Local Heating Technique Research Articles

Research on Shape-Controllable Localized Heating Method Driven by Digital Microfluidics.

The localized heating technique, which minimizes high-temperature impact on thermally sensitive components and reduces impurity dispersion during encapsulation, has become a focal point in MEMS packaging research. In this study, we propose a method for localized heating at specific positions and shapes. A localized heating device, based on distributed electric field control, is constructed, where a polymer droplet on the lower substrate electrode is driven into a liquid column under the influence of a distributed electric field generated between two parallel substrate electrodes. ITO substrate electrodes with various patterns are fabricated, ensuring the shape of the formed liquid column matches the pattern. Leveraging the principles of heat transfer, the temperature of the polymer droplet is regulated via a heating stage to enable targeted heating of defined shapes and areas. Experiments delve into the impact of driving parameters on heating time and efficiency, with results affirming the proposed method's capability to govern localized heating for particular regions and configurations accurately.

Fluorescence-based thermometry for precise estimation of nanoparticle laser-induced heating in cancerous cells at nanoscale.

Photothermal therapy (PTT) has attracted increasing interest as a complementary method to be used alongside conventional therapies. Despite a great number of studies in this field, only a few have explored how temperatures affect the outcome of the PTT at nanoscale. In this work, we study the necrosis/apoptosis process of cancerous cells that occurs during PTT, using a combination of local laser heating and nanoscale fluorescence thermometry techniques. The temperature distribution within a whole cell was evaluated using fluorescence lifetime imaging microscopy during laser-induced hyperthermia. For this, gold nanorods were utilized as nanoheaters. The local near-infrared laser illumination produces a temperature gradient across the cells, which is precisely measured by nanoscale thermometry. This allows one to optimize the PTT conditions by varying concentration of gold nanorods associated with cells and laser power density. During the PTT procedure, such an approach enables an accurate determination of the percentages of apoptotic and necrotic cells using 2D and 3D models. According to the performed cell experiments, the influence of temperature increase during the PTT on cell death mechanisms has been verified and determined. Our investigations can improve the understanding of the PTT mechanisms and increase its therapeutic efficiency while avoiding any side effects.

Investigation of mid-infrared rapid heating of a carbide-bonded graphene coating and its applications in precision optical molding.

Graphene interacts with electromagnetic waves strongly in a wide range from ultra-violet to far-infrared, making the graphene coating suitable for a variety of applications. In this study, a novel localized rapid heating technique utilizing micro-patterned silicon stampers with carbide-bonded graphene coating, which directly heats up by absorbing mid-infrared light radiation, is implemented in rapid precision optical molding. The graphene network, as a functional coating to obtain thermal energy and improve the anti-adhesion of the mold surface, can heat up the mold surface rapidly (up to 18.16 K/s) and evenly above glass transition temperature over a large area within several seconds. Since the graphene coating was around tens of nanometers (∼45 nm) thick, the rapid precision surface molding process can be shortened into tens of seconds. Furthermore, the thermal response and repeatability of the graphene coated silicon wafer is investigated by repeated thermal cycling. This novel rapid precision surface molding technique is successfully tested to replicate grating structures and periodic patterns from silicon molds to thermoplastic substrates with high accuracy. Compared with conventional methods, this new approach can achieve much higher replication fidelity with a shorter cycle time and lower energy consumption.

