Small Force Sensors Research Articles

EFFECT OF SUBSTRATE AND WALKING SURFACES ON CENTRAL METATARSAL FOOT PAD WEIGHT LOADING IN MAGELLANIC PENGUINS (SPHENISCUS MAGELLANICUS) WITH AND WITHOUT PODODERMATITIS: AN EX VIVO STUDY.

Pododermatitis is common in penguins kept under human care. Substrate optimization plays an important role in prevention and treatment; however, there is limited information on biomechanical properties of commonly used substrates on penguin feet. The objectives were to test the ability of different substrates to decrease weight loading on the central metatarsal pad of penguin feet in an ex vivo model using feet with and without bumblefoot harvested from two Magellanic penguin (Spheniscus magellanicus) cadavers. Penguin feet were attached to a digital force gauge mounted onto a stand for compression testing at 2.5 and 5 kg. Forces at the central metatarsal pad were measured in triplicate using small force sensors. Tested substrates included five granular surfaces (sand, wet sand, pea gravel, wet pea gravel, and crushed ice), three compliant surfaces (short-leaf Astroturf, long-leaf Astroturf, and neoprene), and three firm surfaces (tile, rubber drainage mat, and 3M Safety-Walk Wet Area Matting). Data were analyzed using linear mixed models. There were multifaceted effects of applied pressures, substrate surfaces, and pododermatitis on central metatarsal measured pressures. In general, doubling compression forces resulted in higher measured pressures in all firm and compliant surfaces but not in granular surfaces. Firm surfaces were associated with higher recorded plantar pressures at 2.5 kg, but different significance groupings emerged at 5 kg with a high-, medium-, and low-pressure cluster of surfaces. Pododermatitis lesions resulted in significant alterations in statistical significance clustering among substrate surfaces and unique substrate behaviors. The results of this study could help in making recommendations pertaining to foot health for penguin exhibits.

Development and evaluation of vesicourethral anastomosis bench-top model for measurement of traction force on urethra in robotic surgery.

In vesicourethral anastomosis (VUA), which is part of robot-assisted radical prostatectomy, surgeons must proceed carefully to avoid urethral damage. We developed and evaluated a VUA bench-top model that can measure the traction force on the urethra during robotic surgery. The VUA model included the urethra, bladder, pelvic bones, and a small force sensor that was capable of measuring the traction force on the urethra. Eight skilled and eight novice urologists performed a VUA task in robotic surgery. The skilled surgeons assessed the model's realism and usefulness as a training tool using a 5-point Likert scale. The evaluation items [task time, maximum force, force volume, and length of time that specific excessive forces were applied to the urethra (2, 3, 4, and ≥ 5 N)] were compared between the skilled and novice surgeons using the Mann-Whitney U test. Measurements were conducted in four directions with respect to the maximum force on the urethra: 11-1, 2-4, 5-7, and 8-10 o'clock. The quality of the model was scored 3.7 to 4.9 points for all 16 items in 4 domains except for "Usefulness compared with animal models." There were differences in the task time and almost all force parameters between the skilled and novice surgeons. We developed a relatively high-quality VUA bench-top model that measures traction force on the urethra, and we have revealed differences in the forces of action on the urethra in two groups of surgeons with different skill levels.

Accurate Localization of First and Second Heart Sounds via Template Matching in Forcecardiography Signals.

Cardiac auscultation is an essential part of physical examination and plays a key role in the early diagnosis of many cardiovascular diseases. The analysis of phonocardiography (PCG) recordings is generally based on the recognition of the main heart sounds, i.e., S1 and S2, which is not a trivial task. This study proposes a method for an accurate recognition and localization of heart sounds in Forcecardiography (FCG) recordings. FCG is a novel technique able to measure subsonic vibrations and sounds via small force sensors placed onto a subject's thorax, allowing continuous cardio-respiratory monitoring. In this study, a template-matching technique based on normalized cross-correlation was used to automatically recognize heart sounds in FCG signals recorded from six healthy subjects at rest. Distinct templates were manually selected from each FCG recording and used to separately localize S1 and S2 sounds, as well as S1-S2 pairs. A simultaneously recorded electrocardiography (ECG) trace was used for performance evaluation. The results show that the template matching approach proved capable of separately classifying S1 and S2 sounds in more than 96% of all heartbeats. Linear regression, correlation, and Bland-Altman analyses showed that inter-beat intervals were estimated with high accuracy. Indeed, the estimation error was confined within 10 ms, with negligible impact on heart rate estimation. Heart rate variability (HRV) indices were also computed and turned out to be almost comparable with those obtained from ECG. The preliminary yet encouraging results of this study suggest that the template matching approach based on normalized cross-correlation allows very accurate heart sounds localization and inter-beat intervals estimation.

