Healthcare Monitoring Devices Research Articles

Biomechanical Energy‐Driven Hybridized Generator as a Universal Portable Power Source for Smart/Wearable Electronics

AbstractThe fast growth of smart electronics requires novel solutions to power them sustainably. Portable power sources capable of harvesting biomechanical energy are a promising modern approach to reduce battery dependency. Herein, a novel elastic impact‐based nonresonant hybridized generator (EINR‐HG) is reported to effectively harvest biomechanical energy from diverse human activities outdoors. Through the rational integration of a nonlinear electromagnetic generator with two contact‐mode triboelectric nanogenerators, the proposed EINR‐HG generates hybrid electrical output simultaneously under the same mechanical excitations. By introducing a flux‐concentrator with a nanowire‐nanofiber surface modification, significant improvement in the energy harvesting efficiency of the EINR‐HG is achieved. After optimizing using simulations and vibration tests, the as‐fabricated EINR‐HG delivers an outstanding normalized power density of 3.13 mW cm−3 g−2 across a matching resistance of 1.5 kΩ at 6 Hz under 1 g acceleration. Under human motion testing, the EINR‐HG generates an optimal output power of 131.4 mW with horizontal handshaking. With a customized power management circuit, the EINR‐HG serves as a universal power source that successfully drives commercial smart electronics, including smart bands and smartphones. This work shows the massive potential of biomechanical energy‐driven hybridized generators for powering personal electronics and portable healthcare monitoring devices.

A flexible pressure sensor based on melamine foam capped by copper nanowires and reduced graphene oxide

High-performance flexible pressure sensors with high sensitivity and large sensing range are vital components of the system for physiological signals collection, human-machine interaction and artificial intelligence. Herein, a flexible pressure sensor of copper nanowires/reduced graphene oxide/melamine foam (CuRGOMF) was fabricated by coating reduced graphene oxide (RGO) and in-situ growing of copper nanowires (Cu NWs) on the skeleton of melamine foam (MF). The as-prepared sensor features high sensitivity at wide working range (0.011 kPa−1, 0–1.5 kPa; 0.088 kPa−1, 1.5–10 kPa and 0.024kPa−1, 10–18 kPa) and cyclic stability (5000 cycles). The human motions of finger bending, grasping, clicking the mouse and picking up/dropping objects can be successfully detected in real-time based on the CuRGOMF sensor. The CuRGOMF sensor illustrates a promising candidate for healthcare monitoring and wearable device in artificial intelligence.

Emerging intraoral biosensors.

Biomedical devices that involved continuous and real-time health-care monitoring have drawn much attention in modern medicine, of which skin electronics and implantable devices are widely investigated. Skin electronics are characterized for their non-invasive access to the physiological signals, and implantable devices are superior at the diagnosis and therapy integration. Despite the significant progress achieved, many gaps remain to be explored to provide a more comprehensive overview of human health. As the connecting point of the outer environment and human systems, the oral cavity contains many unique biomarkers that are absent in skin or inner organs, and hence, this could become a promising alternative locus for designing health-care monitoring devices. In this review, we outline the status of the oral cavity during the communication of the environment and human systems and compare the intraoral devices with skin electronics and implantable devices from the biophysical and biochemical aspects. We further summarize the established diagnosis database and technologies that could be adopted to design intraoral biosensors. Finally, the challenges and potential opportunities for intraoral biosensors are discussed. Intraoral biosensors could become an important complement for existing biomedical devices to constitute a more reliable health-care monitoring system.

