End-to-End Automatic Classification of Retinal Vessel Based on Generative Adversarial Networks with Improved U-Net.

The retinal vessels in the human body are the only ones that can be observed directly by non-invasive imaging techniques. Retinal vessel morphology and structure are the important objects of concern for physicians in the early diagnosis and treatment of related diseases. The classification of retinal vessels has important guiding significance in the basic stage of diagnostic treatment. This paper proposes a novel method based on generative adversarial networks with improved U-Net, which can achieve synchronous automatic segmentation and classification of blood vessels by an end-to-end network. The proposed method avoids the dependency of the segmentation results in the multiple classification tasks. Moreover, the proposed method builds on an accurate classification of arteries and veins while also classifying arteriovenous crossings. The validity of the proposed method is evaluated on the RITE dataset: the accuracy of image comprehensive classification reaches 96.87%. The sensitivity and specificity of arteriovenous classification reach 91.78% and 97.25%. The results verify the effectiveness of the proposed method and show the competitive classification performance.

A cost-effective smartphone-based device for rapid C-reaction protein (CRP) detection using magnetoelastic immunosensor.

C-Reaction protein (CRP) is a marker of nonspecific immunity for vital signs and wound assessment, and it can be used to diagnose infections in clinical medicine. However, measuring CRP level currently requires hospital-based instruments, high-cost reagents, and a complex process, all of which have limited its full capabilities for self-detection, a growing trend in modern medicine. In this study, we developed a novel smartphone-based device using advanced methods of magnetoelastic immunosensing to mitigate these limitations. We combined a system-on-chip (SoC) hardware architecture with smartphone apps to realize the sampling of resonance frequency shift on magnetoelastic chips, which can determine the ultra-sensitivity to mass change caused by the binding of anti-CRP antibody and CRP. Through detecting a multi-group of samples, we found that the resonance frequency shift was linearly proportional to the CRP concentration in the range from 0.1 to 100 µg mL-1, with a sensitivity of 12.90 Hz µg-1 mL-1 and a detection limit of 2.349 × 10-4 µg mL-1. Meanwhile, compared with the large-scale instrument used in clinical settings, the performance of our device was stable and significantly more portable, rapid and cost-effective, offering excellent potential for modern home-based diagnosis.

Self-Powered Respiratory Monitoring Strategy Based on Adaptive Dual-Network Thermogalvanic Hydrogels.

As a low-grade sustainable heat source, the breath waste heat exhaled by human bodies is always ignored, although producing a greater temperature than ambient. Converting this heat into electric energy for use as power sources or detecting signals is extremely important in cutting-edge wearable medicine. This heat-to-electricity conversion is possible with thermogalvanic hydrogels. However, challenges remain in their antifreezing and antidrying properties, significantly restricting the durability of thermogalvanic gels in practical applications. Herein, a dual-network poly(vinyl alcohol)/gelatin (PVA/GEL) gel thermogalvanic device with Fe(CN)63-/4- as a redox pair is developed, with an outstanding low-temperature durability and antidrying capacity. These features result from the use of a binary H2O/GL (glycerin) solvent to limit hydrogen bonding between water molecules. The prepared thermogalvanic gel patch is capable of easily converting physiological data into understandable electrical impulses using the temperature difference between the ambient environment and the heat produced by human breathing, realizing a simple self-powered respiratory monitoring strategy for the first time. Even below zero temperature, the gel patch-based mask can operate normally, implying it fits into low-temperature environments. This study sheds fresh light on the development of active wearable medical electronics that are powered by demic low-level heat.

Synthesis of MoS2 Nanochains by Electrospinning for Ammonia Detection at Room Temperature.

MoS2 nanochains were successfully prepared via facile electrospinning and a hydrothermal process. The morphology of MoS2 nanochains was evaluated by field emission scanning electron microscopy and high-resolution transmission electron microscopy. A slurry composed of the MoS2 nanochains was coated on a silver electrode to detect ammonia. The detection range of ammonia was between 25 and 500 ppm. MoS2 nanochains offered outstanding sensing response, repeatable reproducibility, and excellent selectivity with a detection limit of 720 ppb. The responsiveness of MoS2 nanochains to ammonia remained unchanged for 1 week.

Magnetoelastic Immunosensor via Antibody Immobilization for the Specific Detection of Lysozymes.

