Pressure Sensor Matrix Research Articles

Printed pressure sensor matrix with organic field-effect transistors

The paper presents the construction and fabrication method of a pressure sensor matrix with organic field-effect transistors. The sensor structure consists of a matrix of air-gap transistors which is realized by roll-to-roll processing and laminating methods. High aspect ratio spacer structures are made by inkjet printing.The sensor cell transistor senses the applied force on the top substrate due to changes in the air-gap dimension. The sensor matrix has measurement range of 0.4kPa−1–4.4kPa−1, sensitivity 0.4±0.1kPa−1 and time response better than 300ms. The structure is scalable and it has a sensitivity comparable to state of the art pressure sensor matrices that use organic field-effect transistors. Its fabrication process, however, includes standard, low cost mass production steps of printed electronics and it can be transferred to a roll-to-roll process.

Monitoring Dietary Behavior with a Smart Dining Tray

In this article, the authors investigate a new source of information for dietary monitoring: pressure distribution on the surface underneath dining plates. Pressure sensing has been used to consider the weight of the eaten food. The core idea behind their work is that dynamic pressure information can also be used to distinguish between various cutlery-related activities, such as cutting, poking, stirring, or scooping. The authors show how to spot such individual actions in continuous datastreams, assign them to specific containers (main plate, salad bowl), count them (how many bites taken), and relate them to different abstract food categories. They consider two sensing modalities: (1) textile pressure-sensor matrix technology facilitating a smart that looks and feels like a standard tablecloth but provides detailed information on the spatial and temporal pressure; and (2) standard force sensitive resistor (FSR) sensors placed underneath a rigid tray. They also present the results of a new, comprehensive study with 10 subjects, each of whom consumed a total of eight meals chosen from 17 possible main dishes with six possible side dishes; results show an average accuracy of up to 94 percent. This article is part of a special issue on pervasive food.

Non-intrusive sleep pattern recognition with ubiquitous sensing in elderly assistive environment

The quality of sleep may be a reflection of an elderly individual's health state, and sleep pattern is an important measurement. Recognition of sleep pattern by itself is a challenge issue, especially for elderly-care community, due to both privacy concerns and technical limitations. We propose a novelmulti-parametric sensing system called sleep pattern recognition system (SPRS). This system, equipped with a combination of various non-invasive sensors, can monitor an elderly user's sleep behavior. It accumulates the detecting data from a pressure sensor matrix and ultra wide band (UWB) tags. Based on these two types of complementary sensing data, SPRS can assess the user's sleep pattern automatically via machine learning algorithms. Compared to existing systems, SPRS operateswithout disrupting the users' sleep. It can be used in normal households with minimal deployment. Results of tests in our real assistive apartment at the Smart Elder-care Lab are also presented in this paper.

Pressure sensor matrix for indirect measurement of grip and push forces exerted on a handle

To date, a large part of workers is exposed to vibrations (23% in Europe) which can negatively impact on their health. This work discusses the importance of measuring grip and push forces in the context of hand-arm vibration tests, bearing in mind the state-of-art of current standards. It proposes a method for indirect measurement of coupling forces using a matrix of polymeric pressure capacitive sensors and discusses the model used for defining these quantities. The matrix of pressure sensors is wrapped around the tool handle and the acting forces, exchanged with the handle, are derived from the pressure values measured by the matrix. Calibration is presented and the effect of curvature is discussed. The work continues with the experimental validation of the model proposed for push force measurements carried out through lifting tests using known masses with a cylindrical handle. An experimental correction coefficient is defined in correlation to the type of grip. The method for measuring the push force, thus corrected, is assessed by means of push force tests on an instrumented handle. Finally the experimental data are analysed in order to assess the uncertainty of the proposed method for measuring the push force, highlighting the contribution of the different sources of uncertainty. The proposed measurement method allows to measure the push and the grip force (known influencing quantities for the measurement of the hand-arm vibration) during tool test and without modifying the handles.

