Localized Resistive Heating Research Articles

Life at high temperature observed in vitro upon laser heating of gold nanoparticles

Thermophiles are microorganisms that thrive at high temperature. Studying them can provide valuable information on how life has adapted to extreme conditions. However, high temperature conditions are difficult to achieve on conventional optical microscopes. Some home-made solutions have been proposed, all based on local resistive electric heating, but no simple commercial solution exists. In this article, we introduce the concept of microscale laser heating over the field of view of a microscope to achieve high temperature for the study of thermophiles, while maintaining the user environment in soft conditions. Microscale heating with moderate laser intensities is achieved using a substrate covered with gold nanoparticles, as biocompatible, efficient light absorbers. The influences of possible microscale fluid convection, cell confinement and centrifugal thermophoretic motion are discussed. The method is demonstrated with two species: (i) Geobacillus stearothermophilus, a motile thermophilic bacterium thriving around 65 °C, which we observed to germinate, grow and swim upon microscale heating and (ii) Sulfolobus shibatae, a hyperthermophilic archaeon living at the optimal temperature of 80 °C. This work opens the path toward simple and safe observation of thermophilic microorganisms using current and accessible microscopy tools.

Research on ablation characteristics of XLPE Cable buffer layer based on electrothermal coupling method

Ablative white spots are often been found on the buffer layer by disassembling high-voltage XLPE fault cables. To study the ablation characteristics of buffer layer, the white spot chemical elements in different positions of the buffer layer were analysed by using Energy Dispersive Spectrometer (EDS), and the conductivity of the white spots buffer layer were measured. The results of EDS showed that the white spots outside the buffer ablation area are the gouache precipitated by itself. The Conductivity measurements results showed that the precipitation of sodium polyacrylate reduces the conductivity of the buffer layerCwhich affected the local resistance heating when the overvoltage happened. Based on the experimental results of conductivity measurement, the electrothermal coupling simulation model of high voltage XLPE cable was established, and the heat generation characteristics of white spots buffer layer were calculated when the high frequency overvoltage happening. The simulation results show that the higher the overvoltage frequency is, the greater the resistance heating is generated and the higher the temperature is caused around the white spots buffer layer, finally it may be ablated by electric heating.

CA-535-02 HIGH POWER SHORT DURATION (HPSD) VERSUS LOWER POWER LONGER DURATION (LPLD) ATRIAL FIBRILLATION ABLATION: A PROSPECTIVE MULTICENTRE RANDOMISED CONTROLLED STUDY. THE HI-LO HEAT STUDY

RF ablation for pulmonary vein isolation (PVI) in AF is associated with risk of esophageal thermal injury (ETI). High power short duration (HPSD) ablation results in preferential local resistive heating over distal conductive heating. HPSD ablation shortens procedural times with no increase in complications. However evidence had been limited by non-randomised studies.

Fabrication of Si protrusions by local melting of a narrow current path on a Si wafer via resistive heating

Si protrusions were fabricated by surface melting and resolidifying of a Si(111) wafer covered with a 100 nm thick molybdenum (Mo) layer, in which a narrow region was generated using a microgrinder. This region results in a narrow current path and thus localized resistive heating, leading to specific melting of the Si in the path. The melted Si flowed away from the path to both sides, which were at temperatures lower than that of the path. Consequently, two Si protrusions ∼400 μm in height capped with Mo silicide precipitates were formed on each side of the burned-out path, as revealed by scanning electron microscopy with energy-dispersive X-ray spectroscopy. The formation mechanism was discussed in terms of the non-uniform temperature, surface tension, interdiffusion, and freezing-point depression of the surface. This study revealed the potential of fabricating an array of self-assembled Si protrusions by resistive heating of narrow paths.

Current-Dependent Dynamics of Bidirectional Self-Folding for Multi-Layer Polymers Using Local Resistive Heating

Abstract The purpose of this paper is to characterize the dynamics and direction of self-folding of pre-strained polystyrene (PSPS) and non-pre-strained styrene (NPS), which results from local shrinkage using a new process of directed self-folding of polymer sheets based on a resistively heated ribbon that is in contact with the sheets. A temperature gradient across the thickness of this shape memory polymer (SMP) sheet induces folding along the line of contact with the heating ribbon. Varying the electric current changes the degree of folding and the extent of local material flow. This method can be used to create practical three-dimensional (3D) structures. Sheets of PSPS and NPS were cut to 10 × 20 mm samples, and their folding angles were plotted with respect to time, as obtained from in situ videography. In addition, the use of polyimide tape (Kapton) was investigated for controlling the direction of self-folding. Results show that folding happens on the opposite side of the sample with respect to the tape, regardless of which side the heating ribbon is on, or whether gravity is opposing the folding direction. The results are quantitatively explained using a viscoelastic finite element model capable of describing bidirectional folds arising from the interplay between viscoelastic relaxation and strain mismatch between polystyrene and polyimide. Given the tunability of fold times and the extent of local material flow, resistive-heat-assisted folding is a promising approach for manufacturing complex 3D lightweight structures by origami engineering.