Lysozymes in human urine have crucial clinical significance as an indicator of renal tubular and glomerular diseases. Most lysozyme detection methods rely on the enzyme-linked immunosorbent assay (ELISA), which is usually a tedious procedure. Meanwhile, aptamer sensors and fluorescence-based techniques for lysozyme detection have emerged in recent studies. However, these methods are time-consuming and highly complex in operation, and some even require exorbitant reagents and instruments, which restricts real-time clinical monitoring as diagnostic approaches. Therefore, a rapid and low-cost lysozyme detection method with facile preparation is still in demand for modern precision medicine. Herein, we propose a magnetoelastic (ME) immunosensor for lysozyme detection by detecting changes in resonance frequency under a magnetostrictive effect. The detection system is composed of a magnetoelastic chip with an immobilized lysozyme antibody, a solenoid coil, and a vector network analyzer. Since the ME sensor is ultrasensitive to mass change, the frequency offset caused by mass change can be utilized to detect the content of lysozyme. The immunosensor is evaluated to possess superior sensitivity of 138 Hz/µg mL-1 in terms of the resonance frequency shift (RFS). In addition, our sensor displays an outstanding performance in specificity experiments and shows a relatively lower detection limit (1.26 ng/mL) than other conventional lysozyme detection methods (such as ELISA, chemiluminescence assay, fluorescence, and aptamer biosensors).

A novel paper biosensor based on Fe3O4@SiO2-NH2and MWCNTs for rapid detection of pseudorabies virus.

In this study, a novel paper biosensor based on Fe3O4@SiO2-NH2magnetic polymer microspheres and multi walled carbon nanotubes (MWCNTs) for rapid detection of pseudorabies virus (PRV) was first developed. Fe3O4@SiO2-NH2were functionalized with PRV antibody and doped in cellulose nitrate paper to fabricate the magnetic paper biosensor with good magnetic response and biocompatibility. Using MWCNTs to build conductive network of sensors, PRV antigen binds specifically to the immunomagnetic microspheres on the sensor, and the resulting immune complex changes the magnetic domain structure of the sensor and the structural gap of MWCNTs, causing the magnetic property and impedance change. TEM and EDS characterization proved that the biosensor was successfully doped with Fe3O4@SiO2-NH2and effectively recognized PRV. Under optimized conditions, the impedance variation was found to be linearly related to the logarithm value of PRV concentrations in the range of 10-1 mg ml-1, with the detection limit of 10 ng ml-1. This paper biosensor demonstrated advantages of portability, high sensitivity and specificity, providing a valuable method for early control of PRV.

A cost-effective smartphone-based device for ankle-brachial index (ABI) detection.

BACKGROUND AND OBJECTIVE: Detectors of ankle-brachial index (ABI) are commonly used in cardiovascular patients who have high-risk levels of arteriosclerosis. Increased evidences suggest that patients with arteriosclerosis possess many risks of geriatric and chronic diseases. Meanwhile, new chronic treatments trend from the hospitals toward family and community health centers, but for arteriosclerosis cases have delivered benefits far below instrument costs. Compared to traditional devices based on cuff pressure, cuffless and non-invasive measures have wider application potential in home health care, especially in the case of physically-restricted or severely symptomatic patients. METHODS: In this study, we developed a simple smartphone-based device for non-invasive ABI monitoring, which consists of four wireless cuffless limbs blood sensors. By identifying and tracking blood flow waveform, a multiparameter fusion (MPF) algorithm is used to estimate blood pressure and generate ABI value. An ARM-based chip STM32 has been adopted as the microcontroller. The ABI calculating program is embedded in C++ and executed by the processor. After generating data, ABI information can be delivered to the smartphone by using Bluetooth. Relying on mobile apps to visualize the data and display on the screen, doctors can monitor cardiovascular patients in real time and analyze the risk levels of arteriosclerosis online. RESULTS: In this paper, the detection conducted by the classical Doppler equipment and prototype were recorded respectively. A statistical evaluation of the verification results obtained from 29 patients and 7 sub-health volunteers is given, which shows that our device can achieve 91.80% and 93.84% accuracy for patients and sub-health volunteers, respectively. In addition, the prototype can be performed stably for a continuous long time monitoring. CONCLUSIONS: According to our studies, the accuracy of our device is sufficient for home medical and chronic disease monitoring within a certain time interval. The smartphone-based ABI device has several apparent advantages over traditional devices, such as portability, cost-effectiveness and energy-efficiency.