Tibiofemoral Contact Biomechanics Following Meniscocapsular Separation and Repair

Meniscocapsular separations are often seen in knees with other intra-articular pathology. The consequences of these tears with regard to knee contact mechanics are currently unknown, and the biomechanical advantages of repair have not been measured. We hypothesize that tears to the meniscocapsular junction will cause an increase in tibiofemoral contact pressure and a decrease in contact area, with a return to more normal conditions after repair. 10 fresh-frozen cadaver knees each underwent 10 cycles of axial compressive loading in full extension under three different testing conditions: intact, meniscocapsular separation, and repair. A pressure sensor matrix was inserted into the medial joint space and used to measure magnitude and location of contact pressure and area. Mean contact pressure increased from 0.80±0.17 MPa in the intact knee to 0.88±0.19 MPa with separation, with a decrease to 0.78±0.14 MPa following repair. Peak pressures followed a similar trend with 2.59±0.41, 3.03±0.48, and 2.84±0.40 MPa for the same three groups, respectively. While none of the changes seen was statistically significant, even these small changes would potentially create degenerative changes at the articular surface over prolonged (i. e., months or years) standing, walking, and activity in the unrepaired state.

Dynamic pressure mapping of personalized handwriting by a flexible sensor matrix based on the mechanoluminescence process.

A self-powered pressure-sensor matrix based on ZnS:Mn particles for more-secure signature collection is presented, by recording both handwritten signatures and the pressure applied by the signees. This large-area, flexible sensor matrix can map 2D pressure distributions in situ, either statically or dynamically, and the piezophotonic effect is proposed to initiate the mechanoluminescence process once a dynamic mechanical strain is applied.

Transparent, low-power pressure sensor matrix based on coplanar-gate graphene transistors.

A novel device architecture for preparing a transparent and low-voltage graphene pressure-sensor matrix on plastic and rubber substrates is demonstrated. The coplanar gate configuration of the graphene transistor enables a simplified procedure. The resulting devices exhibit excellent device performance, including a high transparency of ca. 80% in the visible range, a low operating voltage less than 2 V, a high pressure sensitivity of 0.12 kPa(-1) , and excellent mechanical durability over 2500 cycles.

Clinical Outcomes after Chevron Procedure are Better than Pedobarographic Results

The distal Chevron or Austin procedure, is arguably the most prominent of the distal metatarsal osteotomies. Recent studies in the literature have shown a trend in recommending this osteotomy or one if it’s modifications for even severe hallux valgus deformities. Therefore we aimed to compare the clinical and pedobarographic results after chevron osteotomy in patients with moderate hallux valgus deformity. We investigated a homogeneous lot of 10 patients undergoing hallux valgus correction using distal chevron technique. In order to quantify the improvement of the gait in these patients, several biomechanical parameters have been measured using a matrix of pressure sensors that provide us the vertical reaction forces when the foot is in physical contact with it. Results show an improvement in patient’s velocity and cadence after the surgery, and also a smaller variability in gait. Nevertheless, optimal clinical outcomes are still found to have altered ground reaction forces on pedobarographic assessment.

Smart piezoresistive tunnelling composite for flexible robotic sensing skin

A highly mechanically flexible tactile device based on a metal–elastomer composite material was prepared by an efficient and simple process. The microcasting fabrication technique, used for the preparation of a selfstanding sheet of functional material, gives the possibility of easily fabricating complex-shaped structures suitable for integration on robot surfaces for tactile sensing applications. Under the action of a compressive stress the composite material exhibits a giant piezoresistive effect, varying its electrical resistance by several orders of magnitude. This phenomenon can be tuned by changing the material composition parameters, which directly modify the sensitivity of the sensor. After a comprehensive characterization of the functional properties of the material, an 8 × 8 pressure sensor matrix with dedicated electronics was fabricated and tested.

