Wearable Patch Research Articles

Wearable microfluidic sweat collection platform with a calorimetric flow rate sensor for realtime and long-term sweat rate measurements

This work presents the design and fabrication of a wearable microfluidic patch-based system for sweat collection with a calorimetric flow rate sensor based on heat convection for measuring sweat rate (SR). The effects were predicted using a 3D multi-physics simulator and were verified on a fabricated patch made of polyimide layers. The sensor can detect surface temperature gradients of 302–312 K caused by fluid flowing thru the microfluidic channels at a rate of 0.5–23 µg s−1 that fall within the physiological range of SR. Meanwhile, the relation between flow rate and temperature gradient is highly linear (Pearson r2 = 0.999) and repeatable. This work also demonstrates a low-cost method for patterning microfluidic channels on flexible substrates which can be used for mass production of wearable patches.

Durable Janus membrane with on-demand mode switching fabricated by femtosecond laser

Despite their notable unidirectional water transport capabilities, Janus membranes are commonly challenged by the fragility of their chemical coatings and the clogging of open microchannels. Here, an on-demand mode-switching strategy is presented to consider the Janus functionality and mechanical durability separately and implement them by simply stretching and releasing the membrane. The stretching Janus mode facilitates unidirectional liquid flow through the hydrophilic micropores-microgrooves channels (PG channels) fabricated by femtosecond laser. The releasing protection mode is designed for the in-situ closure of the PG channels upon encountering external abrasion and impact. The protection mode imparts the Janus membrane robustness to reserve water unidirectional penetration under harsh conditions, such as 2000 cycles mechanical abrasion, 10 days exposure in air and other rigorous tests (sandpaper abrasion, finger rubbing, sand impact and tape peeling). The underlying mechanism of gridded grooves in protecting and enhancing water flow is unveiled. The Janus membrane serves as a fog collector to demonstrate its unwavering mechanical durability in harsh real-world conditions. The presented design strategy could open up new possibilities of Janus membrane in a multitude of applications ranging from multiphase separation devices to fog harvesting and wearable health-monitoring patches.

Continuous Glycemic Monitoring Enabled by A Wi‐Fi Energy‐Harvesting Wearable Sweat‐Sensing Patch

AbstractContinuous monitoring of multiple physiological parameters, such as glucose levels, temperature, and heart rate variability (HRV) is crucial for effective diabetes management and mitigating the risks associated with hypoglycemic events. These events often occur without apparent symptoms, posing a challenge for diabetic patients in managing their condition. Therefore, a non‐invasive wearable device capable of continuously measuring multiple body signals to predict hypoglycemic events would be highly beneficial. In this study, a wearable patch that continuously measures glucose, temperature, and HRV is presented. The device uses a novel power harvesting system to convert radiofrequency (RF) signals with the frequency of 2.45 GHz to direct current (DC) signals to extend the battery life for further continuous monitoring. The patch is small and has a conformal structure that can easily fit onto different body parts. The screen‐printed glucose sensor demonstrates a sensitivity of 10.3 nA cm−2 µM−1, a limit of detection (LOD) of 8.9 µM, and a limit of quantification (LOQ) of 27 µM. The device employs a photoplethysmography (PPG) module with a peak‐finding algorithm to calculate the HRV values. In vivo experiments demonstrate the validation of the device's proper operation in glucose, HRV, and temperature measurement.

Continuous Ketone Monitoring via Wearable Microneedle Patch Platform.

Ketone bodies (KBs), especially β-hydroxybutyrate (BHB), have gained tremendous attention as potential biomarkers as their presence in bodily fluids is closely associated with health and wellness. While a variety of blood fingerstick test strips are available for self-testing of BHB, there are major needs for wearable devices capable of continuously tracking changing BHB concentrations. To address these needs, we present here the first demonstration of a wearable microneedle-based continuous ketone monitoring (CKM) in human interstitial fluid (ISF) and illustrate its ability to closely follow the intake of ketone drinks. To ensure highly stable and selective continuous detection of ISF BHB, the new enzymatic microneedle BHB sensor relies on a gold-coated platinum working electrode modified with a reagent layer containing toluidine blue O (TBO) redox mediator, β-hydroxybutyrate dehydrogenase (HBD) enzyme, a nicotinamide adenine dinucleotide (NAD+) cofactor, along with carbon nanotubes (CNTs), chitosan (Chit), and a poly(vinyl chloride) (PVC) outer protective layer. The skin-worn microneedle sensing device operates with a miniaturized electrochemical analyzer connected wirelessly to a mobile electronic device for capturing, processing, and displaying the data. Cytotoxicity and skin penetration studies indicate the absence of potential harmful effects. A pilot study involving multiple human subjects evaluated continuous BHB monitoring in human ISF, against gold standard BHB meter measurements, revealing the close correlation between the two methods. Such microneedle-based CKM offers considerable promise for dynamic BHB tracking toward the management of diabetic ketoacidosis and personal nutrition and wellness.

