Local Heating Effect Research Articles

Cluster-coalesced defects induced by gamma irradiation on pulsed laser deposited VO2 thin films

This contribution reports on the radiation tolerance of Vanadium dioxide thin films subjected to different projectile doses of gamma irradiation (3 kGy-100 kGy). Thin films of vanadium dioxide were deposited by pulsed laser deposition method on silicon substrate. Radiation modifications were investigated by studies on the morphology and electrical properties of vanadium dioxide. Gamma irradiation thermally altered the structural morphology of VO2 thin films, inducing defects like ball clusters characterized by the localized heating effect. At higher doses, cluster defects coalesce to large ball structures, consequently decreasing the overall current density of VO2 thin films.

Three-dimensional heating and patterning dynamics of particles in microscale acoustic tweezers.

Acoustic tweezers facilitate a noninvasive, contactless, and label-free method for the precise manipulation of micro objects, including biological cells. Although cells are exposed to mechanical and thermal stress, acoustic tweezers are usually considered as biocompatible. Here, we present a holistic experimental approach to reveal the correlation between acoustic fields, acoustophoretic motion and heating effects of particles induced by an acoustic tweezer setup. The system is based on surface acoustic waves and was characterized by applying laser Doppler vibrometry, astigmatism particle tracking velocimetry and luminescence lifetime imaging. In situ measurements with high spatial and temporal resolution reveal a three-dimensional particle patterning coinciding with the experimentally assisted numerical result of the acoustic radiation force distribution. In addition, a considerable and rapid heating up to 55 °C depending on specific parameters was observed. Although these temperatures may be harmful to living cells, counter-measures can be found as the time scales of patterning and heating are shown to be different.

Experimental and theoretical determination of the role of ions in atomic layer annealing

The use of a heavier noble gas such as Kr in atomic layer annealing results in higher crystallinity due to higher momentum transfer leading to a more localized and intense surface heating effect occurring over picosecond timescales.

Evaluation of the Effects of Local Heating on Springback Behaviour for AHSS Docol 1400 Sheet Metal

Evaluation of the Effects of Local Heating on Springback Behaviour for AHSS Docol 1400 Sheet Metal

Study on mechanical behavior and microstructure evolution of Al-Mg-Li alloy during electropulsing assisted uniaxial tensile

The mechanical behavior and microstructure evolution of Al-Mg-Li alloys under the effect of electric current was investigated using an electropulsing-assisted uniaxial tensile (EAUT) test combined with microstructure observations. It was found that the localized Joule heating-induced microscale high temperature at the grain boundaries in the necking zone significantly accelerated the grain boundary weakening when necking occurred, which resulted in rapid intergranular fracture and relevant decrease in elongation. Electropulsing induced continuous dynamic recrystallization (CDRX) in the both side layers and the discontinuous dynamic recrystallization (DDRX) in the intermediate layers of the Al-Mg-Li sheet during EAUT testing at 460 °C and higher, promoting the formation of newly near-equiaxed recrystallized grains and weakening of β-fiber texture components. For the conventional high temperature tensile test, only a small amount of recrystallized grains formed along the grain boundaries of the coarse parent grains under the control of DDRX. The occurrence of CDRX during EAUT was substantially attributed to the promoted effect of electropulsing on dislocation glide and climb, which resulted from the combined effect of microscale localized Joule heating around dislocations and the electro-induced enhancement effect on vacancy diffusion.

The effect of local passive heating on skeletal muscle histamine concentration: implications for exercise-induced histamine release.

