This research is supported by the project entitled "Development of impact print-type hot embossing technology for a conductive layer using conductive nano-composite materials" through the Ministry of Trade, Industry and Energy (MOTIE) of Korea (N046100024, 2016).

1. Fabrication of the impact print-type hot embossing process
<ol>
	<li>Make model 1 and combine it with an X-stage (see Figure 1). 
	NOTE: It is recommended that Model 1 be made of aluminum to avoid heat being conducted onto the X-stage. Moreover, it is recommended that the length of Model 1 be the distance between the surface of the heat plate and the lowest height of the bearing plate of the Z-stage as the design of Model 1 varies with the size of the heat plate.</li>
	<li>Combine the X-stage and Z-stage and assemble the Z-stage and Model 2. 
	NOTE: Ensure that Model 2 is made of a metal that can endure the heat from the heat plate (e.g., aluminum). Fixing Model 2 to the Z-stage tightly will ensure the capability of the Z-stage to hold the weight of Model 2 and the impact header.</li>
	<li>Combine Model 2 and the impact header and place the heat plate below Model 1. 
	NOTE: Joining the impact header with the lowest position on Model 2 will ensure that the mover reaches the surface of the heat plate. It is recommended to install the heat plate after raising the Z-stage maximally to avoid any contact of the impact head with the surface of the heat plate. Use suitable software to control the stage.</li>
	<li>Convert the STL files of the film holder (Supplementary File 1 and Supplementary File 2) to GCODE files using suitable software to print the film holder with a three-dimensional (3D) printer. 
	NOTE: The software may vary with the 3D printer used, and some environments may support 3D printer environments without GCODE conversion.</li>
	<li>Use the 3D printer to print the film holder with the GCODE file. 
	NOTE: Using a filament (e.g., Z-HIPS) is recommended because less contraction will occur when printing large parts, such as the film holder.</li>
	<li>Install two film holders onto the end of the heat plate and fix the polymer film onto the film holder, as shown in Figure 1. To ensure that the polymer film is flat on the heat plate, pull the polymer film as much as possible using motion 1 of the film holder (see Figure 1B). To move the polymer film to the side, move the film holder via motion 2 (see Figure 1B). 
	NOTE: To fix the polymer film onto the film holder, it is recommended to use a screw. Glue is insufficient to affix the polymer film onto the film holder, and it is best for the detachment of the polymer film after the patterning experiment.</li>
</ol>
2. Fabrication of the control circuit
NOTE: This process describes the process of constructing the control circuit of the impact header and the X&#8211;Z stage.
<ol>
	<li>Connect the control device that sends the signals (see Table of Materials) to the impact header to control it.</li>
	<li>After connecting the control device to the impact header, input -3 V and +10 V as control signals into the impact header. 
	NOTE: If a +10 V control signal is sent to the impact header (see Figure 1), the mover (impact head) goes down and enters the turn-on state. In this state, the mover hits the polymeric film and engraves the pattern on the polymer film.
	<ol>
		<li>Raise the mover to engrave the next pattern after engraving a pattern using the mover of the impact header. To raise the mover (impact head), apply the -3 V control signal. 
		NOTE: A negative voltage is input to the impact header to prevent the mover from becoming magnetized by the inner remnant flux of the impact header.</li>
	</ol>
	</li>
	<li>If the control device cannot supply a sufficient control signal, use a high-power operation amplifier (e.g., OP-AMP) which amplifies the ~0 V&#8211;5 V control signal to ~-3 V&#8211;+10 V, as shown in Figure 2, to control the impact header.
