Implantable arterial blood pressure sensor

Although blood pressure measurements are well developed, the existing technology in the field of Arterial Blood Pressure (ABP) measurements is not sufficient in terms of long-term ABP waveform assessment. To overcome existing limitations this dissertation proposes, models, designs and tests a new technique of ABP measurements: implantable arterial tonometry.The scope of this dissertation is to study how the geometry of the tonometer and its mechanical properties influence sensor output and stress/strain distribution inside the arterial wall. Two models of tonometer, analytical and numerical, are developed. The relationship between the tonometer response and its effective stiffness is calculated using a lumped parameter model. The contact pressure between the artery and the tonometer as well as the arterial wall stress/strain distribution is studied using a Finite Element numerical model.Based on the theoretical results three prototypes are developed. The piezoelectric dual mode transducer is designed to measure the tonometer-arterial wall contact pressure.The series of in-vitro and in-vivo experiments test the static and dynamic responses of the tonometer.The results indicate the tonometer’s effective stiffness necessary to achieve less than 1% error in the dynamic response of the sensor. The geometry of the tonometer’s measurement area is found, which results in less than 1% of error in quasi-static response of the sensor. In effort to find potential tissue remodeling areas, the internal arterial wall stress/strain distribution generated by the tonometer is found.The experimental results complement the numerical analysis. The static and dynamic characteristics of the prototype tonometer obtained in-vitro and in-vivo are presented. The explanted tunica media remodeling effect is compared with FE analysis results.The presented work states and solves basic problems of implantable arterial tonometry. In addition it provides the in-vitro and in-vivo examination of the theoretical results. The thesis develops tools of modeling, designs, and testing procedures for future researchers willing to develop implantable tonometers.The thesis concludes with a novel design of the implantable tonometer.Ph.D., Biomedical Engineering -- Drexel University, 200

Design and analysis of fingernail sensors for measurement of fingertip touch fouce and finger posture

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (leaves 142-148).A new type of wearable sensor for detecting fingertip touch force and finger posture is presented. Unlike traditional electronic gloves, in which sensors are embedded along the finger and on the fingerpads, this new device does not constrict finger motion and allows the fingers to directly contact the environment without obstructing the human's natural haptic senses. The fingertip touch force and finger posture are detected by measuring changes in the coloration of the fingernail; hence, the sensor is mounted on the fingernail and does not interfere with bending or touching actions. Specifically, the fingernail is instrumented with miniature light emitting diodes (LEDs) and photodetectors in order to measure changes in the reflection intensity when the fingertip is pressed against a surface or when the finger is bent. The changes in intensity are then used to determine changes in the blood volume under the fingernail, a technique termed "reflectance photoplethysmography." By arranging the LEDs and photodetectors in a spatial array, the two-dimensional pattern of blood volume can be measured and used to predict the touch force and posture. This thesis first underscores the role of the fingernail sensor as a means of indirectly detecting fingertip touch force and finger posture by measuring the internal state of the finger. Desired functionality and principles of photoplethysmography are used to create a set of design goals and guidelines for such a sensor.(cont.) A working miniaturized prototype nail sensor is designed, built, tested, and analyzed. Based on fingertip anatomy and photographic evidence, mechanical and hemodynamic models are created in order to understand the mechanism of the blood volume change at multiple locations within the fingernail bed. These models are verified through experiment and simulation. Next, data-driven, mathematical models or filters are designed to comprehensively predict normal touching forces, shear touching forces, and finger bending based on readings from the sensor. A method to experimentally calibrate the filters is designed, implemented, and validated. Using these filters, the sensors are capable of predicting forces to within 0.5 N RMS error and posture angle to within 10 degrees RMS error. Performances of the filters are analyzed, compared, and used to suggest design guidelines for the next generation of sensors. Finally, applications to human-machine interface are discussed and tested, and potential impacts of this work on the fields of virtual reality and robotics are proposed.by Stephen A. Mascaro.Ph.D

The Role of Fluorescence and Human Factors in Quantitative Transdermal Blood and Tissue Analysis Using NIR Raman Spectroscopy

