Name: stereolithographic 3d printing with renewable acrylates
Uploaded: 2018-09-12T15:00:00
Description: Watch this Scientific Journal Video about Stereolithographic 3D Printing with Renewable Acrylates at JoVE.com

This study was supported by GreenPAC Polymer Application Centre as part of Project 140413: &#34;3D Printing in Production&#34;.&#160;We would like to acknowledge Albert Hartman, Corinne van Noordenne, Rens van Leeuwen, Anniek Bruins, Femke Tamminga, Jur van Dijken and Albert Woortman for facilitating the video shooting.

CAUTION: Please consult all relevant material safety data sheets (MSDS) before use.
1. Preparation of Photocurable Resin
NOTE: Please use personal protective equipment (safety glasses, gloves, lab coat) during the following procedure. See our previous work12 for more details on this section.
<ol>
	<li>Pour 50 g of 1,10-decanediol diacrylate (SA5201) in a 500 mL Erlenmeyer flask.</li>
	<li>Add 1.0 g of diphenyl(2,4,6-trimethylbenzoyl)phosphi...

<ol>
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M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+3D+printing+of+biomaterials.">Recent advances in 3D printing of biomaterials.</a> Journal of Biological Engineering. 9, 4 (2015).</li><li>Mechels, F. P. W., Feijen, J., Grijpma, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+on+stereolithography+and+its+applications+in+biomedical+engineering.">A review on stereolithography and its applications in biomedical engineering.</a> Biomaterials. 31, 6121-6130 (2010).</li><li>Skoog, S. A., Goering, P. L., Narayan, R. 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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optical+approach+to+resin+formulation+for+3D+printed+microfluidics.">Optical approach to resin formulation for 3D printed microfluidics.</a> RSC Advances. 5, 106621-106632 (2015).</li><li>Zarek, M., Layani, M., Cooperstein, I., Sachyani, E., Cohn, D., Magdassi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+printing+of+shape+memory+polymers+for+flexible+electronic+devices.">3D printing of shape memory polymers for flexible electronic devices.</a> Advanced Materials. 28, 4449-4454 (2016).</li><li>Ligon-Auer, S. C., Schwentenwein, M., Gorsche, C., Stampfl, J., Liska, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toughening+of+photo-curable+polymer+networks:+A+review.">Toughening of photo-curable polymer networks: A review.</a> Polymer Chemistry. 7, 257-286 (2016).</li><li>Miao, S., Zhu, W., Castro, N. J., Nowicki, M., Zhou, X., Cui, H., Fisher, J. P., Zhang, L. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=4D+printing+smart+biomedical+scaffolds+with+novel+soybean+oil+epoxidized+acrylate.">4D printing smart biomedical scaffolds with novel soybean oil epoxidized acrylate.</a> Scientific Reports. 6, 27226 (2016).</li><li>Voet, V. S. D., Strating, T., Schnelting, G. H. M., Dijkstra, P., Tietema, M., Xu, J., Woortman, A. J. J., Loos, K., Jager, J., Folkersma, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biobased+acrylate+photocurable+resin+formulation+for+stereolithographic+3D+printing.">Biobased acrylate photocurable resin formulation for stereolithographic 3D printing.</a> ACS Omega. 3, 1403-1408 (2018).</li><li>Ligon-Auer, S. C., Liska, R., Stampfl, J., Gurr, M., M&#252;lhaupt, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymers+for+3D+Printing+and+Customized+Additive+Manufacturing.">Polymers for 3D Printing and Customized Additive Manufacturing.</a> Chemical Reviews. 117, 10212-10290 (2017).</li><li>Weng, Z., Zhou, Y., Lin, W., Senthil, T., Wu, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure-property+relationship+of+nano+enhanced+stereolithography+resin+for+desktop+SLA+3D+printer.">Structure-property relationship of nano enhanced stereolithography resin for desktop SLA 3D printer.</a> Composites: Part A. 88, 234-242 (2016).</li><li>Scalera, F., Esposito Corcione, C., Montagna, F., Sannino, A., Maffezzoli, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+characterization+of+UV+curable+epoxy/hydroxyapatite+suspensions+for+stereolithography+applied+to+bone+tissue+engineering.">Development and characterization of UV curable epoxy/hydroxyapatite suspensions for stereolithography applied to bone tissue engineering.</a> Ceramics International. 40, 15455-15462 (2014).</li><li>Lee, H., Fang, N. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micro+3D+Printing+using+a+digital+projector+and+its+application+in+the+study+of+soft+materials+mechanics.">Micro 3D Printing using a digital projector and its application in the study of soft materials mechanics.</a> Journal of Visualized Experiments. (69), e4457 (2012).</li><li>Huemer, K., Squirrell, J. M., Swader, R., Pelkey, K., LeBert, D. C., Huttenlocher, A., Eliceiri, K. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+live+imaging+device+for+improved+experimental+manipulation+of+zebrafish+larvae.">Long-term live imaging device for improved experimental manipulation of zebrafish larvae.</a> Journal of Visualized Experiments. (128), e56340 (2017).</li><li>Decker, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light-induced+crosslinking+polymerization.">Light-induced crosslinking polymerization.</a> Polymer International. 51, 1141-1150 (2002).</li><li>Elliot, J. E., Bowman, C. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Predicting+network+formation+of+free+radical+polymerization+of+multifunctional+monomers.">Predicting network formation of free radical polymerization of multifunctional monomers.</a> Polymer Reaction Engineering. 10, 1-19 (2002).</li><li>Ellakwa, A., Cho, N., Lee, I. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+resin+matrix+composition+on+the+polymerization+shrinkage+and+rheological+properties+of+experimental+dental+composites.">The effect of resin matrix composition on the polymerization shrinkage and rheological properties of experimental dental composites.</a> Dental Materials. 23, 1229-1235 (2007).</li><li>Charton, C., Falk, V., Marchal, P., Pla, F., Colon, P. <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+Tg,+viscosity+and+chemical+structure+of+monomers+on+shrinkage+stress+in+light-cured+dimethacrylate-based+dental+resins.">Influence of Tg, viscosity and chemical structure of monomers on shrinkage stress in light-cured dimethacrylate-based dental resins.</a> Dental Materials. 23, 1447-1459 (2007).</li></ol>