	<ol>
		<li>First, prepare a dual-channel DC power supply (see Table of Materials). After this step, connect four nodes to provide common ground (GND) nodes to all channels: a positive voltage terminal (V1+) and a ground (GND) terminal for channel 1 and a negative voltage terminal (V2-) and ground (GND) for channel 2. An overall connection diagram is shown in Figure 2. 
		NOTE: According to the step described in 2.3.1, positive and negative voltage with different absolute values can be supplied to the operational amplifier (OP-AMP).</li>
		<li>Connect the negative voltage terminal of channel 1 (V1-) of the power supply to the negative power supply voltage terminal (Vs-) of the OP-AMP, as indicated by the blue line in Figure 2. Subsequently, input 3 V Vcc voltage to channel 1. 
		NOTE: According to step 2.3.1, the 3 V Vcc voltage is supplied as -3 V negative voltage to the negative power supply voltage terminal (Vs-) of the OP-AMP.</li>
		<li>Connect the positive voltage terminal of channel 2 (V2+) of the power supply to the positive power supply voltage terminal (Vs+) of the OP-AMP, as indicated by the red line in Figure 2. Subsequently, input 10 V Vcc voltage to channel 2. 
		NOTE: According to step 2.3.1, the 10 V Vcc voltage is supplied as +10 V positive voltage to the positive power supply voltage terminal (Vs+) of the OP-AMP.</li>
		<li>Connect the +output channel of a control device (Vcon+) to the positive input channel (Vin+) of the OP-AMP, as shown by the green line in Figure 2.</li>
		<li>Connect the -output channel of a control device (Vcon-) to the ground (GND) of channel 2 of the power supply, as shown by the black line in Figure 2. 
		NOTE: When connecting the (Vcon-) to the ground (GND), it is possible to connect it to one of the terminals connected during step 2.3.1 in addition to the GND of channel 2.</li>
		<li>Prepare electric resistance of 1 k&#937; and 10 k&#937; values in each case and connect them between the red line and black line, as shown in Figure 2.</li>
		<li>Connect the terminal between 1 k&#937; and 10 k&#937; to the negative input channel of the OP-AMP (Vin-), as shown by the purple line in Figure 2.</li>
		<li>Pull out the lines from the output channel of the OP-AMP (Vout) and one of the electrical terminals described in step 2.3.1. Connect the lines to the impact header, as shown by the orange line in Figure 2.</li>
		<li>Regarding the power supply, set the voltages of channel 1&#8211;3 Vcc and channel 2&#8211;10 Vcc. Subsequently, generate control signals of ~0 V&#8211;5 V from the control device. 
		NOTE: The generated ~0 V&#8211;5 V control signals will be amplified by the OP-AMP to ~-3 V&#8211;+10 V, which is necessary to control the impact header as described in steps 2.2.1 and 2.2.2.</li>
	</ol>
	</li>
</ol>
3. Experiment design
NOTE: This section describes the processes of controlling the impact-type hot embossing device and engraving dot patterns onto the polymer film.
<ol>
	<li>Install a stage-control program (e.g., Micromove) to control the X-stage and Z-stage using a control computer (PC).</li>
	<li>Install DAQ driver software to detect the control device on the control PC that controls the impact header and install an operating program (e.g., MATLAB) to control the control device.</li>
	<li>After installing the software, construct the hardware environment as shown in Figure 3A to conduct the patterning experiment.
	<ol>
		<li>Install the X stage, Z stage, impact header, film holder, and heat plate as shown in Figure 3A to construct the hardware environment.</li>
		<li>Fix the polymer film onto the film holder and adjust the position of the polymer film using motions 1 and 2 (see Figure 1B) to fix the film flatly. 
		NOTE: To keep the film flat while adjusting direction 2, the locations of the two film holders should be parallel. To make the film flat on the heat plate, it is recommended to adjust the film holder by lowering the position according to direction 1, as shown in Figure 1B.</li>