Durability Evaluation: Sustainable Semi-flexible Pavement Mixtures

The modern paving industry requires the production of high-performance pavement using more sustainable approaches. Semi-flexible pavement (SFP), prepared by filling an open-graded asphalt skeleton with cement-based grouting material, has been shown to offer high performance for heavily loaded highway and airport pavement applications. The major aim of this study was therefore to evaluate SFP durability based on more sustainable preparation techniques and materials. In this research, a half warm bitumen emulsion semi-flexible mixture (HWBESFM) was designed using local materials and low energy heating technique; the contribution of various sustainable cementitious grout materials on the durability properties of the mix was then evaluated. The developed grouts were prepared using paper sludge ash (PSA) and silica fume (SF) as supplementary cementitious materials (SCM), and the durability of the HWBESFM was assessed with regard to ageing and water sensitivity. The results showed improvements in water sensitivity of HWBESFM containing OPC+PSA and OPC+SF to 66.62% and 65.73%, respectively, compared with the control mix, which demonstrated sensitivity of roughly 55%. Additionally, slight improvements were noticed in ageing resistance on incorporating SCM, those these results remained uncompetitive to traditional SFP mixtures. Overall, this initial investigation of a sustainable approach could, with some improvement, encourage further development and studies in this area.

A Vision-Based Fuzzy Control to Adjust Compression Speed for a Semi-Dieless Bellows-Forming

A novel semi-dieless bellows forming process with a local heating technique and axial compression has been initiated for the past years. However, this technique requires a high difficulty in maintaining the output quality due to its sensitivity to the processing conditions. The product quality mainly depends on not only the temperature distribution in the radial and axial direction but also the compression ratio during the semi-dieless bellows process. A finite element model has clarified that a variety of temperature produced by unstable heating or cooling will promote an unstable bellows formation. An adjustment to the compression speed is adequate to compensate for the effect of the variety of temperatures in the bellows formation. Therefore, it is necessary to apply a real-time process for this process to obtain accurate and precise bellows. In this paper, we are proposing a vision-based fuzzy control to control bellows formation. Since semi-dieless bellows forming is an unsteady and complex deformation process, the application of image processing technology is suitable for sensing the process because of the possible wide analysis area afforded by applying the multi-sectional measuring. A vision sensing algorithm is developed to monitor the bellows height from the captured images. An adaptive fuzzy has been verified to control bellows formation from 5 mm stainless steel tube in to bellows profile up to 7 mm bellows height, processing speed up to 0.66 mm/s. The adaptive fuzzy control system is capable of appropriately adjusting the compression speed by evaluating the bellows formation progress. Appropriate compression speed paths guide bellows formation following deformation references. The results show that the bellows shape accuracy between target and experiment increase become 99.5% under given processing ranges.

Laser Sintering of Abrasive Layers with Inclusions of Cubic Boron Nitride Grains

One of the mainstream technologies for industrial tools manufacturing is the high-speed local heating technique that drastically increases the productivity of tools manufacturing. With further optimization of sintering processes, it is possible to manufacture industrial processing tools with high density and relatively small grain size. The use of a focused laser beam as a heating source also contributes significantly to the increase in productivity of tool manufacturing and broadens the range of bonding materials that could be used to form the Cubic boron nitride (CBN) containing abrasive layers. The research is mainly focused on the irradiation of CBN grains with lasers of two different wavelengths - λ = 1.06 μm and λ = 10.6 μm. Technological parameters of laser processing were as follows: Laser power P – 200 - 700 W, focal spot diameter d – 3 mm, processing speed V – 0.01 - 2.0 m/min. The density of CBN grains was measured before and after laser irradiation using DA-2 measuring unit according to standard procedure. Bronze and Nickel powders (BrО10 and PS-12 N-WC) were used as a bonding material. They were mixed with CBN grains and were applied onto the steel base plates followed by laser irradiation of the prepacked layer. Scanning electron microscopy (SEM) was used to investigate the microstructure of samples along with local and integral X-ray element analysis. Microhardness of irradiated samples was measured as well. The interaction of laser beam and CBN grains was studied in detail and relationships between key technological parameters and quality of composites (grains durability, wear resistance and bonding strength) was established.