Aerobic exercise induces mast cell degranulation and increases histamine formation by histidine decarboxylase, resulting in an ∼150% increase in intramuscular histamine. The purpose of this study was to determine if the increase in skeletal muscle temperature associated with exercise is sufficient to explain this histamine response. Specifically, we hypothesized that local passive heating that mimics the magnitude and time course of changes in skeletal muscle temperature observed during exercise would result in increased intramuscular histamine concentrations comparable to exercising values. Seven subjects participated in the main study in which pulsed short-wave diathermy was used to passively raise the temperature of the vastus lateralis over 60 min. Heating increased intramuscular temperature from 32.6°C [95% confidence interval (CI) 32.0°C to 33.2°C] to 38.9°C (38.7°C to 39.2°C) (P < 0.05) and increased intramuscular histamine concentration from 2.14 ng/mL (1.92 to 2.36 ng/mL) to 2.97 ng/mL (2.57 to 3.36 ng/mL) (P < 0.05), an increase of 41%. In a follow-up in vitro experiment using human-derived cultured mast cells, heating to comparable temperatures did not activate mast cell degranulation. Therefore, it appears that exercise-associated changes in skeletal muscle temperature are sufficient to generate elevations in intramuscular histamine concentration. However, this thermal effect is most likely due to changes in de novo histamine formation via histidine decarboxylase and not due to degranulation of mast cells. In conclusion, physiologically relevant increases in skeletal muscle temperature explain part, but not all, of the histamine response to aerobic exercise. This thermal effect may be important in generating positive adaptations to exercise training.NEW & NOTEWORTHY The "exercise signal" that triggers histamine release within active skeletal muscle during aerobic exercise is unknown. By mimicking the magnitude and time course of increasing skeletal muscle temperature observed during aerobic exercise, we demonstrate that part of the exercise-induced rise in histamine is explained by a thermal effect, with in vitro experiments suggesting this is most likely via de novo histamine formation. This thermal effect may be important in generating positive adaptations to exercise training.

Serum and plasma brain-derived neurotrophic factor concentration are elevated by systemic but not local passive heating.

Brain-derived neurotrophic factor (BDNF) plays a key role in neuronal adaptations. While previous studies suggest that whole-body heating can elevate circulating BDNF concentration, this is not known for local heating protocols. This study investigated the acute effects of whole-body versus local passive heating on serum and plasma BDNF concentration. Using a water-perfused suit, ten recreationally active males underwent three 90 min experimental protocols: heating of the legs with upper-body cooling (LBH), whole-body heating (WBH) and a control condition (CON). Blood samples were collected before, immediately after and 1 h post-heating for the determination of serum and plasma BDNF concentration, platelet count as well as the BDNF release per platelet. Rectal temperature, cardiac output and femoral artery shear rate were assessed at regular intervals. Serum and plasma BDNF concentration were elevated after WBH (serum: 19.1±5.0 to 25.9±11.3 ng/ml, plasma: 2.74±0.9 to 4.58±2.0; p<0.044), but not LBH (serum: 19.1±4.7 to 22.3±4.8 ng/ml, plasma: 3.25±1.13 to 3.39±0.90 ng/ml; p>0.126), when compared with CON (serum: 18.6±6.4 to 16.8±3.4 ng/ml, plasma: 2.49±0.69 to 2.82±0.89 ng/ml); accompanied by an increase in platelet count (p<0.001). However, there was no change in BDNF content per platelet after either condition (p = 0.392). All physiological measures were elevated to a larger extent after WBH compared with LBH (p<0.001), while shear rate and rectal temperature were higher during LBH than CON (p<0.038). In conclusion, WBH but not LBH acutely elevates circulating BDNF concentration. While these findings further support the use of passive heating to elevate BDNF concentration, a larger increase in shear rate, sympathetic activity and/or rectal temperature than found after LBH appears needed to induce an acute BDNF response by passive heating.

Ag decorated CeO2-x nanojunctions with plasmon-enhanced catalytic performance for mono/multi-color switching

