Objective. To evaluate the imaging capabilities of four polydimethylsiloxane-based acoustic lenses with subsonic refractive indices, focusing on a spherical lens and three designed aspherical lenses with varying focus. Approach. We investigated a spherical lens with a radius curvature of 8 mm (SL-R8), two aspherical lenses with focal lengths of 15 mm and 10 mm (AL15 and AL10), and an aspherical folding lens with a focal length of 10 mm (AFL10). The equation cross-section profile of an aspherical lens is calculated using the assumption that all trajectories passing through the lens have the same flight duration when they reach the focal point. Furthermore, we observed that we can fold this aspherical lens without greatly diminishing its focusing capability. Utilizing circular planar ultrasonic transducers at frequencies of 10 MHz and 15 MHz, we examined the reflected waveforms via pulse-echo tests and measured focal points and beam widths using a needle hydrophone in the acoustic intensity measurement system. The target resolution was assessed using a C-Scan imaging system. Main results. Analysis of the axial and lateral beam profiles revealed that AFL10 and AL10 lenses exhibited narrower beam widths at the focal point. We evaluate the AFL10 and AL10 lenses combined with a 15 MHz transducer for preclinical testing using standard medical phantoms containing microparticles in gelatin- and agar-based matrices. In conclusion, using these twocombinations, C-Scan imaging successfully formed a 25 mu m backscatter inside the phantom image. Significance. Due to their high-resolution capabilities, applying cross-sectional profile equations in the lateral plane of the lens surface in linear ultrasonic array probes offers promises for early-stage medical diagnostics.

This study multifunctional wearable bioelectronics (MWBs) integrated with a piezoelectric sensor and a micropatterned temperature sensor for accurate detection of human physiological signals. Piezoelectric nanocomposite uniformity, stretchability, and adhesion is improved through the functionalization of nanoparticles with glycidyl silane and nonionic surfactants dispersion in the organic polymer matrix. Additionally, crack-free nanometal layers are deposited on the nanocomposite interface with high adhesion by thiol silane functionalization and oxygen plasma treatment. The MWBs exhibit a temperature sensitivity of 7.1 omega degrees C-1 (R2 of 0.999) between 30 degrees C to 40 degrees C, a pressure sensitivity of 72 mV kPa-1 (R2 of 0.998) within 0.5 kPa to 10 kPa, and a stable mechanical durability. MWBs have demonstrated to detect subtle pulse waveforms at an arm-mimicking phantom and human skin, respectively. Furthermore, MWBs are applied to analyze physiological signal characteristics caused by human stress, demonstrating its potential for use in healthcare electronics in various medical applications. Multifunctional wearable bioelectronics (MWBs) are demonstrated with integrated a piezoelectric pulse wave sensor and a temperature sensor for physiological signal detection by enhancing nanocomposite dispersion and metal deposition. The MWBs exhibit high sensitivity and resolution in detecting blood pulse waveforms and skin temperature changes, demonstrating its potential for mental stress analysis.image

UV radiation is considered indispensable from the hygienic, medical, aesthetic, and industrial perspectives. Among the various types of UV radiation, UV-A (with a wavelength of 315-400 nm) has a significant influence because it adversely affects human skin, leading to damage such as blemishes, freckles, and wrinkles. Although various photosensors are developed for monitoring UV-A radiation in real time, these devices have critical issues, such as inefficient fabrication processes, insufficient photoresponsivity, and incompatibility with long-term wearable applications. Here, the authors report on a wearable UV-detecting patch targeted for long-term use in the medical and clinical fields. A wearable UV sensor is fabricated by integrating optimized InGaN/GaN microphotodetectors (mu PDs) in a 3D porous patch. The optical and electrical properties of the device are intensively investigated under various types of optical radiation and input electrical power and show high photoresponsivity (2.82 A W-1) and excellent external quantum efficiency (897.63%). Long-term real-time UV radiation monitoring using the wearable mu PDs is demonstrated; moreover, the by-products can be efficiently removed from human skin surfaces.