Additive manufacturing is applied in fabrication of tailor-made prototypes and small series, when the higher production costs per part can compete with conventional processes since there is no need for production of molds and tools. In the last decade, the revenues from services and products related to additive manufacturing have grown exponentially13. The largest fraction of material sales is from photopolymers. The growth attracted attention and initiated the investments of major industries, <em...

Rapid prototyping enables on-demand production and design freedom and allows the efficient manufacturing of 3D constructs in a layer-by-layer manner1. As a result, 3D printing as a fabrication technique has developed rapidly in recent years2. Various technologies are available, all relying on the translation of virtual models into physical objects, and applying processes such as extrusion, direct energy deposition, powder solidification, sheet lamination and photopolymerization. The latter involves stepwise UV curing of liquid photopolymer resins. In 1986, Hull and co-workers developed the stereolithography apparatus (SLA), a UV laser-based 3D printer. More recently, a similar process called digital light processing (DLP) has become available, in which photopolymerization is initiated by a light projector. Together, DLP and SLA are referred to as stereolithography 3D printing3.
SLA is applied in high-resolution prototyping and fabrication of biomedical devices4,5. This technology is superior to the widely used fused deposition modeling (FDM) in terms of accuracy, surface finishing and resolution6. Depending on the architecture of the product, a support structure is integrated in the 3D model to stabilize the construct during fabrication. Furthermore, a post-printing treatment of manufactured parts is required7,8. Typically, printed objects are washed in an alcohol bath to dissolve unreacted resin, and subsequent curing in an UV oven is performed to guarantee full conversion of the polymerization9.
In general, resins for lithography-based additive manufacturing rely on photocurable systems containing multifunctional acrylates or epoxides10. Current photopolymer resins on the commercial market are fossil-based and expensive, while the availability of low-cost renewable resins is needed to facilitate waste-free and local manufacturing of sustainable 3D products for a biobased economy1,6. Recently, photopolymer resins based on renewable acrylates were developed and successfully applied in stereolithography 3D printing11,12. In this detailed protocol, we demonstrate the rapid prototyping with biobased resins on a commercial stereolithography apparatus. Special attention is paid to critical steps in the procedure, i.e., resin formulation and post-printing treatments, to help new practitioners in the field of additive manufacturing.