Oxide semiconductor nanoparticles (such as TiO2-x, SnO2-x, CeO2-x) with high concentrations of oxygen vacancies play a crucial photocatalytic role in photoreversible color switching systems (PCSSs), but some problems (such as limited photoabsorption and poor carrier separation efficiency) limit their practical applications. To address these issues, with CeO2-x as a model, we reported the construction of metal–semiconductor (Ag-CeO2-x) nanojunctions with plasmon-enhanced catalytic performance for mono/multi-color switching. Ag/CeO2-x nanojunctions were prepared by the solvothermal growth of CeO2-x nanospheres (∼50 nm) and then in-situ decoration with Ag0 nanoparticles (∼6 nm) via NaBH4 reduction. Ag/CeO2-x nanojunctions exhibit high concentration of oxygen vacancies, which results in narrowed bandgap of CeO2-x (Eg = 2.68 eV) and broadened photoabsorption (edge at ∼ 800 nm) compared with CeO2 (Eg = 2.74 eV, ∼650 nm). Simultaneously, Ag0 decoration confers a strong plasmon absorption peak at ∼ 460 nm and a weak/broad photoabsorption tail in visible-near-infrared region (600–1100 nm). Subsequently, by mixing Ag/CeO2-x nanojunctions and different redox dyes, several color switching inks were obtained, and these inks with polymer matrix could be further used to construct rewritable fabrics/papers. Under 435 nm light irradiation, the inks and fabrics/papers exhibit a rapid mono/multi-color switching, resulting from the reduction by photogenerated electrons aided by the plasmon-enhanced photoabsorption and the improved carrier separation. Conversely, 808 nm laser irradiation (in air) triggers the color recovery, due to the plasmonic high localized heating effect. Especially, remote printing/erasure of a broad range of mono/multi-colored images/letters can be performed on the rewritable fabrics/papers. Therefore, Ag/CeO2-x nanojunctions exhibit great potential for rewritable fabrics/papers, and the construction strategy of such metal–semiconductor junctions supplies some insights for the design of novel photocatalysts for color switching.

“Target effect” of pulsed current on the texture evolution behaviour of Ni-based superalloy during electrically-assisted tension

Electrically-assisted manufacturing (EAM) has been proved to be very efficient in homogenizing the alloy with heterogeneous grain distribution due to the local Joule heating effect, which completely differs from the common heat treatment. However, the interaction between pulsed current and texture evolution during deformation have been rarely investigated even though texture is critical for the plastic behaviour of anisotropic material. Here, the effect of pulsed current on texture evolution behaviour has been studied by comparing the evolution behaviours of a Ni-based superalloy under electrically-assisted and quasi-static tension. The result showed that the evolution of easy-to-deform texture into hard one was promoted by the pulsed current, but the further enhancement of the hard-to-deform texture’s intensity was inhibited. This difference could be attributed to the more pronounced local Joule heating effect in the hard-to-deform grain due to larger lattice distance here, and then the softened hard-to-deform grain could rotate itself towards other orientations more easily. This is called “target effect” of pulsed current on the hard-to-deform texture in present work, which further indicates that EAM is effective in the control of homogeneous behaviour of anisotropic materials not only from the microstructure distribution but also from the mechanical property.

Local softening deformation and phase transformation induced by electric current in electrically-assisted micro-compression of Ti–6Al–4V alloy

Electric current induced local softening behaviors were investigated using electrically-assisted micro-compression (EAMC) tests of Ti–6Al–4V alloy in this study. It was found that the flow curves showed a S-shape characteristic at higher current density and larger strain rate, i.e. the local softening dominated by the uneven distribution of Joule heat temperature. Numerical simulations were adopted to analyze the Joule heat temperature and the strain filed distributions in different deformation zones during EAMC. The time functions of the instantaneous strain in the center of softening deformation regions were calculated to contrast the differences between the EAMC and the uniform deformation. It turned out that the plastic strain at the center of the sample was accelerated compared to the rest of the test section during EAMC. Based on the microstructural observations, a α→β→αʹ phase transformation mode was put forward to illustrate the electric current induced phase transformation, in which the “hotspots” effect of local Joule heat was a main driving for the nucleation of new β phase at a relatively low temperature. The proposed local softening deformation method induced by electric current in the fabrication of micro-parts for titanium alloy is possible due to the high heating efficiency for material and controllable temperature field for billet.