Cyclic stress and strain responses of AZ31 magnesium alloy sheet metal at elevated temperatures

Lightweight materials have been widely and increasingly utilized for the automotive industry to reduce the carbon dioxide (CO2) emissions. To replace the existing ordinary steels, the automotive companies have been investigated the other materials to satisfy the specific strength, stiffness and recyclability. Under these circumstances, some researchers have been paying attention to the magnesium alloy sheets. Although the material have low ductility at room temperature due to small number of slip systems, it is the well-known fact that the formability at the elevated temperatures around 200 ºC is drastically improved. In these days, the local heating techniques have been applied to the press forming systems in order to realize the power saving manufacturing systems in spite of the existing systems. Although the warm stamping has some great advantages to improve the formability, the prediction of the deformed sheet metal is not always enough accurate. In order to investigate the stress strain responses for the material at the elevated temperatures, a testing device which can observe the cyclic stress strain responses was developed in the present research. The magnesium alloy sheets were warmed at around 200 ºC to reduce the critical resolved shear stress of slip systems and improved its deformability. The corresponding stress strain responses by finite element method based on the crystal plasticity were calculated. It was found that the calculations could capture the above-mentioned features very well.

Numerical and experimental investigation of plastic injection molding of micro‐engineered surfaces

We carried out experimental and numerical investigations into the effects of injection‐molding parameters on the transcription quality and uniformity of micro‐pillar arrays. For the experiment, we used a precise metallic mold insert, which was shaped like an inverted micro‐pillar array. This was fabricated using UV‐photolithography and a nickel electroforming process. With the mold insert, the effects of the distance from gate and uniformity on the transcription quality could be investigated experimentally by varying the main processing parameters, such as flow rate, polymer melt temperature, and mold wall temperature. The results of the injection molding experiment indicated that increasing the three processing parameters improved the transcription quality of micro‐pillar arrays. In numerical investigation, we used the interpolated domain decomposition method. This was based on 2.5D and 3D simulations, and was used to effectively solve the filling behavior of the polymer melt inside the mold which contains multi‐scale cavities. Numerical results revealed that the transcription quality was significantly affected by the mold wall temperature. Based on the experimental and numerical investigations, the local mold heating (LMH) technique for the high mold wall temperature was employed to enhance the replicability of the micro‐pillar array. The result of injection molding with LMH showed that the transcription quality and uniformity were considerably improved. These numerical and experimental results provide insights into the foundations of the field of injection molding of plastic micro‐engineered surfaces. POLYM. ENG. SCI., 58:E73–E81, 2018. © 2017 Society of Plastics Engineers

Characteristics of joined aluminum foils by local heating technique based on exothermic reaction of Al/Ni multilayer powder materials

Characteristics of joined aluminum foils by local heating technique based on exothermic reaction of Al/Ni multilayer powder materials

Novel localized heating technique on centrifugal microfluidic disc with wireless temperature monitoring system.

Recent advances in the field of centrifugal microfluidic disc suggest the need for electrical interface in the disc to perform active biomedical assays. In this paper, we have demonstrated an active application powered by the energy harvested from the rotation of the centrifugal microfluidic disc. A novel integration of power harvester disc onto centrifugal microfluidic disc to perform localized heating technique is the main idea of our paper. The power harvester disc utilizing electromagnetic induction mechanism generates electrical energy from the rotation of the disc. This contributes to the heat generation by the embedded heater on the localized heating disc. The main characteristic observed in our experiment is the heating pattern in relative to the rotation of the disc. The heating pattern is monitored wirelessly with a digital temperature sensing system also embedded on the disc. Maximum temperature achieved is 82 °C at rotational speed of 2000 RPM. The technique proves to be effective for continuous heating without the need to stop the centrifugal motion of the disc.

Quasi-single mode laser output from a terrace structure added on a Nd(3+)-doped tellurite-glass microsphere prepared using localized laser heating.

A Nd(3+)-doped tellurite-glass terrace microsphere was fabricated, and its laser characteristics using free-space pumping were investigated. A localized laser heating technique was used for preparing the 29-µm-diameter microsphere. The uncoated sphere exhibited many laser lines with 1.3-mW threshold. Fewer laser lines were observed after terrace formation. The terrace microsphere's lasing threshold was 0.6-2.4 mW depending on the pumping position in the terrace. These results indicate that the terrace structure can modify the modes of a microsphere laser and decrease the laser threshold due to an increase in the coupling efficiency between the cavity and free-space beam.