<table>
	<tbody>
		<tr>
			<td>Isobornyl acrylate&#160;</td>
			<td>Sartomer</td>
			<td>SA5102</td>
			<td>Acrylate monomer</td>
		</tr>
		<tr>
			<td>1,10-decanediol diacrylate</td>
			<td>Sartomer</td>
			<td>SA5201</td>
			<td>Acrylate monomer</td>
		</tr>
		<tr>
			<td>Pentaerythritol tetraacrylate</td>
			<td>Sartomer</td>
			<td>SA5400</td>
			<td>Acrylate monomer</td>
		</tr>
		<tr>
			<td>Multifunctional epoxy acrylate</td>
			<td>Sartomer</td>
			<td>SA7101</td>
			<td>Acrylate oligomer</td>
		</tr>
		<tr>
			<td>Diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO), 97%</td>
			<td>Sigma Aldrich</td>
			<td>415952</td>
			<td>Photoinitiator</td>
		</tr>
		<tr>
			<td>2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBOT), 99%</td>
			<td>Sigma Aldrich</td>
			<td>223999</td>
			<td>Optical absorber</td>
		</tr>
		<tr>
			<td>Isopropyl alcohol (IPA), 99%</td>
			<td>Bleko</td>
			<td>1010500</td>
			<td>For alcohol bath (applied in Form Wash)</td>
		</tr>
		<tr>
			<td>Paar Physica MCR300&#160;</td>
			<td>Anton Paar</td>
			<td>-</td>
			<td>Rheometer with parallel plate geometry</td>
		</tr>
		<tr>
			<td>Form 2 Printer</td>
			<td>Formlabs</td>
			<td>-</td>
			<td>Desktop SLA 3D printer</td>
		</tr>
		<tr>
			<td>Form Wash&#160;</td>
			<td>Formlabs</td>
			<td>-</td>
			<td>Washing station</td>
		</tr>
		<tr>
			<td>Form Cure</td>
			<td>Formlabs</td>
			<td>-</td>
			<td>UV oven</td>
		</tr>
		<tr>
			<td>Instron 4301 1KN Series IX</td>
			<td>Instron</td>
			<td>-</td>
			<td>Universal testing machine</td>
		</tr>
		<tr>
			<td>Philips XL30 ESEM-FEG&#160;</td>
			<td>Philips</td>
			<td>-</td>
			<td>Scanning electron microscope</td>
		</tr>
	</tbody>
</table>

stereolithographic 3d printing with renewable acrylates

The accessibility of cost-competitive renewable materials and their application in additive manufacturing is essential for an efficient biobased economy. We demonstrate the rapid prototyping of sustainable resins using a stereolithographic 3D printer. Resin formulation takes place by straightforward mixing of biobased acrylate monomers and oligomers with a photoinitiatior and optical absorber. Resin viscosity is controlled by the monomer to oligomer ratio and is determined as a function of shear rate by a rheometer with parallel plate geometry. A stereolithographic apparatus charged with the biobased resins is employed to produce complex shaped prototypes with high accuracy. The products require a post-treatment, including alcohol rinsing and UV irradiation, to ensure complete curing. The high feature resolution and excellent surface finishing of the prototypes is revealed by scanning electron microscopy.