Effects of forward-flight speed on plume flow and infrared radiation of IRS-integrating helicopter

To address deeper understandings about the aero-thermal performance of an integrating infrared suppressor under more realistic situations, a numerical investigation is motivated in the current study, concerning the effects of forward-flight speed on exhaust plume flow and infrared radiation of the Infrared Suppressor-integrating (IRS-integrating) helicopter, wherein the forward-flight speed is changed from 0 m/s (hover state) to 100 m/s, while both the engine exhaust parameters and the main-rotor operation parameters remains unchanged during different forward-flight velocities. The results show that the interaction between forward-flight flow and downwash flow alters the exhaust plume development and the internal flow inside the IRS-integrating rear fuselage more complicatedly, tightly dependent on the forward-flight speed. Of particular concern is the situation where the forward-flight flow has nearly the same level as the downwash flow, the hot mixing flow could possibly interacts with the helicopter rear fuselage to play a local heating effect. With the increase of forward-flight speed, the ejection coefficient is generally increased and the average exhaust temperature of mixing flow is decreased, leading to a reduction of the infrared radiation intensity of exhaust plume in 3–5 μm band. However, the influence of forward-flight speed on the overall infrared radiation intensity of IRS-integrating helicopter is conjectured not monotonous due to the complicated interaction between forward-flight flow and downwash flow. Under high-speed forward-flight states, the overall infrared radiation intensity of the IRS-integrating helicopter in 3–5 μm band is reduced with the increase of forward-flight speed. With respect to 3–5 μm band, the forward-flight speed has little effect on the infrared radiation in 8–14 μm band.

Photoemission oscillation in epitaxially grown van der Waals β-In2Se3WS2 heterobilayer bubbles* *Project supported by the National Natural Science Foundation of China (Grant Nos. 51732010 and 51972280), the Natural Science Foundation of Hebei Province, China (Grant No. E2019203233), the Research Program of the College Science & Technology of Hebei Province, China (Grant No. ZD2020121).

Thin films of millimeter-scale continuous monolayer WS2 have been grown on SiO2/Si substrate, followed by the deposition of β-In2Se3 crystals on monolayer WS2 to prepare In2Se3/WS2 van de Waals heterostructures by a two-step chemical vapor deposition (CVD) method. After the growth of In2Se3 at elevated temperatures, high densities of In2Se3/WS2 heterostructure bubbles with monolayer to multilayer β-In2Se3 crystals atop are observed. Fluorescence of the resultant β-In2Se3/WS2 heterostructure is greatly enhanced in intensity upon the formation of bubbles, which are evidenced by the Newton’s rings in optical image owing to constructive and destructive interference. In photoluminescence (PL) mapping images of monolayer β-In2Se3/monolayer WS2 heterobilayer bubble, significant oscillatory behavior of emission intensity is demonstrated due to constructive and destructive interference. However, oscillatory behaviors of peak position are also observed and come from a local heating effect induced by an excitation laser beam. The oscillatory mechanism of PL is further verified by changing the exterior pressure of bubbles placed in a home-made vacuum chamber. In addition, redshifted in peak position and broadening in peak width are observed due to strain effect during decreasing the exterior pressure of bubbles.

Reliable Fabrication of Graphene Nanostructure Based on e-Beam Irradiation of PMMA/Copper Composite Structure.

Graphene nanostructures are widely perceived as a promising material for fundamental components; their high-performance electronic properties offer the potential for the construction of graphene nanoelectronics. Numerous researchers have paid attention to the fabrication of graphene nanostructures, based on both top-down and bottom-up approaches. However, there are still some unavoidable challenges, such as smooth edges, uniform films without folds, and accurate dimension and location control. In this work, a direct writing method was reported for the in-situ preparation of a high-resolution graphene nanostructure of controllable size (the minimum feature size is about 15 nm), which combines the advantages of e-beam lithography and copper-catalyzed growth. By using the Fourier infrared absorption test, we found that the hydrogen and oxygen elements were disappearing due to knock-on displacement and the radiolysis effect. The graphene crystal is also formed via diffusion and the local heating effect between the e-beam and copper substrate, based on the Raman spectra test. This simple process for the in-situ synthesis of graphene nanostructures has many promising potential applications, including offering a way to make nanoelectrodes, NEMS cantilever resonant structures, nanophotonic devices and so on.