The thermal response time of a thin-film resistance temperature detector (RTD) array sensor was measured for a high-intensity focused ultrasound (HIFU) phantom. As the temperature inside materials change rapidly within several seconds, it is important to have a temperature sensor with a fast response time to evaluate their performance. However, previous methods for measuring thermal response time were not suitable for thin-film sensors, and there were no quantitative data available. In this study, we used a liquid drop method to measure the thermal time constant of the thin-film RTD, which was found to be 1.0 ± 0.2 ms. This indicates that the thin-film RTD array sensor has a sufficiently fast response time to detect sudden temperature changes inside the tissue-mimicking material (TMM) for validating HIFU devices.

Wearable blood-pressure sensors have recently attracted attention as healthcare devices for continuous non-invasive arterial pressure (CNAP) monitoring. However, the accuracy of wearable blood-pressure (BP) monitoring devices has been controversial due to the low signal quality of sensors, the absence of an accurate transfer function to convert the sensor signals into BP values, and the lack of clinical validation regarding measurement precision. Here, a wearable piezoelectric blood-pressure sensor (WPBPS) is reported, which achieves a high normalized sensitivity (0.062 kPa-1 ), and fast response time (23 ms) for CNAP monitoring. The transfer function of a linear regression model is designed, offering a simple solution to convert the flexible piezoelectric sensor signals into BP values. In order to verify the measurement accuracy of WPBPS, clinical trials are performed on 35 subjects aged from 20 to 80 s after screening. The mean difference between the WPBPS and a commercial sphygmomanometer of 175 BP data pairs is -0.89 ± 6.19 and -0.32 ± 5.28 mmHg for systolic blood pressure (SBP) and diastolic blood pressure (DBP), respectively. By building a WPBPS-embedded wristwatch, the potentially promising use of a convenient, portable, continuous BP monitoring system for cardiovascular disease diagnosis is demonstrated.

This research presents a flexible piezoelectric pressure sensor (FPPS) based on a 40 mu m thick nanocomposite with improved nanoparticle dispersion, enhanced vapor permeability, and stabilized metal deposition for precision pulse wave monitoring. First, the nanocomposite uniformity is improved by mixing the glycidylsilane-functionalized piezoelectric nanoparticles with the nonionic surfactant Triton-added polydimethylsiloxane to reduce interparticle surface energy. Second, the porous piezoelectric nanocomposite with vapor permeability enhancement (approximate to 485 g day(-1) m(-2)) is fabricated by dissolving the citrate particles crystallized in the nanocomposite matrix to form uniform pores. The nanocomposites exhibit good piezoelectric properties with vapor permeability higher than the skin perspiration level (approximate to 432 g day(-1) m(-2)), enabling reliable pulse wave monitoring without skin troubles. Third, the crack-free metal films (100/1 nm thick Au/Cr) are deposited directly on the nanocomposite, whose surface adhesion to the metal films is enhanced through the silane functionalization followed by oxygen plasma treatment. The FPPS, achieving those three major advances, shows a resolution of 0.05 kPa, a sensitivity of 9.07 mV kPa(-1), a linearity (R-squared in a regression model) of 0.999, and a stable durability over 200000 pressure cycles within the pressure range of 0.2-20 kPa. The FPPS, making conformal contact with the skin, is sensitive enough to detect subtle systolic/diastolic blood pressure as well as to discriminate pulse wave variations caused by physical activity and vascular aging. Therefore, our research demonstrates that the FPPS has strong potential for applications in individual cardiovascular monitoring and wearable healthcare.

The use of graphene and two-dimensional materials for industrial, scientific, and medical applications has recently received an enormous amount of attention due to their exceptional physicochemical properties. There have been numerous efforts to incorporate these two-dimensional materials into advanced flexible electronics, especially aimed for wearable biomedical applications. Here, recent advances in two-dimensional materials-based flexible electronic sensors for wearable biomedical applications with regard to both materials and devices are presented.

