Non-invasive Sensor Research Articles

High-Frequency Current Transformer Design and Implementation Considerations for Wideband Partial Discharge Applications

High-frequency current transformers are popular noninvasive inductive wideband sensors. Despite the simplicity in design and operational principle, implementation of such sensors for partial discharge (PD) applications requires careful consideration, particularly in the higher frequency range where traveling wave attenuation and distortion are relevant. First, the role of design variables, including core materials, winding design, and shielding practices on sensor sensitivity and frequency characteristics (transfer impedance), is presented. Next, the suitability of the constructed sensors for PD applications is assessed. The designed wideband sensors are suitable for laboratory applications with standard measurement circuits and controlled conditions. The low-level magnitude and frequency spectrum of the discharge pulses hinders signal integrity in relation to the placement of the sensors within the measurement circuit, signal amplification, and pulse repetition rate (pulse resolution). To enable the most stringent detection levels under 1 pC, efforts are needed in distortionless amplifier design and interference mitigation.

FIRST MICROWAVE TOMOGRAPHY APPROACH TOWARDS A TRULY NONINVASIVE, PAIN-FREE AND WEARABLE BLOOD GLUCOSE MONITORING DEVICE

Despite the advancements in the field of glucose monitoring sensors, the development of noninvasive, wearable, continuous and comfortable systems is still a real challenge. New technologies are required for noninvasive, continuous and effective measurements remaining discreet, painless, comfortable to the patient and avoiding additional costs. This article presents a truly noninvasive microwave tomography prototype designed for glucose monitoring. The system is based on an array of dipole antennas placed in a circular configuration. The transmitted field data are collected using a switch matrix connected to a vector network analyzer. A heterogeneous 3-D arm model and a 3-D electromagnetic solver have been used to model the human arm and to characterize the system. Blood electromagnetic properties are affected by the glucose concentration, a promising correlation between the dielectric properties of blood and glucose level should be investigated. By simulating the antenna array on the arm phantom, the characteristics of the S-parameters were interesting at the frequencies of interest. The transmission coefficient amplitude decreases as the dielectric constant decreases from 63 to 40, and the conductivity increases from 1.5 S/m to 3.5 S/m. For each value of dielectric properties, a given transmission coefficient value can be clearly identified. Experimental measurements validated the arm phantom and confirmed the relationship between the response of the system and the dielectric properties of blood tissue. The armband sensor is designed as an inexpensive, noninvasive, and light weight device suitable for all patients with a high level of discretion. This work, under optimization for preclinical and clinical testing, demonstrates the proof of concept of an innovative microwave tomography system for noninvasive glucose monitoring. Compared to studies with a similar aim, this research may achieve distinct advances and offers promising hope in the field of noninvasive glucose sensors.

Combustion optimization in gas burners of reverberatory furnaces during the melting of nickel alloys

In recent years, due to climate change environmental sustainability programs have been created that require the search for alternatives to reduce air emissions and reduce fuel consumption. The combustion industry is looking for an effective solution to increase the life cycle of its equipment and improve combustion efficiency without neglecting safety or savings. The efficiency of the medium pressure natural gas burners associated with chemical energy, which is converted into heat, that is, the hotter the gaseous products of combustion, the more efficient the burner. The work analyzes the combustion process and their chemical reactions; combustion products obtained in accordance with various conditions; combustion characteristics and factors that influence; and measurement methods needed to optimize combustion and their equipment. In the metallurgical production of nickel, optimization of the burners is very important due to the high temperature used in the reverberatory furnace. That is, the use of a large excess of air would be unfavorably energetic, and the use of a very low excess would result in small intimate mixtures of air and fuel, followed by the release of unreacted reagents and the formation of toxic gases arising at high temperatures. For this reason, the results of this work are an important source of information. The innovation is to automate the use of non-invasive sensors to control the combustion process. The sensors play a fundamental role in the industry, because the information they provide supports the enhanced use of data in the enterprise, increase productivity, efficiency and safety.

