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)phosphine oxide (TPO) and 0.40 g of 2,5-bis(5-tert-butyl-benzoxazol-2-yl)thiophene (BBOT) to the flask.</li>
	<li>Equip the flask with a mechanical stirrer and stir the mixture at 200 rpm for 5 min at room temperature in order to dissolve TPO and BBOT in the acrylate monomer.</li>
	<li>Add 100 g of pentaerythritol tetraacrylate and 100 g of multifunctional epoxy acrylate (see Table of Materials) to the mixture.</li>
	<li>Stir the mixture at 200 rpm for 30 min at 50 &#176;C to ensure a homogeneous resin.</li>
	<li>Remove the mechanical stirrer and fit the flask with a stopper. The flask is wrapped in aluminium foil to protect the biobased acrylate photopolymer resin (BAPR) from light. 
	NOTE: The protocol can be paused here.</li>
	<li>Cover the bottom plate of a rheometer with parallel-plate geometry with the photoresin.</li>
	<li>Set the gap between the plates at 1 mm and cover the rheometer with a UV resistant hood.</li>
	<li>Measure the resin viscosity at room temperature at shear rates from 0.1 to 100 s-1; e.g.,0.100, 0.126, 0.158, 0.200, 0.251, 0.316, 0.398, 0.501, 0.631, 0.794, 1.00, 1.26, 1.58, 2.00, 2.51, 3.16, 3.98, 5.01, 6.31, 7.94, 10.0, 12.6, 15.8, 20.0, 25.1, 31.6, 39.8, 50.1, 63.1, 79.4, and 100 s-1.</li>
</ol>
2. Stereolithographic 3D Printing with Biobased Acrylates
NOTE: See our previous work12 for more details on this section.
<ol>
	<li>Turn on the SLA 3D printer and select open mode.</li>
	<li>Start the model preparation software on a computer. Choose the desired print settings: material (Clear), version (V4) and layer thickness (50 &#181;m).</li>
	<li>Open the digital model of the complex-shaped prototype, a standard tessellation language (.stl) file (see Supplemental Coding File) and choose the location and orientation on the build platform.&#160; Upload the print job from the model preparation software to the SLA 3D printer. 
	NOTE: Depending on the architecture of the product, a support structure can be integrated in the 3D model to stabilize the construct during fabrication. In case of the complex-shaped prototype demonstrated here, a support structure is not required if printed normal to the build direction.</li>
	<li>Pour 200 mL of the biobased photoresin into a resin tank. Open the 3D printer and mount the resin tank properly.</li>
	<li>Mount the build platform and close the 3D printer.</li>
	<li>Start the print job.</li>
	<li>Allow the 3D printer to fabricate complex shaped prototypes.&#160; Do not open the printer until the print job is finished. 
	NOTE: Before printing, make sure the 3D printer is leveled. For the demonstrated protocol, the wavelength of the UV laser is 405 nm. The print time of the object is 2.5 h.</li>
</ol>
3. Post-treatment of 3D Printed Objects
NOTE: Please use personal protective equipment (safety glasses, gloves) during the following procedure.
<ol>
	<li>When the print job is finished, open the printer. Remove the build platform, with the produced parts attached, and close the printer.</li>
	<li>Open the washing station, filled with isopropyl alcohol, and insert the build platform. Start the procedure and rinse for 20 min to remove any unreacted resin.</li>
	<li>When the rinsing procedure is finished, remove the build platform from the washing station and detach the prototypes from the build platform.</li>
	<li>Allow the prototypes to air dry for 30 min. In the meantime, preheat the UV oven at 60 &#176;C. 
	NOTE: Preheating will take at least 15 min. The UV wavelength of the oven is 405 nm, identical to the wavelength of the SLA laser.</li>
	<li>Open the UV oven and quickly place the prototypes on the rotating platform. Close the UV oven and cure for 60 min at 60 &#176;C to ensure complete conversion.</li>
	<li>When the post-curing procedure is finished, open the UV oven and take out the prototypes.</li>
</ol>
4. Characterization of Surface Morphology of Complex-shaped Prototypes
NOTE: See our previous work12 for more details on this section.
<ol>
	<li>Cut ca. 1 cm of internal helix from the complex shaped prototype using a razor blade.</li>
	<li>Attach the sample to the sample holder with double sided carbon conductive tape.</li>
	<li>Prior to imaging, coat the sample with 30 nm Pt/Pd (80:20) on a sputtering system.</li>
	<li>Insert the sample into a scanning electron microscope operating at an accelerating voltage of 5 kV. Acquire several images of the sample at 30X and 120X magnification.</li>
</ol>