This paper presents a microfluidic thermal flowmeter for monitoring injection pumps, which is essential to ensure proper patient treatment and reduce medication errors that can lead to severe injury or death. The standard gravimetric method for flow-rate monitoring requires a great deal of preparation and laboratory equipment and is impractical in clinics. Therefore, an alternative to the standard method suitable for remote, small-scale, and frequent infusion-pump monitoring is in great demand. Here, we propose a miniaturized thermal flowmeter consisting of a silicon substrate, a platinum heater layer on a silicon dioxide thin-membrane, and a polymer microchannel to provide accurate flow-rate measurement. The present thermal flowmeter is fabricated by the micromachining and micromolding process and exhibits sensitivity, linearity, and uncertainty of 0.722 mW/(g/h), 98.7%, and (2.36 ± 0.80)%, respectively, in the flow-rate range of 0.5–2.5 g/h when the flowmeter is operated in the constant temperature mode with the channel width of 0.5 mm. The measurement range of flow rate can be easily adjusted by changing the cross-sectional microchannel dimension. The present miniaturized thermal flowmeter shows a high potential for infusion-pump calibration in clinical settings.

A two-dimensional resistance temperature detector (RTD) array sensor for the measurement of temperature distribution inside a tissue-mimicking material was proposed to validate focused ultrasound (FUS) devices. The fully two-dimensional $10\times10$ RTD array sensor with 1 mm inter-RTD distance was fabricated on the $2.5~ \boldsymbol {\mu } \text{m}$ thick film and placed inside the tissue-mimicking material. The measurement uncertainty for the RTD array was 0.18 K. The temperature distribution inside the phantom caused by a FUS transducer was measured and compared depending on the input power and focal plane. A tissue-mimicking phantom with an implanted RTD array can be applied to validate the performance and safety of both high- and low-intensity focused ultrasound (HIFU and LIFU) devices.

Date Presented 04/13/21 It is important to monitor the status of motor development in children. Standardization for comparing pre- and postintervention results for children with suspected developmental coordination disease should also be implemented. In this study, a digital device for testing manual dexterity was developed, and its accuracy was verified. This device will be used to provide data for early screening and intervention program planning for infants at risk of delayed motor development or disability. Primary Author and Speaker: Yeshin Woo Contributing Authors: Allison J. L'Hotta, Anna H. Bauer, Chih-Hung Chang, Taniya Easow Varughese, Regina A. Abel, Allison King

Optical coherence tomography (OCT) is one of imaging technologies to diagnose ophthalmic diseases and to monitor progresses of treatments. Therefore, OCT and OCT-angiography (OCTA) have actively developed in the field of ophthalmology, and retinal phantoms for evaluation of performance of OCT and OCTA also have been studied. In this presentation, we will show methods and results of a retinal phantom that can evaluate the optical performance of OCT and OCTA. The retinal phantom not only mimicked superficial vascular networks more realistically, but also implemented retinal layers with curvature. It consists of two microfluidic channels corresponding to superficial and deep retinal vessels, two multi-layered thin films, and base plate with retinal curvature. Each was attached with oxygen plasma for 1-min and fluorinated ethylene propylene (FEP) tubes was connected to the inlet and outlet holes. We could obtain cross-sectional OCT images and en-face OCTA images using lab-made OCT system.

The retinal imaging system, such as optical coherence tomography (OCT), OCT-angiography (OCTA) and fluorescein angiography (FA), is the important subject for ophthalmic. The use of such equipment continues to increase and retinal phantoms have also been developed to evaluate and modify its performance and image quality. In this presentation, we will show methods and results of a retinal phantom that can evaluate the optical performance of OCT, OCTA and FA. We implemented superficial vascular networks and full retinal layers which has curvature. We could obtain cross-sectional OCT images and en-face OCTA images using lab-made OCT system. In addition, FA image could also be obtained through sodium fluorescein dye injection.