Measurement of Force Applied by Infant Tongue to Three Types of Artificial Nipple: Investigation of Dynamic Actions in Relation to the Shape and Size of the Artificial Nipple

This study aims to elucidate whether the force applied by an infant's tongue differs or not depending on geometrical differences in the artificial nipples. We developed three sensorized artificial nipple devices using six small force sensors and we have measured the tongue force during sucking in 11 infants. As a result, we have showed that the order of sensor responses and sucking period are similar among different geometries of artificial nipples. However, we have also observed that the maximum force measured differed in different artificial nipples. Furthermore, we have also observed differences in the estimated velocity the tongue movement between individual infants. Overall, this study showed that it is feasible to measure the dynamic properties of artificial nipples toward the definition of clear recommendations for mothers that wish to select the appropriate artificial nipple for their babies on an individual basis. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Effects of Perching Surfaces and Foot Bandaging on Central Metatarsal Foot Pad Weight Loading of the Peregrine Falcon (Falco peregrinus).

Pododermatitis is prevalent in falcons and is characterized by inflammation and infection of the plantar aspect of the feet, particularly at the central metatarsal pad. Suboptimal perch design and increased weight loading on the plantar skin have been proposed as major risk factors for the development of pododermatitis. Prevention and treatment are challenging, but weight load reduction on the affected area of the foot is an accepted goal of initial treatment. To date, to our knowledge no studies have compared the performance of different bandage-perch surface combinations on weight redistribution away from the central metatarsal pad. An ex vivo factorial experiment was designed using the feet from a peregrine falcon cadaver to quantify weight load reduction on the central metatarsal pad with different combinations of perch surfaces (wood, neoprene, artificial turf) and bandages (none, interdigital, silicone shoe). Feet were attached to a digital force gauge mounted on a manual test stand for compression testing. Weight loading at the central metatarsal pad was measured using a small force sensor. Perch-surface combinations in randomized order were tested at 250 g, 500 g, and 1 kg with 9 replicates per foot. At 250 g, all combinations reduced measured metatarsal pad forces, but otherwise performed similarly. As compression forces increased, differences emerged with the shoe combinations performing better overall, followed by a group including the neoprene and artificial turf-interdigital bandage combinations, and a third group including the interdigital/wood and no bandage-artificial turf. All combinations performed better than control (no bandage on wood). This study may assist veterinarians in selecting appropriate perching surface/bandage combinations when treating falcons with pododermatitis.

Sensors for Expert Grip Force Profiling: Towards Benchmarking Manual Control of a Robotic Device for Surgical Tool Movements.

STRAS (Single access Transluminal Robotic Assistant for Surgeons) is a new robotic system based on the Anubis® platform of Karl Storz for application to intra-luminal surgical procedures. Pre-clinical testing of STRAS has recently permitted to demonstrate major advantages of the system in comparison with classic procedures. Benchmark methods permitting to establish objective criteria for ‘expertise’ need to be worked out now to effectively train surgeons on this new system in the near future. STRAS consists of three cable-driven sub-systems, one endoscope serving as guide, and two flexible instruments. The flexible instruments have three degrees of freedom and can be teleoperated by a single user via two specially designed master interfaces. In this study, small force sensors sewn into a wearable glove to ergonomically fit the master handles of the robotic system were employed for monitoring the forces applied by an expert and a trainee (complete novice) during all the steps of surgical task execution in a simulator task (4-step-pick-and-drop). Analysis of grip-force profiles is performed sensor by sensor to bring to the fore specific differences in handgrip force profiles in specific sensor locations on anatomically relevant parts of the fingers and hand controlling the master/slave system.