Cutaneous Carotenoid Level Measured by Multiple Spatially Resolved Reflection Spectroscopy Sensors Correlates with Vegetable Intake and Is Increased by Continual Intake of Vegetable Juice.

Although vegetables are beneficial for human health, in many countries, the recommended vegetable intake is not reached. To assess vegetable intake, it is important to understand vegetable consumption. Therefore, we conducted a cross-sectional and intervention study of 26 healthy individuals (50% women; 37.0 ± 8.9 years) and estimated vegetable intake on the basis of the cutaneous carotenoid level (CCL) with a noninvasive skin carotenoid sensor, considering that vegetable juice intake can increase CCL. Participants consumed vegetable juice containing 350 g of vegetables daily for 4 weeks. Blood carotenoid levels and CCL were measured for 12 weeks. Cross-sectional analysis showed a significant positive correlation between CCL and vegetable intake (r = 0.489). Vegetable juice consumption significantly increased CCL and the blood levels of α-carotene, β-carotene, and lycopene (p < 0.05). The correlation coefficient between the blood level and CCL for lycopene was smaller (r = 0.001) compared to that between the blood level and CCL for α-carotene (r = 0.523) and β-carotene (r = 0.460), likely because of bioavailability differences. In conclusion, noninvasive skin carotenoid measurements are effective for determining vegetable intake, and vegetable juice significantly increases CCL.

Co3O4 Nanoparticles as a Noninvasive Electrochemical Sensor for Glucose Detection in Saliva

A new noninvasive glucose sensor is developed based on Co3O4 particles (Co3O4 NPs), which are synthesized by a single-step hydrothermal method with uniform structure and size. The electrochemical measurements reveal that the device exhibits outstanding performance for glucose detection, achieving a maximal sensitivity of 2495.79[Formula: see text][Formula: see text]A mM[Formula: see text] cm[Formula: see text] with a high [Formula: see text] of 0.99575, a ultra-low detection limit of 9.3[Formula: see text]nM with a signal-to-noise of 3 and linear range up to 3[Formula: see text]mM. The noninvasive glucose sensor can respond swiftly and selectively due to the high electrocatalytic activity of Co3O4 NPs. The sensor also shows its high sensitivity and selectivity in detecting glucose levels in human blood serum and saliva sample, confirming the application potential of Co3O4 NPs in noninvasive detection of glucose.

Piezo-tribo dual effect hybrid nanogenerators for health monitoring

Over the years, nanogenerators for health monitoring have become more and more attractive as they provide a cost-effective and continuous way to successfully measure vital signs, physiological status, and environmental changes in/around a person. Using such sensors can positively affect the way healthcare workers diagnose and prevent life-threatening conditions. Recently, the dual piezo-tribological effect of hybrid nanogenerators (HBNGs) have become a subject of investigation, as they can provide a substantial amount of data, which is significant for healthcare. However, real-life exploitation of these HBNGs in health monitoring is still marginal. This review covers piezo-tribo dual-effect HBNGs that are used as sensors to measure the different movements and changes in the human body such as blood circulation, respiration, and muscle contractions. Piezo-tribo dual-effect HBNGs are applicable within various healthcare settings as a means of powering noninvasive sensors, providing the capability of constant patient monitoring without interfering with the range of motion or comfort of the user. This review also intends to suggest future improvements in HBNGs. These include incorporating surface modification techniques, utilizing nanowires, nanoparticle technologies, and other means of chemical surface modifications. These improvements can contribute significantly in terms of the electrical output of the HBNGs and can enhance their prospects of applications in the field of health monitoring, as well as various in vitro/in vivo biomedical applications. While a promising option, improved HBNGs are still lacking. This review also discusses the technical issue which has prevented so far, the real use of these sensors. • Piezo-tribo dual effect Hybrid Nanogenerators (HNGs) as health monitoring sensors. • HNGs as sensors to measure the different movements and changes in the body. • Application of HNGs as a means of powering noninvasive sensors, and capable of constant patient monitoring. • This review discusses the improvements in terms of the electrical output of the HNGs, their prospects in the field of health monitoring, as well as various in vitro/in vivo biomedical applications. • This review also discusses the technical issue which have prevented so far, the real use of the HNGs as sensors.