		<li>After fixing the polymer film, adjust the temperature of the heat plate to heat the film above the glass transition temperature. 
		NOTE: Each type of film has its own glass transition temperature. Therefore, it is recommended to adjust the temperature of the heat plate to its own glass transition temperature after checking the material properties of the film in the corresponding datasheet.</li>
	</ol>
	</li>
	<li>After setting the hardware, put the control circuit together as shown in Figure 3B to control the stage and the impact header.
	<ol>
		<li>Prepare the PC, control board, power supply, and OP-AMP to construct the control environment as shown in Figure 3B. Connect the devices as shown in Figure 2 and then connect the computer to the control board.</li>
		<li>Enter the 3 Vcc and 10 Vcc values into an OP-AMP through channels 1 and 2 of the power supply respectively, as described in step 2.3.9.</li>
	</ol>
	</li>
	<li>Control the stage and impact header using the control computer.
	<ol>
		<li>Adjust the initial position of impact header by controlling X and Z stages using the stage control program. 
		NOTE: While adjusting the initial position of the impact header, ensure that there is no collision between the impact header and the heat plate. If the position of the Z-stage is too low, the mover will collide with the heat plate, damaging both the mover and the heat plate. If there is damage to both devices, it will hinder the creation of fine patterns on a polymeric material.</li>
		<li>Using the operating program, generate a 5 V control signal from the control device. According to steps 2.3.1&#8211;2.3.9, the OP-AMP will amplify the 5 V control signal to +10 V, turn the impact header on, and engrave the patterns on the polymer film.</li>
		<li>Now generate a 0 V control signal from the control device using the operating program. According to steps 2.3.1&#8211;2.3.9, the OP-AMP will amplify the 0 V control signal to -3 V and turn the impact header off. 
		NOTE: The mover of the impact header will be raised, waiting to engrave the new pattern.</li>
		<li>Move the X-stage into position to engrave the next pattern.</li>
		<li>Engrave patterns 3x on the polymer film by repeating steps 3.5.1&#8211;3.5.4 sequentially.</li>
		<li>Lower the Z-stage 10 &#956;m from the initial position and execute step 3.5.5, counting the number of Z-stage moves. When the number of Z-stage movements exceeds three, move the X-stage to the initial position and raise the impact header maximally by moving the Z-stage. 
		NOTE: Changing the height of the Z-stage will ensure adjustments in the depth and width of the dot pattern.</li>
	</ol>
	</li>
	<li>Detach the polymer film from the film holder and measure the width and depth of each pattern using a confocal microscope (see Table of Materials), as shown in Figure 4A.
	<ol>
		<li>Before starting the measurement process, select the magnification value of the microscope and use the direct observation mode initially to adjust the scanning position of the polymer film. After adjusting the position by means of direct observation, fix the polymer film and change the scanning mode to the laser scanning mode. 
		NOTE: When using the confocal microscope, using an acrylic panel is recommended to fix the sample, as shown in Figure 4B.</li>
		<li>Using the laser scanning mode, measure the depth and width of the dot pattern.</li>
	</ol>
	</li>
	<li>Repeat steps 3.3.2&#8211;3.6.2 after changing the type of film. 
	NOTE: Considering the glass transition temperature of each type of film, set the temperature of the heat plate before placing each film on the heat plate. In this study, the glass transition temperature of PVC film is 100 &#176;C; for PMMA film it is 95 &#176;C, and for PET film it is 75 &#176;C.</li>
</ol>

