This project has been supported by the German Research Foundation (DFG), grant no. BI 1639/9-1.

1. Design of the vocal fold models and 3D printing of parts
<ol>
	<li>Create a multi-layered representation of the common M5 geometry of silicone vocal folds using various soft silicone materials. Design the individual parts using computer-aided design (CAD) software. Check the Supplementary Coding File 1, Supplementary Coding File 2, Supplementary Coding File 3, Supplementary Coding File 4, Supplementary Coding File 5, Supplementary Coding File 6, Supplementary Coding File 7, Supplementary Coding File 8 for details. The files are named according to their function in the model and serve as the foundation for the subsequent steps.</li>
	<li>Compile and organize the necessary files for each step in step 2. Refer to the list of required parts and their quantities in Supplementary Figure 1. See a schematic depiction of mold assembly in Supplementary Figure 2.</li>
	<li>Load the STL files into a 3D printing program to generate G-code files that can be read by the 3D printer.</li>
	<li>Prepare the materials (see Table of Materials) for the 3D print.
	<ol>
		<li>For Supplementary Coding File 2 and Supplementary Coding File 5, use a material that causes less visible layer lines, such as polylactic acid (PLA+) or PC.</li>
		<li>For Supplementary Coding File 1, use a harder material such as Tough PLA or Polyethylene terephthalate glycol (PETG) due to its susceptibility to bending stresses. No further restrictions on the choice of printing material apply to the remaining parts.</li>
	</ol>
	</li>
	<li>Adjust the settings of the 3D printing software for the corresponding selected 3D printer.
	<ol>
		<li>For Supplementary Coding File 2 and Supplementary Coding File 5, set a maximum layer height of 0.1 mm.</li>
		<li>For Supplementary Coding File 1, set the infill value to 100% and the print pattern to ZigZag to achieve better stability. Also, set the build plate adhesion category to Skirt instead of Brim, because the geometry of the parts would make it considerably more difficult to remove the brim.</li>
		<li>For the other parts, use the default settings and layer heights of 0.2 mm.</li>
	</ol>
	</li>
	<li>Print the mentioned parts on the 3D printer. Clean the parts and remove any excess material such as brim or printing errors. Smooth the inner contact surfaces with sandpaper (equal or finer than P1000 recommended).</li>
</ol>
2. Fabrication of the vocal fold models
<ol>
	<li>Gather the following parts and materials for creating the body layer: vocal-fold-positiv (2x), vocalis_mold-cap, vocalis_mold-main-part, vocalis_mold-hull, primary silicone, release agent, and thinner (See Table of Materials for details).
	<ol>
		<li>Apply some release agent to the inside surfaces of all the mold parts.</li>
		<li>Assemble the main part and cap of the mold over the positive and place the mold package in the designated pot. Correct the alignment of the two mold parts if necessary. Ensure the hole in the positive for pouring the silicone faces upwards, and the mold has a stable footing on a flat surface.</li>
		<li>Create a mixture of the primary silicone with three parts of thinner (1:1:3), begin by combining component A with the thinner, and subsequently adding component B. Thoroughly mix the components. A total amount of 6 g of silicone mixture is sufficient for casting the body layer from two vocal fold halves.</li>
		<li>Vacuum the silicone mixture in a vacuum chamber at a minimum of -1 bar sub pressure to prevent air bubbles from forming in the cured silicone body.</li>
		<li>Carefully pour the vacuumed silicone mixture into the mold cavity until it appears filled. Fill the surrounding areas of the mold pot to prevent the very thin silicone mixture from sinking through the mold joints. Check the silicone level during the dripping time and add more if necessary. The drip time for this mixture is between 1-2 h.</li>
