Wearable Thermotherapy Research Articles

Durable Flexible Conductive Fiber Based on Cross-Linking Network Tannic Acid/Polypyrrole for Wearable Thermotherapy Monitoring System.

Intelligent wearable textiles have garnered attention and advancement, particularly in the realms of thermotherapy and health monitoring. As a critical component of intelligent wearable textiles, conductive fibers are expected to have long-term stable and durable conductivity. In this work, a highly stretchable and conductive fiber based on tannic acid/polypyrrole was developed. The conductive network was formed by doping TA into PPy, resulting in enhanced stretchability of PPy on the surface of PU. TA also improves the interface interaction between PPy and PU to gain more firm attachment of PPy, which achieves high conductivity (0.89 ± 0.23 S/cm) and durability. Furthermore, the stretchable conductive fiber also exhibited intelligent responses to electricity, light, and deformation. They can serve as heat sources under the action of electricity and light (temperature was raised to 42 °C under 4 V and 54 °C under solar radiation stimuli) and can also monitor the movements of humans, making them potential applications in thermotherapy textiles and intelligent sensing equipment. A PU/TA/PPy-based all-in-one smart wearable system was fabricated using textile molding technology capable of all-weather thermal therapy and motion detection. This fiber fabrication technology and integrated system offer insights for the future development of smart wearable devices.

Trunk-Inspired SWCNT-Based Wrinkled Films for Highly-Stretchable Electromagnetic Interference Shielding and Wearable Thermotherapy

HighlightsElephant trunk-inspired anisotropic wrinkling structures were formed on a sandwich-like conductive film through a controlled shrinking method.The wrinkled conductive network could withstand up to 200% tensile strain and exhibits a strain-enhanced electromagnetic interference shielding effectiveness when stretching parallel to the electric field polarization direction.

A breathable, designable and flexible leather–heater used in wearable thermotherapy

A breathable, designable and flexible leather–heater used in wearable thermotherapy

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.

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.

Hydrated alginate polysaccharide fabrics grafted with sliver nanocrystals for wearable thermal and health management

The creation of functional components with precise chemistries on carbohydrate polymers is of great significance for future wearable biomedicine and health management. Among various carbohydrate polymers, marine polysaccharide featured with antimicrobial, biodegradable and biocompatible properties is an ideal platform while the water-swelling nature makes it difficult to form stable interface. Here, well-dispersed silver nanoparticles have been in-situ assembled on hydrated alginate fabric (AF), involving chemical absorption of Ag ions and in-situ reduction of conductive Ag layer. Owing to the stable complex formed between Ag ions and carboxyl groups, the Ag-grafted AF exhibits superior Joule heating capability, including low operating voltage (1–3 V), high saturation temperature (63 °C), rapid response time (25 s) and outstanding durability against harsh conditions. Furthermore, the Ag-grafted AF demonstrates noticeable inhibition against E. coli and S. aureus as compared with the pristine AF. This work provides a rational strategy for the functionalization of hydrated polysaccharide and enables wearable thermotherapy devices for human health management.

Super-strong and high-performance electrical film heater derived from silver nanowire/aligned bacterial cellulose film

High-performance electrical Joule heaters with high mechanical properties, low driving voltage, rapid response, and flexibility are highly desirable for portable thermal management. Herein, by using aligned bacterial cellulose (BC) and silver nanowire (AgNW), we fabricated a novel film heater based on Joule heating phenomena. The aligned BC film prepared by stretching BC hydrogel and hot-pressing drying technology showed outstanding mechanical properties and flexibility. The ultrahigh strength of up to 1018 MPa and the toughness of 20 MJ/m3 were obtained for the aligned BC film with 40% wet-stretching (BC-40). In addition, the aligned BC film could be folded into desirable shapes. The AgNW was spray-coated on the surface of aligned BC-40 film and then covered with polydimethylsiloxane to form a P@AgNW@BC heater. P@AgNW@BC heater showed excellent conductivity, which endowed the film heater with an outstanding Joule heating performance. P@AgNW@BC heater could reach ~ 98 ℃ at a very low driving voltage of 4 V with a rapid heating response (13 s) and long-term temperature stability. The P@AgNW@BC heater with such an outstanding heating performance can be used as a flexible heating device for different applications in daily life like deicing/defogging device, wearable thermotherapy, etc.Affiliations: Please check and confirm that the authors and their respective affiliations have been correctly identified and amend if necessary.yes, we confirmed the affiliations are correct.Article title: Kindly check and confirm the edit made in the article title.Thanks, the title is no problem.Graphical