Apparent mass distribution at the feet of standing subjects exposed to whole-body vibration

This study was carried out to investigate the influence of the body posture and of the foot support on the apparent mass distribution at the feet of standing subjects exposed to whole-body vibration. The apparent mass was measured at the driving point through a capacitive pressure sensor matrix, which allowed to separate the contributions of the different foot regions. The overall value was also determined using a conventional measurement system based on piezoelectric load cells. Ten male subjects performed 15 tests with three kinds of feet supports (flat rigid, anatomic rigid and flat soft) in five different postures. Static components of the pressure measurements were exploited to identify which fraction of the weight is supported by the rearfoot, the midfoot and the forefoot in the various test configurations. Factorial design of experiments on different response variables showed that the apparent mass is affected by the posture but not by the type of feet contact surface; conversely, the presence of insoles varies with the apparent mass distribution on the different feet parts. Practitioner Summary: The response of standing subjects to whole-body vibration has always been considered as a global parameter measured at the driving point, neglecting the local phenomena occurring in different foot parts. We have experimentally identified the apparent mass distribution of subjects in different standing postures and with different foot supports.

Martial arts striking hand peak acceleration, accuracy and consistency

The goal of this paper was to investigate the possible trade-off between peak hand acceleration and accuracy and consistency of hand strikes performed by martial artists of different training experiences. Ten male martial artists with training experience ranging from one to nine years volunteered to participate in the experiment. Each participant performed 12 maximum effort goal-directed strikes. Hand acceleration during the strikes was obtained using a tri-axial accelerometer block. A pressure sensor matrix was used to determine the accuracy and consistency of the strikes. Accuracy was estimated by the radial distance between the centroid of each subject's 12 strikes and the target, whereas consistency was estimated by the square root of the 12 strikes mean squared distance from their centroid. We found that training experience was significantly correlated to hand peak acceleration prior to impact (r2=0.456, p =0.032) and accuracy (r2=0. 621, p=0.012). These correlations suggest that more experienced participants exhibited higher hand peak accelerations and at the same time were more accurate. Training experience, however, was not correlated to consistency (r2=0.085, p=0.413). Overall, our results suggest that martial arts training may lead practitioners to achieve higher striking hand accelerations with better accuracy and no change in striking consistency.

Towards non-intrusive sleep pattern recognition in elder assistive environment

Quality of sleep is an important attribute of an elder’s health state and its assessment is still a challenge. The sleep pattern is a significant aspect to evaluate the quality of sleep, and how to recognize elder’s sleep pattern is an important issue for elder-care community. With the pressure sensor matrix to monitor the elder’s sleep behavior in bed, this paper presents an unobtrusive sleep postures detection and pattern recognition approaches. Based on the proposed sleep monitoring system, the processing methods of experimental data and the classification algorithms for sleep pattern recognition are also discussed.

Unmanned air vehicle air data estimation using a matrix of pressure sensors: a comparison of neural networks and look-up tables

Flush airdata sensing (FADS) systems are cost- and weight- effective alternatives to current air data booms for measuring important air data parameters such as airspeed, angle of attack, sideslip, etc. Most applications consider large manned/unmanned air vehicles where the Pitot-static tube is located at the nose tip. However, traditional air data booms can be physically impractical for micro- (unmanned) air vehicles (MAVs) and, in this article, a FADS system mounted on the wing leading edge of a MAV flown at low speeds of Mach 0.07 (wind tunnel experiments under corresponding conditions) is designed. Moreover, two approaches for converting the FADS system pressure to meaningful air data are compared: a neural network (NN) approach and a look-up table (LUT). Results have shown that instrumentation weight and cost were reduced by 80 per cent and 97 per cent, respectively, in comparison to a traditional air data boom. Overall, the NN estimation accuracies were 0.51°, 0.44 lb/ft2, and 0.62 m/s and the LUT estimation accuracies 1.32°, 0.11 lb/ft2, and 0.88 m/s for the angle of attack, static pressure, and airspeed, respectively. It was also found that the LUT has faster execution times while the NN was in most cases more robust to sensor faults. However, while the LUT requires high memory usage, especially for higher dimensions, the NN can be executed in a few lines of code.