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The authors have nothing to disclose

In this study, we implemented the impact print-type hot embossing process and engraved dot patterns with various widths and depths onto a range of polymer films in real time. Among the protocol steps, two steps should be critically considered among all steps. The first is the setting of the temperature of the heat plate (step 3.3.3), and the second is the setting of the initial position of the impact header (step 3.5.1). In step 3.3.3, if the temperature of the heat plate is too high, it becomes difficult to form a patte...

Researchers are actively attempting to miniaturize existing devices and displays and increase the flexibility of these devices1,2. To reduce the width and depth of electrical channels to the micro or nano scale, high-precision technology is necessary. In addition, to increase the flexibility of these devices, the patterns of the electrical channels must be located on a flexible material, such as a polymer film3,4. To meet these conditions, the study of ultrafine microprocessing technology is actively underway.
Ultrafine microfabrication technology has an advantage in that possible patterning materials include not only highly rigid materials such as iron or plastic but also soft materials such as polymer films. Due to these advantages, this technology is widely used as a core process in various fields, such as communications, chemistry, optics, aerospace, semiconductor, and sensors5,6,7. In the ultrafine microprocessing field, LIGA (lithography, electroplating, and molding) or micromachining methods are used8. However, these conventional methods are associated with several problems. LIGA methods require a considerable amount of time and several process steps to create ultrafine patterns and incur a high cost as well because they need many different types of equipment during the processes. In addition, LIGA methods use chemicals that can pollute the environment.
To address this issue, hot embossing process technology has been spotlighted among ultrafine microprocess technologies. Hot embossing is a technology that creates a pattern on a heated polymer film using a micro- or nanoscale embossing mold. Conventional hot embossing technology is divided into the plate type and roll-to-roll type depending on the shape of the mold. The two types of hot embossing technology are different in terms of the shape of the mold, but these two processes are similar in that the embossing mold presses the polymer film onto a heated plate to engrave a pattern onto the polymer film. To engrave the pattern using the hot embossing process, it is necessary to heat the polymer film above the glass transition temperature and to apply an adequate amount of pressure (~30&#8211;50 MPa)9. In addition, the width and depth of the pattern change depending on the temperature of the heated plate, the material, and the shape of the embossing mold. Moreover, the cooling method after the patterning process affects the shape of the pattern on the polymer film.
In the conventional hot embossing process, embossing stamps or rollers can be embossed with the desired pattern, and the embossing mold can be used to print the same pattern onto polymer film surfaces continuously. This feature makes this process suitable not only for mass production but also for fabricating devices with soft materials, such as polymer films10,11,12,13,14. However, the conventional hot embossing method can only create the single pattern engraved in the embossing mold. Therefore, when the user wants to make a new pattern or modify the pattern, they must make a new mold to modify the imprinting pattern. For this reason, conventional hot embossing is costly and time-consuming when creating new patterns or replacing existing designs.
Earlier work introduced the impact-type hot embossing process for producing dot patterns with various widths and depths in real time15. Unlike the conventional hot embossing process, the impact print-type hot embossing method uses an impact header to create patterns on the polymer film. This technology moves the impact header to the desired position with a precision positioning system. A control signal is applied to print patterns at a desired width and depth and at an arbitrary position. The structure of the impact header consists of a mover, a spring, a coil winding, and a core (see Figure 1A)15. Earlier work confirmed through an analysis and experiment that such an impact header can produce the proper force for hot embossing16. The protocol of this paper covers the design of the hardware for the impact-type hot embossing process and the control environment for process control. In addition, we analyze the dot patterns on PET film, PMMA film, and PVC film, all of which are processed with the proposed protocol to verify that the impact print-type hot embossing process can create dot patterns with various widths and depths in real time. The results of these experiments are presented below in the results section, confirming that the embossing process can suitably produce ultrafine patterns.

<table>
	<tbody>
		<tr>
			<td>0.3mm High Quality Clear Rigid Packaging PVC Film Roll For Vacuum Forming</td>
			<td>Sunyo</td>
			<td>SY1023</td>
			<td>PVC film / Thickness : 300&#181;m</td>
		</tr>
		<tr>
			<td>Acryl(PMMA) film</td>
			<td>SEJIN TS</td>
			<td>C200</td>
			<td>PMMA film / Thickness : 175&#181;m</td>
		</tr>
		<tr>
			<td>Confocal Laser Scanning Microscope: 3D-Topography for Materials Analysis and Testing</td>
			<td>Carl Zeiss</td>
			<td>LSM 700</td>
			<td>3D confocal microscope / Supporting Mode : 2D, 2.5D, 3D topography</td>
		</tr>
		<tr>
			<td>DAQ board</td>
			<td>NATIONAL INSTRUMENTS</td>
			<td>USB-6211</td>
			<td>Control board for two stage and impact header / 16 inputs, 16-bit, 250kS/s, Multifunction I/O</td>
		</tr>
		<tr>
			<td>DC Power Supply</td>
			<td>SMART</td>
			<td>RDP-305AU</td>
			<td>3 channel power supply / output voltage : 0~30V, Output current : 0~5A</td>
		</tr>
		<tr>
			<td>L511 stage</td>
			<td>PI</td>
			<td>L511.20SD00</td>
			<td>Z-stage / Travel range : 52mm</td>
		</tr>
		<tr>
			<td>Large Digital Hotplate</td>
			<td>DAIHAN Scientific</td>
			<td>HPLP-C-P</td>
			<td>Heatplate / Max Temp : 350&#186;C</td>
		</tr>
		<tr>
			<td>M531 stage</td>
			<td>PI</td>
			<td>M531.2S1</td>
			<td>X-stage / Travel range : 306mm</td>
		</tr>
		<tr>
			<td>Mylar Polyester PET films</td>
			<td>CSHyde</td>
			<td>48-2F-36</td>
			<td>PET film / Thickness : 50&#181;m</td>
		</tr>
		<tr>
			<td>OPA2541</td>
			<td>BURR-BROWN</td>
			<td>OPA2541BM</td>
			<td>OP-AMP / Output currents : 5A, output voltage : &#177;40V</td>
		</tr>
	</tbody>
</table>

