Array Heat Research Articles

Stretchable, transparent and multifunctional PVC-gel heater: a novel approach to skin-mountable, wearable thermal devices

Electric heaters based on functional materials and innovative designs have been developed for various applications. In this paper, we propose a soft dielectric heater (SDH) using polyvinyl chloride-gel (PVC-gel) as the dielectric heater and hydrogel as stretchable electrodes. Under an AC voltage, the leakage current in the PVC-gel leads to continuous injection and discharge of charges, causing the polarized plasticizers and flexible PVC chains to vibrate and collide, thereby generating heat through dielectric heating. Furthermore, the SDH generates a uniform temperature distribution even under strains up to 400%. Besides, high transmittance over 86% across the visible range renders it suitable for wearable or skin-mountable heaters from an esthetic viewpoint. Its capacitor-like structure achieves a scalable design, enabling extension from a singular cell to a row/column addressable and pixelated array of heaters. The 5 × 5 SDH array can deliver varied thermal information and sensations while maintaining performance even when stretched.

Role of ZnO Capping Layer for Stability in Silver-nanowire-based Functional Heater Arrays

Role of ZnO Capping Layer for Stability in Silver-nanowire-based Functional Heater Arrays

Experimental investigation of microchannel heat sink performance under non-uniform heat load conditions with different flow configurations

Cooling methods for multiple hotspots with high heat flux pose a reliability threat to electronic devices. This study investigates the microchannel-based heat sink performance under various non-uniform heat load conditions for different geometry with three different flow configurations (I, U and Z). An in-house designed Heater Array Unit (HAU) facilitates the generation of both uniform and non-uniform heat loads using a heater power supply. Two different microchannel geometries were employed, namely, microchannel-1 (MC-1) with channel and fin widths of 0.6 mm and 0.33 mm, respectively, and MC-2 with dimensions of 0.64 mm and 0.572 mm. Each microchannel incorporates three manifold configurations (I, U, and Z). Each flow configuration is regulated by flow control valves. Various non-uniform heat load patterns were considered, including streamline, non-streamline, and across-streamline conditions. To assess the thermal performance of the heat sinks the parameters used are thermal resistance (Rth), Nusselt number (Nu), and temperature non-uniformity (Ѱ). Experimental findings indicate that the MC-2 design with an I flow configuration is more suitable for uniform heat load conditions. On the contrary, for some non-uniform heat load cases MC-1 also showed up as a suitable design over MC-2.

Analysis on Heater Array Structure Influence of CRB System through Gasket Injection Flow

Analysis on Heater Array Structure Influence of CRB System through Gasket Injection Flow

Design and performance of an ecosystem‐scale forest soil warming experiment with infrared heater arrays

Abstract How forest ecosystems respond to climate warming will determine forest trajectories over the next 100 years. However, the potential effects of elevated temperature on forests remain unclear, primarily because of the absence of long‐term and large‐size field warming experiments in forests, especially in Asia. Here, we present the design and performance of an ecosystem‐scale warming experiment using infrared (IR) heater arrays in a 60‐year‐old temperate mixed forest at Qingyuan Forest CERN in northeastern China. In paired 108 m2 plots (n = 3), the surface soils were constantly elevated 2°C above control plots with a feedback control system over 4 years (2018–2021). Subsoils down to 60 cm depth were warmed 1.2–2°C. Soil warming did not significantly affect soil moisture either in surface soils or in subsoils. Turn‐off time due to weather extremes (heavy rains, snow) and power outages only accounted for 2.5% of the total warming period. In conclusion, we provide a proof‐of‐principle setup that allows long‐term analysis of forest response to warming temperatures in large‐size field plots. Importantly, our warming experiment demonstrated the feasibility of IR heater arrays for soil warming in tall‐statured forest ecosystems.