Low threshold lasing of bubble-containing glass microspheres by non-whispering gallery mode excitation over a wide wavelength range

Bubble-containing Nd3+-doped tellurite glass microspheres were fabricated by localized laser heating technique to investigate their optical properties for use as microresonators. Fluorescence and excitation spectra measurements were performed by pumping with a tunable CW-Ti:Sapphire laser. The excitation spectra manifested several sharp peaks due to the conventional whispering gallery mode (WGM) when the pumping laser was irradiated to the edge part of the microsphere. However, when the excitation light was irradiated on the bubble position inside the microsphere, “non-WGM excitation” was induced, giving rise to numerous peaks at a broad wavelength range in the excitation spectra. Thus, efficient excitation was achieved over a wide wavelength range. Lasing threshold excited at the bubble position was much lower than that for the excitation at the edges of the microsphere. The lowest value of the laser threshold was 34 μW for a 4 μm sphere containing a 0.5 μm bubble. Efficiency of the excitation at the bubble position with broadband light was calculated to be 5 times higher than that for the edge of the microsphere. The bubble-containing microsphere enables efficient utilization of broadband light excitation from light-emitting diodes and solar light.

Deformation Behavior of Aluminum Alloy Tube in Semi-Dieless Metal Bellows Forming Process with Local Heating Technique

The metal bellows are used in a large number of industrial applications for their flexile and elastic properties. For the traditional manufacturing methods for metal bellows, the dies and (or) tools are required. It is inconvenient to change the shape of metal bellows and also leads to the high cost. To reduce the manufacturing cost and produce the metal bellows with various shapes, the semi-dieless metal bellows forming process was proposed. The deformation behavior of aluminum alloy tube in semi-dieless bellows forming process was investigated in the study. The effects of compression ratio, heating length on the convolution height, pitch of bellows during the semi-dieless bellows forming process were studied. The results showed that the deformation conditions of semi-dieless forming process have significant influences on the shape of aluminum alloy bellows and deformation behavior of aluminum alloy tube in the forming process. The increase of compression ratio, heating temperature and heating length resulted in the increase of pitch and decrease convolution height of aluminum alloy metal bellows.

Development of dieless metal bellows forming process with local heating technique

In the traditional manufacture methods of metal bellows, such as tube bulging and hydroforming, the dies and tools are generally used. In these methods, it is very inconvenient to change the shapes of bellows because the dies and tools should be changed, which often result in extremely high cost. In this study, a novel manufacture method without any dies and tools for producing the metal bellows with various shapes was proposed. This novel method is called as dieless bellows forming process with local heating technique. The factors which affect the shape of metal bellows and the deformation behavior of metal tubes during the dieless metal bellows forming process were investigated by experiment and finite element method simulation in this study. The metal tubes (SUS304, JIS) with the dimensions of 13.8 (D)×2 (t) mm and 25 (D)×2 (t) mm were used to study the availability of the newly proposed method for manufacturing the metal bellows with different tubular materials. As a result, the metal bellows with good shapes were successfully obtained using the newly proposed method. The results also showed that the shape of the metal bellows can be easily changed by adjusting the compression ratio. It was clarified that the deformation parameters, such as compression ratio and heating length, have the significant effects on the convolution height, pitch and deformation behavior of metal tube during dieless metal bellows forming process. The suitable parameters should be chosen to manufacture the metal bellows with the expected shape.

