Flexible Heater Research Articles

A High-Performance and Flexible Electrothermal Heater with Bending Tolerance from Layer-by-Layer Self-Assembled Graphite Nanoplates and Carbon Black on Paper

A High-Performance and Flexible Electrothermal Heater with Bending Tolerance from Layer-by-Layer Self-Assembled Graphite Nanoplates and Carbon Black on Paper

Polyethylenimine-Supported rGO Conformal Coating over AgNWs to Fabricate Strongly Stable and Flexible Transparent Heaters

Polyethylenimine-Supported rGO Conformal Coating over AgNWs to Fabricate Strongly Stable and Flexible Transparent Heaters

Low-temperature fabrication of high-performance AZO/Ag/WO3 multilayer films for flexible heaters

Low-temperature fabrication of high-performance AZO/Ag/WO3 multilayer films for flexible heaters

Color tunable photo-thermochromic elastic fiber for flexible wearable heater

Color tunable photo-thermochromic elastic fiber for flexible wearable heater

SWCNT/PEDOT:PSS/TPU electrothermal composites for flexible, wearable heater under low temperature environmental conditions

This study developed a composite heater incorporating single-walled carbon nanotube (SWCNT), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and thermoplastic polyurethane (TPU). Heaters were fabricated by adjusting the SWCNT weight percentage relative to TPU from 1 wt% to 9 wt%, based on the optimal PEDOT:PSS/SWCNT ratio for achieving the lowest sheet resistance. These membranes were assessed via scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy and their electrical, mechanical, and thermal properties were characterized. The 9 wt% composite heater, which demonstrated a maximum Joule heating performance of 130 °C at 3 V, was examined in detail. The suitability of this heater for wearable and deicing devices was confirmed. These findings highlight the potential of flexible and wearable composite heaters in low temperature environments.

Lightweight 3D-printed heaters: design and applicative versatility

This paper proposes a new strategy for designing a 3D-printed heater that can overcome some criticalities of current commercial heater devices for application in the transport and energy sectors. A semiconductive nanocomposite material, acrylonitrile-butadiene-styrene filled with carbon nanotubes (ABS-CNT), was processed via Fused Filaments Fabrication (FFF). The printing was set to favor the current flow along the printing direction, consequently increasing the material's electrical conductivity. 3D-printed heater geometry, equivalent to several electrical resistances (resistive branches) connected in parallel, was optimized by varying the width, thickness, lengths, and number of branches. The adopted approach resulted in a flexible and scalable low-equivalent resistance value heater. Moreover, the optimized heater's flexibility allows it to be integrated into a curved fiberglass composite. Joule heating tests were experimentally performed and theoretically simulated by a multi-physics model. The numerical prediction resulted in good agreement with the experimental data. The results encourage the application of 3D-printed heaters as functional patches for the thermal management of different devices/components, including complex-shape composite structures.

Optimizing Lasing Parameters for Fabricating an Efficient Flexible Electrothermal Heater Based on Laser-Induced Graphene

This work involved fabrication of an efficient thin film heater from 100 μm thick polyimide (PI) sheet by scribing it using a carbon dioxide lasing machine through optimizing laser power (P), scanning speed (SS), and pulses per inch (PPI). A 15 mm × 15 mm square pattern was designed using CorelDRAW software and scribed in a rastering mode on top of PI with the help of Universal Control Panel (UCP) software of the laser machine. Laser power of 8 %, SS of 4 % and PPI of 1000 were obtained as optimal parameters for producing laser induced graphene (LIG). This LIG exhibited a low sheet resistance of approximately 16.64 Ω/sq and was thermally stable on the PI substrate even after 30 cycles of repeated heating and cooling. The LIG was found to be highly porous with the aid of scanning electron microscope (SEM) and its structure was crystalline from XRD patterns. FTIR was conducted and showed disappearance of functional groups in PI after treatment with the laser beam. Our developed LIG heater showed great electrothermal performance with maximum temperature of approximately 288.7 °C, rate of temperature rise of 107.06 °Cs-1, and time of 1.85 s to reach 63 % of temperature difference at a low input voltage of 6 V with homogeneous temperature distribution seen in the thermal images taken using FLIR camera. This LIG heating element can be placed in confined spaces because of its flexibility, thinness, and lightness. Additionally, its efficient joule heating effect attracts many applications such as seat warmers, anti-fogging equipment, food shelf displays, etc.