A resistive ink based all-printed fabric heater integrated wearable thermotherapy device

A resistive ink based all-printed fabric heater integrated wearable thermotherapy device

A Flexible and Wearable Strain Sensor from Polypyrrole‐Doped Elastomers with Dual Functions in Motion Monitoring and Thermotherapy†

Comprehensive SummaryFlexible strain sensors are essential components of wearable electronic skins. Here we report a new kind of flexible strain sensor by filling conductive nanowires in elastomers featuring a concentration gradient. The fabrication method involves a fast photo‐induced copolymerization of acrylates in the presence of gradient deposited polypyrrole (PPy) nanowires, which is facile and cost‐effective in steadily doping PPy into elastomeric films. The combination of delicately selected polyacrylates as the matrix filled with entangled, nano‐sized PPy endows the sensor good stretchability, sensitive deformation‐electrical signal conversion and high fatigue resistance, which can be used repeatedly without scarifying the sensitivity of electrical signal. Besides, the lower side of the composite films exhibits high light absorption (> 98%) in a wide spectral range (250—2400 nm). Systematic characterizations of the sensors support that the excellent strain sensing and light‐heat conversion performances are essentially dependent on the gradient filling of PPy nanowires. Moreover, the applications of this flexible strain sensor for human motion monitoring and wearable thermotherapy are demonstrated, manifesting a promising option for wearable electronics and personalized healthcare.

Flexibility and shape memory of phase change material capable of rapid electric heating function for wearable thermotherapy

Thermotherapy is often preferable to medication and surgery because of its mild side effects and noninvasiveness. However, current research methods are unable to improve the efficiency of pre-treatment resulting in unportable use, and poor room temperature flexibility has become its critical limitation. Herein, a novel conductive flexible composite phase-change material (CPCM) was prepared for high-performance thermotherapy. Styrene ethylene butylene styrene (SEBS) and expanded graphite (EG) absorb paraffin (PA) and silicone oil onto a three-dimensional network. The CPCM possesses a high energy storage density (100.8–164.5 J/g) and sufficient volume conductivity (383.76 S·m−1) and can improve the thermal conductivity to 1600 % relative to pure PA. Moreover, it is flexible and possesses shape memory at both room temperature and the phase change temperature (44 ℃). The hardness of the material is 44.5 HA at room temperature and can be reduced to 2.0 HA after phase transition. When heated electrically, it heated threefold faster than when heated by hot air. The material was tested by volunteers and was found to maintain a temperature above 40 °C for more than 30 min. The utilization of this CPCM in thermotherapy is a promising low-cost and environmentally friendly strategy.

Durability Study of Thermal Transfer Printed Textile Electrodes for Wearable Electronic Applications.

Textile-based electronics hold great promise because they can endow wearable devices with soft and comfortable characteristics. However, the inherent porosity and fluffiness of fabrics result in high surface roughness, which presents great challenges in the manufacture of high-performance fabric electrodes. In this work, we propose a thermal transfer printing method to address the above challenges, in which electrodes or circuits of silver flake/thermoplastic polyurethane (TPU) composites are prefabricated on a release film by coating and laser engraving and then laminated by hot-pressing to a variety of fabrics and textiles. This universal and scalable production technique enables fabric electrodes to be made without compromising the original wearability, washability, and stretchability of textiles. The prepared fabric electrodes exhibit high conductivity (5.48 × 104 S/cm), high adhesion (≥1750 N/m), good abrasion/washing resistance, high patterning resolution (∼40 μm), and good electromechanical performance up to 50% strain. To demonstrate the potential applications, we developed textile-based radio frequency identification (RFID) tags for remote identification and a large-sized heater for wearable thermotherapy. More importantly, the solvent-free thermal transfer printing technology developed in this paper enables people to DIY interesting flexible electronics on clothes with daily tools, which can promote the commercial application of smart textile-based electronics.

