On-Demand Printing of Wearable Thermotherapy Pad

Kirigami-enabled stretchable laser-induced graphene heaters for wearable thermotherapy

Flexible and stretchable heaters are increasingly recognized for their great potential in wearable thermotherapy to treat muscle spasms, joint injuries and arthritis. However, issues like lengthy processing, high fabrication cost, and toxic chemical involvement are obstacles on the way to popularize stretchable heaters for medical use. Herein, using a single-step customizable laser fabrication method, we put forward the design of cost-effective wearable laser-induced graphene (LIG) heaters with kirigami patterns, which offer multimodal stretchability and conformal fit to the skin around the human body. First, we develop the manufacturing process of the LIG heaters with three different kirigami patterns enabling reliable stretchability by out-of-plane buckling. Then, by adjusting the laser parameters, we confirm that the LIG produced by medium laser power could maintain a balance between mechanical strength and electrical conductivity. By optimizing cutting-spacing ratios through experimental measurements of stress, resistance and temperature profiles, as well as finite element analysis (FEA), we determine that a larger cutting-spacing ratio within the machining precision will lead to better mechanical, electrical and heating performance. The optimized stretchable heater in this paper could bear significant unidirectional strain over 100% or multidirectional strain over 20% without major loss in conductivity and heating performance. On-body tests and fatigue tests also proved great robustness in practical scenarios. With the advantage of safe usage, simple and customizable fabrication, easy bonding with skin, and multidirectional stretchability, the on-skin heaters are promising to substitute the traditional heating packs/wraps for thermotherapy.

Materials-Driven Soft Wearable Bioelectronics for Connected Healthcare

In the era of Internet-of-things, many things can stay connected; however, biological systems, including those necessary for human health, remain unable to stay connected to the global Internet due to the lack of soft conformal biosensors. The fundamental challenge lies in the fact that electronics and biology are distinct and incompatible, as they are based on different materials via different functioning principles. In particular, the human body is soft and curvilinear, yet electronics are typically rigid and planar. Recent advances in materials and materials design have generated tremendous opportunities to design soft wearable bioelectronics, which may bridge the gap, enabling the ultimate dream of connected healthcare for anyone, anytime, and anywhere. We begin with a review of the historical development of healthcare, indicating the significant trend of connected healthcare. This is followed by the focal point of discussion about new materials and materials design, particularly low-dimensional nanomaterials. We summarize material types and their attributes for designing soft bioelectronic sensors; we also cover their synthesis and fabrication methods, including top-down, bottom-up, and their combined approaches. Next, we discuss the wearable energy challenges and progress made to date. In addition to front-end wearable devices, we also describe back-end machine learning algorithms, artificial intelligence, telecommunication, and software. Afterward, we describe the integration of soft wearable bioelectronic systems which have been applied in various testbeds in real-world settings, including laboratories that are preclinical and clinical environments. Finally, we narrate the remaining challenges and opportunities in conjunction with our perspectives.

Electrothermal Phase Change Composite with Flexibility over a Wide Temperature Range for Wearable Thermotherapy

Flexible electrothermal composite phase change materials (PCMs) are promising candidates for portable thermotherapy. However, a great challenge remains to achieve high PCM loading while maintaining reasonable flexibility. Herein, the polypyrrole-decorated melamine foam (PPy@MF) was fabricated and thereafter applied to confine binary PCM mixtures composed of a high-enthalpy long-chain polyethylene glycol (PEG4000) and its short-chain homologue (PEG200) to make the novel PPy@MF-PEG4000+200 composite PCM. At a high loading of up to 74.1% PEG4000 and a high latent heat energy storage density of 150.1 J/g, the composite PCM remained flexible at temperature (-20 °C) far below its phase transition point thanks to the plasticine effect of PEG200. The composite also demonstrated good Joule heating performance, providing fast heating from 28 to 70 °C at low applied voltages (4.5-6.0 V). The energy could be stored efficiently and released to maintain the composites at the proper temperature. The electrothermal performance of the composite remained undisturbed during curved or repeated bending, showing good potential to be used for personal thermal management and thermotherapy.

Bifunctional Smart Textiles with Simultaneous Motion Monitoring and Thermotherapy for Human Joint Injuries

The motion detection and thermotherapy provides a convenient strategy for the diagnosis and rehabilitation assessment of joint injuries. However, it is still challenging to simultaneously achieve accurate joint motion monitoring and on-demand thermotherapy. Herein, core-sheath sensing yarns (CSSYs) is proposed and fabricated for excellent electrical and photothermal heating, which consists of carbon black (CB)-coated nylon (sheath layer), silver-plated nylon and elastic spandex yarns (core layer). The CSSYs demonstrates great joule heating performance, which reaches 75 °C at 2 V applied voltage. The good thermal management performance can be well maintained when weaving these yarns into bifunctional smart textile. Further, the optimized double-ply CSSYs (DPCSSYs) with helically twisted structure possess several appealing sensing performance, including preferable strain sensitivity (0.854), excellent linearity (0.962), and superior durability (over 5000 cycles). The as-woven bifunctional smart textile can provide instant and convenient thermotherapy to the injured joints, and simultaneously monitor the injury and recovery conditions of the joint. Therefore, the designed bifunctional smart textile can provide a promising route for developing next-generation healthcare smart textile.