Experimental and numerical analysis of the energy performance of building windows with solar NIR-driven plasmonic photothermal effects

Thin films made of metallic nanoparticles can exhibit strong photothermal effects (PPE) on near-infrared light irradiation, paving a way for new designs of spectrally selective building windows for solar infrared modulation that operates without the need to compensate for visible transmittance. More importantly, the surface plasmon-induced light-to-heat conversion creates strong localized heating effects with a much smaller fraction resulting in the heating of the substrate. Incorporating such nanoscale PPE into the design of complex building fenestrations, this research conducted a comprehensive analysis to better understand the PPE-induced heating effect and conductive, convective, and radiative heat exchanges between windowpane surfaces and the surrounding indoor and outdoor environments. The authors first developed and then validated a numerical analysis method to incorporate spectral features, solar spectral irradiance, and nanoscale PPE. Subsequently, using the established numerical method, two-dimensional windowpane temperature profiles and solar heat gains were yielded under different boundary conditions. To understand the energy performance of windows with solar near-infrared-dependent PPE, a series of parametric energy simulations was employed. The results show the photothermal coating can be used as a new energy-efficient retrofit technology for single-pane windows, with heating energy saving 16.2–20.8%, which performs similar to the double pane windows. Notably, these energy savings were not achieved by increasing the thermal insulation via additional layers or insulating materials, but rather by the spectrally selective design of glazing materials and utilization of solar near-infrared energy. This work presents the energy saving mechanism on an architectural scale due to the nanoscale surface plasmon-induced photothermal effect and associated heat gain coefficient enhancement. It also poses a fundamental reference for the future integration of this novel nanoscale phenomenon into the building envelope systems.

Effect of local heating on airflow distribution and the concentration of bacteria-carrying particles in the operating room

The concentration and distribution of bacteria-carrying particles (BCPs) in the operating room have an important influence on surgical site infections (SSIs). Local heating is commonly used during surgery to reduce the incidence of perioperative hypothermia (PH). However, the effects of local heating measures on airflow and BCPs have not been thoroughly studied. In order to study the effect of local heating in the operating room on airflow and BCPs, the experiment was carried out in the standard experimental operating room using Bacillus subtilis, and CFD numerical simulation was carried out using k-ε turbulence model and Lagrange particle tracking model. The distribution of airflow and the concentration of BCPs in the operating room was studied in the four cases of no local heating (case 1), heating pad (case 2), warming blanket (case 3), and both heating pad and warming blanket (case 4). The results showed that local heating reduced the airflow rate above the patient's body, which also led to an increase in the concentration of BCPs. At T = 300 s, the concentration of BCPs above the operating table in Case 2, Case 3, and Case 4 was increased by 600 CFU/m3 and 260 CFU/m3 and 670 CFU/m3, respectively, compared with that without local heating. As time goes on, the increment of the concentration of BCPs caused by local heating decreases. It is recommended to use heating pad to keep patients warm from less influence on the concentration of BCPs and airflow distribution. This study provides a reference for reducing patients' SSIs and provides a basis for insulation methods.

Flow-assisted self-healing of the helical structure in a cholesteric liquid crystal.

We employ nonequilibrium molecular dynamics simulations to investigate the structure and dynamics of a cholesteric liquid crystal confined between atomically corrugated solid walls. By choosing walls normal to the helical axis, we can study systems with an arbitrary cholesteric pitch without exposing the cholesteric helix to a spurious stress. We investigate the effects of local heating and flow and their joint effects. A steady-state laminar Poiseuille flow is initiated by means of an external body force. Flow alone (i.e., without local heating) in a direction normal to the helical axis does not affect the cholesteric pitch. If the liquid crystal is heated in a small region, the cholesteric helix becomes unstable and melts locally. However, if local heating and flow are combined, a nontrivial synergistic effect is observed in that the helical structure recuperates the better, the higher the speed of the flow is.