Expandable, serpentine Au nanotrough networks for skin-like electrodes with superior thermal and moisture stability

Flexible and stretchable electrodes as the cornerstone of bioelectronics are bridging human with biomedical devices in an unprecedentedly intimate and safer way. However, maintaining high electrical properties while adapting to moist, complex and dynamic biosurfaces for a prolonged period of usage remains a great challenge. Herein, we demonstrate an omnidirectionally stretchable transparent electrode based on serpentine Au nanotrough (AuNT) networks with highly tunable optoelectronic performances (sheet resistance of down to ∼13 Ω sq−1 at transmittance of 90%). Owing to the junction-free nanoweb structure with an ultralow percolation density, the AuNT networks demonstrate excellent thermal stability as an efficient Joule heater with a wide operating temperature range up to 390 °C. The in-plane buckled AuNT electrode exhibits controllable heat generation upon repetitive tensile strains of 60%, enabling wearable thermotherapy at highly strained joints. Such highly stretchable electrodes can be directly laminated on the balloon catheter as expandable, high-density nanomesh ablators, showing excellent thermal and moisture stability during 15 days of storage under conditions of relative humidity of 85% at 70 °C and over 1000 heating cycles to 60 °C, offering strong potential for biomedical therapeutics, such as thermal ablation and electrochemotherapy.

High-Performance Flexible Transparent Electrical Heater Based on a Robust Ordered Ag Nanowire Micromesh Conductor

High-performance electrical heaters with a rapid thermal response, homogeneous temperature distribution, and chemical and mechanical robustness are desirable for inevitable use in various areas such as defrosting windows and wearable thermotherapy. Herein, optimally engineered ordered Ag nanowire micromeshes are partially embedded in poly(ethylene terephthalate) matrix (Ag NMs/ePET) via a facile spray coating and transfer approach for flexible transparent conductor and electrical heater applications, which exhibit a slight sheet resistance variation of less than 5%. The resultant Ag NMs/ePET heater exhibits uniform heat distribution over the entire film and can achieve a saturation temperature of 134 °C with a rapid response time of 5 s under an input voltage of 6 V. In addition, owing to the large-diameter nanowire micromesh structure and the protective effect of PET encapsulation, the flexible transparent Ag NMs/ePET heater presents excellent mechanical and chemical robustness in extreme environments and still maintains a stable heating performance after 5000 repeated bending cycles (r = 5 mm) and exposure to a corrosive solution. This work lays the foundation for improving the electrical heater performance and provides a facile methodology to fabricate a high-performance flexible transparent conducting film for other innovative applications.

MXene/tissue paper composites for wearable pressure sensors and thermotherapy electronics

Multifunctional pressure sensors with diversified applications exhibited tremendous demand and great potential for commercialization. Herein, pressure sensors with high sensitivity were realized through efficient surface bonding of MXene materials with traditional tissue paper. The sensors exhibited a broad working range of 0-100 kPa with high sensitivity, fast response and recovery time of around 30 ms, excellent mechanical endurance without obvious fatigue over 2000 loading/unloading cycles as well as low detection limit of 0.89 Pa. Based on these excellent sensing properties, physiological signals of pressure sensors were evaluated including gesture, breath and pulse, further revealing the potential for commercial wearable electronics. Moreover, pressure regulation pattern of wearable thermotherapy electronics further demonstrated the intrinsic dominant electro-thermal properties of Ti3C2Tx. We anticipated that the Ti3C2Tx/tissue paper integrated pressure sensor would offer great contributes for developing smart wearable thermotherapy electronics to achieve motion detection and health protection in the future.