IoT-Enabled Healthcare Monitoring: A Systematic Review of Wearable Devices

The Internet of Things (IoT) has revolutionized various aspects of our daily lives, particularly in the healthcare sector. The integration of IoT with wearable devices has opened up new possibilities for healthcare monitoring, enabling the continuous tracking of patients' physiological parameters and promoting personalized medical care. This systematic review examines the current landscape of IoT-enabled wearable devices for healthcare monitoring, their potential applications, and the associated challenges. We conducted a thorough literature search to identify the most relevant and recent studies on IoT-enabled wearable devices for healthcare monitoring. Several devices were discussed, including smartwatches, fitness trackers, wearable electrocardiogram (ECG) monitors, continuous glucose monitoring systems, and smart patches for vital sign monitoring. These wearables offer numerous advantages, such as real-time monitoring, improved patient adherence, early detection of potential health issues, and enhanced patient-physician communication. The review also explores the potential drawbacks and challenges of implementing IoT-enabled wearable devices in healthcare, such as data privacy concerns, device interoperability, and the need for standardized data collection and analysis methods. Moreover, we discuss potential solutions and future research directions to overcome these challenges and promote the widespread adoption of IoT-enabled wearables for healthcare monitoring. In conclusion, IoT-enabled wearable devices have the potential to transform the healthcare sector by facilitating remote patient monitoring, improving treatment outcomes, and reducing healthcare costs. However, addressing the existing challenges and incorporating user feedback in the design and development process is essential for the successful integration of IoT-enabled wearables into the healthcare ecosystem.

Flexible Integrated Sensors: Transverse Piezoresistance and Longitudinal Thermal Resistance of One Single Carbon Fiber Beam

AbstractElectronic skins require to integrate multiple‐sensing functions to sense stimuli from the outside environment (such as pressure, temperature, and humidity), and to distinguish the signals from the different stimuli. Here, reported is the feasibility to use only one single carbon fiber beam (CFB) to simultaneously detect pressure and temperature changes from the outside environment, and the signals from pressure and temperature stimuli can be effectively distinguished through its transverse piezoresistance and longitudinal thermal resistance. This work also reveals that the transverse piezoresistance follows the electron quantum tunneling between the carbon fibers, while the longitudinal thermal resistance follows the impurity scattering mechanism. The flexible pressure sensors, temperature sensors, and their integrated sensors can be easily constructed like blocks to use the same material CFBs, and these sensors have demonstrated unique advantages in wearable healthcare monitoring devices and electronic skin products.

Application of Microfluidics in Wearable Devices

AbstractWearable devices integrated with various electronic modules, biological sensors, and chemical sensors have drawn large public attention. Due to their inherent advantages of superior stretchability, elaborate microstructure, high integration of multiple functions, and low cost, microfluidics are an excellent candidate and have already been widely used in wearable devices. Well‐designed microfluidic devices can realize excellent multiple functions in wearable devices, including sample collecting, handling and storage, sample analysis, signal converting and amplification, mechanic sensing, and power supplying. Moreover, the microfluidic wearable devices with further integration of wireless modules have exhibited potential applications in healthcare monitoring, clinical assessment, and human and intelligent device interaction. This review focuses on the latest advances on multifunctional wearable devices based on microfluidics, primarily including general functions and designs of microfluidic wearable devices, and their specific applications in physiological signal monitoring, clinical diagnosis and therapeutics, and healthcare.

Flexible and Waterproof Resistive Random‐Access Memory Based on Nitrocellulose for Skin‐Attachable Wearable Devices

AbstractMemory for skin‐attachable wearable devices for healthcare monitoring must meet a number of requirements, including flexibility and stability in external environments. Among various memory technologies, organic‐based resistive random‐access memory (RRAM) devices are an attractive candidate for skin‐attachable wearable devices due to the high flexibility of organic materials. However, organic‐based RRAMs are particularly vulnerable to external moisture, making them difficult to apply as skin‐attachable wearable devices. In this research, RRAMs are fabricated that meet the requirements for skin‐attachable wearable devices using a novel organic material, nitrocellulose (NC), which is biocompatible with high water‐resistance and high flexibility. The fabricated NC‐based RRAMs show a stable bipolar resistive switching characteristic. In addition, the formation of a native Al oxide between Al and NC is verified, which is the source of the bipolar switching characteristic of NC‐based RRAMs. Furthermore, electrical and chemical analysis is conducted after dipping and submersion into various solutions as well as deionized water to confirm the water‐resistance of the NC‐based RRAMs. Finally, it is also confirmed that NC‐based RRAMs are suitable for use in skin‐attachable wearable devices through a flexibility test. In conclusion, this study suggests that NC‐based RRAMs can be applied in skin‐attachable wearable devices, simplifying healthcare in the future.