A Flexible, Acoustic Localized Sensor with Mass Block-Beam Structure Based on Polydimethylsiloxane-Silver Nanowires.

The flexible strain sensor is a fast-moving technology and has been used in many fields. The array design and application based on flexible strain sensors have been the current research hotspots. However, there are few reports on research of acoustic positioning using the flexible sensor array. Herein, we designed and realized the consistent fabrication of a thin-film, acoustic sensor array. The acoustic sensing research of the sensor was demonstrated as well. We used a convenient fabrication method to design a flexible acoustic sensor using silver nanowires coated on a thin polydimethylsiloxane (PDMS) film with mass block-beam structure. The acoustic sensor can record sound within a frequency domain of 20-2000 Hz and volume detection range of 83-108 dB. The sensor's resonance frequency is 380 Hz, horizontal distance sound detection limit is 5 cm, and vertical detection limit is 3.5 cm. We also achieved 360° azimuth detection in two-dimensional space with a detection accuracy of 15°. In three-dimensional space, the flexible acoustic sensor array was designed with two flexible acoustic sensors to detect the position of the sound source. This research first proposes the use of flexible acoustic sensors to test the sound source orientation.

A Novel NiFe2O4/Paper-Based Magnetoelastic Biosensor to Detect Human Serum Albumin.

For the first time, a novel NiFe2O4/paper-based magnetoelastic (ME) biosensor was developed for rapid, sensitive, and portable detection of human serum albumin (HSA). Due to the uniquely magnetoelastic effect of NiFe2O4 nanoparticles and the excellent mechanical properties of the paper, the paper-based ME biosensor transforms the surface stress signal induced by the specific binding of HSA and antibody modified on the paper into the electromagnetic signal. The accumulated binding complex generates a compressive stress on the biosensor surface, resulting in a decrease in the biosensor's static magnetic permeability, which correlates to the HSA concentrations. To improve the sensitivity of the biosensor, the concentration of NiFe2O4 nanofluid and the impregnated numbers of the NiFe2O4 nanofluid-impregnated papers were optimized. The experimental results demonstrated that the biosensor exhibited a linear response to HSA concentrations ranging from 10 µg∙mL-1 to 200 µg∙mL-1, with a detection limit of 0.43 µg∙mL-1, which is significantly lower than the minimal diagnosis limit of microalbuminuria. The NiFe2O4/paper-based ME biosensor is easy to fabricate, and allows the rapid, highly-sensitive, and selective detection of HSA, providing a valuable analytical device for early monitoring and clinical diagnosis of microalbuminuria and nephropathy. This study shows the successful integration of the paper-based biosensor and the ME sensing analytical method will be a highly-sensitive, easy-to-use, disposable, and portable alternative for point-of-care monitoring.

Performance of CNTs/GQD-Based Flexible Strain Sensors.

Nanomaterial-based flexible strain sensors have developed rapidly in recent years. Here, we propose a flexible strain sensor based on polydimethylsiloxane with carbon nanotubes (CNTs) and graphene quantum dots (GQDs). Different weight ratios of CNTs and GQDs were used as the sensitive units of the strain sensors. After analyzing the results of current-voltage curves and the strain effects of the sensors, we concluded that the introduction of GQDs played an important role in improving the sensitivity of the sensors. The gauge factor of the as-prepared strain sensors ranges from 0 to 841.42.

Wrinkle Structured Network of Silver-Coated Carbon Nanotubes for Wearable Sensors.

Soft-strain-based sensors are being increasingly used across various fields, including wearable sensing, behavior monitoring, and electrophysiological diagnostics. However, throughout all applications, the function of these sensors is limited because of high sensitivity, high-dynamic range, and low-power consumption. In this paper, we focus on improving the sensitivity and strain range of the soft-strain-based sensor through structure, surface, and sensitive unit treatment. Nanosilver (Ag)-coated hydroxyl-functionalized multi-walled carbon nanotubes (OH-f MWCNTs) were explored for highly acute sensing. With stretching and depositing methods, Ag@OH-f MWCNTs and polydimethylsiloxane (PDMS) are fabricated into a wrinkled and sandwich structure for a soft-strain-based sensor. The electronic properties were characterized in that the gauge factor (GF) = ΔR/R0 was 412.32, and the strain range was 42.2%. Moreover, our soft-strain-based sensor exhibits features including flexibility, ultra-lightweight and a highly comfortable experience in terms of wearability. Finally, some physiological and behavioral features can be sampled by testing the exceptional resistance change, including the detection of breath, as well as facial and hand movement recognition. The experiment exhibits its superiority in terms of being highly sensitive and having an extensive range of sensing.