Hypersensitized Metamaterials Based on a Corona-Shaped Resonator for Efficient Detection of Glucose

In this work, a new design for a real-time noninvasive metamaterial sensor, based on a corona-shaped resonator, is proposed. The sensor was designed numerically and fabricated experimentally in order to be utilized for efficient detection of glucose in aqueous solutions such as water and blood. The sensor was inspired by a corona in-plane-shaped design with the presumption that its circular structure might produce a broader interaction of the electromagnetic waves with the glucose samples. A clear shift in the resonance frequency was observed for various glucose samples, which implies that the proposed sensor has a good sensitivity and can be easily utilized to distinguish any glucose concentration, even though their dielectric coefficients are close. Results showed a superior performance in terms of resonance frequency shift (1.51 GHz) and quality factor (246) compared to those reported in the literature. The transmission variation level ∆|S21| was investigated for glucose concentration in both water and blood. The sensing mechanism was elaborated through the surface current, electric field and magnetic field distributions on the corona resonator. The proposed metamaterials sensor is considered to be a promising candidate for biosensor and medicine applications in human glycaemia monitoring.

Digital Health in Cardiac Rehabilitation and Secondary Prevention: A Search for the Ideal Tool.

Digital health is becoming more integrated in daily medical practice. In cardiology, patient care is already moving from the hospital to the patients’ homes, with large trials showing positive results in the field of telemonitoring via cardiac implantable electronic devices (CIEDs), monitoring of pulmonary artery pressure via implantable devices, telemonitoring via home-based non-invasive sensors, and screening for atrial fibrillation via smartphone and smartwatch technology. Cardiac rehabilitation and secondary prevention are modalities that could greatly benefit from digital health integration, as current compliance and cardiac rehabilitation participation rates are low and optimisation is urgently required. This viewpoint offers a perspective on current use of digital health technologies in cardiac rehabilitation, heart failure and secondary prevention. Important barriers which need to be addressed for implementation in medical practice are discussed. To conclude, a future ideal digital tool and integrated healthcare system are envisioned. To overcome personal, technological, and legal barriers, technological development should happen in dialog with patients and caregivers. Aided by digital technology, a future could be realised in which we are able to offer high-quality, affordable, personalised healthcare in a patient-centred way.

Bacterial cellulose-based re-swellable hydrogel: Facile preparation and its potential application as colorimetric sensor of sweat pH and glucose

Direct deposition of the negatively charged polyelectrolyte, carboxymethyl cellulose (CMC), into a bacterial cellulose (BC) matrix was used as a simple route to fabricate a re-swellable and biocompatible cellulose-based hydrogel. As a result of this non-destructive approach, the physical and mechanical property of the original BC were well-preserved within the resulting BC/CMC hydrogel. As a BC/CMC-based colorimetric pH sensor, it exhibited a rapid response with an easy color differentiation between each pH by the naked eye, and wide linear range of pH 4.0–9.0 with good linearity. For the detection of glucose in sweat, the BC/CMC-based colorimetric glucose sensor provided a low limit of detection (25 μM) with a wide linear detection range (0.0–0.5 mM) and high accuracy. These BC/CMC based sensors could potentially be applied as non-invasive semi-quantitative sensors for on-skin health monitoring.

Prolonged phenanthrene exposure reduces cardiac function but fails to mount a significant oxidative stress response in the signal crayfish (Pacifastacus leniusculus)