		<li>After a curing time of about 1 day, but at least 8 h, remove the mold, including the positive, from the pot. Remove the silicone between the mold and the pot before opening the mold.</li>
		<li>When opening the mold, first carefully remove the lid starting from the back of the positive. Then, remove the main body of the mold. Carefully remove any excess silicone using a scalpel or a side cutter.</li>
	</ol>
	</li>
	<li>Prepare the musosa_mold-back, musosa_mold-main-part, and musosa_mold-hull parts, as well as the secondary silicone and release agent for the production of the epithelium layer. (See Table of Materials). 
	NOTE: Steps 2.1 and 2.2 (body and epithelium layer) can be completed simultaneously.
	<ol>
		<li>Assemble the two mold parts and place them in the hull. Prepare the inside of the mold with some release agent, ensuring that the inner walls are coated according to the usage instructions of the respective release agent. Allow the component to air-dry briefly before proceeding.</li>
		<li>Mix a batch of the secondary silicone without using thinner (1:1:0). If air bubbles have been introduced into the silicone mixture while mixing, degas the mixture as in step 2.1.4. 
		NOTE: Be aware of the short drip time of this mixture, which is about 15 min.</li>
		<li>Pour some of the mixture into the mold and swirl it around (leaving the mold in the hull) until all interior surfaces are coated with silicone.</li>
		<li>Turn the mold over and let excess silicone drain out. Secure the mold in this position over a mesh, grate, or at an angle that allows further silicone drainage.</li>
		<li>Prevent the formation of overhangs in the silicone during the curing process by regularly smoothing it out, especially in the area where the air channel will be located. 
		NOTE: These can also be carefully removed later with pliers.</li>
	</ol>
	</li>
	<li>Prepare for the production of the mucosa intermediate layer by preparing the positive with the vocalis silicone layer from step 2.1, the mold prepared with the epithelium layer from step 2.2, and the silicone and thinner as listed in Table of Materials.
	<ol>
		<li>Create a mixture of the primary silicone with five parts of thinner (1:1:5), begin by combining component A with the thinner, and subsequently adding component B. Thoroughly mix the components. A total amount of 4 g of silicone mixture is sufficient.</li>
		<li>Vacuum the silicone mixture in a vacuum chamber as in step 2.1.4.</li>
		<li>Fill a portion of the silicone mixture into the mucosa mold with the prepared epithelial silicone. Tilt the mold until all interior surfaces of the epithelial silicone are covered with a thin layer of oil to facilitate insertion of the positive. 
		NOTE: Optional: Due to the high proportion of diluent, the mixture has a long drip time of several hours during which the mixture can shrink through evaporation. Therefore, wait about 2-3 h before proceeding with the next steps.</li>
		<li>Carefully insert the positive with the vocal body into the mold. Secure the positive in the mold, for example with a clamp, if the positive floats up on the silicone. Depending on the amount of silicone previously added, it may escape at the filling points.</li>
		<li>Fill the mold in the same way as for the casting of the vocalis layer and top up accordingly if the material sinks.</li>
		<li>Wait 24 h after the drip time has ended for the silicone to completely cure.</li>
		<li>After 24 h, remove the body from the mold. First, remove the mold from the shell. Then, starting with the rear section, open the mold and remove the main part of the mold as well.</li>
		<li>Carefully remove any excess silicone, wash the surface and let the body dry.</li>
	</ol>
	</li>
	<li>Mount the two vocal fold halves at the designated locations on the measurement and assembly module in Supplementary Coding File 8. The connection was designed for two M3 screws and M3 square nuts (DIN 562), but they are not mandatory.</li>
</ol>