Microtentacle Actuators Based on Shape Memory Alloy Smart Soft Composite

AbstractRecent advances in miniature robotics have brought promising improvements in performance by leveraging the latest developments in soft materials, new fabrication schemes, and continuum actuation. Such devices can be used for applications that need delicate manipulation such as microsurgery or investigation of small‐scale biological samples. The shape memory effect of certain alloys is one of the promising actuation mechanisms at small scales because of its high work density and simple actuation mechanism. However, for sub‐millimeter devices, it is difficult to achieve complex and large displacement with shape memory alloy actuators because of the limitation in the fabrication process. Herein, a fabrication scheme for miniaturized smart soft composite actuator is proposed by utilizing two‐photon polymerization. The morphing modes are varied by changing the direction of the scaffold lamination. In addition, the actuation is controlled via local resistive heating of a carbon nanotube layer deposited inside of the actuators. The proposed design can generate a 390 µN force and achieve a bending angle up to 80°. Applications of the actuators are demonstrated by grasping small and delicate objects with single and two finger devices.

Direct Integration of Carbon Nanotubes in CMOS, Towards an Industrially Feasible Process: A Review

This article reviews our work on direct integration of carbon nanotubes (CNTs) in MEMS vehicles and shows initial results in realizing direct CNT integration in CMOS. Extraordinary properties of CNTs are fully exploited if they are closely integrated with signal processing electronics. An example device is a CNT-based gas sensor, where CNTs with their huge surface-to-volume ratio act as a very sensitive sensing element, and the CMOS circuits provide the necessary signal processing for a device to give a standardized, calibrated, low-noise output signal. Direct synthesis of CNTs in CMOS will enable wafer-level, low-cost fabrication of CNT-based devices. A major challenge is the 800–1000 °C CNT synthesis temperature requirement, whereas CMOS-compatible temperature is <300 °C. We synthesized CNTs on purpose-designed MEMS microheaters by local resistive heating to avoid over-heating the bulk of the chip. An applied electric field guides the CNTs to grow towards a second electrode to close electric circuits by making a Si-CNT-Si system. The process is fully controlled through electrical parameters, indicating that the process can be automated and scaled up to wafer-level for a low-cost, high-volume industrial manufacturing process. Characterization of the synthesized CNTs reveals that the hottest region (∼900 °C) ensures low-diameter, less dense and high-quality CNTs. Also, our statistical analysis shows that the electric field guiding is diameter-dependent, ensuring that only well-ordered low-diameter CNTs become part of an electric circuit. Through electrical analysis of the CNT-Si contacts, we found that the Si-CNT-Si systems show either near-ohmic or non-linear (Schottky-like) behaviours depending on the Si doping level. We also demonstrated functionalization of the locally grown CNTs. For direct CNT synthesis on CMOS chips, a high thermal gradient around the CNT growth structure is required to maintain CMOS-compatible temperature. Several promising designs of CNT growth structures and their thermomechanical simulations are presented. Partially suspended microheaters provide thermal isolation to avoid heating the active CMOS region, while keeping reliable mechanical stability. In our attempt to direct CNT-CMOS integration, a purpose-designed CMOS chip is manufactured using a standard AMS 350 nm CMOS process. Layout designs and optical characterization of several fabricated CMOS microstructures are presented.

Design and Fabrication of CMOS Microstructures to Locally Synthesize Carbon Nanotubes for Gas Sensing.