Flexible and Wearable PDMS-Based Triboelectric Nanogenerator for Self-Powered Tactile Sensing.

Flexible electronics devices with tactile perception can sense the mechanical property data of the environment and the human body, and they present a huge potential in the human health system. In particular, the introduction of ultra-flexible and self-powered characteristics to tactile sensors can effectively reduce the problems caused by rigid batteries. Herein, we report a triboelectric nanogenerator (TENG), mainly consisting of an ultra-flexible polydimethylsiloxane (PDMS) film with micro-pyramid-structure and sputtered aluminum electrodes, which achieves highly conformal contact with skin and the self-powered detection of human body motions. The flexible polyethylene terephthalate (PET) film was selected as spacer layer, which made the sensor work in the contact-separation mode and endowed the perfect coupling of triboelectrification and electrostatic induction. Moreover, the controllable and uniform micro-structure PDMS film was fabricated by using the micro-electro-mechanical system (MEMS) manufacturing process, bringing a good sensitivity and high output performance to the device. The developed TENG can directly convert mechanical energy into electric energy and light up 110 green Light-Emitting Diodes (LEDs). Furthermore, the TENG-based sensor displays good sensitivity (2.54 V/kPa), excellent linearity (R2 = 0.99522) and good stability (over 30,000 cycles). By virtue of the compact size, great electrical properties, and great mechanical properties, the developed sensor can be conformally attached to human skin to monitor joint movements, presenting a promising application in wearable tactile devices. We believe that the ultra-flexible and self-powered tactile TENG-based sensor could have tremendous application in wearable electrons.

A Portable Device for Rapid Detection of Human Serum Albumin using an immunoglobulin-coating-based Magnetoelastic Biosensor.

Abnormal protein concentration levels in human body fluids, such as urine, serum etc., are considered to associate with disease states, providing essential information for the pre-clinical diagnosis. This paper presents a wireless immunoglobulin-coated magnetoelastic (ME) biosensor for fast, cost-effective detections of human serum albumin (HSA) with small sample volumes at a microliter scale. This is the first portable resonant sensor based on magnetostrictive effect that can monitor different molecular states of HSA. Anti-HSA Immunoglobulin G (IgG) was immobilized on the surface of the ME sensor to selectively capture HSA. The rapid conjugation between the antibody and antigen changed the sensor surface states and thus induced resonance frequency shifts (RFS), which were monitored in real time for the qualitative and quantitative analysis of HSA. This paper brings forward a System on Chip (SoC)-based system architecture to realize the function of RFS sampling. The performance of the portable device was validated to be comparable to that of the Vector Network Analyzer (VNA) AV3620 using different concentrations of HSA solution. The RFS were linearly proportional to the HSA concentrations in the range from 0.1 to 100 µg/mL with a linearity up to 0.998, a sensitivity of 8.70 Hz/µg.mL-1 and a detection limit of 0.039 µg/mL, indicating good feasibility of this method. Meanwhile, the response of this portable ME biosensor was quick and specific to HSA targets. This ME biosensor shows high potential to be used in diagnosing abnormal HSA.

A Flexible Magnetic Field Sensor Based on AgNWs & MNs-PDMS.

This paper presents a new flexible magnetic field sensor based on Ag nanowires and magnetic nanoparticles doped in polydimethylsiloxane (AgNWs & MNs-PDMS) with sandwich structure. The MNs act as the sensitive unit for magnetic field sensing in this work. Besides, the conductive networks are made by AgNWs during deformation. Magnetostriction leads to the resistance change of the AgNWs & MNs-PDMS sensors. Furthermore, the MNs increase the conductive paths for electrons, leading to lower initial resistance and higher sensitivity of the resulting sensor during deformation. A point worth emphasizing is that the interaction of the AgNWs and MNs plays irreplaceable role in magnetic field sensing, so the resistance change during stretching and shrinking was investigated. The flexible magnetic field sensor based on the mass ratio of MNs and AgNWs is 1:5 showed the highest sensitivity of 24.14 Ω/T in magnetic field sensing experiment. Finally, the magnetostrictive and piezoresistive sensing model were established to explore the mechanism of the sensor.

Probabilistic assessment of visual fatigue caused by stereoscopy using dynamic Bayesian networks.