Effect of glycerol on the mechanical and temperature-sensing properties of pectin films

Temperature-sensitive films embedded in electronic skins (e-skins) can provide temperature feedback to robots, high-tech prostheses, and wearable devices for health care monitoring. Pectin-based films have shown a temperature response at least two orders of magnitude higher than previously reported temperature-sensing materials. However, they are not easily stretchable and tearable, which limit their applications as e-skins that require repetitive bending and mechanical stresses. Here, we show how the addition of glycerol as a plasticizer in the fabrication of pectin-based films improves their mechanical properties. We report how the enhancement of the mechanical performance is accompanied by a decrease in the temperature responsivity. Through thermogravimetric analysis, we show that this reduction in responsivity can be associated with water retention due to the addition of the plasticizer. The link between the water content and the temperature response demonstrates that a dehydrated status of pectin is crucial to record its high temperature responsivity. Combining electrical and thermal characterization with the tensile strength test, we estimate the optimal concentration of glycerol for improving the mechanical properties without compromising the temperature response of the pectin films.

Frequency response masking based FIR filter using approximate multiplier for bio-medical applications

The advancements in medical healthcare networks and bio-medical sensor technologies enabled the use of wearable and body implantable intelligent devices for healthcare monitoring. These battery-operated devices must be capable of very low power operation for ensuring long battery life and also to prevent intense radiations. The major power consuming part of these devices are the multipliers built into the digital filters for performing signal processing operations. This paper proposes a low power signed approximate multiplier architecture for bio-medical signal processing applications. The circuit characteristics and error metrics of the proposed multiplier are estimated to verify its performance advantage over other approximate multipliers. In order to validate the efficacy of the approximate multiplier in real time signal processing applications, a band pass finite impulse response filter (FIR) filter is designed using frequency response masking technique and used in the Pan Tompkins method for the extraction of QRS complex from raw ECG data. The sensitivity, positive predictivity, and detection error rate of the QRS detection method are estimated and the results show that the approximate filtering method implemented gives a comparable performance as that of exact methods.

Rapid-Response, Low Detection Limit, and High-Sensitivity Capacitive Flexible Tactile Sensor Based on Three-Dimensional Porous Dielectric Layer for Wearable Electronic Skin.

Three-dimensional (3D) porous conductive composites explored in highly sensitive tactile sensors have attracted extensive close attention in recent years owing to their peculiar porous structure and unique physical properties in terms of excellent mechanical flexibility, high relative dielectric permittivity, and good elastic property. Herein, we report an practical, efficient, and macroscopic dip-coating process to manufacture rapid-response, low detection limit, high-sensitivity, and highly sensitive capacitive flexible tactile sensors. The fabrication process, tactile perception mechanism, and sensing performance of the developed devices are comparatively investigated. The homogeneous 3D hybrid network constructed by graphene nanoplatelets/carboxyl-functionalized multiwalled carbon nanotubes/silicone rubber composites anchored on polyurethane sponge skeletons exhibits a significantly improved dielectric property, resulting in a high-performance capacitive flexible tactile sensor with a fast response time (∼45 ms), an extremely low-pressure detection limit of ∼3 Pa, excellent sensitivity (∼0.062 kPa-1), and excellent durability and stability over 2000 cycles. Importantly, the flexible devices can be used as the wearable electronic skin and successfully mounted on human skin or a soft-bodied robot to achieve the capability of physiological stimuli monitoring, micropressure monitoring, soft grabbing, etc. Our rapid-response, low detection limit, and high-sensitivity capacitive flexible tactile sensor with a novel 3D porous dielectric layer could be a prospective candidate for the wearable applications in real-time and high-accuracy portable healthcare monitoring devices, advanced human-machine interfaces, and intelligent robot perception systems.

Fully Integrated and Foldable Microdevice Encapsulated with Agarose for Long-Term Storage Potential for Point-of-Care Testing of Multiplex Foodborne Pathogens.

