic finger joints and participate in erosive progression.

A marker-based approach to determine the centers of rotation of finger joints

Background and ObjectiveThe methods proposed in literature to estimate the position of hand joints Centers of Rotation (CoRs) typically require computationally non-trivial optimization routines and exploit a high number of markers to calculate CoRs positions from surface marker trajectories. Moreover, most of the existing works evaluated the accuracy only in simulation. This work proposes a new procedure, based on the Pratt circle fit, to estimate joints CoRs position in 2D through marker-based acquisitions. MethodsThe advantage of the Pratt circle fit lies in its simplicity and computational speed, and in the possibility of exploiting a reduced markerset for calculating CoRs. By applying simplifying assumptions regarding the movement of the fingers (i.e., planar and decoupled flexion-extension movements of each joint occurring in the same flexion plane for all the joints of the finger), it is possible to determine the position of the CoR of each joint in 2D. For this reason, the estimation of the Carpo-MetaCarpal joint of the thumb was not included in this work, as it exhibits a more complex movement associated to the combination of a flexion-extension and adduction-abduction degree of freedom. The errors in estimating CoRs were evaluated by conducting experimental acquisitions on an anthropomorphic robotic hand and comparing the position of the estimated CoR with the real position of the CoR. The repeatability of the method and its capability to estimate anatomically plausible CoRs were evaluated through experimental acquisitions conducted on five healthy volunteers. ResultsErrors in estimating finger joints CoRs were in the order of 0.70 mm and 0.18 mm respectively along the finger longitudinal direction (i.e., x coordinate) and thickness (i.e., y coordinate). Standard Deviations of CoRs positions were comparable to the ones obtained in literature (i.e., below 2 mm and 1 mm respectively for the x and y coordinates), thus demonstrating the repeatability of the method. The Anatomical Plausibility Rate of the proposed approach was between 80% and 100%. ConclusionsThe performance of the Pratt-based CoRs estimation procedure proposed in this work was comparable to other existing methods, with the advantage of exploiting a simple fitting algorithm and a reduced markerset with respect to the state-of-the-art techniques.

Intra- and inter-rater reliability of goniometric finger range of motion using a written protocol.

Goniometric finger range of motion (ROM) is the most common outcome measure used for functional evaluation of finger joints, but its reliability is not well-evaluated. This study aimed to investigate intra- and inter-rater reliability of goniometric finger ROM using a written protocol for active, passive, and composite movements in healthy adults. The design was a single-center, cross-sectional, reliability study. Participants were 20 healthy adults (mean ± standard deviation, 36.4 ± 10.9 years). ROM for active, passive, and composite movements of the fingers was assessed by three occupational therapists with at least 5 years clinical experience in the field of physical disabilities. To standardize the measurement method used, we developed a written protocol, stabilized the wrist position, and trained the evaluators. Intraclass correlation coefficient (ICC) values were used for the reliability analysis. ICC (1,1) was used for intra-rater reliability. ICC (2,1) was used for inter-rater reliability. Hand-shaped heatmaps were used to summarize the reliability data. Most of the results (88.7%) showed moderate to good intra-rater reliability (ICC ≥ 0.50), while inter-rater reliability showed less (69.0%). Both intra- and inter-rater reliability showed no trends between dominant and non-dominant hands, type of movement, finger, or joint. Intra-rater reliability was relatively high and using a written protocol was beneficial. Inter-rater reliability tended to be lower, and differences in the physical structure of both raters and participants may have affected inter-rater reliability values.

RadarHand: A Wrist-Worn Radar for On-Skin Touch-Based Proprioceptive Gestures

We introduce RadarHand, a wrist-worn wearable with millimetre wave radar that detects on-skin touch-based proprioceptive hand gestures. Radars are robust, private, small, penetrate materials, and require low computation costs. We first evaluated the proprioceptive and tactile perception nature of the back of the hand and found that tapping on the thumb is the least proprioceptive error of all the finger joints, followed by the index finger, middle finger, ring finger, and pinky finger in the eyes-free and high cognitive load situation. Next, we trained deep-learning models for gesture classification. We introduce two types of gestures based on the locations of the back of the hand: generic gestures and discrete gestures. Discrete gestures are gestures that start at specific locations and end at specific locations at the back of the hand, in contrast to generic gestures, which can start anywhere and end anywhere on the back of the hand. Out of 27 gesture group possibilities, we achieved 92% accuracy for a set of seven gestures and 93% accuracy for the set of eight discrete gestures. Finally, we evaluated RadarHand’s performance in real-time under two interaction modes: Active interaction and Reactive interaction. Active interaction is where the user initiates input to achieve the desired output, and reactive interaction is where the device initiates interaction and requires the user to react. We obtained an accuracy of 87% and 74% for active generic and discrete gestures, respectively, as well as 91% and 81.7% for reactive generic and discrete gestures, respectively. We discuss the implications of RadarHand for gesture recognition and directions for future works.

Joint angle prediction for a cable-driven gripper with variable joint stiffness through numerical modeling and machine learning

Soft grippers in automation, particularly those with variable joint stiffness, offer promising possibilities for precise manipulation tasks. However, accurately predicting finger joint bending angles in this field poses significant challenges due to the soft and complex nature of the grippers, making modeling and angle prediction difficult. This paper presents the development of a predictive model for precisely controlling bending angles in multi-material printed soft grippers with variable stiffness, which are pivotal for delicate manipulation tasks in automation. In particular, we explore a cable-driven gripper design made of thermoplastic polyurethane and conductive polylactic acid materials, featuring integrated resistive joints for stiffness modulation through controlled Joule heating. A data-driven modeling approach, combining numerical modeling of the gripper and machine learning techniques, was employed for the development of the predictive model. We performed static structural simulations using ANSYS Workbench to measure bending angles under various conditions for developing datasets for model training. In this work, we evaluated several machine learning models such as linear regression, decision tree, and K-nearest neighbor regression models to predict the correlation between temperature, pull distance, and bending angle. The K-nearest neighbor regression model demonstrated the highest accuracy, with a mean absolute error of approximately 11%. These findings underline the importance of precise angle prediction models in enhancing the functionality and reliability of soft grippers, paving the way for their broader application in automation and robotics.