3D Carbon-Based Conductive Network Printed for Glucose Sensors on Curved and Flexible Substrates.

The rising prevalence of diabetes has led to an increased focus on real-time glucose monitoring. Wearable glucose sensor patches allow noninvasive, real-time monitoring, reducing patient discomfort compared to invasive sensors. However, most existing glucose sensor patches rely on complex and contaminating metal vapor deposition technologies, which pose limitations in practical production. In this study, we propose a novel approach for preparing graphite/multiwall carbon nanotubes (MWCNT)/reduced graphene oxide (rGO) using a high-viscosity ink, which can be easily obtained through simple mechanical stirring. To create intricate patterns and enable printing on curved substrates, we employed a 3D printer equipped with an infrared laser ranging system. The ink served as a working electrode, and we developed a three-electrode system patch with a concentric circle structure. Subsequently, the working electrode underwent enzymatic modification with glucose dehydrogenase with flavin adenine dinucleotide (GDH-FAD) using a polymer embedding method. The resulting wearable glucose sensor exhibited a sensitivity of 2.42 μA mM-1 and a linear detection range of 1-12 mM. In addition, the glucose sensor has excellent anti-interference capability and demonstrates good repeatability in simulated real human wear scenarios, which meets the requirements for accurate human detection. These findings provide valuable insights into the development of human health monitoring technologies.

Using a wearable patch to develop a digital monitoring biomarker of inflammation in response to LPS challenge.

Remote inflammation monitoring with digital health technologies (DHTs) would provide valuable information for both clinical research and care. Controlled perturbations of the immune system may reveal physiological signatures which could be used to develop a digital biomarker of inflammatory state. In this study, molecular and physiological profiling was performed following an invivo lipopolysaccharide (LPS) challenge to develop a digital biomarker of inflammation. Ten healthy volunteers received an intravenous LPS challenge and were monitored for 24 h using the VitalConnect VitalPatch (VitalPatch). VitalPatch measurements included heart rate (HR), heart rate variability (HRV), respiratory rate (RR), and skin temperature (TEMP). Conventional episodic inpatient vital signs and serum proteins were measured pre- and post-LPS challenge. The VitalPatch provided vital signs that were comparable to conventional methods for assessing HR, RR, and TEMP. A pronounced increase was observed in HR, RR, and TEMP as well as a decrease in HRV 1-4 h post-LPS challenge. The ordering of participants by magnitude of inflammatory cytokine response 2 h post-LPS challenge was consistent with ordering of participants by change from baseline in vital signs when measured by VitalPatch (r = 0.73) but not when measured by conventional methods (r = -0.04). A machine learning model trained on VitalPatch data predicted change from baseline in inflammatory protein response (R2 = 0.67). DHTs, such as VitalPatch, can improve upon existing episodic measurements of vital signs by enabling continuous sensing and have the potential for future use as tools to remotely monitor inflammation.

A wearable electrostimulation-augmented ionic-gel photothermal patch doped with MXene for skin tumor treatment

A wearable biological patch capable of producing multiple responses to light and electricity without interfering with daily activities is highly desired for skin cancer treatment, but remains a key challenge. Herein, the skin-mountable electrostimulation-augmented photothermal patch (eT-patch) comprising transparent ionic gel with MXene (Ti3C2Tx) doping is developed and applied for the treatment of melanoma under photostimulation at 0.5 W/cm2. The eT-patch designed has superior photothermal and electrical characteristics owing to ionic gels doped with MXene which provides high photothermal conversion efficiency and electrical conductivity as a medium. Simultaneously, the ionic gel-based eT-patch having excellent optical transparency actualizes real-time observation of skin response and melanoma treatment process under photothermal and electrical stimulation (PES) co-therapy. Systematical cellular study on anti-tumor mechanism of the eT-patch under PES treatment revealed that eT-patch under PES treatment can synergically trigger cancer cell apoptosis and pyroptosis, which together lead to the death of melanoma cells. Due to the obvious advantages of relatively safe and less side effects in healthy organs, the developed eT-patch provides a promising cost-effective therapeutic strategy for skin tumors and will open a new avenue for biomedical applications of ionic gels.