Fabrication of assembled and welded Ag/W nanowire composite networks as electrodes for body motion monitoring and flexible heaters

Fabrication of assembled and welded Ag/W nanowire composite networks as electrodes for body motion monitoring and flexible heaters

Designing self-cleaning & flexible multifunctional wearable heater

Wearable fabric heater has aroused wide concern in personalized temperature regulation. However, it is still challenging to develop multifunctional wearable heater with multimodal & fast thermal response, good flexibility, strong abrasion, excellent washability, good antibacterial performance, and recyclability. To accomplish these properties, a self-cleaning & flexible multifunctional wearable heater is designed by spraying mixture of Ti3C2Tx MXene/ZnO composite and PDMS on cotton fabric (CF-MZP). The designed CF-MZP fabric heater shows high photothermal/electrothermal/synergistic conversion properties and fast thermal response (just 30 s). Furthermore, the CF-MZP fabric possesses excellent superhydrophobic and self-cleaning properties that endow the heater with strong abrasion, excellent washability, and good antibacterial performance. Interestingly, the CF-MZP heater also exhibits good breathability, durability and flexible performance, which is demonstrated as a flexible wearable heater attached to knuckle position of a human body, showing steady temperature of around 50.9 °C at a voltage of 3 V or about 80.5 °C upon NIR lamp (0.2 W cm-2) irradiation, either relaxed and bending (90° or 180°) states. Furthermore, the CF-MZP heater can be recycled by separating ordinary oil-water mixture and high viscous heavy oil. Consequently, the designed CF-MZP fabrics provide a good perspective application in self-cleaning, recycled, and flexible wearable heaters.

Highly Stable, Bending-Tolerant, and Sustainable Flexible Heater through a Scalable Papermaking Procedure.

Flexible electrothermal heaters have attracted abundant attention in recent years due to their wide applications, but their preparation with high efficiency remains a challenge. Here in this work, a highly stable and bending-tolerant flexible heater was fabricated with graphite nanosheets and cellulose fibers through a scalable papermaking procedure. Its electrothermal property can be enhanced by a hot-pressing treatment and introduction of cationic polyacrylamide (CPAM) during the papermaking protocol. The flexible heater may quickly reach its maximum temperature of 239.8 °C in around 1 min at a voltage of 9 V. The power density was up to 375.3 °C cm2 w-1. It appeared to have a high tolerance for bending deformation with various curvatures, and the temperature remained stable even under 100 bending with frequency of around 0.17 Hz. Over 100 alternatively heating and cooling cycles, it worked stably as well. It was proved to be used as wearable heating equipment, soft heaters, and aircraft deicing devices, suggesting its great prospect in the field of heat management.

Cohesively improved conductivity, transparency, and stability of Ag NW flexible transparent conductive thin films by covering Al2O3 layer

Developing feasible Ag nanowire (NW) transparent conductive thin films (TCFs) with good conductivity, transparency, mechanical durability, strong adhesion, and high stability is a great challenge. Herein, novel TCFs composed of Ag NWs/Al2O3 on polyethylene terephthalate (PET) substrates with synchronously improved conductivity, transparency, mechanical durability, adhesion, and stability, are prepared. The corresponding values (before coating Al2O3: 13.0 Ω/sq. at 86.1 %, after coating Al2O3: 11.7 Ω/sq. at 87.7 %) indicate that the deposition of Al2O3 enhances the transparency and conductivity of Ag NW networks. Moreover, the resistance does not change significantly after 50 taping cycles and 2000 bending cycles with a bending radius of 5.0 mm, indicating the strong adhesion and good mechanical flexibility of Al2O3/Ag NWs composites. In addition, Al2O3/Ag NWs composites possess excellent stability to resist strong oxidizing, hot and humid environments. As a proof of concept, the flexible transparent heater prepared by Al2O3/Ag NWs composites is successfully demonstrated, verifying the practicability.

Shape memory polymer composite hinges for solar sails

Smart hinges for self-deployable solar sails have been prototyped by using shape memory polymer composites (SMPCs). During hinge lamination, a shape memory (SM) epoxy resin is deposited between carbon fiber reinforced (CFR) plies, and consolidation is obtained by an out-of-autoclave (OOA) process. The smart hinges have been assembled with CFR booms to prototype a small self-deployable square sail. Polymeric supports, made by fused deposition modelling (FDM), have been added for correct assembly and to drive the recovery of the SMPC hinges. Flexible heaters have been used as heating elements for SMPC hinge activation. The sail consisted of a polyimide membrane which was connected with the composite booms by flexible joints. The solar sail prototype size has been limited to 260 × 260 mm2 for on-Earth testing, with 4 hinges at the middle length of the composite booms. Recovery tests have shown the ability of the smart hinges to overcome the sail weight and additional friction forces, and the small sail has been successfully deployed in laboratory. Full recovery has been achieved in less than 3 min under different configurations.