Four representative resin compositions are displayed in Table 1, along with their average biobased carbon content (BC) derived from the individual BC of the components. The resin viscosity (Figure 1) is influenced by the ratio of acrylate monomers and oligomers and typically demonstrates Newtonian behavior. The mechanical properties of parts manufactured from various resins were determined by stress-strain analysis. Figur...

Watch this Scientific Journal Video about Stereolithographic 3D Printing with Renewable Acrylates at JoVE.com

Stereolithographic 3D Printing with Renewable Acrylates

A protocol for additive manufacturing with renewable photopolymer resins on a stereolithography apparatus is presented.

The accessibility of cost-competitive renewable materials and their application in additive manufacturing is essential for an efficient biobased economy. ...

This method can help to understand key subjects in the field of of additive manufacturing, such as resin formulation and post-printing treatment. The main advantage of this technique is that it enables the accurate and on-demand fabrication of sustainable products. This method will provide insight into laser-based stereolithography but it can also be applied to other 3D printing techniques such as Digital Light Processing.To begin, pour 50 grams of 1, 10-decanediol diacrylate in a 500-milliliter Erlenmeyer flask. Add 1.0 grams of TPO and 0.40 grams of BBOT to the flask. Equip the Erlenmeyer flask with a mechanical stirrer and stir the mixture at 200 rpm for five minutes at room temperature in order to dissolve the TPO and BBOT in the acrylate monomer.Add 100 grams of pentaerythritrol tetraacrylate and 100 grams of multi-functional epoxy acrylate to the mixture. Now stir the mixture at 200 rpm for 30 minutes at 50 degrees Celsius to ensure a homogeneous resin. Remove the mechanical stirrer and fit the flask with a stopper.Wrap the flask in aluminum foil to protect the biobased acrylate photopolymer resin from light. Now cover the bottom plate of a rheometer characterized by parallel-plate geometry with the photoresin. Set the gap between the plates at one millimeter and cover the rheometer with a UV-resistant hood.Measure the resin viscosity at room temperature at shear rates from 0.1 to 100 inverse seconds. Turn on the the SLA 3D printer and select the Open mode. Depending on the architecture of the product, a support structure can be integrated in the 3D model to stabilize the construct during fabrication.Start the model preparation software on a computer. To choose the desired print settings, select Clear for material, Version V4, and 50-micron layer thickness. Open the digital model of the complex-shaped prototype which is a standard tesselation language file, then choose the location and orientation on the build platform.Upload the print job to the SLA 3D printer. Now pour 200 milliliters of the biobased photoresin into a resin tank. Open the 3D printer and mount the resin tank properly.Mount the build platform and close the 3D printer. Following preparation of the 3D printer, start the print job. Allow the 3D printer to fabricate complex-shaped prototypes.Do not open the printer until the print job is finished. For the demonstrated protocol, the wavelength of the UV laser is 405 nanometers. The print time of the object is 2.5 hours and is shown here in fast motion.When the print job is finished, open the printer. Remove the build platform with the produced parts attached and close the printer. Open the washing station filled with isopropyl alcohol and insert the build platform.Start the procedure and rinse for 20 minutes to remove any unreacted resin. When the rinsing procedure is finished, remove the build platform from the washing station and detach the prototypes from the build platform. Allow the prototypes to air dry for 30 minutes.In the meantime, preheat the UV oven at 60 degrees Celsius. Open the UV oven and quickly place the prototypes on the rotating platform. Close the UV oven and cure for 60 minutes at 60 degrees Celsius to ensure complete conversion.When the post-curing procedure is finished, open the UV oven and take out the prototypes. To characterize the surface morphology of complex-shaped prototypes, cut approximately one centimeter of internal helix from the complex-shaped prototype using a razor blade. Attach the sample to the sample holder with double-sided, carbon-conductive tape.Prior to imaging, coat the sample with 30 nanometers of platinum palladium on a sputtering system. Now insert the sample into a scanning electron microscope operating at an accelerating voltage of five kilovolts. Acquire several images of the sample at 30X and 120X magnification.The viscosity of the renewable resin is an essential parameter in the 3D printing process and is controlled by the monomer to oligomer ratio. Typically a shear rate of 100 inverse seconds is achieved during the recoat of liquid resin in the printing process. All bioresins have a viscosity below five Pascal seconds and are appropriate for application in stereolithographic printing equipment.Shown here are representative results for the mechanical behavior of the objects printed from various bioresins, including tensile strength and e-modulus. However, optimization of the post-printing treatment by varying the duration of washing, drying, curing, and temperature of curing can lead to a significant improvement in mechanical performance. The smooth surface and high feature resolution of the complex-shaped prototypes is revealed by the electron microscope.The serrated vertical edges of the helices arise from the layer-by-layer SLA printing process, in which the top of an exposed layer receives a larger UV dose compared to the back of a layer. The extent of surface cracking is related to the initial resin viscosity. After its development, this technique paved the way for application of cost-competitive bioresins to facilitate waste-free and local manufacturing of sustainable products.Don't forget that working with acrylates can be hazardous. Precautions such as wearing safety glasses and gloves should always be taken while performing this procedure.