This research is part of an ongoing project aimed at the application of combined near infrared (NIR) Raman and fluorescence spectroscopy to noninvasive in vivo blood analysis including but not limited to glucose monitoring. Coping with practicalities of human factors and exploring ways to obtain and use knowledge gained about autofluorescence to improve algorithms for blood and tissue analysis are the general goals of this research. Firstly, the study investigated the various sources of human factors pertinent to our concerns, such as fingerprints, turgor, skin hydration and pigmentation. We then introduced specialized in vivo apparatus including means for precise and reproducible placement of the tissues relative to the optical aperture, i.e., the position detector pressure monitor (PDPM). Based on solid instrumental performances, appropriate methodology is now provided for applying and maintaining pressure to keep surface tissues immobile during experiments while obtaining the desired blood content and flow. Secondly, in vivo human fingertip skin autofluorescence photobleaching under 200 mW 830 nm NIR irradiation is observed and it is characterized that: i) the majority of the photobleached fluorescence originates from static tissue not blood, ii) the bleaching (1/e point) occurs in 101-102 sec timescale, and also iii) a photobleached region remains bleached for at least 45 min but recovers completely within several hours. A corresponding extensive but not exhaustive in vitro systematic study narrowed down the major contributors of such fluorescence and bleaching to collagen, melanin, plasma and hemoglobin: two major static tissue constituents and two major blood proteins. Thirdly, we established that measuring the inelastic and elastic emissions simultaneously leads to a sensitive probe for volume changes of both red blood cells and plasma. An algorithm based on measurements obtained while performing research needed for this thesis, as well as some empirical calibration approaches, was presented. The calibrated algorithm showed real potential to track hematocrit variations in cardiac pulses, centrifugal loading, blood vessel blockage using tourniquet, and even during as subtle an occurrence as in a Valsalva maneuver. Finally, NIR fluorescence and photochemistry of pentosidine, a representative of the advanced glycation endproducts (AGEs) which accumulate with age and hyperglycemia, was studied. The results indicate that oxygen plays a pivotal role in its photobleaching process. We hypothesized and offered proofs showing that pentosidine is a 1O2 sensitizer that is also subject to attack by the 1O2 resulting in the photobleaching that is observed when probing tissue using NIR. The photobleaching reaction is kinetically first order in pentosidine and ground state oxygen, and in vivo effectively first order with NIR irradiation also

Flexible stretchable electronics for sport and wellbeing applications

Wearable electronics are becoming increasingly widespread in modern society. Though these devices are intended to be worn, integrated into clothing and other everyday objects, the technologies and processes used to manufacture them is no different than those that manufacture laptops and mobile phones. Many of these devices are intended to monitor the user’s health, activity and general wellbeing, within clinical, recreational and assistive environments. Consequently, the inherent incompatibility of these rigid devices with the soft, elastic structure of the human body can in some cases can be uncomfortable and inconvenient for everyday life. For devices to take the step from a ‘wearable’ to an ‘invisible’, a drastic rethinking of electronics manufacturing is required.The fundamental aim of this research is to establish parameters of usefulness and an array of materials with complimentary processes that would assist in transitioning devices to long term almost invisible items that can assist in improving the health of the wearer. In order to approach this problem, a novel architecture was devised that utilised PDMS as a substrate and microfluid channels of Galinstan liquid alloy for interconnects. CO2 laser machining was investigated as a means of creating channels and vias on PDMS substrates. Trace speeds and laser power outputs were investigated in order to find an optimal combination. The results displayed upper limits for power densities; where surpassing this limit resulted in poor repeatability and surface finish. It was found that there was an optimal set of trace speeds that ranged from approximately 120mm/s to 190mm/s that resulted in the most reliable and repeatable performance. Due to the complex nature of a materials variable energy absorption properties, it is not possible to quantify a single optimal parameter set.To understand the performance of these devices in situ, finite element analysis was employed to model deformations that such a device could experience. The aims here were to investigate the bond strength required to prevent delamination, between the silicon-PDMS and PDMS-PDMS bonds, in addition to the stress applied to the silicone die during these deformations. Based upon the applied loads the required bond strengths would need to be at least ~65kPa to maintain PDMS-PDMS adhesion during these tests, while stress on the silicone-PDMS adhesion required an expected v higher ~160kPa, both of which are within the reach of existing bonding techniques that are capable of withstanding a pressure of ~600kPa before failure occurs. Stress on the silicon die did not exceed ~7.8 MPa during simulation, which is well below the fracture stress.By developing knowledge about how various components of such a system will respond during use and under stress, it allows future engineers to make informed design decisions and develop better more resilient products.</div

Actas de SABI2020

Los temas salientes incluyen un marcapasos pulmonar que promete complementar y eventualmente sustituir la conocida ventilación mecánica por presión positiva (intubación), el análisis de la marchaespontánea sin costosos equipamientos, las imágenes infrarrojas y la predicción de la salud cardiovascular en temprana edad por medio de la biomecánica arterial