Screen‐printed dual‐band wearable textile antenna incorporated with EBG structure for WBAN communications

SummaryA dual‐band, wearable coplanar microstrip patch antenna (CPW) integrated with electromagnetic bandgap structure (EBG) to operate dual wireless bands at 2.48 GHz industrial, scientific, and medical band (ISM) and 5.2 GHz WLAN. The proposed textile wearable antenna and EBG structure are screen‐printed using silver conductive ink on the cotton polyester substrate (εr = 1.6) for flexible wearable applications. A 3 × 3 EBG array is realized by a concentric square patch surrounded by the annular square ring to reduce back radiation and increase the forward gain and front‐back ratio. The proposed EBG‐backed antenna, compared with the conventional CPW‐fed antenna, improves forward gain from 2.18 to 6.59 dB at 2.48 GHz and 3.5 to 7.03 dB at 5.2 GHz. Moreover, the EBG array is used to isolate the human body from the antenna and reduces the specific absorption rate (SAR). The antenna is performed with a human phantom tissue model, which exhibits a specific absorption rate of 0.12 W/kg, and 0.260 W/kg for 1 g tissue at 2.48 GHz and 5.2 GHz, respectively.

Wearable Microneedle Patch for Transdermal Electrochemical Monitoring of Urea in Interstitial Fluid.

Microneedle-based wearable electrochemical biosensors are the new frontier in personalized health monitoring and disease diagnostic devices that provide an alternative tool to traditional blood-based invasive techniques. Advancements in micro- and nanofabrication technologies enabled the fabrication of microneedles using different biomaterials and morphological features with the aim of overcoming existing challenges and enhancing sensing performance. In this work, we report a microneedle array featuring conductive recessed microcavities for monitoring urea levels in the interstitial fluid of the skin. Microcavities are small pockets on the tip of each microneedle that can accommodate the sensing layer, provide protection from delamination during skin insertion or removal, and position the sensing layer in a deep layer of the skin to reach the interstitial fluid. The wearable urea patch has shown to be highly sensitive and selective in monitoring urea, with a sensitivity of 2.5 mV mM-1 and a linear range of 3 to 18 mM making it suitable for monitoring urea levels in healthy individuals and patients. Our ex vivo experiments have shown that recessed microcavities can protect the sensing layer from delamination during skin insertion and monitor changing urea levels in interstitial fluid. This biocompatible platform provides alternative solutions to the critical issue of maintaining the performance of the biosensor upon skin insertion and holds great potential for advancing transdermal sensor technology.

Fluorescence-Recovered Wearable Hydrogel Patch for In Vitro Detection of Glucose Based on Rare-Earth Nanoparticles.

The physiological state of the human body can be indicated by analyzing the composition of sweat. In this research, a fluorescence-recovered wearable hydrogel patch has been designed and realized which can noninvasively monitor the glucose concentration in human sweat. Rare-earth nanoparticles (RENPs) of NaGdF4 doped with different elements (Yb, Er, and Ce) are synthesized and optimized for better luminescence in the near-infrared second (NIR-II) and visible region. In addition, RENPs are coated with CoOOH of which the absorbance has an extensive peak in the visible and NIR regions. The concentration of H2O2 in the environment can be detected by the fluorescence recovery degree of CoOOH-modified RENPs based on the fluorescence resonance energy transfer effect. For in vivo detection, the physiological state of oxidative stress at tumor sites can be visualized through its fluorescence in NIR-II with low background noise and high penetration depth. For the in vitro detection, CoOOH-modified RENP and glucose oxidase (GOx) were doped into a polyacrylamide hydrogel, and a patch that can emit green upconversion fluorescence under a 980 nm laser was prepared. Compared with the conventional electrochemical detection method, the fluorescence we presented has higher sensitivity and linear detection region to detect the glucose. This improved anti-interference sweat patch that can work in the dark environment was obtained, and the physiological state of the human body is conveniently monitored, which provides a new facile and convenient method to monitor the sweat status.