Crustaceans are important ecosystem bio-indicators but their response to pollutants such as polyaromatic hydrocarbons (PAHs) remains understudied, particularly in freshwater habitats. Here we investigated the effect of phenanthrene (at 0.5, 1.0 and 1.5 mg L−1), a 3-ringed PAH associated with petroleum-based aquatic pollution on survival, in vivo and in situ cardiac performance, the oxidative stress response and the tissue burden in the signal crayfish (Pacifastacus leniusculus). Non-invasive sensors were used to monitor heart rate during exposure. Phenanthrene reduced maximum attainable heart rate in the latter half (days 8–15) of the exposure period but had no impact on routine heart rate. At the end of the 15-day exposure period, the electrical activity of the semi-isolated in situ crayfish heart was assessed and significant prolongation of the QT interval of the electrocardiogram was observed. Enzyme pathways associated with oxidative stress (superoxide dismutase and total oxyradical scavenging capacity) were also assessed after 15 days of phenanthrene exposure in gill, hepatopancreas and skeletal muscle; the results suggest limited induction of protective antioxidant pathways. Lastly, we report that 15 days exposure caused a dose-dependent increase in phenanthrene in hepatopancreas and heart tissues which was associated with reduced survivability. To our knowledge, this study is the first to provide such a thorough understanding of the impact of phenanthrene on a crustacean.

Using non-invasive MEMS pressure sensors for measuring building envelope air leakage

Micro-electromechanical systems (MEMS)-based sensors have seen significant improvements in accuracy and cost over the past several years, and due to the need for altitude sensing in unmanned aerial vehicles and wearable technologies, absolute pressure sensors have shown the most dramatic improvements. This paper investigates applications of MEMS sensors in commercial buildings, including pairing two absolute pressure sensors to determine differential pressures between different locations in and around buildings. Differential pressure measurements are commonly made in commercial buildings for a number of applications, including static pressure measurements for variable-speed supply fan control, air balancing in hospitals, and for envelope and duct air leakage testing. This paper focuses specifically on envelope air-leakage testing applications of these sensors. The use of continuous pressure measurements in addition to one-time non-intrusive outdoor airflow measurements of rooftop packaged units is investigated. A comparison with standardized leakage testing indicated that continuous measurements with MEMS pressure-sensors were able to estimate envelope leakage to within 3–16% of the standardized test result. In addition, the magnitude and stability of differential pressure differences that can be resolved with absolute pressure sensors are also investigated in the laboratory and the field. Results show that the sensors can be effectively used for pressures seen in low rise buildings with rooftop units.

Differential Microwave Resonator Sensor for Real-Time Monitoring of Volatile Organic Compounds

In this work, a noninvasive microwave gas sensor suitable for accurate and real-time tracking of volatile organic compounds concentration is presented. The proposed differential sensor was comprised of two independent split-ring resonators in power splitter/combiner configuration to enhance the robustness of the sensor to changes in environmental parameters. The design was fabricated on a Rogers RT/duroid 5880 high-frequency substrate and operated at ${f}_{s}= 5.12$ GHz and ${f}_{r}= 5.65$ GHz, referring to the sensing and reference resonant frequencies, respectively. A thin layer of polydimethylsiloxane was used as an interface layer in the sensing resonator region with the strongest electric field to enable gas sensing with high sensitivity. The performance of the sensor was validated by introducing different volatile organic compounds, such as acetone, methanol, ethanol, and isopropyl alcohol. Time-based responses of the sensor demonstrated the capability of the sensor to monitor different concentrations of acetone vapor ranging from low, 387 to 1935 ppm, with the sensitivity of 0.02 mdB/ppm and high concentrations, 3878 to 62048 ppm, with sensitivity of 0.0125 mdB/ppm.

Micro/nanofiber-based noninvasive devices for health monitoring diagnosis and rehabilitation

Recently, in healthcare sectors, specifically for personalized health monitoring, motion sensing, and human–machine interactions, the rising demand for stretchable and soft electronic devices is significant. In particular, stretchable, skin mountable, breathable, wearable, light weight, and highly sensitive sensors are needed for detecting subtle deformation arising from human physiological signals and have potential applications in health diagnosis. In this review, we discuss flexible, noninvasive, and wearable sensors based on micro/nanofibers with unique sensing capabilities for detecting human vital signs such as body motion, temperature, heartbeat, respiration rate, and blood glucose level, which have applications in both fitness-monitoring and medical diagnosis. Here, the latest successful examples of micro/nanofiber based flexible and wearable human vital signs monitoring sensors in the form of film, mat, yarn, fabric, textiles, etc., are outlined and discussed in detail. Discussion includes the fiber fabrication technique, sensing mechanism, device structure, sensor performance, and data processing. Some of the latest fabricated self-powered devices with integrated sensing platforms are also reviewed. Finally, this article reveals the existing challenges that are still to be overcome associated with wearable technologies for applications in health monitoring, diagnosis, and rehabilitation.