Programmable micro-transfer-printing for heterogeneous material integration

Micro-transfer printing is an emerging assembly technique to deterministically transfer ink comprising micro-/nano-objects from a donor substrate to a receiver substrate. This technique has generated increasing interest over the last decade due to its unique capability of integrating diverse heterogeneous materials into various structures and layouts. The growing number of applications enabled by micro-transfer printing includes flexible electronics, sensors, photovoltaics, and micro-LED displays. This work presents a micro-transfer printing approach, which relies on thermally induced adhesion modulation of shape memory polymer materials. An individually addressable micro-fabricated resistive heater array is used to locally deliver the heat for transfer pixel actuation. Selectively transferring chips from a closely packed microchip donor array (pitch: 100 µm, size: 50 × 50 µm2) is demonstrated. The transfer head can be dynamically configured to assemble micro-objects in arbitrary patterns, allowing digital manufacturing, object sorting, or in-line assembly correction of defects. These capabilities, together with the simple and robust structure of the transfer head, can enable high process scalability and flexibility for heterogeneous material integration.

Liquid metal bionic instant self-healing flexible electronics with full recyclability and high reliability

Soft smart electronics with fast self-healing ability, complete recyclability, high reliability have attracted increasing interest. However, flexible electronics are still limited by stability under extreme impact and self-healing speed. Herein, the bio-based α-thioctic acid (TA) and butyl acrylate (BA) recycled copolymer with complete recyclability, excellent self-healing ability, and outstanding adhesion attributed to the abundant hydrogen bonds and disulfide bond was chosen as substrate material. Significantly, the performance of rapid self-healing (5 min, 60 °C) is very similar to the concept of clinic healing by first intention and the bionic idea of suture helping human wound healing. The coupling of mask and plasma treatment was used to enhance the interaction between liquid metal (LM) and substrate in a specific position and further explored the enhancement mechanism. Benefiting the excellent fluidity of liquid metal and the instantaneous bonding of damaged parts, the flexible electronic devices with real-time mechanical and conductivity self-healing performances were fabricated. The Liquid Metal-Bionic Instant Self-Healing Electronic Materials (LM-BISHEM) we developed has many applications in wearable intelligent devices, including bionic electronic skin, human-machine interaction sensor, flexible heater, and soft sensor control array. Based on the materials in this work, a classified closed-loop recycling strategy is proposed to realize the complete recycling of all components.

Lab-on-printed circuit board based water harvesting condensation particle counter for ubiquitous monitoring of airborne ultrafine particles

We have developed a water harvesting condensation particle counter (WHCPC) using lab-on-printed circuit board (PCB) technology. Our method provides an inexpensive, compact, and highly accurate system for the ubiquitous monitoring of airborne ultrafine particles (UFPs). Lab-on-PCB-based WHCPC uses water as the working fluid to monitor harmless UFPs; it does not require water replenishment using a moderated water condensation method. Lab-on-PCB-based WHCPC consists of two main parts, a UFP growth section and a mini-OPC, through which UFPs are grown into micro-sized droplets and the grown droplets are single-counted. The UFP growth section consists of two PCBs and a 3D-printed channel. The heater, temperature sensor, and hydrophilic micropillar array wick, which are essential for the growth of UFPs, are integrated on the PCBs. Simulations were performed to verify the saturated-air generation and water collection in the UFP growth section. The dew points of the inlet and outlet air samples were measured to verify water collection using the moderated water condensation method. Through quantitative experiments using UFPs artificially generated in the laboratory, particles of 9.4 nm could be counted. It was possible to precisely measure the number concentration (2500–270000 N cm−3) over a wide range. In addition, the stability of the proposed system was confirmed through a long-term comparison with the reference CPC in an outdoor environment. The proposed system realized the sensorization of CPC because it could monitor harmless UFPs, with minimal maintenance; the proposed system is also inexpensive and compact.

