Pressure-sensitive Conductive Rubber Research Articles

Development of a Pressure-Sensitive Conductive Rubber Sensor for Analyzing Meniscal Injury in Porcine Models.

The assessment of the distribution of contact pressure on the meniscus is important in the elucidation of kinematics, etiology of joint diseases, and establishment of treatment methods. Compared with sensors widely used in recent years, pressure-sensitive conductive rubber sensors are easy to mold, flexible, durable, and resistant to shearing forces. This study is aimed at developing a rubber sensor for meniscal research and evaluating the pressure distribution after meniscal injury using porcine models. After confirming the reliability of the rubber sensor, contact pressure was obtained from the rubber sensor using the medial meniscus and femur of the porcine knee. Three test conditions of intact meniscus, radial tear, and meniscectomy were prepared, and a compressive load of 100 N was applied. After confirming the high reliability of the rubber sensor, the intact meniscus had the most uniform pressure distribution map, while the pressure in the meniscectomy model was concentrated in the resection region. The high-pressure region was significantly smaller in the intact group than in the radial tear models after 80 and 100 N (P < 0.05). The rubber sensor captured the pressure concentration specific to each examination group and was useful for evaluating the relationship between the pattern of meniscal injury and changes in the biomechanical condition of the knee.

Decoupling of a 3D-force flexible tactile sensor

Due to the frame structure of the three-dimensional force sensor which is made of pressure-sensitive conductive rubber, its output data is coupled seriously. To solve this issue, the force-applied model of the sensor is established based on the wire resistance model, which provides a theoretical basis for sensor dimensionality reduction and decoupling. In this paper, the Cartesian coordinate system is established to realize the judgment of the direction of the three-dimensional force applied on the senor, and the sensor output data is decoupled using the least square method. According to the experiment result, the measurement error of the sensor is small and the decoupling method is proved to be suitable.

Recognition of Force Magnitude Applied to Pressure-Sensitive Conducting Rubber Sensors on the Basis of Frequency Table

This study aims to develop a force sensor system with a pressure-sensitive conductive rubber (PSCR), which shows the decrease of electrical resistance when pressure is applied. The biggest obstacle of the sensor is a poor reproducibility in the characteristic between the force and the resistance of the PSCR, which derived from a hysteresis and time variant properties. In this paper, we propose one method for recognizing a magnitude of the force to the PSCR using frequency tables. The validity of the proposed method is confirmed on the basis of experimental results.

A novel assembled carbon black/carbon nanotubes (CB/MWCNT) nano-structured composite for pressure-sensitive conductive silicon rubber (SR)

In this paper, a novel “grape string” carbon black/multi-wall carbon nanotubes (CB/MWCNT) structure was obtained by electro-static assembly method to enhance the resistance stability of the carbon material filled silicone rubber (SR). Carbon black (CB) and multi-wall carbon nanotubes (MWCNT) were surface modified by sulfonic dodecyl benzene sodium and cetyltrimethylammonium bromide to provide negatively charge and positively charge, respectively. Electric conductive sheet of CB/MWCNT/SR composite was obtained by mixing and vulcanizing. The assembly effect and dispersion state of the composites were analyzed by transmission electron microscopy and scanning electron microscopy. The electrical conductivity and dynamic pressure-resistance characteristic of CB/MWCNT/SR with different doping ratio and dosage were tested. The results show that the proper weight ratio 3:2 of CB:MWCNT for electrostatic assembly can cause the stable “grape string” nano-structure. The conductivity and pressure-resistance characteristic are superior when the volume fraction of “grape string” nano-composites reaches 22%, which will provided with less filler fraction and better stress sensitivity, compared with single component carbon black filler.

生体組織触覚性状の定量化に向けたセンサシステムの開発

The continuous increment of the number of patients of breast cancer in recent years demands the early detection of the cancer. To answer this demand, aiming at providing a tool for easy palpation and early detection of the breast cancer, we develop a tactile sensor system measuring the tactile properties of biological soft tissues. PVDF (Polyvinylidene difluoride) film and PSCR (pressure sensitive conductive rubber) are used as sensitive receptors in the sensor. The sensor is driven by a motor-crank mechanism to apply an oscillatory stress to the object to be evaluated. Both time-domain and frequency-domain parameters of the sensor output for the evaluation of the hardness and thickness of the object are discussed in the paper. This device can detect the alien substance in the object and evaluate hardness regardless of existance of alien substance or not. Experiment results show that it is possible to evaluate the feel of various biological soft tissues using two parameters to be provided from PVDF film and PSCR.