study of a dot-patterning process on flexible materials using impact print-type hot embossing technology

Here we present our study on an impact print-type hot embossing process which can create dot patterns with various designs, widths, and depths in real time on polymer film. In addition, we implemented a control system for the on-off motion and position of the impact header to engrave different dot patterns. We performed dot patterning on various polymer films, such as polyester (PET) film, polymethyl methacrylate (PMMA) film, and polyvinyl chloride (PVC) film. The dot patterns were measured using a confocal microscope, and we confirmed that the impact print-type hot embossing process produces fewer errors during the dot patterning process. As a result, the impact print-type hot embossing process is found to be suitable for engraving dot patterns on different types of polymer films. In addition, unlike the conventional hot embossing process, this process does not use an embossing stamp. Therefore, the process is simple and can create dot patterns in real time, presenting unique advantages for mass production and small-quantity batch production.

The impact print-type hot embossing process is a process that can be used to engrave dot patterns onto a polymer film in real time, as shown in Figure 1. This process can resolve the issues of the high cost and long times for pattern replacement associated with the existing hot embossing process. A control circuit was constructed, as shown in Figure 2 (see steps 2.3&#8211;2.3.9), using the DAQ, OP-AMP, and power supply to carve patterns on various types of polym...

Watch this Scientific Journal Video about Study of a Dot-patterning Process on Flexible Materials using Impact Print-Type Hot Embossing Technology at JoVE.com

Study of a Dot-patterning Process on Flexible Materials using Impact Print-Type Hot Embossing Technology

Impact print-type hot embossing technology uses an impact header to engrave dot patterns on flexible materials in real time. This technology has a control system for controlling the on-off motion and position of the impact header to create dot patterns with various widths and depths on different polymer films.

Here we present our study on an impact print-type hot embossing process which can create dot patterns with various designs, widths, and depths in real ...

study-dot-patterning-process-on-flexible-materials-using-impact-print

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5.9K Views.  Daegu Gyeongbuk Institute of Science and Technology (DGIST). Impact print-type hot embossing technology uses an impact header to engrave dot patterns on flexible materials in real time. This technology has a control system for controlling the on-off motion and position of the impact header to create dot patterns with various widths and depths on different polymer films.

Video: Study of a Dot-patterning Process on Flexible Materials using Impact Print-Type Hot Embossing Technology

Micro 3D Printing Using a Digital Projector and its Application in the Study of Soft Materials Mechanics

Buckling is a classical topic in mechanics. While buckling has long been studied as one of the major structural failure modes1, it has recently drawn new attention as a unique mechanism for pattern transformation. Nature is full of such examples where a wealth of exotic patterns are formed through mechanical instability2-5. Inspired by this elegant mechanism, many studies have demonstrated creation and transformation of patterns using soft materials such as elastomers and hydrogels6-11. Swelling gels are of particular interest because they can spontaneously trigger mechanical instability to create various patterns without the need of external force6-10. Recently, we have reported demonstration of full control over buckling pattern of micro-scaled tubular gels using projection micro-stereolithography (P&mu;SL), a three-dimensional (3D) manufacturing technology capable of rapidly converting computer generated 3D models into physical objects at high resolution12,13. Here we present a simple method to build up a simplified P&mu;SL system using a commercially available digital data projector to study swelling-induced buckling instability for controlled pattern transformation.
A simple desktop 3D printer is built using an off-the-shelf digital data projector and simple optical components such as a convex lens and a mirror14. Cross-sectional images extracted from a 3D solid model is projected on the photosensitive resin surface in sequence, polymerizing liquid resin into a desired 3D solid structure in a layer-by-layer fashion. Even with this simple configuration and easy process, arbitrary 3D objects can be readily fabricated with sub-100 &mu;m resolution.
This desktop 3D printer holds potential in the study of soft material mechanics by offering a great opportunity to explore various 3D geometries. We use this system to fabricate tubular shaped hydrogel structure with different dimensions. Fixed on the bottom to the substrate, the tubular gel develops inhomogeneous stress during swelling, which gives rise to buckling instability. Various wavy patterns appear along the circumference of the tube when the gel structures undergo buckling. Experiment shows that circumferential buckling of desired mode can be created in a controlled manner. Pattern transformation of three-dimensionally structured tubular gels has significant implication not only in mechanics and material science, but also in many other emerging fields such as tunable matamaterials.

