Sensor Pad Research Articles

Two dimensional polymer-embedded quasi-distributed FBG pressure sensor for biomedical applications

We report on the development of a flexible 2D optical fiber-based pressure sensing surface suitable for biomedical applications. The sensor comprises of highly-sensitive Fiber Bragg Grating elements embedded in a thin polymer sheet to form a 2x2 cm(2) sensing pad with a minimal thickness of 2.5mm, while it is easily expandable in order to be used as a building block for larger surface sensors. The fabricated pad sensor was combined with a low physical dimension commercially available interrogation unit to enhance the portability features of the complete sensing system. Sensor mechanical properties allow for matching human skin behavior, while its operational performance exhibited a maximum fractional pressure sensitivity of 12 MPa(-1) with a spatial resolution of 1x1cm(2) and demonstrated no hysteresis and real time operation. These attractive operational and mechanical properties meet the requirements of various biomedical applications with respect to human skin pressure measurements, including amputee sockets, shoe sensors, wearable sensors, wheelchair seating-system sensors, hospital-bed monitoring sensors.

A `pad' sensor for measuring the moisture content of building materials

A range of techniques are available to measure the moisture content of building fabrics. Indeed a thermal dual-probe has been successfully developed by the authors for measuring the moisture content of building fabrics in situ. However, the dual-probe technique has limitations due to the fact that two, small diameter, parallel holes must be drilled for inserting the dual-probe into the material to be measured. It is difficult to drill such holes accurately in many building envelops and thus, such a dual-probe may be most useful for relatively `soft' materials, such as aerated concrete. This paper describes the `proof of concept' of an innovation that surmounts this problem via the development of a `pad' sensor. Instead of the `traditional' dual-probe approach, the heater and temperature sensor are fixed to the surface of a thermally insulated block. The most important benefit of the pad sensor approach is that no holes are required to be drilled in the material of interest. The moisture content of the building envelops can be measured simply by placing the pad sensor against the wall surface. Extensive finite element modelling was carried out to design the pad sensor and a prototype built. Initial experimental work was then carried out to test the pad sensor — the measured moisture content obtained from the pad sensor was compared with the results of a series of gravimetric analyses. Encouraging agreement between the two methods was obtained. Practical application: A thermal dual-probe has been successfully developed by the authors for measuring the moisture content of building fabrics in situ. However, the dual-probe technique has limitations due to the fact that two, small diameter, parallel holes must be drilled for inserting the dual-probe into the material to be measured. This paper describes an innovation that surmounts this problem via the development of a `pad' sensor. The moisture content of the building envelopes can be accurately measured simply by placing the pad sensor against the wall surface. The pad sensor offers a non-destructive method to measure the moisture content and thus is potentially attractive for applications where this issue is of importance e.g. monitoring the moisture content of historical buildings.

Development of Silicon Pad Sensors for a Silicon-Tungsten Calorimeter in High Energy Heavy Ion Experiment

Silicon pad sensors measuring the energy deposit of particles in calorimeter showers have been designed and fabricated for the silicon-tungsten calorimeter to be used in the upgraded Pioneering High Energy Nuclear Interaction Experiment heavy ion experiment. The pad sensor is an array of 4 4 pixels in an active area of about 6 cm 6 cm with three surrounding guardrings The details of the design and of the fabrication process and the electrical characteristics of the sensors are discussed, including the test result obtained with a high-energy beam.

A low-cost through via interconnection for ISM WLP

Wafer level packaging (WLP) for image sensor device has the advantage of small size, high performance and low cost. In WLP technology, in order to form electrical interconnection from image sensor contact pad to the backside of the wafer, several structures have been developed, such as T-contact and through silicon via (TSV). In this paper, a wafer level package of image sensor with new type TSV electrical interconnection for image sensor pad is presented. The target of this development is to reduce process cost and difficulty, and increase yield of image sensor packaging. Key fabrication processes includes glass protecting wafer bonding, device wafer thinning, backside through via etching, via passivation layer deposition, pad oxide opening, via filling and backside re-routing layer formation, etc. Compared to large opening area of tapered via on the backside of CMOS image sensor wafer, only small opening area is need for making via interconnection with vertical sidewall presented in this paper. A fillet structure at bottom corner of via holes can help to reduce sequent process difficulty, so that low-cost and simplified unit processes are successfully adopted in the fabrication process for through via formation. The through via interconnection shows good electrical connection performance, and high-quality photo images are obtained by packaged image sensor device.