義足ソケット内の垂直荷重とせん断荷重測定用センサの開発

A sensor using pressure-sensitive conductive rubber was developed, however this sensor could only measure normal loads and was unable to detect the shearing load and moment. Thus, a flexible contact sensor for three-axis load measurement using an elastic body and a pressure-sensitive conductive material has been developed in a previous study. The sensor has a load detection layer composed of multiple zones. It is possible to separately measure the shear component and components of the load based on the relationship among the voltage changes in each zone. However, the thickness of the sensor was over 5mm. In the present study, a sensor using a prismatic elastic body and a load measurement layer was developed for the normal and shearing force measurement in socket for prosthesis. The sensor is capable of determining the applied normal load, shearing load. To investigated the effectiveness of this sensor, the dependence of the voltage change on the normal force, shearing force. In the result, the thickness of developed thin sensor was 1.2mm.

A Development of Force Distribution Measurement System with High Resolution for Total Knee Arthroplasty

Soft tissue or ligament balancing in total knee arthroplasty is important for ensuring knee joint stability. Correct balancing and appropriate alignment of ligaments extend prosthesis life by preventing unnecessary force fromacting on the prosthesis during routine activities. The current implementation of total knee arthroplasty relies heavily on the subjective “feel” of the surgeon for correct prosthesis implantation onto tibiofemoral components. We developed a force distribution sensing systemto provide quantitative information to surgeons during ligament balancing. The measurement system consists of two main components: two force sensors embedded in trial insert for each condyle and signal acquisition for data processing and force visualization. Sensors were designed and developed using pressure-sensitive conductive rubber that measures changes in resistance in the event of deformation caused by external force. Corresponding voltage measured by circuits is transmitted via an RF transceiver to a computer and visualized as color gradient. Current sensors could measure maximum force of 196.13 N (20 kgf). Results from calibration and experiments on a plastic trial prosthesis indicated that the device has good potential for providing appropriate force distribution information on the knee during total knee arthroplasty procedure.

Application of Conductive Rubber Filled by Carbon Black for 3-D Force Measurement

Pressure-sensitive conductive rubber has been investigated as sensitive material due to its good pressure-resistance characteristics. This paper presents a flexible tactile sensor with new structure. The sensing mechanism is based on body piezoresistive effect of conductive rubber filled by carbon black. To improve the sensor’s flexibility, there is a smart angle design in the arrangement of the wires in lower electrodes layer. Besides, the force model of the sensor has been described. The simulation results indicate the validity of 3-D force measurement of the sensor.

Piezoresistive characteristic of conductive rubber for flexible tactile sensor

In the research of 2D flexible tactile sensor matrix, pressure-sensitive conductive rubber was developed and tested in which carbon black was used as its conductive phase and silicon rubber as its matrix layer. Experiments were undertaken and the resultant data were used for its piezoresistive characteristics investigation for two kinds of electrode connection configurations, the surface directive connection and embedded connection. It is found that due to the rather strong nonlinearity of the piezoresistive characteristic curves obtained, a higher correlation relationship can be obtained by means of quadratic polynomial fitting. It also showed that the embedded electrode assembling has higher fitting accuracy while the surface directive connection has better mechanical sensitivity.

An in-shoe device to measure plantar pressure during daily human activity

In this work, we report the development of a novel device, integrated into a shoe, to monitor plantar pressure under real-life conditions by reducing the spatial and temporal resolution. The device consists of a shoe insole with seven pressure-sensitive conductive rubber sensors and a wireless data transmission unit incorporated into a smaller measurement unit. One advantage of this approach is that the mass and volume of the measurement unit are less than 1/10th and 1/50th, respectively, of that reported for other devices. A comparison experiment was conducted for validation of the device using the F-scan system, and the initial test of the device was conducted by recording unobstructed gaits of one young adult subject and two elderly subjects. Each subject performed a straight, level walking trial at a comfortable speed for 7 m without any assistive device while wearing the in-shoe device. Changes in the plantar pressure during gait were recorded. Compared with the young subject, the pressure under the heel of the elderly subject was found to be smaller and less steep. This in-shoe device can be used to monitor plantar pressure during daily living and is expected to be useful in various clinical applications.