Évaluation tridimensionnelle et optimisation du traitement orthopédique de la scoliose idiopathique adolescente

Adolescent idiopathic scoliosis involves complex tridimensional deformities of the spine, rib cage and pelvis. Moderate curves generally are treated using an orthosis. This paper presents different studies performed over the last fifteen years related to the biomechanical evaluation and optimization of the orthopedic treatment of scoliotic deformities. Patient specific 3D models of the spine, pelvis and rib cage are computed from calibrated radiographs, and are used to calculate 2D and 3D clinical indices. The torso shape is acquired using surface topography. With such internal and external 3D models, the efficacy of the most frequently used orthoses can be analyzed and new treatments can be developed. Pressures generated by a brace on the patient's trunk were measured using a flexible matrix of pressure sensors and displayed over the patient's internal geometry in order to analyze the brace efficacy. Patient specific finite element models have been developed, including the osseo-ligamentous structures as well as the muscles, the neuro-control, trunk growth and its adaptation to the stress. These models were used to analyze the effects of the Boston brace. The electro-myographic activity also was measured to analyze the << active >> correction mechanisms. Adjustment techniques and software are used to help the orthotists with real time feedback when the brace is being fabricated and adjusted to the patient. Residual growth potential is also being added to the computer model to simulate the long term effect of a brace. The improvement of the orthotic treatments of scoliotic deformities is very encouraging. The exploitation of such tools is expected to allow reaching optimal treatment personalized to each patient. double dagger.

Hand vibration: non-contact measurement of local transmissibility

Grip and push forces required for the use of vibrating tools are considered important influencing inputs for the assessment of hand-vibration transmissibility (TR). At present TR measurements are usually referred to the palm of the hand The aims of the present paper are: to present an original measurement procedure for non-contact assessment of the transmissibility of fingers; to report TR data measured on six points of the hand of nine subjects; to correlate TR with: grip, push, hand volume and BMI. Tests have been carried out using a cylindrical handle mounted on an shaker. A laser Doppler vibrometer is used to measure the vibration velocity. Push force is measured using a force platform, whereas grip force is measured using a capacitive pressure sensor matrix wrapped around the handle. Tests have been conducted on nine healthy subjects. Proximal and distal regions of the second, fourth and fifth fingers have been investigated. Tests were carried out using a push force of: 25, 50 and 75 N. The excitation signal was a broadband random vibration in the band 16-400 Hz with un-weighted rms acceleration level of 6 m/s(2). Results show how in general TR values measured on distal points are higher respect to the proximal points. A resonance peak is present for all the measured points in the band 55-80 Hz. ANOVA analysis showed that TR is not significantly dependent on: BMI, hand volume and push force alone. While TR is significantly dependent on: grip force alone, measurement positions and grip and push force together. The proposed procedure shows the advantage to allow local vibration measurement directly on the fingers without the necessity to apply any contact sensor. Results demonstrate how the transmissibility is significantly different on the point where the acceleration is measured.

Conformable, flexible, large-area networks of pressure and thermal sensors with organic transistor active matrixes

Skin-like sensitivity, or the capability to recognize tactile information, will be an essential feature of future generations of robots, enabling them to operate in unstructured environments. Recently developed large-area pressure sensors made with organic transistors have been proposed for electronic artificial skin (E-skin) applications. These sensors are bendable down to a 2-mm radius, a size that is sufficiently small for the fabrication of human-sized robot fingers. Natural human skin, however, is far more complex than the transistor-based imitations demonstrated so far. It performs other functions, including thermal sensing. Furthermore, without conformability, the application of E-skin on three-dimensional surfaces is impossible. In this work, we have successfully developed conformable, flexible, large-area networks of thermal and pressure sensors based on an organic semiconductor. A plastic film with organic transistor-based electronic circuits is processed to form a net-shaped structure, which allows the E-skin films to be extended by 25%. The net-shaped pressure sensor matrix was attached to the surface of an egg, and pressure images were successfully obtained in this configuration. Then, a similar network of thermal sensors was developed with organic semiconductors. Next, the possible implementation of both pressure and thermal sensors on the surfaces is presented, and, by means of laminated sensor networks, the distributions of pressure and temperature are simultaneously obtained.