Wearable electrochemical patch based on iron nano-catalysts incorporated laser-induced graphene for sweat metabolites detection

The development of wearable devices shows great application potential in health management. In this work, we propose the fabrication of a novel wearable electrochemical patch and prove its application in sweat metabolites detection. The patch is developed based on iron nano-catalysts incorporated laser-induced graphene (FeNCs/LIG), which is a newly integrated sensing electrode with unique three-dimensional nanostructure and good electrocatalytic activity. It shows desirable sensing performances for sweat metabolites including tyrosine (Tyr) and uric acid (UA) molecules. The detection limit of Tyr and UA can reach 5.11 μM and 1.37 μM, respectively. Besides, density functional theory calculation deeply reveals that the Fe active sites of FeNCs play an important role in molecule adsorption and electron transference, thus promoting sensing performance. To realize wearable application, a dual-channel hydrogel chip is designed and assembled with FeNCs/LIG. The developed patch is successfully utilized to accurately determination of Tyr and UA in sweat. This work is expected to provide a new non-invasive strategy for evaluating amino acid intake and metabolic level.

MXene-Integrated Single-Stranded Carbon Yarn-Based Wearable Sensor Patch for On-Site Monitoring of Dopamine

MXene-Integrated Single-Stranded Carbon Yarn-Based Wearable Sensor Patch for On-Site Monitoring of Dopamine

Skin‐Inspired Ultrafast Self‐Healing Wearable Patch with Hybrid Cooling for Comfortable and Durable Electromyographic Monitoring

AbstractAs the body's largest organ, the skin is an integrated multisensory system with self‐healing ability and helps stabilize body temperature. It is herein, inspired by natural skin, a wearable patch made from porous polydimethylsiloxane (PDMS) skeleton, poly(vinyl alcohol) (PVA) hydrogel, and silicon oxide (SiO2) particles, offers a combination of self‐healing properties, along with hybrid radiative and evaporative cooling mechanisms, designed for electromyographic (EMG) signal detection and human‐machine interaction. The patch has both high mid‐infrared (MIR) emittance (96%) and visible to near‐infrared (visNIR) reflectance (80%), coupled with efficient water evaporation from the PVA hydrogel, resulting in a hybrid cooling power of 180 W m−2. It obtains a temperature drop of ≈7.7 °C using this patch under a solar intensity of ≈700 W m−2. Furthermore, the patch demonstrates self‐healing ability with ultrafast recovery of electrical conductivity (1 s) and a self‐healing efficiency (≈71%) of fracture strain. Thus, the wearable patch can detect high‐quality EMG signals and provide cooling effects and self‐healing capabilities that enhance comfortability and durability. These features make the patch an advanced solution for developing next‐generation wearable patches that can meet the rigorous demands of durable body temperature control in various applications.

Ambient Light-Driven Wireless Wearable Finger Patch for Monitoring Vital Signs From PPG Signal

Ambient Light-Driven Wireless Wearable Finger Patch for Monitoring Vital Signs From PPG Signal

Exposure Assessment for Wearable Patch Antenna Array at Millimeter Waves

Exposure Assessment for Wearable Patch Antenna Array at Millimeter Waves

Measuring thoracic excursion using a wearable patch antenna

Measuring thoracic excursion using a wearable patch antenna

Sea urchin nanostructured nickel cobaltite modified carbon cloth integrated wearable patches for the on-site detection of the immunosuppressant drug mycophenolate mofetil.

Mycophenolate mofetil (MpM) is a medication used to prevent the rejection of transplanted organs, particularly in kidney, heart, and liver transplant surgeries. It is extremely important to be conscious that MpM can raise the risk of severe infections and some cancers if it exceeds the recommended dose while lower doses will result in organ rejections. So, it is essential to monitor the dosage of MpM in real time in the micromolar range. In this work, we have synthesized 3-aminopropyltriethoxysilane (APTES) functionalized nickel cobaltite (NiCo2O4) and this amino functionalization was chosen to enhance the stability and electrochemical activity of NiCo2O4. The enhanced activity of NiCo2O4 was used for developing an electrochemical sensor for the detection of MpM. APTES functionalized NiCo2O4 was coated on carbon cloth and used as the working electrode. Surface functionalization with APTES on NiCo2O4 was aimed at augmenting the adsorption/interaction of MpM due to its binding properties. The developed sensor showed a very low detection limit of 1.23 nM with linear ranges of 10-100 nM and 1-100 μM and its practical applicability was examined using artificial samples of blood serum and cerebrospinal fluid, validating its potential application in real-life scenarios.