Trunk Balance Evaluation in Adolescent Athletes and Gender Difference using the Dynamic Sitting Balance Device

Objective: The purpose of this study was to quantitatively measure the trunk stability of adolescent athletes using a recently developed, plane-specific, dynamic trunk stability measuring device and to examine gender differences. Methods: This was a cross-sectional study to confirm the difference in dynamic trunk stability between male and female adolescent athletes ranging in age from 12 to 15 years. 15 adolescent athlete cohort was divided into 2 groups by gender. In the dynamic trunk balance evaluator that we developed, the seating surface can be vibrated at a constant cycle (0.2 Hz, 0.4 Hz, 0.6 Hz), the pressure of the seating surface under vibration is detected by three small force sensors installed under the seating surface, and the center of pressure (COP) can be calculated. Measurements were performed for 30 s by one examiner, and each participant was measured three times after two practice attempts. While the seating surface was swaying, the participant's gaze was fixed to a mark about 1 cm in diameter set at a position 2 m in front of the participant at eye height, and the participant was asked to maintain the position of the head constant. The fluctuation of the center of gravity on the seat surface over time was measured, and the total trajectory length of the COP was used as the evaluation item. Results: There were no adverse events during measurement. The results for the total COP trajectory length of male was 2365 ± 176 mm, and that of female was 2674 ± 293 mm. There were significant differences between the male and female groups. In particular, Adolescent female athletes had less dynamic trunk stability in the coronal plane. Conclusion: Adolescent female athletes had less dynamic trunk stability in the coronal plane than their male counterparts. The recently developed device may be a useful tool for assessing the effects of prevention programs on dynamic core stability.

Three‐axis capacitive force sensor with liquid metal electrodes for endoscopic palpation

Endoscopic palpation is a promising technology for detecting tumours that are too small to be detected by CT and magnetic resonance imaging, are not located on tissue surfaces, and cannot be observed using endoscopes. This method uses a small force sensor mounted on the tip of an endoscope. It is desirable that the sensor can scan tissue surfaces and continuously measure the stiffness of organs. Prior work developed a ballpoint-pen-like capacitive force sensor and carried out proof of principle experiments; however, the sensor was too large to be mounted on an endoscope. This study designed three-dimensional (3D) microfluidic channels encapsulating liquid metal to develop a sensor that is small enough to be mounted on an endoscope. Eight polydimethyl siloxane layers with channel structures were assembled and filled with Galinstan, a commercial liquid metal, to form 3D electrodes. The sensor was experimentally characterised and verified to be applicable to endoscopic palpation.

Soft-rubber-packaged Pb(Zr,Ti)O3 MEMS touch sensors for human–machine interface applications

We proposed and developed soft-rubber-packaged Pb(Zr,Ti)O3 (PZT) microelectromechanical systems (MEMS) force sensors as human–machine interface sensors of human touch and input. To achieve small and highly sensitive sensors with low-power-consumption, a small PZT MEMS cantilever was used as the sensing element, and it was covered with soft rubber, poly(dimethylsiloxane) (PDMS), to prevent the cracking of the brittle PZT film when touching the sensor. The PDMS packaging does not affect the ferroelectric characteristics of the sensing PZT film, because the hysteresis and impedance changes of the PZT are less than 5%. The sensor dimensions are 5 × 5 × 1.1 mm3. The sensor generated charges without requiring voltage supply. The sensor generated an electric charge of 7.8 pC under an applied force of 1 N. The sensitivity was adjusted by changing the hardness of the soft rubber package: hard rubber provides high sensitivity, but the sensor is easily cracks. Hence, a sensor with a durometer hardness A of 35.6 was found to be optimal as a human–machine interface sensors of human touch of approximately 5–7 N because it has a linear sensitivity at force smaller than 5 N and the bending is small at forces larger than 5 N, which leads to a highly durable sensor. The sensor with a durometer hardness A of 35.6 did not break or crack until the applied force reached 40 N. By packaging brittle PZT MEMS cantilevers with soft rubber, small-force sensors can be constructed, leading to small, low-energy-consumption human–machine interface sensors.