Fabrication of Metal Nanowire Based Stretchable Mesh Electrode for Wearable Heater Application

In recent years, human-convenient smart wearable devices have attracted considerable attention as emerging applications in smart healthcare systems, soft robotics, and human-machine interfaces. In particular, resistive film heaters with mechanical flexibility and excellent mechanical and electrothermal performance have recently been widely explored for wearable thermotherapy applications. Here, we present a simple and efficient way of fabricating highly flexible and stretchable resistive film heaters based on a patterned silver nanowire (AgNW)/polymer composite structure. The AgNW/polymer composite electrodes were successfully prepared using a photolithographically patterned polymer mold based selective transfer of a AgNW percolation network. The photolithographic mold patterning process allows the heater fabrication to be precise and reproducible. The mesh-patterned AgNW/polymer composite heater exhibited the excellent electrothermal performance of ~46.7 oC at 3 V. This low-voltage operation is highly desirable in practical wearable device applications. Moreover, the AgNW/polymer heater can be stretched up to 20% without significant degradation in electrothermal performance thanks to its open-cell architecture, suggesting that the device can stably transfer heat to the skin after being attached to various body parts with curvilinear surfaces. The experimental results suggest that the mesh-structured AgNW/polymer composite heaters are highly feasible for use as a wearable thermotherapy tool in many emerging applications.

Fatigue-Free Electrodes Enabled Joule Heating Device for Wearable Thermotherapy

Wearable Joule heating devices have received tremendous attention from researchers due to their applications in personal thermal management systems, like thermal management cloth, and healthcare application, such as wearable thermotherapy. Permeability, stretchability, dynamic stability, and conductivity are essential factors for electrothermal heating devices. Wearable devices usually work under cyclic loading of low stain, so fatigue, mechanical failure induced by cyclic loading at low strain level, is a common disease for metal electrodes. Fatigue-free materials are of great importance to ensure robustness for long-term application. Stretchable electrodes, such as noble metal nano mesh, conductive fillers-based elastomer and metal nanowires have been used to fabricate wearable heater. Liquid metal (LM) has also attracted lots of attention due to its high conductivity and fluidity at room temperature. Such fluidity not only makes LM attractive materials for flexible devices, but also render LM fatigue-free attribute. Many manufacturing methods, such as direct ink writing, screen printing and spray coating have been applied to fabricate LM based electrodes for flexible devices. Recently, electrospun technique have also been applied to fabricate LM particles doped polymer fibers, but LM based conductive fiber electrodes have not yet been fabricated using electrospun process. Here, a LM particles embedded fibers network electrode is fabricated using electrospun method, followed by wrapping a polymer layer on the fiber surface. The LM particles embedded in the electrospun fibers form interconnected network, which exhibits excellent electrical conductivity, high mechanical stretchability, and good fatigue performance. Such network electrode could be directly used as a Joule heater, which is permeable, stretchable and fatigue-free. High conductivity of the electrodes ensures low driving voltage for this electrothermal heating devices. High stretchability of the electrode ensures good Joule heating performance at high strain level. In addition, the uniform fibers size could induce large-scale uniform heating. The LM fiber electrodes could be cut into various patterns to fit curvilinear surface of human skin. Also, the ultrathin and compliant nature of the LM fiber electrode enable seamless attachment with human skin, which could ensure high thermal transfer efficiency. The combination of good electrical and mechanical performances of the LM fiber-based Joule heater enable long-term wearable thermotherapy.

Rapid and economic preparation of wearable thermotherapy pad based on simple cut-patterning of metal foil supported by plastic sheets.

Stretchable and skin-mountable heaters have found application in the emerging industry of wearable thermotherapy devices. However, despite their excellent heating performances, most of them commonly suffer from complex, time-consuming, costly, or insufficiently reproducible fabrication processes. In this study, we report a simple, economic, and reproducible strategy to fabricate high-performance stretchable heaters based on facile cut-patterning of plastic sheet/metal foil/plastic sheet (PMP) structures. Further, this method can be executed without expensive materials or cumbersome material synthesis. The fabricated PMP heater is confirmed to exhibit excellent and uniform heating performance at a low voltage and satisfactory electrothermal stability even under high strain and repeated loads. Additionally, the proposed heater designs can be easily customized by simply changing the computer-aided design drawings during the cutting process, which also enables fabrication of devices with large area. The fabricated PMP heater is confirmed to be able to maintain conformal contact with target surfaces even under stretched conditions, inducing a fairly uniform temperature distribution. Finally, it is successfully demonstrated that a PMP heating band can be easily worn on the wrist and is capable of transferring enough heat to increase blood perfusion in the heated area even at a low voltage, highlighting its potential in wearable thermotherapy.