We demonstrate controlled pattern transformation of swelling gel tubes by elastic instability. A simple projection micro stereo-lithography setup is built using an off-the-shelf digital data projector to fabricate three-dimensional polymeric structures in a layer-by-layer fashion. Swelling hydrogel tubes under mechanical constraint display various circumferential buckling modes depending on dimension.

Buckling is a classical topic in mechanics. While buckling has long been studied as one of the major structural failure modes1, it has recently drawn new ...

Fast Imaging Technique to Study Drop Impact Dynamics of Non-Newtonian Fluids

In the field of fluid mechanics, many dynamical processes not only occur over a very short time interval but also require high spatial resolution for detailed observation, scenarios that make it challenging to observe with conventional imaging systems. One of these is the drop impact of liquids, which usually happens within one tenth of millisecond. To tackle this challenge, a fast imaging technique is introduced that combines a high-speed camera (capable of up to one million frames per second) with a macro lens with long working distance to bring the spatial resolution of the image down to 10 &#181;m/pixel. The imaging technique enables precise measurement of relevant fluid dynamic quantities, such as the flow field, the spreading distance and the splashing speed, from analysis of the recorded video. To demonstrate the capabilities of this visualization system, the impact dynamics when droplets of non-Newtonian fluids impinge on a flat hard surface are characterized. Two situations are considered: for oxidized liquid metal droplets we focus on the spreading behavior, and for densely packed suspensions we determine the onset of splashing. More generally, the combination of high temporal and spatial imaging resolution introduced here offers advantages for studying fast dynamics across a wide range of microscale phenomena.

Drop impact of non-Newtonian fluids is a complex process since different physical parameters influence the dynamics over a very short time (less than one tenth of a millisecond). A fast imaging technique is introduced in order to characterize the impact behaviors of different non-Newtonian fluids.

In the field of fluid mechanics, many dynamical processes not only occur over a very short time interval but also require high spatial resolution for ...

Development of an Experimental Setup for the Measurement of the Coefficient of Restitution under Vacuum Conditions

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their behavior for single stages of a process or even an entire process. For the simulation with occurring particle-particle and particle-wall contacts, the value of the coefficient of restitution is required. It can be determined experimentally. The coefficient of restitution depends on several parameters like the impact velocity. Especially for fine particles the impact velocity depends on the air pressure and under atmospheric pressure high impact velocities cannot be reached. For this, a new experimental setup for free-fall tests under vacuum conditions is developed. The coefficient of restitution is determined with the impact and rebound velocity which are detected by a high-speed camera. To not hinder the view, the vacuum chamber is made of glass. Also a new release mechanism to drop one single particle under vacuum conditions is constructed. Due to that, all properties of the particle can be characterized beforehand.

The coefficient of restitution is a parameter that describes the loss of kinetic energy during collision. Here, a free-fall setup under vacuum conditions is developed to be able to determine the coefficient of restitution parameter for particles in micrometer range with high impact velocities.