Flow Control Based on Feature Extraction in Continuous Casting Process.

The flow structure in the mold of a continuous steel caster has a significant impact on the quality of the final product. Conventional sensors used in industry are limited to measuring single variables such as the mold level. These measurements give very indirect information about the flow structure. For this reason, designing control loops to optimize the flow is a huge challenge. A solution for this is to apply non-invasive sensors such as tomographic sensors that are able to visualize the flow structure in the opaque liquid metal and obtain information about the flow structure in the mold. In this paper, ultrasound Doppler velocimetry (UDV) is used to obtain key features of the flow. The preprocessing of the UDV data and feature extraction techniques are described in detail. The extracted flow features are used as the basis for real time feedback control. The model predictive control (MPC) technique is applied, and the results show that the controller is able to achieve optimum flow structures in the mold. The two main actuators that are used by the controller are the electromagnetic brake and the stopper rod. The experiments included in this study were obtained from a laboratory model of a continuous caster located at the Helmholtz-Zentrum Dresden Rossendorf (HZDR).

External temperature sensor assisted a new low power photoplethysmography readout system for accurate measurement of the bio-signs.

This study presents an external temperature sensor assisted a new low power, time-interleave, wide dynamic range, and low DC drift photoplethysmography (PPG) signal acquisition system to obtain the accurate measurement of various bio signs in real-time. The designed chip incorporates a 2-bit control programmable transimpedance amplifier (TIA), a high order filter, a 3:8 programmable gain amplifier (PGA) and 2 × 2 organic light-emitting diode (OLED) driver. Temperature sensor is used herein to compensate the adverse effect of low-skin-temperature on the PPG signal quality. The analog front-end circuit is implemented in the integrated chip with chip area of 2008 μm × 1377 μm and fabricated via TSMC T18 process. With the standard 1.8 V, the experimental result shows that the measured current sensing range is 20 nA–100 uA. The measured dynamic range of the designed readout circuit is 80 dB. The estimated signal to noise ratio is 60 dB@1 uA, and the measured input referred noise is 60.2 pA/Hz½. The total power consumption of the designed chip is 31.32 µW (readout) + 1.62 mW (OLED driver@100% duty cycle). The non-invasive PPG sensor is applied to the wrist artery of the 40 healthy subjects for sensing the pulsation of the blood vessel. The experimental results show that for every 1 °C decrease in mean ambient temperature tends to 0.06 beats/min, 0.125 mmHg and 0.063 mmHg increase in hear rate (HR), systolic (SBP) and diastolic (DBP), respectively. Similarly, for every 1 °C increase in mean ambient temperature tends to 0.13 beats/min, 0.601 mmHg and 0.121 mmHg increase in HR, SBP and DBP, respectively. The measured accuracy and standard error for the HR estimation are 96%, and − 0.022 ± 2.589 beats/minute, respectively. The oxygen stauration (SpO2) measurement results shows that the mean absolute percentage error is less than 5%. The resultant errors for the SBP and DBP measurement are − 0.318 ± 5.19 mmHg and − 0.5 ± 1.91 mmHg, respectively.Electronic supplementary materialThe online version of this article (10.1007/s00542-020-05106-y) contains supplementary material, which is available to authorized users.