In this study, we fabricated a fully integrated and foldable microdevice encapsulated with 2-hydroxyethyl agarose for long-term storage of reagents for the integration of isothermal amplification and subsequent colorimetric detection for the monitoring of multiplex foodborne pathogens. The microdevice comprises a reaction zone and a detection zone. Both zones were made of a thin polycarbonate film and sealed by an adhesive film to make the microdevice foldable. The 2-hydroxyethyl agarose with loop-mediated isothermal amplification (LAMP) reagents and silver nitrate were deposited in the reaction and detection chambers, respectively, for long-term maintenance of reagent activity. A thin graphene-based heater associated with a handheld battery was employed to supply a constant temperature for on-chip amplification for 30 min. To simplify the sample manipulation process, a folding motion was adopted to allow the loading of LAMP amplicons from the reaction to the detection chambers and a colorimetric strategy was used for simple visual read-out of the results on-site. Using the agarose, the reagents were successfully stored and the reagent activity was maintained for at least 45 days. Prior to performing multiplex detections, the spiked juice was thermally lysed and purified with polydopamine-coated paper. The amplifications of Salmonella spp. and Escherichia coli O157:H7 (E. coli O157:H7) were successfully demonstrated based on the stable isothermal condition attained by the heater. The microdevice can detect the low concentration of E. coli O157:H7 at 2.5 × 102 copies per mL. The introduced microdevice acts as a simple and user-friendly platform for the identification of foodborne pathogens, paving the way for the construction of a truly portable, read-out microdevice for use as a public healthcare monitoring device.

A Highly Sensitive and Cost‐Effective Flexible Pressure Sensor with Micropillar Arrays Fabricated by Novel Metal‐Assisted Chemical Etching for Wearable Electronics

AbstractAs one of the most significant constituent parts of wearable electronic systems, flexible pressure sensors can accommodate irregular surfaces and perform spatial mapping when subjected to external pressure or strain stimuli. Herein, a wearable flexible pressure sensor integrated with two interlocked micropillar arrays is demonstrated by a facile and cost‐effective metal‐assisted chemical etching (MaCE) method with the assistance of polymer microspheres lithography technique. The flexible sensor, with micropillars of 2.6 µm in diameter, 6.6 µm in height, and 3 µm in pitch, exhibits superior sensitivity of −4.48 kPa−1 (0–100 Pa), rapid response and relaxation time of 52 and 40 ms, respectively, low detection limit of <1 Pa, and outstanding working stability over 5000 cycles of pressure loading/unloading. The prepared sensors are successfully demonstrated in detecting finger motions and monitoring human pulse signals, paving the promising route for its function in wearable electronic skins, soft robotics, and healthcare monitoring devices, etc.

Wearable, Ultrawide-Range, and Bending-Insensitive Pressure Sensor Based on Carbon Nanotube Network-Coated Porous Elastomer Sponges for Human Interface and Healthcare Devices.

Flexible and wearable pressure sensors have attracted a tremendous amount of attention due to their wider applications in human interfaces and healthcare monitoring. However, achieving accurate pressure detection and stability against external stimuli (in particular, bending deformation) over a wide range of pressures from tactile to body weight levels is a great challenge. Here, we introduce an ultrawide-range, bending-insensitive, and flexible pressure sensor based on a carbon nanotube (CNT) network-coated thin porous elastomer sponge for use in human interface devices. The integration of the CNT networks into three-dimensional microporous elastomers provides high deformability and a large change in contact between the conductive CNT networks due to the presence of micropores, thereby improving the sensitivity compared with that obtained using CNT-embedded solid elastomers. As electrical pathways are continuously generated up to high compressive strain (∼80%), the pressure sensor shows an ultrawide pressure sensing range (10 Pa to 1.2 MPa) while maintaining favorable sensitivity (0.01-0.02 kPa-1) and linearity ( R2 ∼ 0.98). Also, the pressure sensor exhibits excellent electromechanical stability and insensitivity to bending-induced deformations. Finally, we demonstrate that the pressure sensor can be applied in a flexible piano pad as an entertainment human interface device and a flexible foot insole as a wearable healthcare and gait monitoring device.