Localized droplet heating by hydrophobic pins: Influence of pin area and droplet size on heat transfer

Localized heating of hydrophobic droplet is considered and the effects of restricted area heating and droplet size on heat transfer are examined. Samples composing of vertical steel pins located in Perspex holders are designed and manufactured. Sample surfaces are hydrophobized via depositing treated silica nanoparticles by dip coating method. Hydrophobicity of pin and Perspex surfaces are evaluated simultaneously securing uniform wetting state over sample surface. Droplet is heated via pin while creating a localized heating effect on droplet fluid. The experiments are conducted obtaining flow structures in droplet liquid. Simulations are also performed predicting thermal state in droplet liquid during heating while adopting conditions of the experiments. It is found that hydrophobizing of samples results in uniform contact angle (150° ± 2°) over the entire surface having hysteresis of 6° ± 3°. Enlarging pin diameter and droplet size alter flow structures inside droplet; hence, center of circulating structures changes, which modify the ratio of convection over conduction currents at droplet liquid interface. Increasing pin diameter enhances the Nusselt and the Bond numbers, which becomes more apparent as droplet volume increases.

Raman micro-spectroscopic map estimating in vivo precision of tumor ablative effect achieved by photothermal therapy procedure

Photothermal-therapy (PTT) inculcates near-infrared laser guided local heating effect, where high degree of precision is expected, but not well proven to-date. An ex vivo tissue biochemical map with molecular/biochemical response showing the coverage area out of an optimized PTT procedure can reveal precision information. In this work, Raman-microscopic mapping and linear discriminant analysis of spectra of PTT treated and surrounding tissue areas ex vivo are done, revealing three distinct spectral clusters/zones, with minimal overlap between the core treated and adjacent untreated zone. The core treated zone showed intense nucleic-acid, cytochrome/mitochondria and protein damage, an adjacent zone showed lesser degree of damages and far zone showed minimal/no damage. Immunohistochemistry for γH2AX (DNA damage marker protein) in PTT exposed tissue also revealed similar results. Altogether, this study reveals the utility of Raman-microspectroscopy for fine-tuning safety parameters and precision that can be achieved from PTT mediated tumor ablation in preclinical/clinical application.

Light-Fueled Beating Coffee-Ring Deposition for Droplet Evaporative Crystallization.

Condensed deposition favors biochemical analysis, bioassays, and clinical diagnosis, but the existing strategies may suffer from low resolution, inaccurate control, cross-contamination, or miscellaneous apparatus. Herein, we propose a noncontact light strategy to enable the condensed deposition for droplet evaporative crystallization, in which the photothermal effect of a focused infrared laser is employed to induce intense evaporation. Due to the localized heating effect, not only can the droplet evaporative crystallization on the hydrophobic substrate be promoted, but also the resultant intensified Marangoni flow enables the movement of the early-formed crystals, preventing the pinning of the triple-phase contact line. Synergy of the Marangoni flow and nonuniform evaporation makes the solutes tend to accumulate near the focused light beam region, which facilitates the condensed deposition. More importantly, this light strategy not only enables condensed deposition on the hydrophobic surface with low hysteresis, but also works successfully on the hydrophilic substrate with high hysteresis via adjusting input laser power. It is demonstrated that the light strategy proposed in the present study has great potential for relevant applications.

Local laser heating effects in monolayer WS2 probed by photoluminescence

In this article, we report the local heating effects induced by laser irradiation in mechanically exfoliated WS2 monolayers and the characterization of the resulting inhomogeneous temperature field with the technique of photoluminescence spectroscopy. By comparatively measuring the PL spectra of the monolayer WS2 in different contact conditions as well as in air and vacuum, we confirm the existence of remarkable heating in the monolayer due to laser irradiation. In particular, it is found that a specific excitonic emission peak could be used to characterize the inhomogeneous Gaussian-like thermal field and the heat transfer behaviors. Based on the dependence of the excitonic emission energy on temperature, the local temperature induced by laser irradiation may be obtained, i.e., a local temperature up to 213 °C was found at the central region of the irradiated area in vacuum for the excitation power of 450 μW. Such optical method may be applied to the measurement of local heating effects in 2D semiconductors and relevant van der Waals devices.