Carbon nanotubes (CNTs) can be grown locally on custom-designed CMOS microstructures to use them as a sensing material for manufacturing low-cost gas sensors, where CMOS readout circuits are directly integrated. Such a local CNT synthesis process using thermal chemical vapor deposition (CVD) requires temperatures near 900 °C, which is destructive for CMOS circuits. Therefore, it is necessary to ensure a high thermal gradient around the CNT growth structures to maintain CMOS-compatible temperature (below 300 °C) on the bulk part of the chip, where readout circuits are placed. This paper presents several promising designs of CNT growth microstructures and their thermomechanical analyses (by ANSYS Multiphysics software) to check the feasibility of local CNT synthesis in CMOS. Standard CMOS processes have several conductive interconnecting metal and polysilicon layers, both being suitable to serve as microheaters for local resistive heating to achieve the CNT growth temperature. Most of these microheaters need to be partially or fully suspended to produce the required thermal isolation for CMOS compatibility. Necessary CMOS post-processing steps to realize CNT growth structures are discussed. Layout designs of the microstructures, along with some of the microstructures fabricated in a standard AMS 350 nm CMOS process, are also presented in this paper.

Characterization and modeling of reverse‐bias breakdown in Cu(In,Ga)Se2 photovoltaic devices

AbstractPartial shading of series‐connected thin‐film photovoltaic modules can force shaded cells into reverse bias, which can cause rapid and irreversible power loss and reduce the practical module lifespan. Unfortunately, this is a common occurrence in field‐deployed modules due to the myriad of environmental factors that can result in partial shading. In this work, we identify as‐grown nonuniformities in the Cu(In,Ga)Se2 (CIGS) absorber layers as the points of origin for the damage induced under reverse‐bias conditions. The structure and chemistry associated with inclusions and voids in the CIGS films cause these features to act as resistive heating elements in reverse‐bias conditions. This localized resistive heating provides the energy required to induce thermal runaway breakdown in the CIGS devices, resulting in damage to charge collection and reduced active area of a device. This mechanism is also described with a robust device model to connect the experimental observations with their physical origins.

Electric hot incremental sheet forming of Ti-6Al-4V titanium, AA6061 aluminum, and DC01 steel sheets

Single point incremental forming (SPIF) is an emerging forming process for rapid prototyping and manufacturing of complex components from sheet metals. Recently, the use of electric current for the local resistance heating of the deformation area has attracted much attention in SPIF. In order to further study the electric hot incremental sheet forming (EHISF), in the present research, the effect of utilizing various lubricants on the formability of Ti-6Al-4V, AA6061, and DC01 sheet metals is experimentally investigated by forming a truncated cone under different feed rates, vertical pitches, and electric currents. To this end, the Taguchi design of experiment (DOE) and the analysis of variance (ANOVA) are employed. The results showed that the formability of Ti-6Al-4V and AA6061 sheets can be improved using the EHISF. For both the sheets, the lubricant and the electric current have significant effects on the maximum achievable forming depth. In addition, the formability of the DC01 sheet is highly affected by the lubricant and the feed rate. The results of the DC01 sheet showed that at the considered wall angle, the maximum forming depth in the EHISF does not change, compared to the cold SPIF, but the thickness distribution of the formed part at a higher temperature is more uniform.

Tailored properties of hot stamping steel by resistance heating with local temperature control

Local austenization by local heating temperature control of blanks is one of the methods to obtain hot stamping parts with tailored properties. Resistance heating is a novel heating technology with high efficiency and rapid heating rate. In this paper, a heat transfer model was firstly developed to describe the steady temperature distribution of the blank during resistance heating. Then two resistance heating schemes to achieve tailored properties of hot stamping steel were investigated by experiments. One scheme is local resistance heating by adjusting the electrode position. And the other scheme is resistance heating with middle insulation. The results showed that the developed model could provide adequate accuracy in calculating the blank temperature field. For the local resistance heating, the percentage of high temperature region in heating zone was about 70 %. From the non-heating region to the middle heating region, hardness increased from 200 to 515 HV10. And the length ratio between high and low hardness regions could he controlled by adjusting electrode positions. For the resistance heating with middle insulation, a 340~360 HV10 medium hardness region with the length of 80mm was observed. The total length of transition hardness regions was about 60 mm. In summary, the local resistance heating scheme showed more advantages including shorter transition region and significant hardness difference.