Angled-stencil lithography based metal mesh/Ti3C2Tx MXene hybrid transparent electrodes for low-power and high-performance wearable thermotherapy

Transparent and wearable devices have aroused immense research interest for their widespread applications, however, the fabrication of homogeneous devices is an outstanding challenge to manifest low-power wearable thermotherapy devices.

An Ultrahigh Sensitive Paper-Based Pressure Sensor with Intelligent Thermotherapy for Skin-Integrated Electronics.

Porous microstructure pressure sensors that are highly sensitive, reliable, low-cost, and environment-friendly have aroused wide attention in intelligent biomedical diagnostics, human–machine interactions, and soft robots. Here, an all-tissue-based piezoresistive pressure sensor with ultrahigh sensitivity and reliability based on the bottom interdigitated tissue electrode and the top bridge of a microporous tissue/carbon nanotube composite was proposed. Such pressure sensors exhibited ultrahigh sensitivity (≈1911.4 kPa−1), fast response time (<5 ms), low fatigue of over 2000 loading/unloading cycles, and robust environmental degradability. These enabled sensors can not only monitor the critical physiological signals of the human body but also realize electrothermal conversion at a specific voltage, which enhances the possibility of creating wearable thermotherapy electronics for protecting against rheumatoid arthritis and cervical spondylosis. Furthermore, the sensor successfully transmitted wireless signals to smartphones via Bluetooth, indicating its potential as reliable skin-integrated electronics. This work provides a highly feasible strategy for promoting high-performance wearable thermotherapy electronics for the next-generation artificial skin.

Wafer-scale 2D PtTe2 layers-enabled Kirigami heaters with superior mechanical stretchability and electro-thermal responsiveness

With increasing interests in emergent wearable technologies such as e-skin healthcare devices, it is essential to develop new materials that can satisfy their demanded attributes; e.g., mechanical strain-invariant electrical and thermal properties. In this regard, two-dimensional (2D) transition metal dichalcogenide (TMD) layered materials have received tremendous attention owing to their intrinsic suitability, such as large tolerance limits under mechanical deformation coupled with decent electrical and thermal properties. However, these intrinsic advantages are often compromised upon their large wafer-scale integrations onto deformable substrates, which is commonly observed with conventional liquid-based or mechanical exfoliation approaches. In this paper, we demonstrate high-performance electrically-stretchable heaters by combining 2D platinum ditelluride (PtTe2) layers – a relatively unexplored class of 2D TMDs – with a strain engineering design scheme. We directly grew wafer-scale 2D PtTe2 layers on soft polyimide (PI) substrates by taking advantage of their low growth temperature. We verified their intrinsically low sheet resistance as low as 19.4 Ω/□ (thus, high electrical conductivity), which is superior to most other 2D TMDs. We then explored their Joule heating efficiencies and demonstrated they greatly surpass the performances of previously explored flexible heaters employing state-of-the-art nanomaterials including graphene, silver nanowires (Ag NWs), carbon nanotubes (CNTs) and their hybrids. By employing Kirigami patterning approaches for judicious strain engineering, we developed high-efficiency skin attachable 2D PtTe2 layers-based Kirigami heaters, which exhibited nearly strain-invariant excellent electrical-thermal properties; e.g., voltage-driven reliable heat generation upon a cyclic application/termination of 70% tensile stretch for 1000 times. We believe this study on intrinsically metallic 2D layered material will open up new venues for futuristic high-performance large-scale stretchable electronic applications of wearable thermotherapy, e-textile, and soft actuators.