Flexible Patch Research Articles

Combinatorial wound healing therapy using adhesive nanofibrous membrane equipped with wearable LED patches for photobiomodulation.

Wound healing is the dynamic tissue regeneration process replacing devitalized and missing tissue layers. With the development of photomedicine techniques in wound healing, safe and noninvasive photobiomodulation therapy is receiving attention. Effective wound management in photobiomodulation is challenged, however, by limited control of the geometrical mismatches on the injured skin surface. Here, adhesive hyaluronic acid–based gelatin nanofibrous membranes integrated with multiple light-emitting diode (LED) arrays are developed as a skin-attachable patch. The nanofibrous wound dressing is expected to mimic the three-dimensional structure of the extracellular matrix, and its adhesiveness allows tight coupling between the wound sites and the flexible LED patch. Experimental results demonstrate that our medical device accelerates the initial wound healing process by the synergetic effects of the wound dressing and LED irradiation. Our proposed technology promises progress for wound healing management and other biomedical applications.

Flexible patch with printable and antibacterial conductive hydrogel electrodes for accelerated wound healing

Electrical stimulation can facilitate wound healing with high efficiency and limited side effects. However, current electrical stimulation devices have poor conformability with wounds due to their bulky nature and the rigidity of electrodes utilized. Here, a flexible electrical patch (ePatch) made with conductive hydrogel as electrodes to improve wound management was reported. The conductive hydrogel was synthesized using silver nanowire (AgNW) and methacrylated alginate (MAA), with the former chosen as the electrode material considering its antibacterial properties, and the latter used due to its clinical suitability in wound healing. The composition of the hydrogel was optimized to enable printing on medical-grade patches for personalized wound treatment. The ePatch was shown to promote re-epithelization, enhance angiogenesis, mediate immune response, and prevent infection development in the wound microenvironment. In vitro studies indicated an elevated secretion of growth factors with enhanced cell proliferation and migration ability in response to electrical stimulation. An in vivo study in the Sprague-Dawley rat model revealed a rapid wound closure within 7 days compared to 20 days of usual healing process in rodents.

Microwave Imaging for Breast Tumor Detection Using a CPW Antenna

Objectives: This work is devoted to the study and design of a small and flexible CPW patch antenna (26x30x0.64) mm3 for microwave tumor detection. Methods : The suggested flexible CPW antenna for breast cancer detection is made with a Rogers RO 3010 substrate (0.64 mm thickness). The simulation was carried out using HFSS software and the experimental validation was done with liquid phantoms which have the same EM characteristics of breast and tumor. Two tumor phantoms of different sizes, 8 and 15 mm, were tested. Two scenarios for breast cancer detection are proposed. In the first scenario, the proposed CPW antenna is used only as a receiver of the RF signal traveling through the breast. In the second scenario, two CPW antennas are used, one as a transmitter and the other as a receiver. Findings: Both the simulation and experimental results in free space of the antenna performance show that the resonance frequency of the proposed antenna is around 4.5 GHz and there is a good agreement between the simulated and experimental results. In addition, the proposed antenna has a gain of 2 dB at the desired frequency. The achieved radiation efficiency of the antenna is 86%. The comparative study of the transmission coefficient (S12) in the two scenarios yielded almost the same results, and the tumor detection was demonstrated at the frequency of 2.95 GHz with both tumor sizes (without tumors: S12 =-43.72 dB; with tumors: S12 =-55.36dB for the 15 mm tumor and S12 =-48.36 dB for the 8 mm one). Novelty: The proposed CPW antenna is useful as a sensor for tumor detection because of its relatively high radiation efficiency, flexible and small size. Keywords: Microwave imaging; breast cancer detection; tumor; CPW antenna; Phantom

Flexible polymeric patch based nanotherapeutics against non-cancer therapy.

Flexible polymeric patches find widespread applications in biomedicine because of their biological and tunable features including excellent patient compliance, superior biocompatibility and biodegradation, as well as high loading capability and permeability of drug. Such polymeric patches are classified into microneedles (MNs), hydrogel, microcapsule, microsphere and fiber depending on the formed morphology. The combination of nanomaterials with polymeric patches allows for improved advantages of increased curative efficacy and lowered systemic toxicity, promoting on-demand and regulated drug administration, thus providing the great potential to their clinic translation. In this review, the category of flexible polymeric patches that are utilized to integrate with nanomaterials is briefly presented and their advantages in bioapplications are further discussed. The applications of nanomaterials embedded polymeric patches in non-cancerous diseases were also systematically reviewed, including diabetes therapy, wound healing, dermatological disease therapy, bone regeneration, cardiac repair, hair repair, obesity therapy and some immune disease therapy. Alternatively, the limitations, latest challenges and future perspectives of such biomedical therapeutic devices are addressed.