One stone for four birds: Multifunctional MXene-coated PET fabric with favorable photothermal, antibacterial, flame retardant, and EMI shielding properties

Polyethylene terephthalate (PET) woven fabrics are gradually becoming the main substrate for breathable multifunctional wearable electronic textiles owing to their lightweight, high strength, good chemical resistance, and low cost. The coating process of MXene was modeled and optimized by the response surface methodology (RSM). Simultaneous effects of cycles and time on the performance of MXene-coated PET fabric were studied. Noticeably, the optimized flexible, breathable, and washable PET heater with the RSM approach exhibited exceptional multifunctional performances with a low loading amount and maintained its inherent properties. The lightweight wearable heater demonstrated superior electrical conductivity and excellent photothermal properties with a wide temperature range. Furthermore, the excellent relative electromagnetic shielding (up to 59.5 dB/mm in X-band) and antibacterial activity of the multifunctional heater against Escherichia coli (E. Coli) within a short time of 20 min reached over 98% without the addition of disinfecting agents. More significantly, MXene created the flame retardancy of PET fabrics and anti-dripping performance, representing safety in service. These multifunctional wearable MXene-based heaters are outstanding candidates for heating management and health protection in the future with high sensitivity, fast response, easy processability, and suitable durability.

Comparative Analysis of Peltier Devices and Flexible Heater Strips for Enhancing Bandwidth in Thermo-Active Soft Actuators

Soft actuators are a new generation of robotic actuators designed for safer and more adaptable physical human-robot interaction, that can be triggered by various stimulating mechanisms, including pneumatic, electric, electromagnetic, light, magnetic, and thermal sources. Among the different types of soft actuators, thermoresponsive ones that utilize heat as the stimulus show great potential due to their ability to deliver a relatively high force-to-size ratio without the need for external air pumps, tethers, high voltage sources, or complex designs. However, a major drawback of such actuators is their limited bandwidth. Traditional methods rely on Joule heating for actuation, with the actuator deflating when the heat source is turned off and ambient temperature takes over. Recently, the Peltier mechanism has been introduced as an alternative approach for active heating and cooling. This research paper presents a comparative analysis of the Peltier and flexible heater mechanisms in terms of the bandwidth and energy consumption of phase-change thermo-active soft actuators. The study aims to assess the potential of Peltier-based actuation in addressing the bandwidth limitations observed in traditional soft actuators. The findings reveal that Peltier-based actuation can significantly improve actuation speed in thermoresponsive soft actuators. However, it is important to note that the performance of Peltier-based actuators decreases after a few cycles unless additional measures, such as the use of an external fan, are implemented. This increase in performance comes at the cost of higher energy consumption, which should be carefully considered in practical applications.

Inkjet-printed heater on flexible substrates for low voltage applications

Flexible heaters (FHs) have applications ranging from defoggers to flexural warmers, food processors, and thermotherapy. Printed FHs are particularly of interest as they offer unique advantages like high resolution, customization, low cost, and ease of fabrication. Here, we report printed FHs on polyethylene terephthalate substrate. The heater design is optimized to operate on a low voltage of five volts and yield high temperatures with a uniform temperature distribution across the surface. The heater has a fast response time of 15 s to reach its maximum temperature and does not show any degradation in performance after three months of operation. The heater maintains its temperature after continuous use for two hours and exhibits a minimum change in temperature upon bending. We have also developed and tested designs for zone heaters and nano heaters, where zone heater is suited for applications requiring heating in specified locations on a surface only. Whereas nano heater has an area of 1 mm2 and can produce high temperatures in this small area. Finally, we developed similar printed heaters on paper and polyimide (PI) substrates as well. Paper-based heater can achieve a temperature of 210 °C and can be used in disposable applications due to its low cost, whereas PI heater can achieve a temperature of 380 °C and is suitable for attaining high temperatures. These results manifest the use of FHs for various practical applications.

Оптимизация эксплуатации газобаллонного оборудования технологического транспорта АК «АЛРОСА», использующего компримированный природный газ в качестве моторного топлива в условиях Якутии

The paper justifies the relevance of using compressed natural gas as the motor fuel for utility vehicles in conditions of the high north and the Republic of Yakutia. Natural gas as an alternative energy carrier is stated to have a number of advantages over diesel fuel, however, its use in extremely low temperatures, in particular, in Yakutia, is associated with some challenges. A number of technical solutions are proposed to maintain a constant temperature of compressed natural gas contained in the gas cylinders onboard of the utility vehicles. The paper provides a detailed description of the methods to maintain the required temperature of the compressed natural gas in the gas cylinders using heat from the exhaust gases of the combustion engine, as well as by means of flexible electric strip heaters. One of the possible ways to separate heavy hydrocarbons (C5-C7) that negatively affect the performance characteristics of the combustion engines and the operation efficiency of the gas cylinder equipment is described for production of the compressed natural gas for utility vehicles. Technical requirements are determined for rubber products of the gas cylinder equipment that operate at low ambient temperatures. The article suggests the optimal quality characteristics of the frost-resistant rubbers and sealing materials that are most suitable for application in conditions of Yakutia.