Selective Thermochemical Growth of Hierarchical ZnO Nanowire Branches on Silver Nanowire Backbone Percolation Network Heaters

The development of hydrothermal growth enabled facile growth of ZnO nanowire over a large area at mild environments, yet its usage in actual electronic devices has been restricted due to poor spatial selectivity in the growth and a difficulty in the integration to other components. We introduce a local thermochemical growth of ZnO nanowire branches on Ag nanowire backbone percolation networks by electrical current induced local resistive heating in liquid environment for easy fabrication of metal–semiconductor hierarchical nanowire structure. Through vacuum filtration transfer and laser ablation process, patterned conductive network composed of ZnO nanoparticle functionalized Ag nanowire percolation network was prepared as a conductive network for localized resistive heating. Upon the application of proper bias voltage, highly localized temperature field was generated in the vicinity of the patterned Ag nanowire network heater to induce the selective growth of ZnO nanowire from the Ag nanowire backbone. As the temperature rise is related to the electrical current flow, ZnO nanowire was selectively synthesized at the area subject to the maximum current density, which was defined by the laser ablation technique. It was further confirmed that the characteristics of grown ZnO nanowires could be controlled by changing the growth condition.

Molybdenum Sheet Local Resistance Heating Test Device

Molybdenum Sheet Local Resistance Heating Test Device

Multiscale modeling of localized resistive heating in nanocrystalline metals subjected to electropulsing

Many electrically assisted processes have been reported to induce changes in microstructure and metal plasticity. To understand the physics-based mechanisms behind these interesting phenomena, however, requires an understanding of the interaction between the electric current and heterogeneous microstructure. In this work, multiscale modeling of the electric current flow in a nanocrystalline material is reported. The cellular automata method was used to track the nanoscale grain boundaries in the matrix. Maxwell's electromagnetic equations were solved to obtain the electrical potential distribution at the macro scale. Kirchhoff's circuit equation was solved to obtain the electric current flow at the micro/nano scale. The electric current distribution at two representative locations was investigated. A significant electric current concentration was observed near the grain boundaries, particularly near the triple junctions. This higher localized electric current leads to localized resistive heating near the grain boundaries. The electric current distribution could be used to obtain critical information such as localized resistive heating rate and extra system free energy, which are critical for explaining many interesting phenomena, including microstructure evolution and plasticity enhancement in many electrically assisted processes.

Electrosynthesis of Glycerol Carbonate from Glycerol and Potassium Carbonate on Nickel Electrodes

The growing biodiesel industry leads to an excess production of glycerol by-product which is of low value but costly to store or dispose because glycerol is not suitable as fuel due to its sooty flame while its discharge to water leads to eutrophication. On the other hand, industrial carbon dioxide could be readily captured by scrubbing with potassium hydroxide to form potassium carbonate. With the tightening of greenhouse gas emission standards and the introduction of carbon cap and trade quota, carbon utilization becomes increasingly important both on environment and economic perspective. The combination of glycerol and carbon dioxide, in the form of dissolved carbonate ions, to produce glycerol carbonate would solve both glycerol and carbon dioxide emission problems altogether. In addition, glycerol carbonate is a valuable chemical feedstock in high industrial demand for its widespread use as solvents, surfactants, chemical feedstock and polymer materials. Compared to conventional catalysis, the electrochemical route dramatically reduces heating and pressurization requirement without using noble metal catalysts. The electrochemical synthesis of glycerol carbonate from glycerol and potassium carbonate enables utilizing electrical power to upgrade the glycerol waste into valuable glycerol carbonate while consuming carbon dioxide, under much milder conditions. The electrosynthesis of glycerol carbonate has been performed under ambient temperature and pressure on nickel plate electrodes, using potassium carbonate dissolved in glycerol with varying water dilution. The formation of glycerol carbonate was confirmed by both the characteristic peak on Cyclic Voltammetry and the Liquid Chromatography-Mass Spectrometry (LC-MS) analysis. Interestingly, comparison of LC-MS spectra with the analytical standard showed the carbonate insertion into glycerol molecule to be regiospecific, producing exclusively the more common and valuable 5-membered-ring glycerol 1,2 carbonate, instead of 6-membered-ring glycerol 1,3 carbonate. Based on this observation, it was postulated that the reaction occurred by simultaneous attack of 1,2 -OH groups of glycerol, making 1,3 bond formation impossible due to insufficient molecular “arm” length of carbonate species. LC-MS analysis revealed further C=O bond hydrogenation of glycerol 1,2 carbonate to 4-(Hydroxymethyl)-1,3-dioxolan-2-ol and dimerization of glycerol carbonate. The glycerol carbonate hydrogenation was found to be favorable under low current density such that most of glycerol carbonate formed was hydrogenated. The color change from colorless to brown of reaction mixture indicated the electrochemical dehydrogenation of glycerol to acrolein followed by subsequent polymerization to brown polyacrolein as by-product, similar to the color change observed for mixture after intense heating. Under high current density, both the polyacrolein formation and the hydrogen evolution were found to be more prevalent due to a combined effect of electrochemical polarization and local resistive heating, reducing reaction selectivity and energy efficiency. Addition of water is found to be beneficial by reducing heating requirement, resistive loss and side reactions. From the results, the novel electrochemical upgrading of glycerol waste while utilizing carbon dioxide is successfully demonstrated. However, by-product formation and energy efficiency challenges remain to be overcome for economic viability as the future “green” industrial production of valuable glycerol carbonate. While this discovery of the alternative glycerol electrochemical carbonatation has shed some light into the possible reaction mechanism, further mechanistic study is needed for better understanding of the reaction mechanism. Figure 1