A Study of the Reliability of a New Dynamic Trunk Balance Measuring Device

Objective: A new method of evaluating sitting balance that improved on a previous device was developed. However, the reliability of body trunk balance measured by this device is unknown. The purpose of this study was to verify its reliability within and between examiners. Methods: This was a cross-sectional study involving healthy adult males (age 20 to 45 years) who were able to walk. The seating surface could be vibrated at a constant cycle (0.2 Hz, 0.4 Hz, 0.6 Hz), the pressure of the seating surface under vibration was detected by three small force sensors installed under the seating surface, and the center of pressure (COP) could be calculated. Measurements were performed by two examiners, and each participant was measured three times in a sitting position. The platform was tilted to the left and right at a front face inclination angle ± 7°, with two cycles in 10 s (0.2 Hz), while the participant’s gaze was fixed to a mark 2 m in front of the participant at eye height, and the participant was asked to maintain the position of the head constant. Measurement was then performed for 30 s. The fluctuation of the center of gravity on the seat surface over time was measured, and the total trajectory length of the COP was used as the evaluation item. To examine the reliability of the measuring instrument, ICC (1.3) was obtained as the intra-class correlation coefficient for intra-examiner reliability, and ICC (2.1) was obtained for inter-examiner reliability. Results: The ICC for intra-examiner reliability was 0.815, and that for inter-examiner reliability was 0.789. No adverse events occurred during balance evaluation. Conclusion: This device could be used to evaluate dynamic trunk balance with relatively high reliability. Thus, the present device appears to be useful for quantitatively evaluating dynamic trunk balance conveniently and safely.

Nondestructive Detection of a Crack in a Triangular Cantilever Beam Based on Frequency Measurement

Triangular cantilevers are usually used as small force sensors in the transverse direction. Analyzing the effect of a crack on transverse vibration of a triangular cantilever will be of value to users and designers of cantilever deflection force sensors. We present a method for prediction of location and size of a crack in a triangular cantilever beam based on measurement of the natural frequencies in this paper. The crack is modeled as a rotational spring. The beam is treated as two triangular beams connected by a rotational spring at the crack location. Formulae for representing the relation between natural frequencies and the crack details are presented. To detect crack details from experiment results, the plots of the crack stiffness versus its location for any three natural modes can be obtained through the relation equation, and the point of intersection of the three curves gives the crack location. The crack size is then calculated using the relation between its stiffness and size. An example to demonstrate the validity and accuracy of the method is presented.

Detection of Multiple Cracks in Triangular Cantilevers Based on Frequency Measurements

Triangular cantilevers are used as small force sensors. Prediction of location and size of multiple cracks from experimental results will be of value to users and designers of cantilever deflection force sensors. We extend a method for prediction of location and size of multiple cracks in rectangular cantilevers to deal with triangular cantilevers in this paper. The cracks are assumed to introduce local flexibility change and are modeled as rotational springs. The beam is divided into a number of segments, and each segment is associated with a damage index, which can be calculated through the relationship between the damage index and strain energy of each segment and the changes in the frequencies caused by the cracks. The location of cracks can be obtained with high accuracy with sufficient segment numbers. The size of a crack can be calculated through the relationship between the crack size and its stiffness, which can be obtained from the damage index related to the crack. The maximum error in prediction of the crack position in the case of double cracks is less than 15%, and it is less than 25% in prediction of the crack size.

광섬유 브래그 격자를 이용한 촉각센서용 유연 단위 힘 센서 개발

This paper describes the flexible force sensor using fiber Bragg grating (FBG) and silicone rubber for the tactile sensation to detect the distributed normal force. The newly designed FBG flexible force has simple structure and can be easily multiplexed with simple wiring compared with the other electric mechanical sensors. We designed the flexible silicone rubber transducer and found the optimum embedding position of FBG in the transducer using the finite element analysis. This flexible force sensor has good performance and is immunity to the electromagnetic field compared with any other kinds of small force sensors for tactile sensation.