Hybrid Transfer Printing of Liquid Metals and Allied Inks for Rapid Fabrication of Multifunctional Soft Electronics.

The newly emerging liquid metal flexible electronics are gaining increasing applications over the world due to their outstanding adaptability and printability. Here, we proposed a generalized purpose thermo-activated hybrid transfer printing method for the rapid fabrication of multifunctional soft electronics, which can significantly reduce the difficulty facing existing technologies. This printing involves two delivery and deposition processes of liquid metals and the allied inks (toners) based on their adhesion selection mechanisms. Through developing office supplies, the laser printer could directly print toner masks on soft substrates, such as polydimethylsiloxane film. The heating plate was applied to remove the toner sacrificial mask after rolling liquid metal inks, resulting in retaining the liquid metal circuits on the target substrate. For illustration, diverse materials and inks are adapted to the strategy of constructing flexible electronics. Particularly, colorful circuits, flexible heaters, transparent circuitry, and soft programmable light-emitting diode array displays with multilayer circuits have been fabricated and tested. This general and easily accessible method allows for the rapid acquisition of user-designed soft electronics and is expected to promote the widespread use of flexible electronics in e-skin, sensing, displays, etc.

Stretchable and Transparent Heaters Based on Hydrophobic Ionogels with Superior Moisture Insensitivity.

Flexible and stretchable transparent heaters (THs) have been widely used in various applications, including deicing and defogging of flexible screens as well as thermotherapy pads. Ionic THs based on ionogels have emerged as a promising alternative to conventional electronic THs due to their unique advantages in terms of transparency-conductance conflict, uniform heating, and interfacial adhesion. However, the commonly used hydrophilic ionogels inevitably introduce a moisture-sensitive issue. In this work, we present a stretchable and transparent hydrophobic ionogel-based heater that utilizes ionic current-induced Joule heating under high-frequency alternating current. This ionogel-based TH exhibits exceptional multifunctional properties with low hysteresis, a fracture strain of 840%, transmittance of 93%, conductivity of 0.062 S m-1, temperature resistance up to 165 °C, voltage resistance up to 120 V, heating rate of 0.1 °C s-1, steady-state temperature at 115 °C, and uniform heating even when bent or stretched (up to 200%). Furthermore, it maintains its heating performance when it is directly exposed to water. This hydrophobic ionogel-based TH expands the range of materials available for ionic THs and paves the way for their practical applications.

The Macromolecular Design of Poly(styrene-isoprene-styrene) (SIS) Copolymers Defines their Performance in Flexible Electrothermal Composite Heaters.

Electric cars are desirable for their environmental and economic benefits yet face limitations in range in cold weather due to the increased energy demands for cabin heating. To provide efficient heating for vehicles, flexible composite electrothermal heaters offer a viable solution owing to their lightweight design, efficiency, and adaptability for use within and beyond vehicle interiors. The current study aims to improve electrothermal heater stability and performance by understanding the impact of the polymer structure on composite properties. We explore how the presence and molecular structure of olefinic bonds within the polyisoprene block of styrenic triblock copolymers affect thermal stability and performance. Composite electrothermal heaters were fabricated by dispersing carbon black (CB) as the heating material in three triblock copolymer matrices, poly(styrene-1,4-isoprene-styrene) (1,4-SIS), poly(styrene-3,4-isoprene-styrene) (3,4-SIS), and its hydrogenated version poly(styrene-ethylene-propylene-styrene) (SEPS). The chemical structure and thermal properties of each copolymer were linked to electrothermal performance measurements of composite heaters to establish structure-function relationships. Notably, 3,4-SIS with 28 wt % CB demonstrated the highest thermal and electrical conductivity, resulting in uniform heat distribution. The outcomes unambiguously demonstrate that the olefinic structure of SIS copolymers enhances the electric and thermal conductivity, leading to enhanced electrothermal performance of prototype heaters compared to that of the hydrogenated copolymer.

Flexible Grid Graphene Electrothermal Films for Real-Time Monitoring Applications.

Flexible electrothermal films are crucial for protecting equipment and systems in cold weather, such as ice blockages in natural gas pipelines and icing on aircraft wings. Therefore, a flexible electric heater is one of the essential devices in industrial operations. One of the main challenges is to develop flexible electrothermal films with low operating voltage, high steady-state temperature, and good mechanical stability. In this study, a flexible electrothermal film based on graphene-patterned structures was manufactured by combining the laser induction method and the transfer printing process. The grid structure design provides accurate real-time monitoring for the application of electrothermal films and shows potential in solving problems related to deicing and clearing ice blockages in pipelines. The flexible electrothermal film can reach a high heating temperature of 165 °C at 15 V and exhibits sufficient heating stability. By employing a simple and efficient method to create a flexible, high-performance electrothermal film, we provide a reliable solution for deicing and monitoring applications.