3D Printing of Multilayered Silicone Vocal Fold Models

<ol>
	<li>Drechsel, J. S., Thomson, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+supraglottal+structures+on+the+glottal+jet+exiting+a+two-layer+synthetic,+self-oscillating+vocal+fold+model.">Influence of supraglottal structures on the glottal jet exiting a two-layer synthetic, self-oscillating vocal fold model.</a> J Acoust Soc Am. 123 (6), 4434-4445 (2008).</li><li>Stevens, K. A., Shimamura, R., Imagawa, H., Sakakibara, K. I., Tokuda, I. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Validating+Stereo-endoscopy+with+a+synthetic+vocal+fold+model.">Validating Stereo-endoscopy with a synthetic vocal fold model.</a> Acta Acustica United with Acustica. 102 (4), 745-751 (2016).</li><li>Murray, P. R., Thomson, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthetic,+multi-layer,+self-oscillating+vocal+fold+model+fabrication.">Synthetic, multi-layer, self-oscillating vocal fold model fabrication.</a> J Vis Exp. (58), e3498 (2011).</li><li>Spencer, M., Siegmund, T., Mongeau, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+superior+surface+strains+and+stresses,+and+vocal+fold+contact+pressure+in+a+synthetic+larynx+model+using+digital+image+correlation.">Determination of superior surface strains and stresses, and vocal fold contact pressure in a synthetic larynx model using digital image correlation.</a> J Acoust Soc Am. 123 (2), 1089-1103 (2008).</li><li>Scherer, R. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intraglottal+pressure+profiles+for+a+symmetric+and+oblique+glottis+with+a+divergence+angle+of+10+degrees.">Intraglottal pressure profiles for a symmetric and oblique glottis with a divergence angle of 10 degrees.</a> J Acoust Soc Am. 109 (4), 1616-1630 (2001).</li><li>Zhang, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanics+of+human+voice+production+and+control.">Mechanics of human voice production and control.</a> J Acoust Soc Am. 140 (4), 2614-2635 (2016).</li><li>Birkholz, P., Wang, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Studientexte zur Sprachkommunikation: Elektronische Sprachsignalverarbeitung. , 58-66 (2017).</li><li>Murray, P. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Flow-induced responses of normal, bowed, and augmented synthetic vocal fold models. , (2011).</li><li>Alipour, F., Vigmostad, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+vocal+folds+elastic+properties+for+continuum+modeling.">Measurement of vocal folds elastic properties for continuum modeling.</a> J Voice. 26 (6), e21-29 (2012).</li><li>Chhetri, D. K., Zhang, Z., Neubauer, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+young's+modulus+of+vocal+folds+by+indentation.">Measurement of young's modulus of vocal folds by indentation.</a> J Voice. 25 (1), 1-7 (2011).</li><li>H&#228;sner, P., Birkholz, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reproducibility+and+aging+of+different+silicone+vocal+folds+models.">Reproducibility and aging of different silicone vocal folds models.</a> J Voice. , (2023).</li><li>Gabriel, F., H&#228;sner, P., Dohmen, E., Borin, D., Birkholz, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Studientexte zur Sprachkommunikation: Elektronische Sprachsignalverarbeitung. , 221-230 (2019).</li><li>H&#228;sner, P., Prescher, A., Birkholz, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+wavy+trachea+walls+on+the+oscillation+onset+pressure+of+silicone+vocal+folds.">Effect of wavy trachea walls on the oscillation onset pressure of silicone vocal folds.</a> J Acoust Soc Am. 149 (1), 466-475 (2021).</li><li>Birkholz, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Studientexte zur Sprachkommunikation: Elektronische Sprachsignalverarbeitung. , (2016).</li><li>Boersma, P., Weenink, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Praat,+a+system+for+doing+phonetics+by+computer.">Praat, a system for doing phonetics by computer.</a> Glot. Int. 5, 341-345 (2001).</li><li>Fukui, K., Shintaku, E., Honda, M., Takanishi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+vocal+cord+model+for+anthropomorphic+talking+robot+based+on+human+biomechanical+structure.">Mechanical vocal cord model for anthropomorphic talking robot based on human biomechanical structure.</a> Trans Japan Soc Mech Eng Ser C. 73 (734), 2750-2756 (2007).</li><li>Syndergaard, K. L., Dushku, S., Thomson, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrically+conductive+synthetic+vocal+fold+replicas+for+voice+production+research.">Electrically conductive synthetic vocal fold replicas for voice production research.</a> J Acoust Soc Am. 142 (1), 63 (2017).</li></ol>

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

The manufacturing process presented here involves critical steps that significantly impact its success. Firstly, it should be noted that the presented manufacturing process does not solve the problem of oil saturation in the vocal fold body material but rather circumvents certain negative side effects. The outgassing and the associated shrinkage and surface waviness still persist, albeit to a lesser extent. A solution to these problems would involve the use of an ultra-soft silicone or alternative material that combines ...