Quality by design approach for simultaneous determination of original active pharmaceutical ingredient quinabut and its impurities by using HPLC. Message 1

Aim. The aim of study was to develop and validate a simple, highly robust (quality by design (QbD) approach), precise and accurate method using high performance liquid chromatography for the simultaneous determination of original active pharmaceutical ingredient Quinabut and its impurities. Materials and methods. Experiments were performed on a Shimadzu LC-20 Prominence HPLC separation module, equipped with a quaternary gradient pump, temperature controlled column heater, sampler manager and diode array detector and LC-20 Chemstation for data analysis (Shimadzu Corporation, Japan). Same software was used for data acquisition and processing of results. X-Terra RP18 (4.6×150 mm, 5 μm) analytical chromatographic column provided by Waters Corporation (Milford, MA) was used for all optimization experiments. Mobile phase A: acetonitrile R. Mobile phase B: 0.025 M phosphate buffer solution. Samples were chromatographed in gradient mode. Flow rate of the mobile phase: 0.7 mL/min. Column temperature: 40 °С. Detection: at 233 nm wavelength. Injection volume: 50 μl. Results. Screening of the influence of four chromatographic factors on different chromatographic responses was performed as the initial step of analytical method optimization. A randomized fractional factorial experimental design (24–1) of resolution IV with central point was used. Buffer pH, amount of acetonitrile in mobile phase A, the amount of phosphate buffer solution in mobile phase B and column temperature were selected as factors of interest, and were used to generate the fractional factorial experimental design. Linearity was established in the range of LOQ level to 0.2% having regression coefficients 0.9977. Calibration curve – y = 0.0132 + 0.9902. Since Δt for the content of quinabut is less than max δ, the technique is stable over time. The possibility of contamination of the sample by decomposition products by keeping it under stressful conditions (irradiation of the substance solution with UV light (UV irradiation with mercury lamp light); acid hydrolysis with 0.1 M hydrochloric acid solution; oxidative decomposition) was investigated. As a result of the irradiation with UV light, the impurity peaks for about 8.74 min (impurity C) and 12.68 min (impurity B) are additionally revealed. Their content exceeds the limits of normalization and is 0.6% and 3.7%, respectively. Therefore, the powder of the substance and its solutions should be stored away from direct sunlight. The column temperature and the speed of the mobile phase within ± 10% did not significantly affect the test results. The results were found to be within the assay variability limits during the entire process. Conclusion. 1) The optimization of a new analytical method capable of simultaneous determination of quinabut assay and its impurities drug products was performed with a single fractional factorial experimental design. Only 11 experiments were needed for the optimization, while at least 16 experiments would be needed to cover the same analytical method operational region of the first optimization step with a traditional one factor at time (OFAT) approach. 2) HPLC method was developed and validated for the simultaneous detection and quantitation of quinabut and its impurities. 3) The final analytical method optimized with QbD approach was validated according to ICHQ2R1 guideline. The method proved to be sensitive, selective, precise, linear, accurate and stability-indicating. 4) The method was successfully applied to the analysis of demonstrating acceptable precision and adequate sensitivity for the detection and quantitation of quinabut and its impurities. So it may be reasonable to claim that the method can be extended to the analysis of drug formulations and stability samples as well. This optimization reflects in saving of time and resources since one stability study includes hundreds of samples tested during the product’s shelf life.

Can irrigating more frequently mitigate detrimental heat wave effects on perennial ryegrass growth and persistence?

Heat waves are problematic for grazing livestock systems in regions dependant on temperate (cool-season) pasture species, owing to the often minimal heat tolerance (thermotolerance) of these pastures. A field experiment in north-west Tasmania, Australia, tested the hypothesis irrigating more frequently reduces detrimental heat wave effects on perennial ryegrass (Lolium perenne L.) above-ground growth and short-term persistence (measured via basal frequency). Heat wave conditions were imposed using freestanding infrared heater arrays fitted with a novel control system designed for evaluating heat wave mitigation options. The control system enabled the extent of warming to be regulated, whilst applying an equal infrared flux (heating) to all heated plots. Increasing the frequency of irrigation events suppressed crown temperature (plant-soil interface) elevation under heaters. When irrigation was applied every 2, 5 or 10 days, median crown temperature elevation under heaters equalled 5.5 °C, 6.5 °C and 7.0 °C, respectively. However, detrimental effects of imposed heat wave conditions on perennial ryegrass growth were not mitigated by more frequent irrigation events. This resulted from the small differences in crown temperature elevation between irrigation frequency treatments, combined with supraoptimal crown temperatures occurring <10% of the time during the simulated 10-day heat wave events. The infrequent occurrence of supraoptimal crown temperatures: (i) resulted from mild ambient conditions (mean ambient air temperature, 17.2 °C); and (ii) explains why applied heating only reduced perennial ryegrass growth by 13 kg DM ha−1 day−1 (23%) when heaters were operated, with no residual effect in the accompanying recovery regrowth cycle. Applied heating also had no appreciable effect on perennial ryegrass basal frequency. Under more extreme heat wave conditions, irrigation frequency may have a larger effect on perennial ryegrass tissue temperature and subsequent growth, especially in environments characterised by higher crown temperatures.