(Invited) Biomimetic Electronic Skins for Wearable Sensors

Flexible physical sensors with high sensitivities have gained great attentions in the fields of wearable sensors, robotic skins, and biomedical diagnostics. Here, we introduce several biomimetic approaches to develop high-performance flexible electronic skins and their applications in wearable sensors. First, by mimicking the structures and functions of fingertip skin, we introduce highly-sensitive, multifunctional, and stretchable electronic skins. Inspired by the interlocked microstructures found in epidermal-dermal ridges in human skin, piezoresistive interlocked microdomes are employed for the demonstration of stress-direction-sensitive, stretchable electronic skins. We show that interlocked microdome arrays possess highly direction-sensitive detection capability of various mechanical stimuli including normal, shear, stretching, bending, and twisting forces. We also demonstrate that ferroelectric skins with fingerprint-like patterns and interlocked microstructures can detect and discriminate multiple spatio-temporal tactile stimuli including static and dynamic pressure, vibration, and temperature with high sensitivities. For wearable device applications, we show that stretchable electronic skins attached on the human skin can be used as wearable healthcare monitoring devices, which are able to distinguish various mechanical stimuli applied in different directions, selectively monitor different intensities and directions of air flows and vibrations, and sensitively monitor human breathing flows and voice vibrations. In addition, dynamic touch sensing ability is employed for precise detection of acoustic sounds, and discrimination of various surface textures. For skin attachable devices, we also introduce smart adhesive pads based on octopus-inspired theremoresponsive adhesive pads. Finally, we demonstrate conductive and ultrathin nanomembranes for skin-attachable microphones and speakers.

Water-Resistant and Skin-Adhesive Wearable Electronics Using Graphene Fabric Sensor with Octopus-Inspired Microsuckers.

Wearable and skin-attachable electronics with portable/wearable and stretchable smart sensors are essential for health-care monitoring devices or systems. The property of adhesion to the skin in both dry and wet environments is strongly required for efficient monitoring of various human activities. We report here a facile, low-cost, scalable fabrication method for skin-adhesive graphene-coated fabric (GCF) sensors that are sensitive and respond fast to applied pressure and strain. With octopus-like patterns formed on the side of the GCF that touches the skin, the GCF adheres strongly to the skin in both dry and wet environments. Using these characteristics, we demonstrate efficient monitoring of a full range of human activities, including human physiological signals such as wrist pulse and electrocardiography (ECG), as well as body motions and speech vibrations. In particular, both measurements of ECG and wrist-bending motions were demonstrated even in wet conditions. Our approach has opened up a new possibility for wearable and skin-adherent electronic fabric sensors working even in wet environments for health-care monitoring and medical applications in vitro and in vivo.

“Off-on” signal amplification strategy amperometric immunosensor for ultrasensitive detection of tumour marker

Reducing background signal is an effective method to improve the sensitivity of amperometric immunosensors, which are significant in the detection of cancer. Herein, a novel immunosensor probe was synthesised using zeolitic imidazolate framework-hydroquinone-bovine serum albumin (ZIF-8-HQ-BSA). Based on the probe, an “off-on” strategy was applied in the immunosensor to amplify ΔI, the current signal “turn off and on”. The ZIF-8-HQ-BSA probe initially showed little current signal since ZIF-8 and BSA exhibit poor conductivity. To amplify the current signal “turn on”, the structure of ZIF-8 was broken after treatment with HCl, releasing hydroquinone to be absorbed by the polyaniline hydrogel substrate. Hydroquinone can produce a strong signal and also exhibits strong catalytic ability for H2O2 to further enhance the signal. Following this method, the immunosensing platform was used to detect cytokeratins antigen 21-1 (CYFRA21-1) in human serum and revealed a wide liner range from 0.1 pg mL−1 to 100 ng mL−1 with a low detection limit of 0.65 pg mL−1 (S/N = 3), demonstrating good consistency with an electrochemiluminescence immunoassay. Thus, the amperometric immunosensing platform discussed in this work has high potential for application in healthcare monitoring, clinical diagnostics, and biomedical devices.

High piezo-resistive performances of anisotropic composites realized by embedding rGO-based chitosan aerogels into open cell polyurethane foams.