Conformal metal crack detection sensor based on flexible graphene film antenna

Crack detection of metal structures is an important procedure to ensure the safe operation of metal structures. In this work, a metal crack sensor based on a highly conductive flexible graphene film is proposed. The sensor is designed based on conformal microstrip antenna composed of a flexible graphene film radiation patch and a flexible dielectric substrate. The prepared sensor exhibited a detection sensitivity of 36.82 MHz/mm demonstrated by both experimental and simulation results. Moreover, benefiting from the flexible nature of the graphene film, the proposed sensor shows good conformality which makes up the shortcoming of the traditional rigid crack detection device.

IoT-Enabled Integrated Smart Wound Sensor for Multiplexed Monitoring of Inflammatory Biomarkers at the Wound Site

Chronic wounds that stall at the inflammatory phase of healing may create several life-threatening complications such as tissue damage, septicemia, and organ failures. In order to prevent these adverse clinical outcomes and accelerate the wound healing process, it is crucial to monitor the wound status in real-time so that immediate therapeutic interventions can be implemented. In addition, continuous monitoring of the wound status can prevent drug overdose at the wound site, leading to on-demand and personalized drug delivery. Inflammatory mediators, such as Interleukin-6 (IL-6) and Interleukin-10 (IL-10) are promising indicators for the progression of wound healing and predictors of disease severity. Toward this end, this work reports a flexible wound patch for multiplexed monitoring of IL-6 and IL-10 at the wound site in order to provide real-time feedback on the inflammation phase of the wound. An optimized composition of gold nanoparticles integrated multiwalled carbon nanotube was demonstrated to improve sensor performance substantially. The sensor also exhibited excellent repeatable, reversible, and drift characteristics. A miniaturized Internet-of-things (IoT)-enabled potentiostat was also developed and integrated with the flexible sensor to realize a wearable system. This IoT-enabled wearable device provides a smart and cost-effective solution to improving the existing wound care through continuous, real-time, and in-situ monitoring of multiple wound biomarkers.

Drag Coefficient of Submerged Flexible Vegetation Patches in Gravel Bed Rivers

Vegetation patches and strips either along riverbanks or in channel beds are essential for the protection of erosion and sedimentation processes. In the present study, the drag coefficient Cdv of submerged flexible vegetation patches in gravel bed rivers was investigated. A total of 13 vegetation patches with different densities were studied in disparate reaches of the Padena Marbor and Beheshtabad gravel bed rivers in Iran. Water depths, flow velocities, and particle grain sizes around these vegetation patches were collected. The Saint-Venant equation and various empirical equations for estimating the drag coefficient were applied to study hydrodynamics in the presence of vegetation patches under nonuniform flow conditions. Furthermore, the drag coefficient factor of flexible vegetation was used to represent the flexibility of vegetation patches and drag characteristics, which were explored from the perspective of material mechanics. The results showed that the calculated values of Cdv exhibited nonuniform variations with the increase in the Reynolds number along the streamwise direction due to flow nonuniformity. Two effects caused by flexible vegetation patches were observed, namely, the sheltering effect (for Red>580) and blockage effect (for Red<450). In most of the vegetated patches, the sheltering effect was dominant, which reduced the drag coefficient. Finally, a fitting formula was proposed based on the drag coefficient factor and Cauchy number.

Highly integrated watch for noninvasive continual glucose monitoring

This article reports a highly integrated watch for noninvasive continual blood glucose monitoring. The watch employs a Nafion-coated flexible electrochemical sensor patch fixed on the watchband to obtain interstitial fluid (ISF) transdermally at the wrist. This reverse iontophoresis-based extraction method eliminates the pain and inconvenience that traditional fingerstick blood tests pose in diabetic patients’ lives, making continual blood glucose monitoring practical and easy. All electronic modules, including a rechargeable power source and other modules for signal processing and wireless transmission, are integrated onto a watch face-sized printed circuit board (PCB), enabling comfortable wearing of this continual glucose monitor. Real-time blood glucose levels are displayed on the LED screen of the watch and can also be checked with the smartphone user interface. With 23 volunteers, the watch demonstrated 84.34% clinical accuracy in the Clarke error grid analysis (zones A + B). In the near future, commercial products could be developed based on this lab-made prototype to provide the public with noninvasive continual glucose monitoring.