Gold@mesoporous polydopamine nanoparticles modified self-healing hydrogel for sport-injuring therapy

Sports-related damage is a prevalent issue, which a combination therapy including photothermal irradiation, self-healing dressing and antibacterial treatment is an effective way to rehabilitate it. In the study, a multifunctional hydrogel was developed to meet the requirement. Firstly, mesoporous polydopamine (MPDA) was prepared, where gold nanoparticles (Au NPs) were formed in its mesoporous structure, to construct Au@MPDA NPs with nanosize about 200 nm. Synergetic and efficient photothermal effect was achieved by the combination of the two photothermal agents. The Au@MPDA NPs were then added to modify polyvinyl alcohol-carboxymethyl chitosan-borax (PCB) hydrogel. Via rheological property characterization, cell experiments and antibacterial evaluation, high photothermal efficiency and effective antibacterial activity of Au@MPDA@PCB hydrogel was obtained with the aid of Au@MPDA NPs, together with self-healing property. When treated in motion-related tissue, the modified hydrogel showed excellent adaptive property and photothermal effect in situ. This study is beneficial for developing a novel rehabilitation treatment strategy for sports-related injuries.

Electronic Textiles for Wearable Point-of-Care Systems

Traditional public health systems are suffering from limited, delayed, and inefficient medical services, especially when confronted with the pandemic and the aging population. Fusing traditional textiles with diagnostic, therapeutic, and protective medical devices can unlock electronic textiles (e-textiles) as point-of-care platform technologies on the human body, continuously monitoring vital signs and implementing round-the-clock treatment protocols in close proximity to the patient. This review comprehensively summarizes the research advances on e-textiles for wearable point-of-care systems. We start with a brief introduction to emphasize the significance of e-textiles in the current healthcare system. Then, we describe textile sensors for diagnosis, textile therapeutic devices for medical treatment, and textile protective devices for prevention, by highlighting their working mechanisms, representative materials, and clinical application scenarios. Afterward, we detail e-textiles' connection technologies as the gateway for real-time data transmission and processing in the context of 5G technologies and Internet of Things. Finally, we provide new insights into the remaining challenges and future directions in the field of e-textiles. Fueled by advances in chemistry and materials science, textile-based diagnostic devices, therapeutic devices, protective medical devices, and communication units are expected to interact synergistically to construct intelligent, wearable point-of-care textile platforms, ultimately illuminating the future of healthcare system in the Internet of Things era.

Laser-Induced Graphene Heater Pad for De-Icing

The replacement of electro-thermal material in heaters with lighter and easy-to-process materials has been extensively studied. In this study, we demonstrate that laser-induced graphene (LIG) patterns could be a good candidate for the electro-thermal pad. We fabricated LIG heaters with various thermal patterns on the commercial polyimide films according to laser scanning speed using an ultraviolet pulsed laser. We adopted laser direct writing (LDW) to irradiate on the substrates with computer-aided 2D CAD circuit data under ambient conditions. Our highly conductive and flexible heater was investigated by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, X-ray diffraction, and Brunauer-Emmett-Teller. The influence of laser scanning speed was evaluated for electrical properties, thermal performance, and durability. Our LIG heater showed promising characteristics such as high porosity, light weight, and small thickness. Furthermore, they demonstrated a rapid response time, reaching equilibrium in less than 3 s, and achieved temperatures up to 190 °C using relatively low DC voltages of approximately 10 V. Our LIG heater can be utilized for human wearable thermal pads and ice protection for industrial applications.

Recent advances in printed flexible heaters for portable and wearable thermal management

Flexible resistive heaters (FRHs) with high heating performance, large-area thermal homogeneity, and excellent thermal stability are very desirable in modern life, owing to their tremendous potential for portable and wearable thermal management applications, such as body thermotherapy, on-demand drug delivery, and artificial intelligence. Printed electronic (PE) technologies, as emerging methods combining conventional printing techniques with solution-processable functional ink have been proposed to be promising strategies for the cost-effective, large-scale, and high-throughput fabrication of printed FRHs. This review summarizes recent progress in the main components of FRHs, including conductive materials and flexible or stretchable substrates, focusing on the formulation of conductive ink systems for making printed FRHs by a variety of PE technologies including screen printing, inkjet printing, roll-to-roll (R2R) printing and three-dimensional (3D) printing. Various challenges facing the commercialization of printed FRHs and improved methods for portable and wearable thermal management applications have been discussed in detail to overcome these problems.