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The authors have nothing to disclose.

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, e.g., aerospace, automotive, medical. Therefore, the field of 3D printing is expected to further expand in the upcoming years.
We have demonstrated an efficient method for the accurate and on-demand fabrication of sustainable products with renewable photopolymer resins on a stereolithographic 3D printer. The use of low-cost biobased acrylates as the main component makes these resins potentially cost-competitive with respect to their commercial counterparts. Moreover, the bioresin formulations were successfully applied in a standardized SLA 3D printing process, thereby using the same procedure and settings as applied for commercial resins. The viscosity of the acrylate 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 s-1 is achieved during the recoat of liquid resin in the printing process14,15. In this region, all bioresins have a viscosity below 5 Pa&#183;s (Figure 1) and are appropriate for application in stereolithographic printing equipment.
Lithography-based additive manufacturing is recognized for its excellent surface quality and precision in comparison to FDM and selective laser sintering (SLS)16,17. This is clearly demonstrated by the photographic and microscopic images representing the complex shaped prototypes (Figure 4). To the contrary, the mechanical properties of produced parts are limited due to the limited choice of materials suited for the SLA process18,19. Acrylate systems in general show brittleness and poor impact resistance due to high crosslink density and inhomogeneous network architecture. Consequently, the materials 3D printed from the renewable acrylate resins have an ultimate strength of 2-8 MPa (Figure 2), which is lower in comparison to commercial products12. Nevertheless, optimization of the post-treatment, by varying the duration of washing, drying, curing and temperature of curing, leads to a significant improvement in mechanical performance (Figure 3).
Microscopic analysis reveals the high feature resolution and excellent surface finishing of the produced prototypes under high magnification (Figure 4). 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 layer8. The cracks observed on the surface of the fabricated prototypes can result from shrinkage forces developed in the UV curing process. Shrinkage in acrylate systems is found to be inversely related to the resin viscosity20,21. Hence, the extent of cracking (Figure 4) is reduced when applying more viscous photoresins (Figure 1).