This paper proposes a method that automatically measures non-invasive blood pressure (BP) based on an auscultatory approach using Korotkoff sounds (K-sounds). There have been methods utilizing K-sounds that were more accurate in general than those using cuff pressure signals only under well-controlled environments, but most were vulnerable to the measurement conditions and to external noise because blood pressure is simply determined based on threshold values in the sound signal. The proposed method enables robust and precise BP measurements by evaluating the probability that each sound pulse is an audible K-sound based on a deep learning using a convolutional neural network (CNN). Instead of classifying sound pulses into two categories, audible K-sounds and others, the proposed CNN model outputs probability values. These values in a Korotkoff cycle are arranged in time order, and the blood pressure is determined. The proposed method was tested with a dataset acquired in practice that occasionally contains considerable noise, which can degrade the performance of the threshold-based methods. The results demonstrate that the proposed method outperforms a previously reported CNN-based classification method using K-sounds. With larger amounts of various types of data, the proposed method can potentially achieve more precise and robust results.

Cell counting has become an essential method for monitoring the viability and proliferation of cells. A hemacytometer is the standard device used to measure cell numbers in most laboratories which are typically automated to increase throughput. The principle of both manual and automated hemacytometers is to calculate cell numbers with a fixed volume within a set measurement range (10 5 ~ 10 6 cells/ml). If the cell concentration of the unknown sample is outside the range of the hemacytometer, the sample must be prepared again by increasing or decreasing the cell concentration. We have developed a new hemacytometer that has a multi-volume chamber with 4 different depths containing different volumes (0.1, 0.2, 0.4, 0.8 µl respectively). A multi-volume hemacytometer can measure cell concentration with a maximum of 10 6 cells/ml to a minimum of 5 × 10 3 cells/ml. Compared to a typical hemacytometer with a fixed volume of 0.1 µl, the minimum measurable cell concentration of 5 × 10 3 cells/ml on the multi-volume hemacytometer is twenty times lower. Additionally, the Multi-Volume Cell Counting model (cell concentration calculation with the slope value of cell number in multi-chambers) showed a wide measurement range (5 × 10 3 ~ 1 × 10 6 cells/ml) while reducing total cell counting numbers by 62.5% compared to a large volume (0.8 µl-chamber) hemacytometer.

Optical coherence tomography (OCT) angiography (OCTA) has been actively studied as a noninvasive imaging technology to generate retinal blood vessel network maps for the diagnoses of retinal diseases.Given that the uses of OCT and OCTA have increased in the field of ophthalmology, it is necessary to develop retinal phantoms for clinical OCT for product development, performance evaluation, calibration, certification, medical device licensing, and production processes.We developed a retinal layer-mimicking phantom with microfluidic channels based on microfluidic fabrication technology using polydimethylsiloxane (PDMS) and titanium dioxide (TiO 2 ) powder.We implemented superficial and deep retinal vessels using microfluidic channels.In addition, multilayered thin films were synthesized with multiple spin-coating processes that comprised layers that corresponded to the retinal layers, including the ganglion cell layer (GCL), inner plexiform layer (IPL), and inner nuclear layer (INL).The phantom was formed by merging the multilayered thin film, and microfluidic channels were assembled with an optical lens, water chamber, and an aluminum tube case.Finally, we obtained cross-sectional OCT images and en-face OCTA images of the retinal phantom using lab-made ophthalmic OCT.From the cross-sectional OCT image, we could compare each of the layer thicknesses of the phantom with the corresponding layer thicknesses of the human retina.In addition, we obtained en-face OCTA images with injections of intralipid solutions.It is shown that this phantom will be able to be potentially used as a convenient tool to evaluate and standardize the quality and accuracy of OCT and OCTA images.