Real-Time Monitoring System of Dieless Bellows Forming Using Machine Vision

Dieless bellows forming using local heating technique is an advanced flexible forming technology to produce bellows from straight tube without the use of dies. The deformation is induced by applying continuous compression, and local heating. Advantages of these processes are the absence of dies, applicability for various materials, suitability for flexible forming process including low batch production, flexibility on workpiece sizes and output geometries. However, the implementation of these processes is still low owing to the low quality, reproducibility, and production speed. The limitation of these dieless forming processes using local heating is caused by the absence of dies required to form the desired profile. Therefore deformation depends on temperature, length of heating zone, processing speed, speed ratio of feeding to fabrication speeds. In order to enhance the product quality in these dieless forming with local heating, real-time monitoring are necessary to identify deformation progress. Machine vision based on image processing technique was selected to monitor deformation behavior on dieless bellows forming process. The present paper describes real-time monitoring using image processing approach to monitor dimensional profile and temperature distribution during the process. The results show that machine vision is effective and efficient to monitor dynamic deformation of dieless bellows forming proces and able to identify abnormal process condition.

Development of Vision-Based Fuzzy Control System for Dieless Tube-Drawing and Bellows Forming Processes by Local Heating Technique

Development of Vision-Based Fuzzy Control System for Dieless Tube-Drawing and Bellows Forming Processes by Local Heating Technique

On-chip fabrication of air-bubble-containing Nd3+-doped tellurite glass microsphere for laser emission

We fabricated an air-bubble-containing glass microsphere on a substrate by using localized heating technique. Nd3+-doped tellurite glass cullets on a substrate were melted by a CW-Ti:sapphire laser at the wavelength of 810 nm and with the power density of more than 4.8 MW/cm2 to obtain tellurite glass microspheres with the diameter of 5 to 200 μm. The localized heating technique using laser is useful to form a bubble at a certain place in the microsphere. Both air-bubble-containing and bubble-free spheres showed lasing actions at around the wavelength of 1065 nm. The average laser thresholds of the air-bubble-containing and bubble-free microspheres with the size of 20-50 μm were 0.78 mW and 5.25 mW, respectively.

A current-induced localized heating technique for fabrication of carbon nanomaterials

A commercial copper clad laminate was used to fabricate the carbon nanomaterials using a localized heating technique. The surface Cu layer was patterned to a Cu trace and served as a localized heating source as it was current-stressed. Thermal decomposition of phenol formaldehyde, which was the primary constituent of the bottom paper phenolic board, took place primarily near the Cu trace and the carbon nanomaterials were formed directly on the board. The products contain carbon nanosheets and tubular carbon nanofibers.

Local heating method for growth of aligned carbon nanotubes at low ambient temperature

We use a highly localized resistive heating technique to grow vertically aligned multiwalled nanotube films and aligned single-walled nanotubes on substrates with an average temperature of less than 100°C. The temperature at the catalyst can easily be as high as 1000°C but an extremely high temperature gradient ensures that the surrounding chip is held at much lower temperatures, even as close as 1μm away from the local heater. We demonstrate the influence of temperature on the height of multiwalled nanotube films, illustrate the feasibility of sequential growth of single-walled nanotubes by switching between local heaters and also show that nanotubes can be grown over temperature-sensitive materials such as resist polymer.

Tunable Stress and Controlled Thickness Modification in Graphene by Annealing

Graphene has many unique properties which make it an attractive material for fundamental study as well as for potential applications. In this paper, we report the first experimental study of process-induced defects and stress in graphene using Raman spectroscopy and imaging. While defects lead to the observation of defect-related Raman bands, stress causes shift in phonon frequency. A compressive stress (as high as 2.1 GPa) was induced in graphene by depositing a 5 nm SiO(2) followed by annealing, whereas a tensile stress ( approximately 0.7 GPa) was obtained by depositing a thin silicon capping layer. In the former case, both the magnitude of the compressive stress and number of graphene layers can be controlled or modified by the annealing temperature. As both the stress and thickness affect the physical properties of graphene, this study may open up the possibility of utilizing thickness and stress engineering to improve the performance of graphene-based devices. Local heating techniques may be used to either induce the stress or reduce the thickness selectively.