stereolithographic-3d-printing-with-renewable-acrylates

Research

JoVE Journal

Chemistry

Determination of Carbonyl Functional Groups in Bio-oils by Potentiometric Titration: The Faix Method

Carbonyl compounds present in bio-oils are known to be responsible for bio-oil property changes upon storage and during upgrading. Specifically, carbonyls cause an increase in viscosity (often referred to as &#39;aging&#39;) during storage of bio-oils. As such, carbonyl content has previously been used as a method of tracking bio-oil aging and condensation reactions with less variability than viscosity measurements. Additionally, carbonyls are also responsible for coke formation in bio-oil upgrading processes. Given the importance of carbonyls in bio-oils, accurate analytical methods for their quantification are very important for the bio-oil community. Potentiometric titration methods based on carbonyl oximation have long been used for the determination of carbonyl content in pyrolysis bio-oils. Here, we present a modification of the traditional carbonyl oximation procedures that results in less reaction time, smaller sample size, higher precision, and more accurate carbonyl determinations. While traditional carbonyl oximation methods occur at room temperature, the Faix method presented here occurs at an elevated temperature of 80 &#176;C.

Here we present a potentiometric titration technique for accurately quantifying carbonyl compounds in pyrolysis bio-oils.

Carbonyl compounds present in bio-oils are known to be responsible for bio-oil property changes upon storage and during upgrading. Specifically, carbonyls ...

Temperature-programmed Deoxygenation of Acetic Acid on Molybdenum Carbide Catalysts

Temperature programmed reaction (TPRxn) is a simple yet powerful tool for screening solid catalyst performance at a variety of conditions. A TPRxn system includes a reactor, furnace, gas and vapor sources, flow control, instrumentation to quantify reaction products (e.g., gas chromatograph), and instrumentation to monitor the reaction in real time (e.g., mass spectrometer). Here, we apply the TPRxn methodology to study molybdenum carbide catalysts for the deoxygenation of acetic acid, an important reaction among many in the upgrading/stabilization of biomass pyrolysis vapors. TPRxn is used to evaluate catalyst activity and selectivity and to test hypothetical reaction pathways (e.g., decarbonylation, ketonization, and hydrogenation). The results of the TPRxn study of acetic acid deoxygenation show that molybdenum carbide is an active catalyst for this reaction at temperatures above ca. 300 &#176;C and that the reaction favors deoxygenation (i.e., C-O bond-breaking) products at temperatures below ca. 400 &#176;C and decarbonylation (i.e., C-C bond-breaking) products at temperatures above ca. 400 &#176;C.

Presented here is a protocol for the operation of a micro-scale temperature-programmed reactor for evaluating the catalytic performance of molybdenum carbide during acetic acid deoxygenation.

Temperature programmed reaction (TPRxn) is a simple yet powerful tool for screening solid catalyst performance at a variety of conditions. A TPRxn system ...