Reconfigurable and Latchable Shape‐Morphing Dielectric Elastomers Based on Local Stiffness Modulation

AbstractProgrammable soft materials exhibiting dynamically reconfigurable, reversible, fast, and latchable shape transformation are key for applications ranging from wearable tactile actuators to deployable soft robots. Multimorph soft actuator sheets with high load‐bearing capacity are reported, capable of bending on multiple axis, made by combining a single dielectric elastomer actuator (DEA) with two layers of shape memory polymers (SMPs) fibers and an array of stretchable heaters. The rigidity of the SMP fibers can be reduced by two orders of magnitude by Joule heating, thus allowing the orientation and location of soft and hard regions to be dynamically defined by addressing the heaters. When the DEA is then actuated, it bends preferentially along the soft axis, enabling the device to morph into multiple distinct configurations. Cooling down the SMPs locks these shape changes into place. A tip deflection angle of over 300° at 5 kV is achieved with a blocking force of over 27 mN. Devices using two antagonistic DEAs are also reported that attain more complex shapes. Multimorphing is demonstrated by gripping objects with different shapes. An analytical model is developed to determine the design parameters that offers the best trade‐off between large actuation and high holding forces.

A Multifunctional Electronic Skin Empowered with Damage Mapping and Autonomic Acceleration of Self‐Healing in Designated Locations

Integrating self-healing capabilities into soft electronic devices and sensors is important for increasing their reliability, longevity, and sustainability. Although some advances in self-healing soft electronics have been made, many challenges have been hindering their integration in digital electronics and their use in real-world conditions. Herein, an electronic skin (e-skin) with high sensing performance toward temperature, pressure, and pH levels-both at ambient and/or in underwater conditions is reported. The e-skin is empowered with a novel self-repair capability that consists of an intrinsic mechanism for efficient self-healing of small-scale damages as well as an extrinsic mechanism for damage mapping and on-demand self-healing of big-scale damages in designated locations. The overall design is based on a multilayered structure that integrates a neuron-like nanostructured network for self-monitoring and damage detection and an array of electrical heaters for selective self-repair. This system has significantly enhanced self-healing capabilities; for example, it can decrease the healing time of microscratches from 24 h to 30 s. The electronic platform lays down the foundation for the development of a new subcategory of self-healing devices in which electronic circuit design is used for self-monitoring, healing, and restoring proper device function.

An integrated smart heating control system based on sandwich-structural textiles

Integrated fabrics with a smart heating control system (HCS) are attractive in warming and thermotherapy for human healthcare management. Metal nanofibers (NFs) networks with high flexibility, conductivity and gas permeability are ideal functional materials for wearable electronics. Herein, a novel sandwich-structural (Ag NFs/fabrics/Pt NFs) textile for a HCS is constructed, where a Ag NF network film was functioned as a wearable heater and Pt NF network arrays were functioned as wearable temperature sensors. Conductivity and mechanical stability of the metal NFs were enhanced by crosslinking the free-standing fiber networks, resulting in high thermo-stability, thermal resistance (163.5 °C W−1 cm2) and temperature sensitivity (0.135% °C−1) of the HCS. The HCS can simultaneously realize heating and temperature distribution detection, demonstrating only 0.57% average error between the simulated resistance-to-temperature diagram of Pt NF arrays and actual temperature mapping. In addition, the HCS can be stuck on the skin for thermochromic fabrics, real-time heating and temperature detection/control through a Bluetooth device in a smartphone wirelessly.