Hand digit control in children: age-related changes in hand digit force interactions during maximum flexion and extension force production tasks

We studied the finger interactions during maximum voluntary force (MVF) production in flexion and extension in children and adults. The goal of this study was to investigate the age-related changes and flexion-extension differences of MVF and finger interaction indices, such as finger inter-dependency (force enslaving (FE): unintended finger forces produced by non-instructed fingers during force production of an instructed finger), force sharing (FS; percent contributions of individual finger forces to the total force at four-finger MVF), and force deficit (FD; force difference between single-finger MVF and the force of the same finger at four-finger MVF). Twenty-five right-handed children of 6-10 years of age and 25 adults of 20-24 years of age participated as subjects in this study (five subjects at each age). During the experiments, the subjects had their forearms secured in armrests. The subjects inserted the distal phalanges of the right hand into C-shaped aluminum thimbles affixed to small force sensors with 200 of flexion about the metacarpophalangeal (MCP) joint. The subjects were instructed to produce their maximum isometric force with a single finger or all four fingers in flexion or extension. In order to examine the effects of muscle-force relationship on MVF and other digit interaction indices, six subjects were randomly selected from the group of 25 adult subjects and asked to perform the same experimental protocol described above. However, the MCP joint was at 800 of flexion. The results from the 20' of MCP joint flexion showed that (1) MVF increased and finger inter-dependency decreased with children's age, (2) the increasing and decreasing absolute slopes (N/year) from regression analysis were steeper in flexion than extension while the relative slopes (%/year) with respect to adults' maximum finger forces were higher in extension than flexion, (3) the larger MVF, FE, and FD were found in flexion than in extension, (4) the finger FS was very similar in children and adults, (5) the FS pattern of individual fingers was different for flexion and extension, and (6) the differences between flexion and extension found at 20 degrees MCP joint conditions were also valid at 80 degrees MCP joint conditions. We conclude that (a) the finger strength and independency increase from 6 to 10 years of age, and the increasing trends are more evident in flexion than in extension as indexed by the absolute slopes, (b) the finger strength and finger independency is greater in flexion than in extension, and (c) the sharing pattern in children appears to develop before 6 years of age or it is an inherent property of the hand neuromusculoskletal system. One noteworthy observation, which requires further investigation, was that FE was slightly smaller in the 80 degrees condition than in the 20 degrees condition for flexion, but larger for extension for all subjects. This may be interpreted as a greater FE when flexor or extensor muscles are stretched.

Distribution of grip force in three different functional prehension patterns

Normative data of the grip force distribution necessary to complete functional tasks are limited. Small force sensors have been specially designed for accurate measurement of the dynamic handgrip force distribution by attaching them to the palmar surface of the hand. Seventeen healthy participants performed three different tasks, each requiring a different functional prehension pattern. When cylindrical objects were manipulated, the highest average grip forces were found at the fingertips and the thumb, followed by the middle finger. In a spherical grasp pattern, the contributions by the thumb, ring and small fingers always exceeded 71% of the total grip force. The highest local forces of 9.9 N were measured when a zip was closed with a tip pinch. Individual finger forces were found to differ by gender, but not by hand dimension and age. The results are useful for biomechanical modelling of the hand, for designing ergonomic tool grips, and for evaluating hand function.

Tactile sensor arrays using fiber Bragg grating sensors

This paper describes two kinds of 3 × 3 force sensor arrays using fiber Bragg gratings (FBG) and transducers for tactile sensation to detect a distributed normal force. One array is developed for a large area tactile sensor that has good sensitivity but low spatial resolution, similar to human body skin. The other is for a small area tactile sensor that has good sensitivity and spatial resolution, similar to human finger skin. The transducer is designed such that it is not affected by chirping and light loss. We also present the fabrication process and experimental verification of the prototype sensors. Experimental tests show that the newly designed sensors have good performance: good sensitivity, repeatability, and no-hysteresis. The load calibration is accomplished by a verified uniaxial load cell. In order to provide a more precise measurement, temperature compensation is applied to all taxels. These force sensor arrays are flexible enough to be attached to a curved surface and they also have simple wiring compared with other types of small force sensors for tactile sensation.