Application of micro- and mini-bioreactors in biomedicine development and production

Micro- and mini-bioreactors are characterized by their miniature working volume and comprehensive monitoring of process data, e.g., biomass, pH, dissolved oxygen, and fluorescence that are on par with conventional bench-top systems. The technical advancements of micro- and mini-bioreactors are supported by single-use material and micro-manufacturing, non-invasive optical sensors, automation such as industrial robotics and the integration of design of experiment software with data acquisition and process control. Owing to the miniature scales, micro-bioreactors typically feature lower turbulence intensity and energy dissipation rate, resulting in different mass transfer, mixing and shear conditions as compared to industrial scale equipment. Mini-bioreactors, nevertheless, are closer to large vessels. Micro- and mini-bioreactors are used mostly in screening and process development nowadays, owing to their combined high throughput and richness of data. They are also the hardware that will enable "precision medicine" in the near future.

(Invited) Development of the Hydrogel-Based Biosensors for Non-Invasive Perspiration Analysis

Non-invasive diagnostic sensors for biomarkers are generally required as an alternative to blood-based diagnoses for the next generation of advanced healthcare. Sweat is one of the promising bodily fluids that are non-invasively accessible source of biomarkers. However, it is difficult to collect small amount of sweat from human skin surface in a periodic or continuous manner. Whereas wearable-type of tattoo- and microfluidics-based biosensors have enabled in-situ and real-time sampling and monitoring of sweat biomarkers, it has been necessary to induce continuous perspiration under special conditions such as with exercise, in a high-temperature environment, or with the use of cholinergic agonist-assisted perspiration. These circumstances are not practical in the application of sweat sensors for daily health diagnostics. In this presentation, we show our new perspiration sensor, a hydrogel-based touch sensor pad for the non-invasive extraction and detection of sweat components. The sensor was composed of the printed electrochemical biosensing working and planar liquid-junction Ag/AgCl reference electrodes fully covered with an agarose hydrogel including a sweat-extraction solution, Phosphate Buffer Saline (PBS). We found that biocompatible PBS with physiological osmotic pressure was suitable to continuous extraction of sweat. In this study, an enzyme-based L-lactate sensor was fabricated as a model because L-lactate is included in sweat in relatively high concentrations. L-lactate was oxidized by Lactate oxidase (LOx) to generate hydrogen peroxide, which oxidize reduced form of prussian blue (PB) immobilized on the working electrode surface. The LOx / PB-modified electrode was fabricated by screen-printing of a carbon-graphite ink including PB on an Au electrode, followed by drop-casting of a mixture of LOx with chitosan as a matrix to immobilize LOx on the electrode. The structure of the screen-printed planar liquid-junction Ag/AgCl reference electrode was composed of a silver-lead pattern, Ag/AgCl active layer, internal electrolyte layer, polyurethane-based liquid junction, and insulation layer on a substrate. Then, a silicone rubber sheet with a 6 mm diameter through-hole was attached to the electrode film as to expose the active area of working and reference electrodes to the through-hole. A low melting point agarose prepolymer solution in PBS was drop-deposited onto the through-hole in the silicone sheet, and incubated at room temperature to induce gelation. We measured the potentiometric response of the sensor electrodes when the ball of the subject’s forefinger contacted the agarose gel surface. After 20 s of time lag for diffusion of extracted L-lactate in the gel, the potential difference started to increase, followed by approaching steady-state. This result suggested successful extraction and detection of sweat L-lactate using this device. Without LOx, no potentiometric response was observed upon touching the gel with the subject’s forefinger, suggesting that the extracted sweat compounds except for L-lactate did not affect the sensor response. This new type of touch sensor pad integrated with biosensors will enable non-invasive and daily periodic monitoring of sweat biomarkers without harsh exercise-, environmental temperature control, and cholinergic agonist-assisted perspiration. In a future study, we will apply the present sensor to the other sweat analytes such as D-glucose (diabetes biomarker), electrolytes (heat stroke biomarker), ammonium ion (anaerobic exercise biomarker), and some cytokines (immune response biomarker) to evaluate the sensor characteristics in more detail.