A large-area, flexible pressure sensor matrix with organic field-effect transistors for artificial skin applications.

It is now widely accepted that skin sensitivity will be very important for future robots used by humans in daily life for housekeeping and entertainment purposes. Despite this fact, relatively little progress has been made in the field of pressure recognition compared to the areas of sight and voice recognition, mainly because good artificial "electronic skin" with a large area and mechanical flexibility is not yet available. The fabrication of a sensitive skin consisting of thousands of pressure sensors would require a flexible switching matrix that cannot be realized with present silicon-based electronics. Organic field-effect transistors can substitute for such conventional electronics because organic circuits are inherently flexible and potentially ultralow in cost even for a large area. Thus, integration of organic transistors and rubber pressure sensors, both of which can be produced by low-cost processing technology such as large-area printing technology, will provide an ideal solution to realize a practical artificial skin, whose feasibility has been demonstrated in this paper. Pressure images have been taken by flexible active matrix drivers with organic transistors whose mobility reaches as high as 1.4 cm(2)/V.s. The device is electrically functional even when it is wrapped around a cylindrical bar with a 2-mm radius.

Development of Selection System of Comfort Pillow

The purpose of this study was to develop the selection system of comfort pillow according to subject's head shape. 3-D scanner was used to measure the head shape of Korean. The head shapes were classified into 4 types. When a pillow was pressed by head, the height of pillow was estimated by the relationship of the pillow stiffness and pressure distribution of head and neck. The height, shape, and stiffness of pillow were investigated and their relations were found. The selection rule of comfort pillow was determined by the relationship among the head shape of subject, the height, shape, and stiffness of pillow. There was a significant correlation between the satisfaction and selected pillow. The developed final system consisted of a measurement stand, pressure sensor matrix, 3D scanner, analysis S/W and PC.

A study of hand grip pressure distribution and EMG of finger flexor muscles under dynamic loads.

A matrix of miniature and flexible pressure sensors is proposed to measure the grip pressure distribution (GPD) at the hand-handle interface of a vibrating handle. The GPD was acquired under static and dynamic loads for various levels of grip forces and magnitudes of vibration at different discrete frequencies in the 20-1000 Hz range. The EMG of finger flexor muscles was acquired using the silver-silver chloride surface electrodes under different static and dynamic loads. The measured data was analysed to study the influence of grip force, and magnitude and frequency characteristics of handle vibration on: (i) the local concentration of forces at the hand-handle interface; and (ii) the electrical activity of the finger flexor muscles. The results of the study revealed high interface pressure near the tips of index and middle fingers, and base of the thumb under static grip conditions. This concentration of high pressure shifted towards the middle of the fingers under dynamic loads, irrespective of the grip force, excitation frequency, and acceleration levels. The electrical activity of the finger flexor muscles increased considerably with the grip force under static as well as dynamic loads. The electrical activity under dynamic loads was observed to be 1.5-6.0 times higher than that under the static loads.

A high resolution pneumatic proximity to tactile sensing device

This paper describes the formulation and development of a pneumatic sensing device for automated recognition of objects within flexible manufacturing environments. This sensing device utilises a densely packed matrix of IC pressure sensors, providing continuous variable output. The sensing head incorporates a corresponding matrix of air jets which form boundary layers when striking the objects of interest. The back pressure levels from these form the basis for the tasks of object detection and recognition,. Objects and their features are recognised by their ‘back-pressure map’. Precise information can be obtained about features and anomalies down to a resolution of 10 μm. The system here described is a research prototype and has been evaluated on a simple test rig: in this form its is not at a stage where it can be applied to a recognition situation on the shop floor. Nevertheless the system is novel and it is hoped to publish details of an industrially applicable package in due course.