The Discrete Element Method is used for the simulation of particulate systems to describe and analyze them, to predict and afterwards optimize their ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Adsorption Device Based on a Langatate Crystal Microbalance for High Temperature High Pressure Gas Adsorption in Zeolite H-ZSM-5

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate crystal microbalance, LCM) and its use for gas adsorption measurements in zeolite H-ZSM-5. Prior to the adsorption measurements, zeolite H-ZSM-5 crystals were synthesized on the gold electrode in the center of the LCM, without covering the connection points of the gold electrodes to the oscillator, by the steam-assisted crystallization (SAC) method, so that the zeolite crystals remain attached to the oscillating microbalance while keeping good electroconductivity of the LCM during the adsorption measurements. Compared to a conventional quartz crystal microbalance (QCM) which is limited to temperatures below 80 &#176;C, the LCM can realize the adsorption measurements in principle at temperatures as high as 200-300 &#176;C (i.e., at or close to the reaction temperature of the target application of one-stage DME synthesis from the synthesis gas), owing to the absence of crystalline-phase transitions up to its melting point (1,470 &#176;C). The system was applied to investigate the adsorption of CO2, H2O, methanol and dimethyl ether (DME), each in the gas phase, on zeolite H-ZSM-5 in the temperature and pressure range of 50-150 &#176;C and 0-18 bar, respectively. The results showed that the adsorption isotherms of these gases in H-ZSM-5 can be well fitted by Langmuir-type adsorption isotherms. Furthermore, the determined adsorption parameters, i.e., adsorption capacities, adsorption enthalpies, and adsorption entropies, compare well to literature data. In this work, the results for CO2 are shown as an example.

A protocol for high-temperature and high-pressure gas adsorption measurements on zeolite H-ZSM-5 using an adsorption measurement device based on a langatate crystal microbalance is presented. Prior to the adsorption measurements, the synthesis of zeolite H-ZSM-5 on the langatate crystal microbalance sensor by the steam-assisted crystallization (SAC) method is demonstrated.

We present a high-temperature and high-pressure gas adsorption measurement device based on a high-frequency oscillating microbalance (5 MHz langatate ...

Challenges in Rheological Characterization of Highly Concentrated Suspensions &#8212; A Case Study for Screen-printing Silver Pastes

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the manifold requirements during processing and application of such complex fluids. In this investigation, measuring protocols for a conclusive assessment of different process relevant rheological parameters have been evaluated. This includes the determination of yield stress, viscosity, wall slip velocity, structural recovery after large deformation and elongation at break as well as tensile force during filament stretching.
The importance of concomitant video recordings during parallel-plate rotational rheometry for a significant determination of rheological quantities is demonstrated. The deformation profile and flow field at the sample edge can be determined using appropriate markers. Thus, measurement parameter settings and plate roughness values can be identified for which yield stress and viscosity measurements are possible. Slip velocity can be measured directly and measuring conditions at which plug flow, shear banding or sample spillover occur can be identified clearly. 
Video recordings further confirm that the change in shear moduli observed during three stage oscillatory shear tests with small deformation amplitude in stage I and III but large oscillation amplitude in stage II can be directly attributed to structural break down and recovery. For the pastes investigated here, the degree of irreversible, shear-induced structural change increases with increasing deformation amplitude in stage II until a saturation is reached at deformations corresponding to the crossover of G' and G'', but the irreversible damage is independent of the duration of large amplitude shear. 
A capillary breakup elongational rheometer and a tensile tester have been used to characterize deformation and breakup behavior of highly filled pastes in uniaxial elongation. Significant differences were observed in all experiments described above for two commercial screen-printing silver pastes used for front side metallization of Si-solar cells.

A protocol for a robust and application relevant rheological characterization of highly concentrated suspensions is presented. Silver pastes used for screen-printing application in solar cell production are employed as model systems.

A comprehensive rheological characterization of highly concentrated suspensions or pastes is mandatory for a targeted product development meeting the ...

Predicting Catalyst Extrudate Breakage Based on the Modulus of Rupture

The mechanical strength of extruded catalysts and their natural or forced breakage by either collision against a surface or by a compressive load in a fixed bed are important phenomena in catalyst technology. The mechanical strength of the catalyst is measured here by its bending strength or flexural strength. This technique is relatively new from the perspective of applying it to commercial catalysts of typical sizes used in the industry. Catalyst breakage by collision against a surface is measured after a fall of the extrudates through the ambient air in a vertical pipe. Quantifying the impact force is done theoretically by applying Newton's second law. Measurement of catalyst breakage due to stress in a fixed bed is done following the standard procedure of the bulk crush strength test. Novel here is the focus on measuring the reduction in the length to diameter ratio of the extrudates as a function of the stress.