Microfluidic-based Synthesis of Covalent Organic Frameworks (COFs): A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The first COF was reported in 2005 with much effort centered on the establishment of new synthetic routes for its preparation. To date, most available synthetic methods for COF synthesis are based on bulk mixing under solvothermal conditions. Therefore, there is increasing interest in developing systematic protocols for COF synthesis that provide for fine control over reaction conditions and improve COF processability on surfaces, which is essential for their use in practical applications. Herein, we present a novel microfluidic-based method for COF synthesis where the reaction between two constituent building blocks, 1,3,5-benzenetricarbaldehyde (BTCA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB), takes place under controlled diffusion conditions and at room temperature. Using such an approach yields sponge-like, crystalline fibers of a COF material, hereafter called MF-COF. The mechanical properties of MF-COF and the dynamic nature of the approach allow the continuous production of MF-COF fibers and their direct printing onto surfaces. The general method opens new potential applications requiring advanced printing of 2D or 3D COF structures on flexible or rigid surfaces.

Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

We present a novel microfluidic-based method for synthesis of covalent organic frameworks (COFs). We demonstrate how this approach can be used to produce continuous COF fibers, and also 2D or 3D COF structures on surfaces.

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The ...

Preparation of Chitosan-based Injectable Hydrogels and Its Application in 3D Cell Culture

The protocol presents a facile, efficient, and versatile method to prepare chitosan-based hydrogels using dynamic imine chemistry. The hydrogel is prepared by mixing solutions of glycol chitosan with a synthesized benzaldehyde terminated polymer gelator, and hydrogels are efficiently obtained in several minutes at room temperature. By varying ratios between glycol chitosan, polymer gelator, and water contents, versatile hydrogels with different gelation times and stiffness are obtained. When damaged, the hydrogel can recover its appearances and modulus, due to the reversibility of the dynamic imine bonds as crosslinkages. This self-healable property enables the hydrogel to be injectable since it can be self-healed from squeezed pieces to an integral bulk hydrogel after the injection process. The hydrogel is also multi-responsive to many bio-active stimuli due to different equilibration statuses of the dynamic imine bonds. This hydrogel was confirmed as bio-compatible, and L929 mouse fibroblast cells were embedded following standard procedures and the cell proliferation was easily assessed by a 3D cell cultivation process. The hydrogel can offer an adjustable platform for different research where a physiological mimic of a 3D environment for cells is profited. Along with its multi-responsive, self-healable, and injectable properties, the hydrogels can potentially be applied as multiple carriers for drugs and cells in future bio-medical applications.

Here we describe a facile preparation of chitosan-based injectable hydrogels using dynamic imine chemistry. Methods to adjust the hydrogel&#8217;s mechanical strength and its application in 3D cell culture are presented.

The protocol presents a facile, efficient, and versatile method to prepare chitosan-based hydrogels using dynamic imine chemistry. The hydrogel is ...

Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen reduction reaction. Spontaneous galvanic displacement was used to deposit Pt layers onto Ni nanowire substrates. The synthesis approach produced catalysts with high specific activities and high Pt surface areas. Hydrogen annealing improved Pt and Ni mixing and specific activity. Acid leaching was used to preferentially remove Ni near the nanowire surface, and oxygen annealing was used to stabilize near-surface Ni, improving durability and minimizing Ni dissolution. These protocols detail the optimization of each post-synthesis processing step, including hydrogen annealing to 250 &#176;C, exposure to 0.1 M nitric acid, and oxygen annealing to 175 &#176;C. Through these steps, Pt-Ni nanowires produced increased activities more than an order of magnitude than Pt nanoparticles, while offering significant durability improvements. The presented protocols are based on Pt-Ni systems in the development of fuel cell catalysts. These techniques have also been used for a variety of metal combinations, and can be applied to develop catalysts for a number of electrochemical processes.

&#160; The protocol describes the synthesis and electrochemical testing of platinum-nickel nanowires. Nanowires were synthesized by the galvanic displacement of a nickel nanowire template. Post-synthesis processing, including hydrogen annealing, acid leaching, and oxygen annealing were used to optimize nanowire performance and durability in the oxygen reduction reaction.