A new method to measure heart rate with EMFi and PVDF materials

In this paper we propose a new simple method to measure the heart rate of a person sitting on a chair or lying in a bed. The heart rate is measured with a thin sensor pad consisting of separate electromechanical film (EMFi) and polyvinylidenefluoride (PVDF) transducers located beneath the leg of chair or bed. This study aims to evaluate the operation of the sensor system with measurements, and also to compare the results provided by the two transducer materials. Based on the results obtained here, the heart rates measured with the transducers mainly corresponded to the values of reference ECG signal. Some minor differences between the heart rate values of PVDF and EMFi appeared, especially in supine position, possible due to the material sensitivities to different force directions. However, to conclude, both materials seem to be convenient for this kind of measurement of heart rate.

Enhancing DNA hybridization kinetics through constriction-based dielectrophoresis

The enhancement of signal sensitivity through the scaling-down of sensors presents mass transport limitations that can arrest the sensitivity gains obtained as a result of miniaturization. To alleviate these limitations, we study the application of constriction-based dielectrophoresis methods to enhance transport through pre-concentration of target DNA in the vicinity of the diffusion layer of the sensor, on which capture probe DNA molecules were immobilized. We demonstrate that constriction-based DEP pre-concentration was not impeded by scaling-down of the sensor, as long as the sensor electrode was composed of nanostructured edges and was coupled to an equally scaled down insulating constriction within a microfluidic channel to enhance the focusing effects of the constrictions and edges. Furthermore, as a result of the high focusing fields, pre-concentration of single-stranded target DNA occurred in the vicinity of the sensor pad within the relatively high ionic strength buffers required for DNA hybridization, with minimal degradation of capture probe molecules. Finally, constriction-based DEP resulted in an almost immediate pre-concentration of target DNA in the vicinity of the sensor electrode diffusion layer, resulting in a ten-fold enhancement of the DNA hybridization kinetics at target concentration values down to the sensitivity limit of 10 pM for the sensor platform.

Estimate of Floor Reaction Force vector using Foot-Pressure Sensor

As people grow older, the ability to walk becomes ever more important to live an independent life. A simple system that is useful for evaluation and analysis of gait is necessary. Our goal is to design a wearable gait analyzer. In this study, we estimated the floor reaction force vector using an ultra-thin pair of wearable sensor pads. The floor reaction force vector, when someone is walking, is in the direction of the body's center of gravity. The gap separating the floor reaction force vector and the body's center of gravity generates a rotation moment, which is what we used to create this equation. Our evaluation method will be useful for future development of sensor systems.

Evaluation of the force acting on the back of the horse with an English saddle and a side saddle at walk, trot and canter

Force transmission under an English saddle (ES) at walk, trot and canter is commonly evaluated, but the influence of a side saddle (SS) on the equine back has not been documented. Force transmission under a SS, with its asymmetric construction, is different from an ES in walk, trot and canter, expressed in maximum overall force (MOF), force in the quarters of the saddle mat, and centre of pressure (COP). The biomechanics of the equine back are different under a SS compared to ES. Thirteen horses without clinical signs of back pain ridden in an indoor riding school with both saddles were measured using an electronic saddle sensor pad. Synchronous kinematic measurements were carried out with tracing markers placed along the back in front of (withers, W) and behind the saddle (4th lumbar vertebra, L4). At least 6 motion cycles at walk, trot and canter with both saddles (ES, SS) were measured. Out of the pressure distribution the maximum overall force (MOF) and the location of the centre of pressure (COP) were calculated. Under the SS the centre of pressure was located to the right of the median and slightly caudal compared to the COP under the ES in all gaits. The MOF was significantly different (P<0.01) between saddles. At walk, L4 showed significantly larger (P<0.01) vertical excursions under the ES. Under the SS relative horizontal movement of W was significantly reduced (P<0.01) at trot, and at canter the transversal movement was significantly reduced (P<0.01) . In both trot and canter, no significant differences in the movement of L4 were documented. The results demonstrate that the load under a SS creates asymmetric force transmission under the saddle, and also influences back movement. To change the load distribution on the back of horses with potential back pain and as a training variation, a combination of both riding styles is suitable.