Vocal fold models are used to simulate and investigate human voice production under normal and pathological conditions1,2. One of the biggest challenges in creating vocal fold models is to achieve a realistic softness and flexibility that closely approximates those of humans. To achieve these properties, silicone elastomers are often used, which are diluted with high amounts of silicone oil to achieve the corresponding elasticity moduli3,4. Another crucial factor in creating realistic vocal fold models is layering, as vocal folds consist of multiple layers of varying softness, which determine the pattern of flow-induced vibration and the frequency at which vibration is possible.
In this study, we created a typical vocal fold model. We used the common geometry provided by Scherer5, which represents typical dimensions for male vocal folds with 17 mm length according to Zhang6 and consists of three layers: one layer for the vocalis muscle (body layer), one for the entire mucosal layer (cover layer), and one for the epithelium. This structure can be seen in the coronal cross-section view in Figure 1.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/66222/66222fig01v2.jpg" /> 
Figure 1: Coronal cross-section of the larynx modules. Coronal cross-section of the larynx modules illustrating the widest width of the vocal folds (8.5 mm). Each vocal fold comprises a body layer, a cover layer, and an epithelium layer. This figure has been modified from13. Reproduced from H&#228;sner, P., Prescher, A., Birkholz, P. Effect of wavy trachea walls on the oscillation onset pressure of silicone vocal folds. J Acoust Soc Am.149 (1), 466-475 (2021) with the permission of the Acoustical Society of America. <a href="https://www.jove.com/files/ftp_upload/66222/66222fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Other publications use partially only one layer7, two layers without epithelium layer2 or model the mucosa with multiple layers3. Usually, the layers are cast from the inside out, i.e., starting with the deepest layer. The epithelium, which is very thin with 30 &#181;m thickness, is cast at the end over the entire body to envelop it with a sturdy skin8.
The cover layer in the model is the softest part, with Young&#39;s modulus of about 1.1 kPa9. For the body layer, the approximate Young&#39;s modulus in the transverse direction using in vitro measurements10 is 2 kPa. In vivo, the Young&#39;s modulus of the thyroarytenoid muscle may be higher due to the presence of fibers in the longitudinal direction as well as the possible tensing of the muscle. To achieve this extremely low Young&#39;s modulus, it is necessary to add a high amount of silicone oil to the silicone mixture (approximately 72%). However, the manufacturer strongly advises against using an oil proportion greater than 5%. In general, the addition of silicone oil to the elastomer is intended to increase flow and drip time, as well as reduce the shrinkage of the cured silicone polymer. It helps the silicone to cure more uniformly, thereby reducing stress in the material. Its purpose is to optimize the moldability and properties of the cured material, rather than to increase its softness, although this is also a consequence. This is because silicone oil is chemically inert, meaning that it cannot polymerize itself and is not integrated into the network of the silicone polymer11. Instead, it remains as a liquid phase in the polymer matrix, weakening the polymer structure at higher levels and potentially causing it to dissolve out of the cured material and adhere to the surface. As a result, other negative properties such as curing disorders, uneven vulcanization, chemical shrinkage, and brittleness are possible. Vocal fold models with high silicone oil contents were investigated with regard to aging and reproducibility, and it was found that there is a high variability in the properties of different models and a change in their properties over time11.
When producing vocal fold models in the conventional way7,12, the stickiness of the epithelial layer can be a problem as it can affect the homogeneity of vibration and lead to rupture of the epithelium. Although the silicone used to make the epithelium is undiluted, it can be assumed that the oil that leaks from the neighboring mucosa layer has similar effects on the silicone as if it had been diluted. The problem of stickiness was addressed by adding various powders such as talcum or carbon powder as an intermediate layer between the mucosa and the epithelial layer12. This approach may have been successful because the oil was partially absorbed by the powder and, as a result, the stickiness of the epithelial surface could be reduced.
In this publication, we show that the problem of stickiness can be circumvented by a slight modification of the process of vocal fold manufacturing. By changing the order of layering and starting with the undiluted epithelial silicone (so-called closed silicone), non-sticky super-soft vocal fold models can be produced. This change involves unusual types of molds and methods that are best presented and explained in the form of a video. In this paper, we describe our manufacturing process in detail and demonstrate how the properties of the vocal fold models can be characterized in an application.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>3D Printer</td>
			<td>ULTIMAKER</td>
			<td></td>
			<td>Type S5</td>
		</tr>
		<tr>
			<td>3D Printing software</td>
			<td>ULTIMAKER CURA</td>
			<td></td>
			<td>Version 5.2.2</td>
		</tr>
		<tr>
			<td>CAD Software</td>
			<td>Autodesk Inventor&#160;</td>
			<td></td>
			<td>Version 2023</td>
		</tr>
		<tr>
			<td>High Speed Camera</td>
			<td>XIMEA GmbH</td>
			<td></td>
			<td>MQ013CG-ON</td>
		</tr>
		<tr>
			<td>PLA+ 3D Printer Material&#160;</td>
			<td>eSun</td>
			<td>none</td>
			<td>white</td>
		</tr>
		<tr>
			<td>Primary silicone</td>
			<td>KauPo Plankenhorn</td>
			<td>09301-005-000041</td>
			<td>EcoFlex 00-30</td>
		</tr>
		<tr>
			<td>Release Agent</td>
			<td>KauPo Plankenhorn</td>
			<td>09291-006-000001</td>
			<td>UTS Universal</td>
		</tr>
		<tr>
			<td>Secondary silicone</td>
			<td>KauPo Plankenhorn</td>
			<td>09301-005-000181</td>
			<td>DragonSkin NV10</td>
		</tr>
		<tr>
			<td>Silicone Thinner</td>
			<td>KauPo Plankenhorn</td>
			<td>09301-010-000002</td>
			<td></td>
		</tr>
		<tr>
			<td>Tougth PLA 3D Printer Material&#160;</td>
			<td>BASF</td>
			<td></td>
			<td>black</td>
		</tr>
	</tbody>
</table>