A Flexible, Wearable, and Wireless Biosensor Patch with Internet of Medical Things Applications.

Monitoring the vital signs and physiological responses of the human body in daily activities is particularly useful for the early diagnosis and prevention of cardiovascular diseases. Here, we proposed a wireless and flexible biosensor patch for continuous and longitudinal monitoring of different physiological signals, including body temperature, blood pressure (BP), and electrocardiography. Moreover, these modalities for tracking body movement and GPS locations for emergency rescue have been included in biosensor devices. We optimized the flexible patch design with high mechanical stretchability and compatibility that can provide reliable and long-term attachment to the curved skin surface. Regarding smart healthcare applications, this research presents an Internet of Things-connected healthcare platform consisting of a smartphone application, website service, database server, and mobile gateway. The IoT platform has the potential to reduce the demand for medical resources and enhance the quality of healthcare services. To further address the advances in non-invasive continuous BP monitoring, an optimized deep learning architecture with one-channel electrocardiogram signals is introduced. The performance of the BP estimation model was verified using an independent dataset; this experimental result satisfied the Association for the Advancement of Medical Instrumentation, and the British Hypertension Society standards for BP monitoring devices. The experimental results demonstrated the practical application of the wireless and flexible biosensor patch for continuous physiological signal monitoring with Internet of Medical Things-connected healthcare applications.

Flexible wearable MXene Ti3C2-Based power patch running on sweat

Flexible supercapacitors (FSCs) have received a lot of interest as portable power sources for wearable electronics. The biocompatibility of electrodes and electrolytes in wearable FSCs is important to consider although research into these topics is still in its early stages. In this work, we developed a wearable FSC that uses MXene Ti3C2 nanosheets and polypyrrole-carboxymethylcellulose nanospheres composite (Ti3C2@PPy-CMC) as the active electrode material and sweat as the electrolyte. The electrochemical performances of Ti3C2@PPy-CMC FSC were analyzed using an artificial sweat solution and exhibited excellent specific capacitance, power density, cycling stability, and bending stability. To demonstrate a real application of Ti3C2@PPy-CMC FSC, a sweat-chargeable FSC patch has been developed that can be applied directly to human clothing and skin to power a portable electronic gadget when the wearer is exercising. A comprehensive electrochemical study of the FSC patch was also conducted in various sweat secretion body regions such as the finger, foot sole, and wrist. Ti3C2@PPy-CMC composite's outstanding electrochemical performance indicates its potential capabilities and biocompatibility in wearable energy storage devices.

Flexible and Transparent Circularly Polarized Patch Antenna for Reliable Unobtrusive Wearable Wireless Communications

This paper presents a circularly polarized flexible and transparent circular patch antenna suitable for body-worn wireless-communications. Circular polarization is highly beneficial in wearable wireless communications, where antennas, as a key component of the RF front-end, operate in dynamic environments, such as the human body. The demonstrated antenna is realized with highly flexible, robust and transparent conductive-fabric-polymer composite. The performance of the explored flexible-transparent antenna is also compared with its non-transparent counterpart manufactured with non-transparent conductive fabric. This comparison further demonstrates the suitability of the proposed materials for the target unobtrusive wearable applications. Detailed numerical and experimental investigations are explored in this paper to verify the proposed design. Moreover, the compatibility of the antenna in wearable applications is evaluated by testing the performance on a forearm phantom and calculating the specific absorption rate (SAR).

Hard polymeric porous microneedles on stretchable substrate for transdermal drug delivery

Microneedles offer a convenient transdermal delivery route with potential for long term sustained release of drugs. However current microneedle technologies may not have the mechanical properties for reliable and stable penetration (e.g. hydrogel microneedles). Moreover, it is also challenging to realize microneedle arrays with large size and high flexibility. There is also an inherent upper limit to the amount and kind of drugs that can be loaded in the microneedles. In this paper, we present a new class of polymeric porous microneedles made from biocompatible and photo-curable resin that address these challenges. The microneedles are unique in their ability to load solid drug formulation in concentrated form. We demonstrate the loading and release of solid formulation of anesthetic and non-steroidal anti-inflammatory drugs, namely Lidocaine and Ibuprofen. Paper also demonstrates realization of large area (6 × 20 cm2) flexible and stretchable microneedle patches capable of drug delivery on any body part. Penetration studies were performed in an ex vivo porcine model supplemented through rigorous compression tests to ensure the robustness and rigidity of the microneedles. Detailed release profiles of the microneedle patches were shown in an in vitro skin model. Results show promise for large area transdermal delivery of solid drug formulations using these porous microneedles.