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. Figure 2 displays the representative outcome on a universal testing machine in terms of E-modulus and tensile strength. The effect of the post-printing treatment on the product performance is depicted in Figure 3. The smooth surface and high feature resolution of complex shaped prototypes is revealed by the electron microscope (Figure 4). The extent of surface cracking is related to the initial resin viscosity.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td rowspan="2">Resin</td>
			<td>TPO</td>
			<td>BBOT</td>
			<td>SA5102</td>
			<td>SA5201</td>
			<td>SA5400</td>
			<td>SA7101</td>
			<td>BC</td>
		</tr>
		<tr>
			<td>% w/w</td>
			<td>% w/w</td>
			<td>% w/w</td>
			<td>% w/w</td>
			<td>% w/w</td>
			<td>% w/w</td>
			<td>%</td>
		</tr>
		<tr>
			<td>BAPR-&#945;</td>
			<td>0.40</td>
			<td>0.16</td>
			<td>20</td>
			<td>40</td>
			<td></td>
			<td>40</td>
			<td>67</td>
		</tr>
		<tr>
			<td>BAPR-&#946;</td>
			<td>0.40</td>
			<td>0.16</td>
			<td></td>
			<td>60</td>
			<td></td>
			<td>40</td>
			<td>64</td>
		</tr>
		<tr>
			<td>BAPR-&#947;</td>
			<td>0.40</td>
			<td>0.16</td>
			<td></td>
			<td>20</td>
			<td>40</td>
			<td>40</td>
			<td>44</td>
		</tr>
		<tr>
			<td>BAPR-&#948;</td>
			<td>0.40</td>
			<td>0.16</td>
			<td></td>
			<td></td>
			<td>60</td>
			<td>40</td>
			<td>34</td>
		</tr>
	</tbody>
</table>
Table 1: Renewable acrylate resin formulation. Characteristics of representative bioacrylate resins, depicting resin composition and biobased carbon content.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58177/58177fig1.jpg" /> 
Figure 1: Rheological behavior of renewable acrylate resins prior to 3D printing. Viscosity as a function of shear rate for uncured BAPR samples. Figure is adapted with permission (copyright 2018 American Chemical Society).12 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58177/58177fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58177/58177fig2.jpg" /> 
Figure 2: Mechanical performance of 3D products fabricated from various bioresins by a stereolithography apparatus. Tensile strength (red) and Young&#39;s modulus (cyan) of produced parts from cured BAPRs. The tensile bars (ISO 527-2-1BA) were printed normal to the build direction. Error bars indicate the standard deviation. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58177/58177fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58177/58177fig3.jpg" /> 
Figure 3: Influence of post-printing treatment on mechanical performance of 3D products. Tensile strength of produced parts post-treated under various conditions. The tensile bars (ISO 527-2-1BA) were printed normal to the build direction. Error bars indicate the standard deviation. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58177/58177fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58177/58177fig4.jpg" /> 
Figure 4: Visual and microscopic representation of complex-shaped prototypes fabricated from various bioresins by a stereolithography apparatus. (A) Photo of rook tower prototype printed with BAPR-&#945; (top) and SEM images of corresponding internal helix (bottom). (B) Photo of rook tower prototype printed with BAPR-&#946; (top) and SEM images of corresponding internal helix (bottom). (C) Photo of rook tower prototype printed with BAPR-&#947; (top) and SEM images of corresponding internal helix (bottom). (D) Photo of rook tower prototype printed with BAPR-&#948; (top) and SEM images of corresponding internal helix (bottom). Figure is adapted with permission (copyright 2018 American Chemical Society)12. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/58177/58177fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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. ...

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

Nanyang Technological University

Research

JoVE Journal

Chemistry

9.4K Views.  NHL Stenden University of Applied Sciences. A protocol for additive manufacturing with renewable photopolymer resins on a stereolithography apparatus is presented.

Video: Stereolithographic 3D Printing with Renewable Acrylates

Photodynamic Therapy with Blended Conducting Polymer/Fullerene Nanoparticle Photosensitizers

In this article a method for the fabrication and reproducible in-vitro evaluation of conducting polymer nanoparticles blended with fullerene as the next generation photosensitizers for Photodynamic Therapy (PDT) is reported. The nanoparticles are formed by hydrophobic interaction of the semiconducting polymer MEH-PPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]) with the fullerene PCBM (phenyl-C61-butyric acid methyl ester) in the presence of a non-compatible solvent. MEH-PPV has a high extinction coefficient that leads to high rates of triplet formation, and efficient charge and energy transfer to the fullerene PCBM. The latter processes enhance the efficiency of the PDT system through fullerene assisted triplet and radical formation, and ultrafast deactivation of MEH-PPV excited stated. The results reported here show that this nanoparticle PDT sensitizing system is highly effective and shows unexpected specificity to cancer cell lines.

This protocol describes a method for the fabrication of conducting polymer nanoparticles blended with fullerene. These nanoparticles were investigated for their potential use as a next generation photosensitizers for Photodynamic Therapy (PDT).

In this article a method for the fabrication and reproducible in-vitro evaluation of conducting polymer nanoparticles blended with fullerene as the next ...

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 ...