manufacturing process for non-adhesive super-soft vocal fold models

This study aims to develop super-soft, non-sticky vocal fold models for voice research. The conventional manufacturing process of silicone-based vocal fold models results in models with undesirable properties, such as stickiness and reproducibility issues. Those vocal fold models are prone to rapid aging, leading to poor comparability across different measurements. In this study, we propose a modification to the manufacturing process by changing the order of layering the silicone material, which leads to the production of non-sticky and highly consistent vocal fold models. We also compare a model produced using this method with a conventionally manufactured vocal fold model that is adversely affected by its sticky surface. We detail the manufacturing process and characterize the properties of the models for potential applications. The outcomes of the study demonstrate the efficacy of the modified fabrication method, highlighting the superior qualities of our non-sticky vocal fold models.&#160;The findings contribute to the development of realistic and reliable vocal fold models for research and clinical applications.

The fabricated vocal fold model was integrated into the measurement setup depicted in Supplementary Figure 3 at the vocal folds position. The setup, extensively detailed in a previous publication13, comprises a multi-stage controllable airflow source that stimulates the vocal fold models into oscillation, along with an array of measuring instruments that record data such as sound pressure, static pressure at specific positions, and volume velocity. For the measurements, the airflo...

Watch this Scientific Journal Video about Manufacturing Process for Non-Adhesive Super-Soft Vocal Fold Models at JoVE.com

Author Spotlight: Advancements in the Fabrication of Synthetic Vocal Fold Models for Phonetic and Robotic Applications

This study demonstrates the manufacturing of non-sticky and super-soft vocal fold models by introducing a specific way to create the vocal fold layers, providing a detailed description of the manufacturing procedure, and characterizing the properties of the models.