Development of Multifunctional E-skin Sensors

Electronic skin (e-skin) is a hot topic due to its enormous potential for health monitoring, functional prosthesis, robotics, and human-machine-interfaces (HMI). For these applications, pressure and temperature sensors and energy harvesters are essential. Their performance may be tuned by their films micro-structuring, either through expensive and time-consuming photolithography techniques or low-cost yet low-tunability approaches. This PhD thesis aimed to introduce and explore a new micro-structuring technique to the field of e-skin – laser engraving – to produce multifunctional e-skin devices able to sense pressure and temperature while being self-powered. This technique was employed to produce moulds for soft lithography, in a low-cost, fast, and highly customizable way. Several parameters of the technique were studied to evaluate their impact in the performance of the devices, such as moulds materials, laser power and speed, and design variables. Amongst the piezoresistive sensors produced, sensors suitable for blood pressure wave detection at the wrist [sensitivity of – 3.2 kPa-1 below 119 Pa, limit of detection (LOD) of 15 Pa], general health monitoring (sensitivity of 4.5 kPa-1 below 10 kPa, relaxation time of 1.4 ms, micro-structured film thickness of only 133 µm), and robotics and functional prosthesis (sensitivity of – 6.4 × 10-3 kPa-1 between 1.2 kPa and 100 kPa, stable output over 27 500 cycles) were obtained. Temperature sensors with micro-cones were achieved with a temperature coefficient of resistance (TCR) of 2.3 %/°C. Energy harvesters based on micro-structured composites of polydimethylsiloxane (PDMS) and zinc tin oxide (ZnSnO3) nanowires (NWs; 120 V and 13 µA at > 100 N) or zinc oxide (ZnO) nanorods (NRs; 6 V at 2.3 N) were produced as well. The work described herein unveils the tremendous potential of the laser engraving technique to produce different e-skin devices with adjustable performance to suit distinct applications, with a high benefit/cost ratio

Feature Papers in Electronic Materials Section

This book entitled "Feature Papers in Electronic Materials Section" is a collection of selected papers recently published on the journal Materials, focusing on the latest advances in electronic materials and devices in different fields (e.g., power- and high-frequency electronics, optoelectronic devices, detectors, etc.). In the first part of the book, many articles are dedicated to wide band gap semiconductors (e.g., SiC, GaN, Ga2O3, diamond), focusing on the current relevant materials and devices technology issues. The second part of the book is a miscellaneous of other electronics materials for various applications, including two-dimensional materials for optoelectronic and high-frequency devices. Finally, some recent advances in materials and flexible sensors for bioelectronics and medical applications are presented at the end of the book

Smart Sensors for Healthcare and Medical Applications

This book focuses on new sensing technologies, measurement techniques, and their applications in medicine and healthcare. Specifically, the book briefly describes the potential of smart sensors in the aforementioned applications, collecting 24 articles selected and published in the Special Issue “Smart Sensors for Healthcare and Medical Applications”. We proposed this topic, being aware of the pivotal role that smart sensors can play in the improvement of healthcare services in both acute and chronic conditions as well as in prevention for a healthy life and active aging. The articles selected in this book cover a variety of topics related to the design, validation, and application of smart sensors to healthcare

The Feasibility Of Using Infra-Red Radiation In Determining Tooth-Vitality

The aim of this Study was to investigate the feasibility of infra-red radiation determining human tooth-vitality, the basis being that a vital tooth with an internal blood-supply may emit more infra-red radiation and be warmer than a non-vital tooth. The commonest pulp tests are sensibility tests which assess the ability of the nerve fibres within the pulp to respond to a stimulus applied to the tooth, rather than assess the pulp blood-flow. Development of the vitality test involved cooling the tooth-tissues and capturing the emitted infra-red radiation of re-warming with a thermal camera. Cooling and re-warming of tooth-slices enabled calculation of thermal conductivity and thermal diffusivity of the mineralised tissues - enamel and dentine - and production of a thermal map which characterised these. Sixteen extracted human molar teeth were tested in a cross-over-study with simulated vitality at four flow-rates: 0.5ml/min, 0.15ml/min, 0.08ml/min and 0.03ml/min under two conditions: pulsed and non-pulsed. The cross-over-design allowed paired testing of the same tooth and independent testing of two dissimilar teeth. The area under the re-warming curve between vital and non-vital teeth was statistically tested. Statistical significance was shown between the paired vital and non-vital teeth at all pulsed flow-rates, and non-pulsed flow-rates of 0.15ml/min and 0.5ml/min. Only the pulsed flow-rate of 0.5ml/min was significant for dissimilar teeth. A thermal map demonstrated re-warming of the vital tooth before the non-vital tooth. The results suggest infra-red radiation may determine tooth-vitality when the teeth are of the same size and shape, with a blood-flow of 0.03ml/min or above. This could be a realistic blood-flow for the human tooth. Testing teeth of differing size and shape may determine vitality at a blood-flow of 0.5ml/min - higher than realistically expected in the human tooth. Clinically, the vitality test between a vital and non-vital root-treated tooth points to this model being inverted. This may be due to the insulating nature of the materials used to restore the non-vital tooth. Further clinical investigation is justified to validate the vitality test