Strain Sensing Behavior of 3D Printable and Wearable Conductive Polymer Composites Filled with Silane‐Modified MWCNTs

Inside Cover: In article number 2100663, Minghua Zhang, Jianke Du, and co-workers, demonstrate that conductive polymers filled by ACB and silane-modified multi-walled carbon nanotubes (MWCNTs-MTES) possess superior printability, stretchability, conductivity, and strain sensing behavior. A flexible wearable strain-sensing skin patch is printed, and it can successfully record motion signals on human joints with good stability and repeatability, showing potential applications in the field of healthcare and motion monitoring.

Self-Bonded Hydrogel Inverse Opal Particles as Sprayed Flexible Patch for Wound Healing.

Wound healing is an important issue for regenerative medicine. Attempts in this area tend to develop functional wound patches to promote the healing. Here, we present self-bonded hydrogel inverse opal particles as sprayed flexible patch for wound healing. Such particles were fabricated by infusing drugs-loaded gelatin (GT) and carrageenan (CG) pregel into inverse opal scaffolds, which were composed of biocompatible hyaluronic acid methacryloyl (HAMA) and gelatin methacryloyl (GelMA) with graphene oxide quantum dots (GO QDs) doping. Due to the photothermal conversion capability of GO QDs and temperature reversible phase-changing performance of GT/CG, the hybrid particles could undergo GT/CG liquid transformation under the near-infrared (NIR) irradiation, which made them adhere to each other and finally form a flexible patch. Following by the phase-change of GT/CG hydrogel, the encapsulated drugs were also controllably released from the inverse opal scaffold. As the inverse opal scaffolds of the hybrid particles were maintained, their drug release induced refractive index changes could be detected as visual structural color shifting, which could be utilized to monitor their delivery processes. Based on these features, we have demonstrated that the self-bonded particles, administered in the form of spray, could be applied for wound tissue healing and drug delivery monitoring. These results indicate that the self-bonded hydrogel particles have potential value as a multifunctional patch for clinical applications.

Challenges and Strategies in Developing an Enzymatic Wearable Sweat Glucose Biosensor as a Practical Point-Of-Care Monitoring Tool for Type II Diabetes.

Recently, several studies have been conducted on wearable biosensors. Despite being skin-adhesive and mountable diagnostic devices, flexible biosensor patches cannot truly be considered wearable biosensors if they need to be connected to external instruments/processors to provide meaningful data/readings. A realistic and usable wearable biosensor should be self-contained, with a fully integrated device framework carefully designed and configured to provide reliable and intelligent diagnostics. There are several major challenges to achieving continuous sweat monitoring in real time for the systematic and effective management of type II diabetes (e.g., prevention, screening, monitoring, and treatment) through wearable sweat glucose biosensors. Consequently, further in-depth research regarding the exact interrelationship between active or passive sweat glucose and blood glucose is required to assess the applicability of wearable glucose biosensors in functional health monitoring. This review provides some useful insights that can enable effective critical studies of these unresolved issues. In this review, we first classify wearable glucose biosensors based on their signal transduction, their respective challenges, and the advanced strategies required to overcome them. Subsequently, the challenges and limitations of enzymatic and non-enzymatic wearable glucose biosensors are discussed and compared. Ten basic criteria to be considered and fulfilled in the development of a suitable, workable, and wearable sweat-based glucose biosensor are listed, based on scientific reports from the last five years. We conclude with our outlook for the controllable, well-defined, and non-invasive monitoring of epidermal glucose for maximum diagnostic potential in the effective management of type II diabetes.