Manufacturing Process for Non-Adhesive Super-Soft Vocal Fold Models

This study aims to develop super-soft, non-sticky vocal fold models for voice research. The conventional manufacturing process of silicone-based vocal ...

manufacturing-process-for-non-adhesive-super-soft-vocal-fold-models

Research

JoVE Journal

Engineering

700 Views.  Technische Universität Dresden. This study demonstrates the manufacturing of non-sticky and super-soft vocal fold models by introducing a specific way to create the vocal fold layers, providing a detailed description of the manufacturing procedure, and characterizing the properties of the models.

Video: Author Spotlight: Advancements in the Fabrication of Synthetic Vocal Fold Models for Phonetic and Robotic Applications

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 ...

Digital Printing of Titanium Dioxide for Dye Sensitized Solar Cells

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less environmentally damaging with lower processing temperatures presenting a viable and low cost alternative to conventional production. This paper further enhances these environmental credentials by evaluating the digital printing and therefore additive production route for these cells. This is achieved here by investigating the formation and performance of a metal oxide photoelectrode using nanoparticle sized titanium dioxide. An ink-jettable material was formulated, characterized and printed with a piezoelectric inkjet head to produce a 2.6 &#181;m thick layer. The resultant printed layer was fabricated into a functioning cell with an active area of 0.25 cm2 and a power conversion efficiency of 3.5%. The binder-free formulation resulted in a reduced processing temperature of 250 &#176;C, compatible with flexible polyamide substrates which are stable up to temperatures of 350 &#730;C. The authors are continuing to develop this process route by investigating inkjet printing of other layers within dye sensitized solar cells.

This paper investigates the suitability of inkjet printing for the manufacturing of dye-sensitized solar cells. A binder-free TiO2 nanoparticle ink was formulated and printed onto a FTO glass substrate. The printed layer was fabricated into a cell with an active area of 0.25 cm2 and an efficiency of 3.5%.

Silicon solar cell manufacturing is an expensive and high energy consuming process. In contrast, dye sensitized solar cell production is less ...

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.

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

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 ...

Fabrication Procedures and Birefringence Measurements for Designing Magnetically Responsive Lanthanide Ion Chelating Phospholipid Assemblies

Bicelles are tunable disk-like polymolecular assemblies formed from a large variety of lipid mixtures. Applications range from membrane protein structural studies by nuclear magnetic resonance (NMR) to nanotechnological developments including the formation of optically active and magnetically switchable gels. Such technologies require high control of the assembly size, magnetic response and thermal resistance. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and its lanthanide ion (Ln3+) chelating phospholipid conjugate, 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA), assemble into highly magnetically responsive assemblies such as DMPC/DMPE-DTPA/Ln3+ (molar ratio 4:1:1) bicelles. Introduction of cholesterol (Chol-OH) and steroid derivatives in the bilayer results in another set of assemblies offering unique physico-chemical properties. For a given lipid composition, the magnetic alignability is proportional to the bicelle size. The complexation of Ln3+ results in unprecedented magnetic responses in terms of both magnitude and alignment direction. The thermo-reversible collapse of the disk-like structures into vesicles upon heating allows tailoring of the assemblies&#39; dimensions by extrusion through membrane filters with defined pore sizes. The magnetically alignable bicelles are regenerated by cooling to 5 &#176;C, resulting in assembly dimensions defined by the vesicle precursors. Herein, this fabrication procedure is explained and the magnetic alignability of the assemblies is quantified by birefringence measurements under a 5.5 T magnetic field. The birefringence signal, originating from the phospholipid bilayer, further enables monitoring of polymolecular changes occurring in the bilayer. This simple technique is complementary to NMR experiments that are commonly employed to characterize bicelles.

Fabrication procedures for highly magnetically responsive lanthanide ion chelating polymolecular assemblies are presented. The magnetic response is dictated by the assembly size, which is tailored by extrusion through nanopore membranes. The assemblies&#39; magnetic alignability and temperature-induced structural changes are monitored by birefringence measurements, a complimentary technique to nuclear magnetic resonance and small angle neutron scattering.