The SUCIMA project: A status report on high granularity dosimetry and proton beam monitoring

The SUCIMA collaboration has been developing instruments and methods for real-time, high granularity imaging of extended electron sources. In particular, dosimetry of intravascular brachytherapy β sources has been intensively studied, together with monitoring of hadrontherapy beams by imaging of secondary electrons emitted by a non-disruptive target. The paper reports the latest results on absolute dosimetry with a large-area silicon strip detectors and on beam monitoring with a hybrid pad sensor.

The Peroneal Groove Deepening Procedure: A Biomechanical Study of Pressure Reduction

The goal of this study was to identify pressure changes throughout the peroneal groove after a groove deepening procedure. We hypothesized that pressures would decrease. Twelve fresh-frozen foot and ankle specimens were used. A thin pressure strip containing four sensor pads was secured within the peroneal groove with pads 1 through 4 positioned at the calcaneofibular ligament (CFL) and at the distal, middle, and proximal groove, respectively. The midstance phase of gait was simulated with loads applied to the plantar foot and posterior tibial tendon and to the peroneus longus and brevis tendons. Pressures were recorded with the ankle in neutral, plantarflexion, dorsiflexion, inversion, and eversion. Groove deepening was done by osteotomizing the posterior fibular wall. Pressure readings were then recorded. Average pressures for each of the four sensor pads after the procedure were compared to those obtained before the procedure. The mean pressure overlying the CFL increased at all five ankle positions; however, these changes were not significant. Significant decreases in pressure were noted within the distal and middle groove at all ankle positions after the peroneal groove deepening procedure. Pressure within the proximal groove increased at all but one position, with a significant difference noted in neutral and plantarflexion. Pressures within the middle and distal peroneal groove significantly decreased after a groove deepening procedure. Combining this technique with peroneal tendon debridement may be advantageous for treatment of partial peroneal tendon tears or recalcitrant peroneal tendinitis.

Intrarater reliability of the KT1000 arthrometer in determining anterior translation of the glenohumeral joint

Taylor JD, Bandy WD. Intrarater reliability of the KT1000 arthrometer in determining anterior translation of the glenohumeral joint. Arch Phys Med Rehabil 2005;86:826–9. Objectives To establish intrarater reliability of the KT1000 arthrometer in determining glenohumeral anterior translation and to determine if a difference existed between measurements of glenohumeral anterior translation in 2 testing positions. Design Intrarater reliability study. Setting Academic laboratory. Participants Convenience sample of 15 unimpaired volunteers (mean age ± standard deviation, 25±4y). Interventions Not applicable. Main outcome measures Subjects were positioned supine with the shoulder in 20° of abduction and 0° of external rotation (position 1) and 90° of abduction and 90° of external rotation (position 2). The KT1000 was placed on the shoulder with the tibia sensor pad near the joint line and the patella sensor pad over the coracoid process. Testing involved an anteriorly directed force of 67N. Testing procedures were repeated after 1 week. Results The intraclass correlation coefficients (ICCs) for intrarater reliability for position 1 (ICC=.93; 95% confidence interval [CI], .81–.98) and for position 2 (ICC=.93; 95% CI, .80–.97) were excellent. The degree of anterior translation measured in position 1 was significantly greater than in position 2 ( t=4.79, P<.01). Conclusions Use of the KT1000 to measure glenohumeral anterior translation in the 2 testing positions appears to be a relatively simple, reliable method. Because testing position 1 allowed significantly greater anterior translation than testing position 2, the 2 positions should not be used interchangeably.

DIGITAL DEVICE AND TECHNIQUE FOR SENSING DISTRIBUTION OF SPRAY DEPOSITION

Assessment of spray deposition often relies on the use of water- and oil-sensitive paper or other stain-basedtechniques to document extent of coverage and distribution. The procedure requires the placement, collection, scanning, andpost-processing of deposition stains on cards, and is time consuming and labor intensive. An electronic sensor, coupled witha wireless network for transmission of in situ data, would have great advantages over current methods typically used in spraydeposition research. A prototype technique and sensor for detecting and quantifying spray deposition were developed andevaluated. The device is capable of sensing the presence and location of multiple droplets on a sensor surface, is reusableand potentially inexpensive. The sensor detects the presence of discrete fluid droplets on the sensor surface when dropletscomplete electrical circuits positioned in an array. The sensitivity of the system is controlled by setting a reference (threshold)voltage in a voltage comparator circuit, while spatial sensitivity is determined by the physical separation of sensing pointson the sensing array. The sensor differs from previously reported designs in that the deposition is quantified as a series ofdiscrete, digital indications instead of a spatially integrated response. This capability allows spatial distribution of spray,not just an estimate of quantity, to be determined. The sensor was tested using spray applications of fine, medium, and coarseASAE standard sprays. The performance of the sensor prototype, defined as measurement of covered area of stain deposition,was best when detecting coarse sprays. Future development will include fabrication of a sensing array with a higher spatialresolution of sensor pads, incorporation of more elegant algorithms for detailed scans of the sensing surface, and interfacingthe sensor with a wireless communication system.