There are numerous biological processes which are related to heat production, and the heat information can be used in various applications, for example the diagnosis of disease or the investigation of antibiotics by measuring metabolism of biological samples. Therefore, it is very useful to develop a device which can measure small amounts of heating power corresponding to sub-microwatt level. In this study, a chip calorimeter is developed which can measure sub-microwatt power level. The size of the chip calorimeter is 8 mm × 10 mm and the chip is designed to have four identical measurement units. In each chip, there is a platinum (Pt) electrode to generate heat in the centre and two thermopiles on both sides of the heater. Thermopile consists of a serial connection of 73 bismuth (Bi) and aluminium (Al) thermopiles. The whole chip unit is inserted in the double thermostat which is maintained within 20 mK using film heater and natural convection with two temperature controllers. The generated heat from the heater was measured with the depicted thermopile and the resolution was found to be less than sub-microwatt. Various methods to improve the heat power resolution are discussed. The developed chip calorimeter can be used for biological research by measuring metabolic heat of cells in the future research.

Simultaneous measurement of skin physiological and physical properties are important for the diagnosis of skin diseases and monitoring of human performance, since it provides more comprehensive understanding on the skin conditions. Current skin analysis devices, however, require each of probes and unique protocols for the measurement of individual skin properties, resulting in inconvenience and increase of measurement uncertainty. This paper presents a pen-type skin analyzing device capable tomeasure three key skin properties at the same time: transepidermal water loss (TEWL), skin conductance, and skin hardness. It uses a single truncated hollow cone (THC) probe integrated with a humidity sensor, paired electrodes, and a load cell for the multimodal assessment of the skin properties. The present device measured TEWL with a sensitivity of 0.0068 (%/s)/(g/m2/h) and a linearity of 99.63%, conductance with a sensitivity of 1.02 µS/µS and a linearity of 99.36%, and hardness with a sensitivity of 0.98 Shore 00/Shore 00 and a linearity of 99.85%, within the appropriate ranges for the human skin. The present pen-type device has a high potential for the skin health diagnosis as well as the human performance monitoring applications.

Abstract A surface flow sensor is needed if turbulent drag force is to be measured over a vehicle, such as a car, a ship, and an airplane. In case of automobile industry, there are no automobile manufacturers which measure surface flow velocity over a car for wind tunnel testing. Instead, they rely on particle image velocimetry (PIV), pressure sensitive paint (PSP), laser Doppler anemometry (LDA), pitot tubes, and tufts to get information regarding the turbulent drag force. Surface flow sensors have not devised yet. This study aims at developing a surface flow sensor for measuring turbulent drag force over a rigid body in a wind tunnel. Two sensing schemes were designed for the fiber-optic distributed sensor and the thermal mass flow sensor. These concepts are introduced in this paper. As the first attempt, a thermal mass flow sensor has been fabricated. It was flush-mounted on the surface of a test section in the wind tunnel to measure the surface flow velocity. The thermal mass flow sensor was operated by either constant current or constant resistance modes. Resistance ratio was changed as the electric current was increased by the constant current mode, while power ratio was saturated as the resistance was increased by the constant resistance mode. Either the resistance ratio or the power ratio was changed with the flow velocity measured by a Pitot tube, located at the center of test section.

A high throughput apoptosis assay using 3D cultured cells was developed with a micropillar/microwell chip platform. Live cell apoptosis assays based on fluorescence detection have been useful in high content screening. To check the autofluorescence of drugs, controls (no caspase-3/7 reagent in the assay) for the drugs are necessary which require twice the test space. Thus, a high throughput capability and highly miniaturized format for reducing reagent usage are necessary in live cell apoptosis assays. Especially, the expensive caspase-3/7 reagent should be reduced in a high throughput screening system. To solve this issue, we developed a miniaturized apoptosis assay using micropillar/microwell chips for which we tested seventy drugs (six replicates) per chip and reduced the assay volume to 1 µL. This reduced assay volume can decrease the assay costs compared to the 10–40 µL assay volumes used in 384 well plates. In our experiments, among the seventy drugs, four drugs (Cediranib, Cabozatinib, Panobinostat, and Carfilzomib) induced cell death by apoptosis. Those results were confirmed with western blot assays and proved that the chip platform could be used to identify high potency apoptosis-inducing drugs in 3D cultured cells with alginate.