Bicelles are tunable disk-like polymolecular assemblies formed from a large variety of lipid mixtures. Applications range from membrane protein structural ...

Additive Manufacturing of Functionally Graded Ceramic Materials by Stereolithography

An additive manufacturing technology is applied to obtain functionally graded ceramic parts. This technology, based on digital light processing/stereolithography, is developed within the scope of the CerAMfacturing European research project. A three-dimensional (3-D) hemi-maxillary bone-like structure is 3-D printed using custom aluminum oxide polymeric mixtures. The powders and mixtures are fully analyzed in terms of rheological behavior in order to ensure proper material handling during the printing process. The possibility to print functionally graded materials using the Admaflex technology is explained in this document. Field-emission scanning electron microscopy (FESEM) show that the sintered aluminum oxide ceramic part has a porosity lower than 1% and no remainder of the original layered structure is found after analysis.

This manuscript describes the processing of single multifunctional ceramic components (e.g., combinations of dense-porous structures) additively manufactured by stereolithography.

An additive manufacturing technology is applied to obtain functionally graded ceramic parts. This technology, based on digital light ...

O-cresol Concentration Online Measurement Based On Near Infrared Spectroscopy Via Partial Least Square Regression

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the prediction of the components in industrial processes. The ability to record spectra for solid and liquid samples without any pretreatment is advantageous and the method is widely used. However, the disadvantages of analyzing high-dimensional near-infrared spectral data include information redundancy and multicollinearity of the spectral data. Thus, we propose to use partial least squares regression method, which has traditionally been used to reduce the data dimensionality and eliminate the collinearity between the original features. We implement the method for predicting the o-cresol concentration during the production of polyphenylene ether. The proposed approach offers the following advantages over component regression prediction methods: 1) partial least squares regression solves the multicollinearity problem of the independent variables and effectively avoids overfitting, which occurs in a regression analysis due to the high correlation between the independent variables; 2) the use of the near-infrared spectra results in high accuracy because it is a non-destructive and non-polluting method to obtain information at microscopic and molecular scales.

The protocol describes a method of predicting o-cresol concentration during the production of polyphenylene ether using near-infrared spectroscopy and partial least squares regression. To describe the process more clearly and completely, an example of predicting the o-cresol concentration during the production of polyphenylene is used to clarify the steps.

Unlike macroscopic process variables, near-infrared spectroscopy provides process information at the molecular level and can significantly improve the ...

Manufacturing, Control, and Performance Evaluation of a Gecko-Inspired Soft Robot

This protocol presents a method for manufacturing, control, and evaluation of the performance of a soft robot that can climb inclined flat surfaces with slopes of up to 84&#176;. The manufacturing method is valid for the fast pneunet bending actuators in general and might, therefore, be interesting for newcomers to the field of actuator manufacturing. The control of the robot is achieved by means of a pneumatic control box that can provide arbitrary pressures and can be built by only using purchased components, a laser cutter, and a soldering iron. For the walking performance of the robot, the pressure-angle calibration plays a crucial role. Therefore, a semi-automated method for the pressure-angle calibration is presented. At high inclines (&#62; 70&#176;), the robot can no longer reliably fix itself to the walking plane. Therefore, the gait pattern is modified to ensure that the feet can be fixed on the walking plane.

This protocol provides a detailed list of steps to be performed for the manufacturing, control and evaluation of the climbing performance of a gecko-inspired soft robot.

This protocol presents a method for manufacturing, control, and evaluation of the performance of a soft robot that can climb inclined flat surfaces with ...