Thermal state of electronic assemblies equipped with an array of heaters and coolers (HACs) subjected to natural convection

In this study, the thermal state of microelectronic assemblies equipped with an array of heaters and coolers (HACs) subjected to the natural convection is described. According to the intended electronics application, a 3×3 array of distinct heat sources and a 2×2 array of distinct coolers are connected on one perpendicular wall of the rectangular module. The rectangular enclosure is entirely occupied by porous material permeated with a water-Cu nanofluid. The Brinkman and Forchheimer extended Darcy flow model is employed to model the fluid flow within the porous material. 3D Navier-Stokes and energy equations are solved numerically based on the finite volume discretization technique. Thermal state and flow field are analyzed, regarding the wide range of considered parameters namely, the Darcy number, the rectangular module side aspect ratio, the Rayleigh number and the nanoparticles volume fraction. The outcomes expose that the overall Nusselt number intensifies by mixing the Cu powder nanoparticles into the base fluid and with an increase in the Rayleigh number. The heat transfer attains its maximum when the side aspect ratio of the module assumes values between 1.5 and 2. This work helps to improve thermoregulation of electronic assemblies via nanofluid saturated porous media.

Photonic topological phase transition on demand

Abstract On-demand, switchable phase transitions between topologically nontrivial and trivial photonic states are demonstrated. Specifically, it is shown that the integration of a two-dimensional array of coupled ring resonators within a thermal heater array enables unparalleled control over topological protection of photonic modes. Importantly, auxiliary control over a spatial phase modulation opens up a way to guide topologically protected edge modes along generated virtual boundaries. The proposed approach can lead to practical realizations of topological phase transitions in many photonic applications, including topologically protected photonic memory/logic devices, robust optical modulators, and switches.

Experimental investigation of bubble coalescence heat transfer during nucleate pool boiling

This study focuses on analyzing the bubble dynamics during coalescence for nucleate pool boiling and its effects on the heat transfer. The study uses experimental observations and heat flux measurements to characterize the bubble dynamics, fluid flows and thermal effects due to nucleation, coalescence and departure during nucleate pool boiling. The investigations used using various types of microheaters 50–200 µm in size etched on glass substrates to obtain time and space resolved heat transfer measurements. The purpose is to describe the dynamics of the fluid motion as well as the thermal interactions with and without coalescence between growing and departing bubbles. The investigations were performed for various spacings and positions on the heater array with various subcoolings and wall superheats. The experimental investigations illustrate the mechanisms promoting bubble coalescence and the effect of coalescence on the wall heat transfer. The heat flux for boiling with coalescence fluctuated much more than for single bubble boiling due to the vaporization of the liquid layer trapped between the bubbles. In some cases, the heat fluxes during coalescence were as large as during nucleation and departure with some very large heat flux peaks that could lead to damaging thermal stresses in the surface.

Controlled infrared heating of an artic meadow: challenge in the vegetation establishment stage