Anisotropic aerogel-foam composites were developed by embedding a reduced graphene oxide (rGO)/chitosan aerogel directly into an open-cell polyurethane foam through an in situ bidirectional freeze-drying process. The resulting aerogel-foam composites possess both excellent compression-resilience performance and stable piezo-resistive properties due, respectively, to the excellent mechanical properties of polyurethane foams and to the presence of a chitosan-based aerogel loaded with rGO. The latter, indeed, provides outstanding electrical properties due to its conductive and parallel flat lamellar structure. It has been proven that both mechanical and piezo-resistive properties are stable even after 1000 loading/unloading cycles and a reduction of the electrical resistance of about 86% is observed upon the application of a 60% strain. The high sensitivity, long cycling life, and reliable performance over a wide strain range make this unique anisotropic aerogel-foam composite a highly promising candidate for the production of wearable sensors and healthcare monitoring devices.

SAFE: SDN-Assisted Framework for Edge–Cloud Interplay in Secure Healthcare Ecosystem

Improved quality of life has lead the healthcare industry to geographically expand and support real-time services. Following this trend, a surge of healthcare monitoring devices has substantially overgrown in the global market. These devices tend to generate data in humongous quantity that need real-time analysis with seamless and secure transmission to the computing nodes. The existing computing and networking infrastructures fall short to cater the services with desirable quality of service. Hence, to overcome these challenges, the proposed work presents a comprehensive platform referred as software defined network ( SDN) Assisted Framework for Edge–Cloud Interplay in Secure Healthcare Ecosystem ( SAFE ). The objectives of SAFE include: first, an offloading scheme to support edge–cloud interplay, second, an SDN-assisted virtualized flow management scheme, and, third, a secure Lattice-based cryptosystem. Finally, the proposed scheme is validated on different performance parameters. Additionally, a security evaluation of the designed cryptosystem is also presented. The results obtained indicate the supremacy of the designed framework.

IoT Data Analytics

Development of big data and IoT is rapidly increasingly and affecting all the major technologies and the business by increasing the benefits for the individual and organisations. The increasing growth of data of IoT devices has played a major role for use of Big Data. Big data is categorize into three aspects (a) Variety (b) Volume (c) Velocity. These categories are introduced by Gartner to describe the elements of big data challenges. Various opportunities are presented by the capability to analyze and utilize huge amounts of IoT data, including applications in smart cities, smart transport and grid systems, energy smart meters, and remote patient healthcare monitoring devices. The more popularity of Internet of Things day by day has made a big data analytics challenging because of the processing and collection of data through different sensors in the IoT network. T data are totally different from normal big data collected through systems in terms of characteristics because of the various sensors and objects involved during data collection, which include heterogeneity, noise, variety, and rapid growth.

KEH-Gait: Using Kinetic Energy Harvesting for Gait-based User Authentication Systems

With the rapid development of sensor networks and embedded computing technologies, miniaturized wearable healthcare monitoring devices have become practically feasible. For many of these devices, accelerometer-based user authentication systems by gait analysis are becoming a hot research topic. However, a major bottleneck of such system is it requires continuous sampling of accelerometer, which reduces battery life of wearable sensors. In this paper, we present KEH-Gait , which advocates use of output voltage signal from kinetic energy harvester (KEH) as the source for gait recognition. KEH-Gait is motivated by the prospect of significant power saving by not having to sample the accelerometer at all. Indeed, our measurements show that, compared to conventional accelerometer-based gait detection, KEH-Gait can reduce energy consumption by 82.15 percent. The feasibility of KEH-Gait is based on the fact that human gait has distinctive movement patterns for different individuals, which is expected to leave distinctive patterns for KEH as well. We evaluate the performance of KEH-Gait using two different types of KEH hardware on a data set of 20 subjects. Our experiments demonstrate that, although KEH-Gait yields slightly lower accuracy than accelerometer-based gait detection when single step is used, the accuracy problem can be overcome by the proposed Probability-based Multi-Step Sparse Representation Classification (PMSSRC). Moreover, the security analysis shows that the EER of KEH-Gait against an active spoofing attacker is 11.2 and 14.1 percent using two different types of KEH hardware, respectively.