Parallel Active Cantilever Arrays in AFMS to Enable High-Throughput Inspections

Active Probe Atomic Force Microscopy with Quattro-Parallel Cantilever Arrays for High-Throughput Large-Scale Sample Inspection

An Atomic Force Microscope&#160;(AFM) is&#160;a powerful and versatile tool for nanoscale surface studies to capture 3D topography images of samples. However, due to their limited imaging throughput, AFMs have not been widely adopted for large-scale inspection purposes. Researchers have developed high-speed AFM systems to record dynamic process videos in chemical and biological reactions at tens of frames per second, at the cost of a small imaging area of up to several square micrometers. In contrast, inspecting large-scale nanofabricated structures, such as semiconductor wafers, requires nanoscale spatial resolution imaging of a static sample over hundreds of square centimeters with high productivity. Conventional AFMs use a single passive cantilever probe with an optical beam deflection system, which can only collect one pixel at a time during AFM imaging, resulting in low imaging throughput. This work utilizes an array of active cantilevers with embedded piezoresistive sensors and thermomechanical actuators, which allows simultaneous multi-cantilever operation in parallel operation for increased imaging throughput. When combined with large-range nano-positioners and proper control algorithms, each cantilever can be individually controlled to capture multiple AFM images. With data-driven post-processing algorithms, the images can be stitched together, and defect detection can be performed by comparing them to the desired geometry. This paper introduces principles of the custom AFM using the active cantilever arrays, followed by a discussion on practical experiment considerations for inspection applications. Selected example images of silicon calibration grating, highly-oriented pyrolytic graphite, and extreme ultraviolet lithography masks are captured using an array of four active cantilevers (&#34;Quattro&#34;) with a 125 &#181;m tip separation distance. With more engineering integration, this high-throughput, large-scale imaging tool can provide 3D metrological data for extreme ultraviolet (EUV) masks, chemical mechanical planarization (CMP) inspection, failure analysis, displays, thin-film step measurements, roughness measurement dies, and laser-engraved dry gas seal grooves.

Author Spotlight: Introduction to Active Probe Atomic Force Microscopy with Quattro-Parallel Cantilever Arrays

Large-scale sample inspection with nanoscale resolution has a wide range of applications, especially for nanofabricated semiconductor wafers. Atomic force microscopes can be a great tool for this purpose, but are limited by their imaging speed. This work utilizes parallel active cantilever arrays in AFMs to enable high-throughput and large-scale inspections.

An Atomic Force Microscope&#160;(AFM) is&#160;a powerful and versatile tool for nanoscale surface studies to capture 3D topography images of samples. ...

Imaging of the Microstructural Failure Mechanism in the Human Hip

Imaging the bone microstructure under progressively increasing loads allows for observing the microstructural failure behavior of bone. Here, we describe a protocol for obtaining a sequence of three-dimensional microstructural images of the entire proximal femur under progressively increasing deformation, causing clinically relevant fractures of the femoral neck. The protocol is demonstrated using four femora from female donors aged 66-80 years at the lower end of bone mineral density in the population (T-score range = &#8722;2.09 to &#8722;4.75). A radio-transparent compressive stage was designed for loading the specimens replicating a one-leg stance, while recording the applied load during&#160;micro-computed tomography (micro-CT) imaging. The field of view was 146 mm wide and 132 mm high, and the isotropic pixel size was 0.03 mm. The force increment was based on finite-element predictions of the fracture load. The compressive stage was used to apply the displacement to the specimen and enact the prescribed force increments. Sub-capital fractures due to opening and shear of the femoral neck occurred after four to five load increments. The micro-CT&#160;images and the reaction force measurements were processed to study the bone strain and energy absorption capacity. Instability of the cortex appeared at the early loading steps. The subchondral bone in the femoral head displayed large deformations reaching 16% before&#160;fracture, and a progressive increase in the support capacity up to&#160;fracture. The deformation energy linearly increased with the displacement up to&#160;fracture, while the stiffness decreased to near-zero values immediately before&#160;fracture. Three-fourths of the fracture energy was taken by the specimen during the final 25% force increment. In conclusion, the protocol developed revealed a remarkable energy absorption capacity, or damage tolerance, and a synergic interaction between the cortical and trabecular bone at an advanced donor age.

The protocol enables the measurement of the deformation of the bone microstructure in the entire proximal human femur and its toughness by combining large-volume micro-CT scanning, a custom-made compressive stage, and advanced image processing tools.

Imaging the bone microstructure under progressively increasing loads allows for observing the microstructural failure behavior of bone. Here, we describe ...