Experimental Study on Electroplastic Effect in AISI 316L Austenitic Stainless Steel

Electrically Assisted Manufacturing (EAM) is a recently developed method for materials forming based on the Electro-Plastic Effect (EPE) induced by electric current on the flow properties of the material and enhancing their workability. In this technique, the concept of dislocations/electrons interaction and the localized resistive heating provided by electric current were found to be the main responsible for the observed increase in materials formability. However, the joule heating may hinder the induced EPE, since heat and electricity are contemporarily both present, and separation between these two contributions is mandatory to better understand the solely effect of electricity on plastic flow. The present experimental work on an AISI 316L austenitic stainless steel is aimed to study EPE by separating the effects of current from those of heating during EAM uniaxial tensile test, in order to ascribe the relative contributions.

Ultrafast dynamics of near-field enhancements at an off-resonance nano-dimer via femtosecond laser excitations

Giant electric-field enhancements localized on nano-antennas are important for the optical near-field applications in fields such as super-resolution imaging, near-field optical tweezers, and photothermal therapy. Physically, the field enhancement requires plasmon resonance with respect to structure matching. We report a tunable near-field effect, including localized electric-field enhancement and resistive heating at an off-resonance Au nano-sphere dimer via femtosecond laser irradiation. The near field was strongly modified (up to 81 times) with respect to time evolution at a laser fluence of . The results are explained as thermal dynamics manipulation of the Au nano-sphere dimer plasmon resonances. This study provides a new alternative route to tailoring the near-field enhancement for wide applications in nano-antennas.

Direct observation of resistive heating at graphene wrinkles and grain boundaries

We directly measure the nanometer-scale temperature rise at wrinkles and grain boundaries (GBs) in functioning graphene devices by scanning Joule expansion microscopy with ∼50 nm spatial and ∼0.2 K temperature resolution. We observe a small temperature increase at select wrinkles and a large (∼100 K) temperature increase at GBs between coalesced hexagonal grains. Comparisons of measurements with device simulations estimate the GB resistivity (8–150 Ω μm) among the lowest reported for graphene grown by chemical vapor deposition. An analytical model is developed, showing that GBs can experience highly localized resistive heating and temperature rise, most likely affecting the reliability of graphene devices. Our studies provide an unprecedented view of thermal effects surrounding nanoscale defects in nanomaterials such as graphene.

Hot Stamping Parts with Tailored Properties by Local Resistance Heating

Hot stamping parts, such as B-pillar, crash beams and bumpers, with the tailored mechanical properties, fulfil the requirements of anti-collision properties of the vehicle. In this work, a resistance heating system was developed in terms of Joule's Law. Local resistance heating was proposed to achieve the tailored mechanical properties of hot stamping parts by adjusting temperature distribution of the heated blank. The results indicated that the tailored temperature distribution of the blank was realized and the temperature field of the blank could be divided into three regions: high temperature, transition and unheated region. The Vickers hardness of high temperature region varied from 470 HV10 to 500 HV10. While for transition region, it ranged from 160 HV10 to 470 HV10, and that of the unheated region was 160±5 HV10. It demonstrated that the blank with tailed properties was obtained.

Electrically assisted blanking using the electroplasticity of ultra-high strength metal alloys

The electroplastic tensile behavior of ultra-high strength steels (UHSS) subject to a single pulse of electric current is briefly introduced, and electrically-assisted (EA) blanking, which utilizes this electroplastic characteristic, is suggested. The experimental result shows that the blanking load of EA blanking is clearly lower than that of blanking with local resistance heating, which is lower than that of cold blanking. No significant change in material properties was observed in the EA blanked parts at the electric energy densities selected in the present study. EA blanking or trimming is expected to minimize or even eliminate the need for expensive and time-consuming laser trimming in the manufacture of automotive parts using UHSS.