Platinum-nickel (Pt-Ni) nanowires were developed as fuel cell electrocatalysts, and were optimized for the performance and durability in the oxygen ...

Obtaining 3D Chemical Maps by Energy Filtered Transmission Electron Microscopy Tomography

Energy filtered transmission electron microscopy tomography (EFTEM tomography) can provide three-dimensional (3D) chemical maps of materials at a nanometric scale. EFTEM tomography can separate chemical elements that are very difficult to distinguish using other imaging techniques. The experimental protocol described here shows how to create 3D chemical maps to understand the chemical distribution and morphology of a material. Sample preparation steps for data segmentation are presented. This protocol permits the 3D distribution analysis of chemical elements in a nanometric sample. However, it should be noted that currently, the 3D chemical maps can only be generated for samples that are not beam sensitive, since the recording of filtered images requires long exposure times to an intense electron beam. The protocol was applied to quantify the chemical distribution of the components of two different heterogeneous catalyst supports. In the first study, the chemical distribution of aluminum and titanium in titania-alumina supports was analyzed. The samples were prepared using the swing-pH method. In the second, the chemical distribution of aluminum and silicon in silica-alumina supports that were prepared using the sol-powder and mechanical mixture methods was examined.

This paper describes a protocol to achieve 3D chemical maps combining energy filtered imaging and electron tomography. The chemical distribution of two catalyst supports formed by elements that are difficult to distinguish by other imaging techniques was studied. Each application consists of mapping overlapped chemical elements - respectively spaced-ionization edges.

Energy filtered transmission electron microscopy tomography (EFTEM tomography) can provide three-dimensional (3D) chemical maps of materials at a ...

Methionine Functionalized Biocompatible Block Copolymers for Targeted Plasmid DNA Delivery

Reversible addition-fragmentation chain transfer (RAFT) polymerization integrates the advantages of radical polymerization and living polymerization. This work presents the preparation of methionine functionalized biocompatible block copolymers via RAFT polymerization. Firstly, N,N-bis(2-hydroxyethyl)methacrylamide-b-N-(3-aminopropyl)methacrylamide (BNHEMA-b-APMA, BA) was synthesized via RAFT polymerization using 4,4&#8217;-azobis(4-cyanovaleric acid) (ACVA) as an initiating agent and 4-cyanopentanoic acid dithiobenzoate (CTP) as the chain transfer agent. Subsequently, N,N-bis(2-hydroxyethyl)methacrylamide-b-N-(3-guanidinopropyl)methacrylamide (methionine grafted BNHEMA-b-GPMA, mBG) was prepared by modifying amine groups in APMA with methionine and guanidine groups. Three kinds of block polymers, mBG1, mBG2, and mBG3, were synthesized for comparison. A ninhydrin reaction was used to quantify the APMA content; mBG1, mBG2, and mBG3 had 21%, 37%, and 52% of APMA, respectively. Gel permeation chromatography (GPC) results showed that BA copolymers possess molecular weights of 16,200 (BA1), 20,900(BA2), and 27,200(BA3) g/mol. The plasmid DNA (pDNA) complexing ability of the obtained block copolymer gene carriers was also investigated. The charge ratios (N/P) were 8, 16, and 4 when pDNA was complexed completely with mBG1, mBG2, mBG3, respectively. When the N/P ratio of mBG/pDNA polyplexes was higher than 1, the Zeta potential of mBG was positive. At an N/P ratio between 16 and 32, the average particle size of mBG/pDNA polyplexes was between 100-200 nm. Overall, this work illustrates a simple and convenient protocol for the block copolymer carrier synthesis.

This work presents the preparation of methionine functionalized biocompatible block copolymers (mBG) via the reversible addition-fragmentation chain transfer (RAFT) method. The plasmid DNA complexing ability of the obtained mBG and their transfection efficiency were also investigated. The RAFT method is very beneficial for polymerizing monomers containing special functional groups.