Study on Pressure and Temperature Characteristics of Sensitive Rubber Composite

In order to design and fabricate the flexible force sensor , we have researched the piezoresistivity of silicon rubber/ carbon black composites and given the academic calculation formula between pressure and electrical resistivity. The experiments illustrate that the homogenization of carbon black and the elastic modulus of composites can be improved effectively by dispersing nanosize silica filler and using organic solvent . As a result , the piezoresistivity of composites can be improved. Carbon black content of 10% with good pressure-sensitive conductive rubber, heat-sensitive in a certain pressure range is also good.Moreover , the fore - sensitive device fabricated by the composites is free from the limitation of the surface shape of the tested objects which can be widely applied to various squeeze stress measurement on any regular and unregular curve surfaces.

Touch-sensitive augmented reality system for development of handheld information appliances

Handheld information devices such as digital cameras and smart-phones are products that unify hardware and software. The body of such products is compact, but it has various functions. Usability is one of the most important factors affecting their commercial competitiveness. However, it is difficult to estimate usability precisely in the design process. Because of usability is strongly affected by the shape of the body, the types and arrangement of the switches etc. In order to accurately evaluate the usability of these products, users must operate them directly. However it is difficult to manufacture prototypes that are operable. Therefore, we have adopted an augmented reality technique to solve the problem. This paper introduces, a touch-sensitive augmented reality system, and describes the construction of a touch sensor made of pressure sensitive conductive rubber, a fingertip tracing method using an LED marker, and an augmented reality system. Finally, we have conducted basic system evaluations.

2A2-A12 ユニバーサルロボットハンド用分布型触覚センサの開発

We propose a tactile sensor for Universal Robot Hand. The sensor has three layers composed of a urethane gel, a pressure sensitive conductive rubber and a electrode sheet and can measure a pressure distribution on front, tip and both sides of a finger. A FPGA(field programmable gate array) embedded in a drive circuit drives the sensor, and it selects sensing points and measures pressure distributions. We describe details about the sensor and show results of evaluation experiment.

Soft Areal Tactile Sensor Using Tomography Algorithm

Using inverse problem analysis, we designed a soft areal tactile sensor with pressure-sensitive conductive rubber that does not need complex central wiring because we estimate conductivity change, i.e., pressure on the sensor, in the center based on electrical impedance tomography (EIT), i.e., a type of inverse problem analysis. We discuss results demonstrating the sensor's effectiveness.

Biomechanical Characteristics of Nonbridging External Fixators for Distal Radius Fractures

Nonbridging external fixation is becoming popular for distal radius fractures, although its biomechanical characteristics have not been documented. This study evaluated the biomechanical characteristics of nonbridging external fixators for distal radius fractures. We tested 3 currently available nonbridging fixators (F-Wrist fixator, Hoffman II Compact, and Pennig Dynamic Wrist Fixator) and determined their relative stiffness under axial compression, torsion, and bending moments (dorsal, volar, radial, and ulnar aspects) using a uniform unstable distal radius fracture model. The contact pressure and its total load on the fracture plane were also measured to evaluate the mechanical stimuli at the stable fracture site using a pressure-sensitive conductive rubber sensor. Differences were observed in the stiffness: the Pennig fixator was the stiffest, whereas the F-Wrist fixator was the least rigid. The total load transmitted from the wrist joint to the fracture plane depended on the fixator stiffness in axial compression. By determining the biomechanical characteristics of nonbridging external fixators, these data may help the clinician when deciding on a particular device for nonbridging external fixation.

513 感圧性導電ゴムを用いたトラクション荷重検出に関する基礎的研究(OS2-2,オーガナイズドセッション2:バイオミメティクスと人間支援系バイオメカニクス,学術講演)

513 感圧性導電ゴムを用いたトラクション荷重検出に関する基礎的研究(OS2-2,オーガナイズドセッション2:バイオミメティクスと人間支援系バイオメカニクス,学術講演)

1136 チェアスキー滑降時のシート-臀部間の接触圧力分布測定(S11-3 計測と力学-生体への応用(3),S11 計測と力学-生体への応用)

A sit-ski is used by the disabled person in a sitting posture. Bi-ski and mono-ski are a kind of the sit-skis. The sit-ski generally known in the Paralympics is mono-ski. While the mono-ski is for personal use, the bi-ski is for general use. The seat shape of the bi-ski, therefore, is simple compared with that of mono-ski. If the sitting position is kept on bi-ski seat for a long time, pressure ulcer may develop in buttocks. However the study on measurement of contact pressure distribution between the bi-ski seat and buttocks has not been done so far and there is no standard of pressure ulcer prevention. In this research, the measurement of contact pressure distribution at an interface between buttocks and bi-ski seat during skiing was realiged dynamically and quantitatively by the wireless pressure measurement system utilizing the pressure sensitive conductive rubber (PSCR) sensor. Pressure loading pattern and pressure value when going on bi-ski were actually measured for a paraplegic person.