BackgroundGlobal warming is going to affect both agricultural production and carbon storage in soil worldwide. Given the complexity of the soil-plant-atmosphere continuum, in situ experiments of climate warming are necessary to predict responses of plants and emissions of greenhouse gases (GHG) from soils. Arrays of infrared (IR) heaters have been successfully applied in temperate and tropical agro-ecosystems to produce uniform and large increases in canopy surface temperature across research plots. Because this method had not yet been tested in the Arctic where consequences of global warming on GHG emission are expected to be largest, the objective of this work was to test hexagonal arrays of IR heaters to simulate a homogenous 3 °C warming of the surface, i.e. canopy and visible bare soil, of five 10.5-m2 plots in an Arctic meadow of northern Norway.ResultsOur results show that the IR warming setup was able to simulate quite accurately the target + 3 °C, thereby enabling us to simulate the extension of the growing season. Meadow yield increased under warming but only through the lengthening of the growing season. Our research also suggests that, when investigating agricultural systems on the Arctic, it is important to start the warming after the vegetation is established,. Indeed, differential emergence of meadow plants impaired the homogeneity of the warming with patches of bare soil being up to 9.5 °C warmer than patches of vegetation. This created a pattern of soil crusting, which further induced spatial heterogeneity of the vegetation. However, in the Arctic these conditions are rather rare as the soil exposed by snow melt is often covered by a layer of senescent vegetation which shelters the soil from direct radiation.ConclusionsConsistent continuous warming can be obtained on average with IR systems in an Arctic meadow, but homogenous spatial distribution requires that the warming must start after canopy closure.

Permafrost Degradation and Subsidence Observations during a Controlled Warming Experiment

Global climate change has resulted in a warmer Arctic, with projections indicating accelerated modifications to permafrost in the near future. The thermal, hydrological, and mechanical physics of permafrost thaw have been hypothesized to couple in a complex fashion but data collection efforts to study these feedbacks in the field have been limited. As a result, laboratory and numerical models have largely outpaced field calibration datasets. We present the design, execution, and initial results from the first decameter-scale controlled thawing experiment, targeting coupled thermal/mechanical response, particularly the temporal sequence of surface subsidence relative to permafrost degradation at depth. The warming test was conducted in Fairbanks, AK, and utilized an array of in-ground heaters to induce thaw of a ~11 × 13 × 1.5 m soil volume over 63 days. The 4-D temperature evolution demonstrated that the depth to permafrost lowered 1 m during the experiment. The resulting thaw-induced surface deformation was ~10 cm as observed using a combination of measurement techniques. Surface deformation occurred over a smaller spatial domain than the full thawed volume, suggesting that gradients in cryotexture and ice content were significant. Our experiment provides the first large field calibration dataset for multiphysics thaw models.

Design and Fabrication of an Experimental Microheater Array Powder Sintering Printer

Microheater array powder sintering (MAPS) is a novel additive manufacturing process that uses an array of microheaters to selectively sinter powder particles. MAPS shows great promise as a new method of printing flexible electronics by enabling digital curing of conductive inks on a variety of substrates. For MAPS to work effectively, a microscale air gap needs to be maintained between the heater array and the conductive ink. In this article, we present an experimental MAPS printer with air gap control for printing conductive circuits. First, we discuss design aspects necessary to implement MAPS. An analysis is performed to validate that the design can maintain the desired air gap between the microheaters and the sintering layer, which consists of a silver nanoparticle ink. The printer is tested by printing conductive lines on a flexible plastic substrate with silver nanoparticle ink. Results show MAPS performs on par with or better than the existing fabrication methods for printed electronics in terms of both the print quality (conductivity of the printed line) and print speed, which shows MAPS’ great promise as a competitive new method for digital production of printed electronics.

Nanocrescent Optical Antennas for Ultrafast Photonic PCR

Ultrafast photonic polymerase chain reaction (PCR), which thermal cycling utilizing rapid plasmonic conversion of the light to heat drastically reduced time-consuming thermal cycling step. However, to enable rapid precision medicine in the point-of-care (POC), quantitative and multiplexed realtime PCR is necessary. Here we present a hexagonally packed nanocrescent optical antenna array for realtime ultrafast photonic PCR. We theoretically demonstrated that each nanocrescent antennae have an internal cavity with ∼ 0.1 fL volume and liquid within the cavity is heated up from 25 °C to 95 °C in nanosecond scale. We also experimentally demonstrated that hexagonally packed nanocrescent cavity heater array exhibited fast heating in the macroscale (22.4 ± 3.1 °C). In order to demonstrate real-time PCR on the chip, we integrated hexagonally packed nanocrescent array to the microfluidic chip. We believe that this hexagonally packed nanocrescent optical antenna impact both life science and ultrafast precision molecular diagnostics.