Assessing rectal temperature with a novel non-invasive sensor

Athletes, soldiers, and workers who perform intense physical activities under extreme hot conditions might encounter increased physiological thermal strain. Consequently, the increase in body core temperature (Tc) might result in heat exhaustion and heatstroke. Thus, continuously following changes in Tc is of utmost importance. Recently, the Tcore sensor (Dräger, Germany), which employs a unique dual-sensor heat flux technology, became commercially available to measure Tc, in a hospital-controlled environment. This study aimed to evaluate the possibility of using the Tcore sensor to accurately monitor rectal temperature (Tre), reflecting Tc, under exercise-heat stress. Thirteen healthy young males completed the study protocol, consisting of 90min of moderate exercise (walking on a treadmill - 5km/h, 4% elevation) under controlled hot/dry and hot/wet climatic conditions (30°C/60% rh, 34°C/40% rh, and 40°C/40% rh). Tcore sensors were placed on the forehead and the left wrist. Temperatures from both Tcore sensors were recorded continuously together with Tre using a rectal thermistor. The original algorithm used by the company to estimate Tre from the Tcore sensor was found to be inadequate under the study's conditions and new models for the forehead and the wrist measurements were developed. Nearly 150,000 measurement sets (after filtering) were used to build independent MATLAB software algorithms and test their reliability according to the cross-validation algorithm. Bland-Altman analysis was used to compare between the results obtained by the new models to Tre. The database consisted of a large Tre range (36.5-38.9°C). The mean errors of the models were close to zero, and the mean absolute errors were 0.20±0.16°C and 0.27±0.20°C for the forehead and wrist, respectively. 95% of the measurements from the forehead model and 86% from the wrist model were within ±0.5°C of Tre, and 78% (forehead) and 64% (wrist) were within ±0.3°C. Root Mean Square Deviation (RMSD) values were 0.29°C and 0.40°C for the forehead and wrist models, respectively. The developed models show the feasibility to use the Tcore sensor for assessing Tre under exercise-heat conditions. Furthermore, the sensor was found to be adequate for use on the wrist as well, which might be more practical for use in field conditions.

Inverse Opal Films for Medical Sensing: Application in Diagnosis of Neonatal Jaundice.

A non-invasive, at-home test for neonatal jaundice can facilitate early jaundice detection in infants, improving clinical outcomes for neonates with severe jaundice and helping to prevent the development of kernicterus, a type of brain damage whose symptoms include hearing loss, impairment of cognitive capacity, and death. Here a photonic sensor that utilizes color changes induced by analyte infiltration into a chemically functionalized inverse opal structure is developed. The sensor is calibrated to detect differences in urinary surface tension due to increased bile salt concentration in urine, which is symptomatic of abnormal liver function and linked to jaundice. The correlation between neonatal urinary surface tension and excess serum bilirubin, the physiologic cause of neonatal jaundice, is explored. It is shown that these non-invasive sensors can improve the preliminary diagnosis of neonatal jaundice, reducing the number of invasive blood tests and hospital visits necessary for healthy infants while ensuring that jaundiced infants are treated in a timely manner. The use of inverse opal sensors to measure bulk property changes in bodily fluids can be extended to the detection of several other conditions, making this technology a versatile platform for convenient point-of-care diagnosis.

Real-Time Optical Monitoring of Endotracheal Tube Displacement.

Proper ventilation of a patient with an endotracheal tube (ETT) requires proper placement of the ETT. We present a sensitive, noninvasive, operator-free, and cost-effective optical sensor, called Opt-ETT, for the real-time assessment of ETT placement and alerting of the clinical care team should the ETT become displaced. The Opt-ETT uses a side-firing optical fiber, a near-infrared light-emitting diode, two photodetectors with an integrated amplifier, an Arduino board, and a computer loaded with a custom LabVIEW program to monitor the position of the endotracheal tube inside the windpipe. The Opt-ETT generates a visual and audible warning if the tube moves over a distance set by the operator. Displacement prediction is made using a second-order polynomial fit to the voltages measured from each detector. The system is tested on ex vivo porcine tissues, and the accuracy is determined to be better than 1.0 mm. In vivo experiments with a pig are conducted to test the performance and usability of the system.