PURPOSE: In this article, we develop a dynamic Bayesian network (DBN) model to measure 3D visual fatigue. As far as our information goes, this is the first adaptation of a DBN structure-based probabilistic framework for inferring the 3D viewer's state of visual fatigue. METHODS: Our measurement focuses on the interdependencies between each factor and the phenomena of visual fatigue in stereoscopy. Specifically, the implementation of DBN with using multiple features (e.g. contextual, contactless and contact physiological features) and dynamic factor provides a systematic scheme to evaluate 3D visual fatigue. RESULTS: In contrast to measurement results between the mean opinion score (MOS) and Bayesian network model (with static Bayesian network and DBN), the visual fatigue in stereoscopy at time slice t is influenced by a dynamic factor (time slice t-1). In the presence of dynamic factors (time slice t-1), our proposed measuring scheme based on DBN is more comprehensive. CONCLUSION: (i) We cover more features for inferring the visual fatigue, more reliably and accurately; (ii) at different time slices, the dynamic factor features are significant for inferring the visual fatigue state of stereoscopy.

Sandwich-type Surface Stress Biosensor Based on Self-Assembled Gold Nanoparticles in PDMS Film for BSA Detection.

Poly(dimethylsiloxane) (PDMS) films composed of gold nanomaterials have drawn increasing interest for their application in biosensors. However, gold and PDMS exhibit poor compatibility, limiting their sensitivity in biosensing. Herein, we reported a surface stress biosensor based on a gold nanoparticle-PDMS (AuNP-PDMS) composite film to detect bovine serum albumin (BSA). The AuNP-PDMS film was fabricated by in situ reduction of PDMS and further reduction of glucose. The compatibility between gold and PDMS was improved via a two-step reduction of AuNPs. The surface stress biosensor can specifically detect BSA molecules within the 0-50 µg/mL concentration range using the direct assay and the sandwich assay. The sandwich assay amplified the surface stress and reduced the limit of detection to 0.035 µg/mL, which is lower than that achieved by the direct assay. The sandwich-type biosensor also exhibits stability, repeatability, and specificity. This study is expected to drive the development of new methods for biomolecule detection.

Zero-energy-state-oriented tunability of spin polarization in zigzag-edged bowtie-shaped graphene nanoflakes under an electric field.

A comprehensive first-principles study of the correlation between zero-energy states and the tunability of the spin-selective semiconducting properties of zigzag-edged bowtie-shaped graphene nanoflakes under an electric field is presented for the first time. We demonstrate that the spin degenerate semiconducting ground state can be lifted by the electric field. In particular, we find that the number of zero-energy states ('the nullity') defined by the structural configuration determines the complexity and efficiency of the tunability of spin polarization. The fine-tuning of spin-dependent properties by the electric field originates from the manipulation of spin-polarized molecular orbital energies. We expect this study to aid the design of more effective and controllable low-dimensional molecular spintronics.

A Novel Magnetoelastic Nanobiosensor for Highly Sensitive Detection of Atrazine.

Here, we firstly report a wireless magnetoelastic (ME) nanobiosensor, based on ME materials and gold nanoparticles (AuNPs), for highly sensitive detection of atrazine employing the competitive immunoassay. In response to a time-varying magnetic field, the ME material longitudinally vibrates at its resonance frequency which can be affected by its mass loading. The layer of AuNPs coating on the ME material contributes to its biocompatibility, stability, and sensitivity. The atrazine antibody was oriented immobilized on the AuNPs-coated ME material surface through protein A, improving the nanobiosensor's performance. Atomic force microscope (AFM) analysis proved that the immobilization of atrazine antibody was successful. Furthermore, to enhance the sensitivity, atrazine-albumin conjugate (Atr-BSA) was induced to compete with atrazine for binding with atrazine antibody, amplifying the signal response. The resonance frequency shift is inversely and linearly proportional to the logarithm of atrazine concentrations ranging from 1 ng/mL to 100 µg/mL, with the sensitivity of 3.43 Hz/µg mL-1 and the detection limit of 1 ng/mL, which is significantly lower than the standard established by US Environmental Protection Agency (EPA). The experimental results indicated that the ME nanobiosensor displayed strong specificity and stability toward atrazine. This study provides a new convenient method for rapid, selective, and highly sensitive detection of atrazine, which has implications for its applications in water quality monitoring and other environmental detection fields.