Clinical human activity recognition based on a wearable patch of combined tri-axial ACC and ECG sensors.

In digital medicine, human activity recognition (HAR) can be used to track and assess a patient's progress throughout rehabilitation, enhancing the quality of life for the elderly and the disabled. A patch-type flexible sensor that integrated dynamic electrocardiogram (ECG) and acceleration signal (ACC) was used to record the signals of the various behavioral activities of 20 healthy volunteers and 25 patients with pneumoconiosis. Seven HAR tasks were then carried out on the data using four different deep learning methods (CNN, LSTM, CNN-LSTM and GRU). When ECG and ACC were obtained simultaneously, the overall accuracy rates of HAR for healthy group were 0.9371, 0.8829, 0.9843 and 0.9486 by the CNN, LSTM, CNN-LSTM and GRU models, respectively. In contrast, the overall accuracy rates of HAR for the pneumoconiosis patients' group were 0.8850, 0.7975, 0.9425 and 0.8525 by the four corresponding models. The accuracy of HAR for both groups using all four models is higher than when only ACC signal is detected. The addition of the ECG signal significantly improves HAR outcomes in the group of healthy individuals, while having relatively less enhancing effects on the group of patients with pneumoconiosis. When ECG and ACC signals were combined, the increase in HAR accuracy was notable compared to cases where no ECG data was provided. These results suggest that the combination of ACC and ECG data can represent a novel method for the clinical application of HAR.

Redox-Concatenated Aptamer Integrated Skin Mimicking Electrochemical Patch for Noninvasive Detection of Cortisol.

This research focuses on developing and validating a wearable electrochemical biosensor called the concatenated aptamer integrated skin patch, also known as the Captain Patch. The main objective is to detect cortisol levels in sweat, which can provide valuable insights into an individual's health. The biosensor utilizes a corrugated surface that mimics the skin, allowing for better attachment and an improved electrochemical performance. The study demonstrates the successful application of Captain Patch on the human body by using artificially spiked sweat samples. The results indicate good measurement accuracy and conformity when the patch is worn on the body. However, for long-term usage, the patch needs to be changed every 3-4 h or worn three times a day to enable monitoring of cortisol levels. Despite the need for frequent patch changes, the cost-effectiveness and ease of operation make these skin patches suitable for longitudinal cortisol monitoring and other sweat analytes. By customization of the biorecognition probe, the developed biowearable can be used to monitor a variety of vital biomarkers. Overall, Captain Patch, with its capability of detecting specific health markers such as cortisol, hints at the future potential of wearables to offer valuable data on various other biomarkers. Our approach presents the first step in integrating a cost-effective wearable electrochemical patch integrated with a redox-concatenated aptamer for noninvasive biomarker detection. This personalized approach to monitoring can lead to improved patient outcomes and increased patient engagement in managing their health.

Self-powered wearable electrical stimulation patch with integrated triboelectric nanogenerator for tendinopathy treatment

Tendinopathy is a common musculoskeletal disease for which researchers have proposed various treatments but with limited efficacy. Here, we propose a self-powered wearable electrical stimulation (ES) patch with an integrated triboelectric nanogenerator (TENG) for tendinopathy treatment. The ES patch comprises a freeze-dried PVDF-TrFE/PA6 TENG and a pair of interdigital electrodes (IDTs). The bionically designed ES patch is attached directly to affected tendons. It undergoes deformation and friction during movement and generates pulsed electric output, which is then converted into an electric field via the IDTs to treat tendinopathy. In vitro experiments showed that the self-powered ES patch greatly increased mitochondrial function in degenerative tendon stem/progenitor cells (TSPCs) and promoted tenogenesis. In vivo experiments revealed that the ES patch significantly improved the gait motor function of tendinopathy rats, boosted collagen regeneration, and drastically reduced the degree of tissue inflammatory infiltration and recovery time. Our study demonstrated the great potential of wearable electrical stimulation patches for effectively treating tendinopathy.