Design of a portable near infrared system for topographic imaging of the brain in babies

A portable topographic near-infrared spectroscopic (NIRS) imaging system has been developed to provide real-time temporal and spatial information about the cortical response to stimulation in unrestrained infants. The optical sensing array is lightweight, flexible, and easy to apply to infants ranging from premature babies in intensive care to children in a normal environment. The sensor pad consists of a flexible double-sided circuit board onto which are mounted multiple sources (light-emitting diodes) and multiple detectors (p-i-n photodiodes), all electrically encapsulated in silicone rubber. The control electronics are housed in a box with a medical grade isolated power supply and linked to a PC fitted with a data acquisition card, the signal acquisition and analysis being performed using LABVIEW™. The signal output is displayed as an image of oxy- and deoxyhemoglobin concentration ([HbO2], [Hb]) changes at a frame rate of 3 Hz. Experiments have been conducted on phantoms to determine the sensitivity of the system, and the results have been compared to theoretical simulations. The system has been tested in volunteers by imaging changes in forearm muscle oxygenation, following blood pressure cuff occlusion to obtain typical [Hb] and [HbO2] plots.

The forces applied by female and male chiropractors during thoracic spinal manipulation

Background On average, women weigh less, have a smaller frame, and are less muscular than men. Since the peak thrust force applied during spinal manipulative treatments can be quite high and must be reached in a very short period of time, one might question the physical ability of women to generate such high forces. Objective To study the forces generated by male and female chiropractors as they deliver spinal manipulation to the thoracic spine. Methods Fourteen male and 14 female experience-matched chiropractors participated in this study. They each manipulated 1 of 9 asymptomatic male adult subjects of similar height and weight. The clinicians were asked to manipulate a transverse process in the vicinity of T4 and T9. Any technique could be used as long as the treatment thrust was in a posterior to anterior direction and the hand contact fit onto the sensor pad (area = 100 cm 2). Results There were no significant differences ( P<.05) between male and female chiropractors for any measurements in the upper thoracic area. For the lower thoracic manipulations, the preload forces for the male chiropractors were significantly greater ( P<.05) than those for the female chiropractors. The remaining variables were the same between the 2 groups. Conclusions Female chiropractors produce, from a mechanical point of view, similar manual treatments as their male colleagues.

Passive acoustic monitoring of human physiology during activity indicates health and performance of soldiers and firefighters

The Army Research Laboratory has developed a unique gel‐coupled acoustic physiological monitoring sensor that has acoustic impedance properties similar to the skin. This facilitates the transmission of body sounds into the sensor pad, yet significantly repels ambient airborne noises due to an impedance mismatch. The sensor’s sensitivity and bandwidth produce excellent signatures for detection and spectral analysis of diverse physiological events. Acoustic signal processing detects heartbeats, breaths, wheezes, coughs, blood pressure, activity, motion, and voice for communication and automatic speech recognition. The health and performance of soldiers, firefighters, and other first responders in strenuous and hazardous environments can be continuously and remotely monitored with body‐worn acoustic sensors. Comfortable acoustic sensors can be in a helmet or in a strap around the neck, chest, and wrist. Noise‐canceling sensor arrays help remove out‐of‐phase motion noise and enhance covariant physiology by using two acoustic sensors on the front sides of the neck and two additional acoustic sensors on each wrist. Pulse wave transit time between neck and wrist acoustic sensors will indicate systolic blood pressure. Larger torso‐sized arrays can be used to acoustically inspect the lungs and heart, or built into beds for sleep monitoring. Acoustics is an excellent input for sensor fusion.