Influence of the femoral tunnel location and angle on the contact pressure in the femoral tunnel in anterior cruciate ligament reconstruction.

The causes of bone tunnel enlargement after anterior cruciate ligament reconstruction have not been thoroughly investigated. A malpositioned femoral tunnel and an acute femoral tunnel angle may increase the mechanical stress in the femoral tunnel. Controlled laboratory study. Three femoral tunnels (normal, anterior, and acute) and the tibial tunnel were made in four fresh-frozen cadaveric knees. Aluminum cylinders containing pressure-sensitive conductive rubber sensors at the joint entrance were inserted into the femoral tunnels. Dynamic changes in the contact pressure of the graft in the femoral tunnel were measured. Peak contact pressures and dynamic changes in contact pressure for the normal and anterior femoral tunnels demonstrated no differences. Maximum contact pressure of the graft was observed at the anterior portion with the knee in full extension and at the posterior portion with deep knee flexion. Consistent contact pressure occurred at the anterior aspect of the acute femoral tunnel throughout the range of motion. Mean contact pressure at the anterior region of the acute femoral tunnel was significantly higher than that of the normal femoral tunnel at 60 degrees, 90 degrees, and 120 degrees of knee flexion. The consistent contact pressure in the anterior aspect of the acute femoral tunnel may erode the anterior portion of the femoral tunnel, resulting in bone tunnel enlargement. The femoral tunnel direction in anterior cruciate ligament reconstruction is an important factor in reducing femoral tunnel enlargement.

Pressure distribution in the humeroradial joint and force transmission to the capitellum during rotation of the forearm: effects of the Sauvé-Kapandji procedure and incision of the interosseous membrane

A biomechanical study was undertaken, using four fresh cadaveric arms, to evaluate the changes in pressure distribution in the humeroradial joint (H-R joint) during rotation of the forearm before and after the Sauvé-Kapandji procedure (S-K procedure) and also after incision of the interosseous membrane (IOM) following the S-K procedure. The pressure distribution was measured with a pressuresensitive conductive rubber sensor while the forearm was rotated. Force transmitted to the capitellum was calculated from the measured pressure. In the intact specimens, pressure was concentrated on the medial side of the capitellum in pronation and on the posterolateral side in supination. The pattern of change after the S-K procedure and that after incision of the IOM following the S-K procedure were almost the same as that in the intact forearm. Although the force transmitted to the capitellum increased after the S-K procedure, there were no significant differences between the forces before and after the S-K procedure. However, the force increased significantly after incision of the IOM following the S-K procedure when the forearm was supinated more than 35°, and it was concentrated on the posterior side of the capitellum. The IOM seemed to have an important axial load-bearing function in the forearm position supinated more than 35°. The S-K procedure in patients suffering from distal radioulnar joint disorders with IOM injury is likely to induce H-R joint osteoarthritis, so it should be avoided in these patients.

Bioengineering. Dynamic Evaluation of the Contact Characteristics and Three-Dimensional Motion for the Ankle Joint with Lateral Ligament Injuries.

The purpose of this study was to clarify the dynamic changes in contact pressure distribution and three-dimensional ankle joint motion before and after lateral ligament injuries. Five fresh and frozen intact cadaveric ankles were examined. Each ankle was mounted on a specially designed frame that preserved five degrees of freedom motion. The direct linear transformation technique was used to measure the three-dimensional ankle motion, and a pressure-sensitive conductive rubber sensor was inserted into the talocrural joint space to determine the contact pressure distribution. The contact area on the talus for intact ankle moved anteriorly and laterally with increasing dorsiflexion. An area of high pressure was observed in the medial aspect of the articular surface after the ligament was cut. Supination significantly increased after a combined anterior talofibular ligament (ATF) and calcaneofibular ligament (CF) were cut in comparison with after only an ATF was cut, and no significant differences were observed in motional properties under each experimental condition.