Reversible addition-fragmentation chain transfer (RAFT) polymerization integrates the advantages of radical polymerization and living polymerization. This ...

Inkjet Printing All Inorganic Halide Perovskite Inks for Photovoltaic Applications

A method for synthesizing photoactive inorganic&#160;perovskite quantum dot inks and an inkjet printer deposition method, using the synthesized inks, are demonstrated. The ink synthesis is based on a simple wet chemical reaction and the inkjet printing protocol is a facile step by step method. The inkjet printed thin films have been characterized by X-ray diffraction, optical absorption spectroscopy, photoluminescent spectroscopy, and electronic transport measurements. X-ray diffraction of the printed quantum dot films indicates a crystal structure consistent with an orthorhombic room temperature phase with (001) orientation. In conjunction with other characterization methods, the X-ray diffraction&#160;measurements show high quality films can be obtained through the inkjet printing method.

A protocol for synthesizing inorganic-lead-halide hybrid perovskite quantum dot inks for inkjet printing and the protocol for preparing and printing the quantum dot inks in an inkjet printer with post characterization techniques are presented.

A method for synthesizing photoactive inorganic&#160;perovskite quantum dot inks and an inkjet printer deposition method, using the synthesized inks, are ...

Reactive Inkjet Printing and Propulsion Analysis of Silk-based Self-propelled Micro-stirrers

In this study, a protocol for using reactive inkjet printing to fabricate enzymatically propelled silk swimmers with well-defined shapes is reported. The resulting devices are an example of self-propelled objects capable of generating motion without external actuation and have potential applications in medicine and environmental sciences for a variety of purposes ranging from micro-stirring, targeted therapeutic delivery, to water remediation (e.g., cleaning oil spills). This method employs reactive inkjet printing to generate well-defined small-scale solid silk structures by converting water soluble regenerated silk fibroin (silk I) to insoluble silk fibroin (silk II). These structures are also selectively doped in specific regions with the enzyme catalase in order to produce motion via bubble generation and detachment. The number of layers printed determines the three-dimensional (3D) structure of the device, and so here the effect of this parameter on the propulsive trajectories is reported. The results demonstrate the ability to tune the motion by varying the dimensions of the printed structures.

This protocol demonstrates the ability to utilize reactive inkjet printing to print self-motile biocompatible and environmentally friendly micro-stirrers for use in biomedical and environmental applications.

In this study, a protocol for using reactive inkjet printing to fabricate enzymatically propelled silk swimmers with well-defined shapes is reported. The ...

3D Depth Profile Reconstruction of Segregated Impurities Using Secondary Ion Mass Spectrometry

The presented protocol combines excellent detection limits (1 ppm to 1 ppb) using secondary ion mass spectrometry (SIMS) with reasonable spatial resolution (~1 &#181;m). Furthermore, it describes how to obtain realistic three-dimensional (3D) distributions of segregated impurities/dopants in solid state materials. Direct 3D depth profile reconstruction is often difficult to achieve due to SIMS-related measurement artifacts. Presented here is a method to identify and solve this challenge. Three major issues are discussed, including the i) nonuniformity of the detector being compensated by flat-field correction; ii) vacuum background contribution (parasitic oxygen counts from residual gases present in the analysis chamber) being estimated and subtracted; and iii)&#160;performance of all steps within a stable timespan of the primary ion source. Wet chemical etching is used to reveal the position and types of dislocation in a material, then the SIMS result is superimposed on images obtained via scanning electron microscopy (SEM). Thus, the position of agglomerated impurities can be related to the position of certain defects. The method is fast and does not require sophisticated sample preparation stage; however, it requires a high-quality, stable ion source, and the entire measurement must be performed quickly to avoid deterioration of the primary beam parameters.

The presented method describes how to identify and solve measurement artifacts related to secondary ion mass spectrometry as well as obtain realistic 3D distributions of impurities/dopants in solid state materials.