Here we present a protocol to measure the modulus of rupture of an extruded catalyst and the breakage of said catalyst extrudates by collision against a surface or by compression in a fixed bed.

The mechanical strength of extruded catalysts and their natural or forced breakage by either collision against a surface or by a compressive load in a ...

A Fabrication and Measurement Method for a Flexible Ferroelectric Element Based on Van Der Waals Heteroepitaxy

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on high-density data storage and low-power consumption capabilities. However, the high-quality oxide based nonvolatile memory on flexible substrates is often constrained by the material characteristics and the inevitable high-temperature fabrication process. In this paper, a protocol is proposed to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica. The versatile deposition technique and measurement method enable the fabrication of flexible yet single-crystalline non-volatile memory elements necessary for the next generation of smart devices.

In this paper, we present a protocol to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica.

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on ...

Fabrication of Flexible Image Sensor Based on Lateral NIPIN Phototransistors

Flexible photodetectors have been intensely studied for the use of curved image sensors, which are a crucial component in bio-inspired imaging systems, but several challenging points remain, such as a low absorption efficiency due to a thin active layer and low flexibility. We present an advanced method to fabricate a flexible phototransistor array with an improved electrical performance. The outstanding electrical performance is driven by a low dark current owing to deep impurity doping. Stretchable and flexible metal interconnectors simultaneously offer electrical and mechanical stabilities in a highly deformed state. The protocol explicitly describes the fabrication process of the phototransistor using a thin silicon membrane. By measuring I-V characteristics of the completed device in deformed states, we demonstrate that this approach improves the mechanical and electrical stabilities of the phototransistor array. We expect that this approach to a flexible phototransistor can be widely used for the applications of not only next-generation imaging systems/optoelectronics but also wearable devices such as tactile/pressure/temperature sensors and health monitors.

We present a detailed method to fabricate a deformable lateral NIPIN phototransistor array for curved image sensors. The phototransistor array with an open mesh form, which is composed of thin silicon islands and stretchable metal interconnectors, provides flexibility and stretchability. The parameter analyzer characterizes the electrical property of the fabricated phototransistor.

Flexible photodetectors have been intensely studied for the use of curved image sensors, which are a crucial component in bio-inspired imaging systems, ...

Theoretical Calculation and Experimental Verification for Dislocation Reduction in Germanium Epitaxial Layers with Semicylindrical Voids on Silicon

Reduction of threading dislocation density (TDD) in epitaxial germanium (Ge) on silicon (Si) has been one of the most important challenges for the realization of monolithically integrated photonics circuits. The present paper describes methods of theoretical calculation and experimental verification of a novel model for the reduction of TDD. The method of theoretical calculation describes the bending of threading dislocations (TDs) based on the interaction of TDs and non-planar growth surfaces of selective epitaxial growth (SEG) in terms of dislocation image force. The calculation reveals that the presence of voids on SiO2 masks help to reduce TDD. Experimental verification is described by germanium (Ge) SEG, using an ultra-high vacuum chemical vapor deposition method and TD observations of the grown Ge via etching and cross-sectional transmission electron microscope (TEM). It is strongly suggested that the TDD reduction would be due to the presence of semicylindrical voids over the SiO2 SEG masks and growth temperature. For experimental verification, epitaxial Ge layers with semicylindrical voids are formed as the result of SEG of Ge layers and their coalescence. The experimentally obtained TDDs reproduce the calculated TDDs based on the theoretical model. Cross-sectional TEM observations reveal that both the termination and generation of TDs occur at semicylindrical voids. Plan-view TEM observations reveal a unique behavior of TDs in Ge with semicylindrical voids (i.e., TDs are bent to be parallel to the SEG masks and the Si substrate).

Theoretical calculation and experimental verification are proposed for a reduction of threading dislocation (TD) density in germanium epitaxial layers with semicylindrical voids on silicon. Calculations based on the interaction of TDs and surface via image force, TD measurements, and transmission electron microscope observations of TDs are presented.