Low-Cost Flexible Graphite Monopole Patch Antenna for Wireless Communication Applications

This research investigates a monopole patch antenna for Wi-Fi applications at 2.45 and 5.2 GHz, and WiMax at 3.5 GHz. A low-cost and flexible graphite sheet with good conductivity, base on graphite conductive powder and glue is used to create a radiator patch and ground plane. Instead of commercially available conductive inks or graphite sheets, we use our self-produced graphite liquid to create the graphite sheet because it is easy to produce and inexpensive. The antenna structure is formed using a low-cost and easy hand-screen printing approach that involved placing graphite liquid on a bendable polyester substrate. This research focuses on designing and developing a low-cost, thin, light, and flexible patch antenna for wireless communication and smart glass applications. The proposed antenna utilizes CST microwave software for simulations to improve the parameters before fabrication and measurement. The simulation and measurement results for the reflection coefficients at 2.45 GHz, 3.5 GHz, and 5.20 GHz are reliable and cover the required resonance frequencies, antennas gain are 1.91, 1.98, and 1.87 dB, respectively. Additionally, the radiation patterns of both results are omnidirectional. In the experiments, bending the proposed patch antenna along with the cylinder with the radii of 60, 40, and 25 mm yielded the same measurement results as the unbent patch antenna.

Flexible Intelligent Array Patch Based on Synergy of Polyurethane and Nanofiber for Sensitive Monitor and Smart Treatment

Flexible Intelligent Array Patch Based on Synergy of Polyurethane and Nanofiber for Sensitive Monitor and Smart Treatment

A review on bending analysis of polymer-based flexible patch antenna for IoT and wireless applications

Flexible electronics have the potential to address the future demands for low power consumption, flexibility, low cost, scalability, and large manufacturing in a shorter amount of time. The low cost and bending capabilities of a flexible wearable wireless application have piqued the interest of academics. Wearable flexible antennas made of a variety of polymers such as Polydimethylsiloxane (PDMS), Polyimides (PI), Polyethylene Terephthalate (PET), Polytetrafluoroethylene (PTFE) and Kapton polyimide are currently in demand for research and development. Various prominent polymers are evaluated for their ability to bend in this detailed work. The widespread acceptance of Internet-of-Things (IoT) applications to support a wide range of technologies. That will enable a wide range of new applications to be enabled via wireless connectivity. Such applications need a comprehensive inspection of the bending and deformation properties of materials. The purpose of this paper is to compare traditional flexible materials with popular polymers materials. The article examines the physical, electrical, and mechanical properties of certain commonly used polymer substrates and delivers a complete analysis and review of them. The results show that bending various polymers has a significant impact on antenna performance metrics.

Flexible Patch Antenna Array Operating at Microwaves Based on Thin Composite Material

This paper presents an innovative route to fabricate conformal patch antenna arrays based on a flexible mesh-style conductive fabric / E-glass fiber composite laminate with improved performance at microwaves. On the one hand, the ohmic loss in the antenna array is restricted by integrating a highly conductive fabric into an E-glass fiber composite laminate and by using it as feeding lines and radiating elements after its precise machining by laser technology. On the other hand, the dielectric loss is restricted by inserting a foam layer (with dielectric characteristics close to those of the air) between the laminate substrate and the ground plane which is made of the highly conductive mesh-style fabric. The bending effect of the antenna array on its radiation pattern is minimized by applying a phase offset through phase shifters at the feeding lines of the most curved patches. The high radiation performance in gain and efficiency at 5.8 GHz (11.9 dBi and 75% in a flat configuration, and 8.7 dBi and 75% in a 50 mm-radius bending configuration, respectively), the seamless integration process, and the flexible mechanical properties of such composite antenna arrays pave the way for their promising and efficient integration into various devices, objects, and vehicles made of composite laminate materials.

Design of Flexible 3.2 GHz Rectangular Microstrip Patch Antenna for S-Band Communication

This paper presents the design, simulation, realization and analysis of flexible microstrip patch antenna for S-band applications. The proposed design also adopts the conformal structure by utilizing flexible substrate. Conformal or flexible structure allows the antenna to fit with any specified shape as desired. The antenna patch dimensions is 43 mm × 25 mm without SMA connector. The patch is etched on the flexible dielectric substrate, pyralux FR 9111, with a relative dielectric constant of εr = 3 and the thickness of substrate, h = 0.025 mm. The antenna is designed to resonate at 3.2 GHz. The return loss (RL) of the simulation is -35.80 dB at the center frequency of 3.2 GHz. The fabricated antenna prototype was measured at different bending angles scenarios including 0º, 30º, 60º, and 90º. The measurement of antenna prototype shows that the center frequency is shifted to the higher frequency of 3.29 GHz, compared to the simulation result. Among these scenarios, measurement at bending angle of 90º gives the best performance with RL = - 31.38 dB at 3.29 GHz, the bandwidth is 80 MHz, and the impedance ZA = 48.36 + j2.04 Ω. Despite a slight differences from simulation results, the designed antenna still performs well as expected.