Performance of a radiation hard 128 channel analogue front-end chip for the readout of a silicon-based hybrid photon detector

The performance is described of a front-end chip, the SCT128A-LC chip, originally developed for the readout of a silicon based Hybrid Photon Detector (HPD), which is part of an RICH detector to be run in an LHC experimental environment. The relatively low signal charge from single photoelectrons, impinging on the silicon pad sensor, put very stringent requirements on the noise performance of the front-end chip. An absolute noise calibration using X-ray sources and a 241Am γ source was performed. It is demonstrated that sufficiently good signal over noise ratio can be obtained to use this chip for the read-out of an HPD in LHC experiments.

Unique gel-coupled acoustic sensor array monitors human voice and physiology

The health and performance of soldiers, firefighters, and other first responders in strenuous and hazardous environments can be continuously and remotely monitored with body-worn acoustic sensors. The Army Research Laboratory’s gel-coupled acoustic physiological monitoring sensor has acoustic impedance properties similar to the skin that facilitate the transmission of body sounds into the sensor pad, yet significantly repel ambient airborne noises due to an impedance mismatch. Acoustic signal processing detects physiological events such as heartbeats, breaths, wheezes, coughs, blood pressure, activity, motion, and voice for communication and automatic speech recognition. Acoustic sensors can be in a helmet or in a strap around the neck, chest, and wrist. Although the physiological sounds have high SNR, the acoustic sensor also responds to motion-induced artifacts that sometimes obscure meaningful physiology. A noise-canceling sensor array configuration helps remove motion noise by using two acoustic sensors on the front sides of the neck and 2 additional acoustic sensors on each wrist. The motion noise detected on all 4 sensors will be dissimilar and out of phase, yet the physiology on all 4 sensors is covariant. Pulse wave transit time between neck and wrist will indicate systolic blood pressure. Data from a firefighter experiment will be presented.

Silicon detector for a Compton camera in nuclear medical imaging

Electronically collimated gamma cameras based on Compton scattering in silicon pad sensors may improve imaging in nuclear medicine and biomedical research. The work described concentrates on the silicon pad detector for a prototype Compton camera. The silicon pad sensors are read out using low noise very large scale integration (VLSI) CMOS chips and novel fast triggering chips. Depending on the application, a lightweight and dense packaging of sensors and its readout electronics on a hybrid is required. We describe the silicon pad sensor and their readout on the newly designed hybrid. We also present a modular and low-cost data acquisition system (CCDAQ) based on a digital signal processor which is interfaced to the EPP port of widely available personal computers. Using the CCDAQ and the hybrids energy spectra of gamma-ray photons from technetium (/sub 43//sup 99m/Tc) and americium (/sub 95//sup 241/Am) were acquired with an energy resolution of 2.45 keV full-width at half-maximum (FWHM) for the 140.5-keV photo-absorption line of /sub 43//sup 99m/Tc. For all pads, the discrimination threshold in the trigger chip was between 15 and 25 keV.

A multilevel input system with force-sensitive elements

Force-sensitive multilevel input elements are introduced as the basic building blocks for compact-size input devices in mobile environments. Compared with switch-type keys, multilevel elements can decrease the number of keys on a keyboard while maintaining the input capacity. A multilevel input mechanism using force-sensitive sensor pads is demonstrated in a three-level three-element tactile chording system with multimodal feedback. Two schemes are introduced to segment the output range of the sensor into levels. For relatively unpracticed users, the scheme based on maximum finger forces gives an average error rate of 20.2% and an input time of 2.24 s for a chord of three inputs. Reclassification of the experimental data using Gaussian segmentation shows that significant improvement of the performance can be expected.

The influence of bed firmness on sleep quality

We studied the relationship between sleep quality and bed surface firmness. Nine men were investigated, sleeping in their homes for at least 5 consecutive nights on a soft and a more firm mattress using a sensor pad placed under the mattress and a solid-state recording device. The subjective feeling of sleep quality did not always agree with the recorded sleep data. The difference was most marked when changing from the subject's own to one of the test mattresses. For the same subject the results were reproducible between nights provided there were no external disturbing factors. Four of the 9 subjects slept significantly better on the softer of the two mattresses and 2 on the hard mattress. The difference in sleep quality observed among the subjects tested makes it necessary to relate the results to the same person rather than considering a whole group as an entity. The adaptation period for a new sleep surface extended to many days.