The authors acknowledge funding from the Australian Research Council and UNSW Australia via the Discovery Research program (DP210100094).

1. Preparation of 3D printing program and 3D printer
<ol>
	<li>Design the digital model for 3D printing following the steps below.
	<ol>
		<li>Open a computer-assisted design program (see Table of Materials).</li>
		<li>In the x-y plane, create a rectangle centered on the origin having dimensions of 80 mm x 40 mm, then extrude along the positive z-axis for 1.5 mm to make a solid rectangular prism, called the base object.</li>
		<li>Above the base object, i.e., at z = 1.5 mm, draw the desired surface patterns (in this case, two yin-yang symbols) on the surface of the rectangular prism.</li>
		<li>Extrude the surface patterns in selected regions 0.05 mm along the positive z-axis to create a slightly raised pattern relative to the base object.</li>
		<li>Export the 3D model to provide a stereolithography file with .STL file extension. 
		NOTE: In this work, dog-bone-shaped specimens were designed27. For other desired models to be printed, follow steps 1.1.1-1.1.5.</li>
		<li>Open a 3D printer slicing program (see Table of Materials) to enable single-layer settings.</li>
		<li>Open the converted .STL files from the computer hard drive by clicking on File &#62; Open then navigating to the saved .STL file.</li>
		<li>Arrange the 3D models on the build platform using the &#34;Model Rotate&#34; and &#34;Model Move&#34; buttons to fit at least 1 mm between all objects on the build stage.</li>
		<li>By entering text in the entry field boxes in the right-hand panel, change the parameters as mentioned in Table 1.</li>
		<li>Click on the blue Slice button in the bottom left-hand corner and save it as a slice file with an extension of. PWS or other 3D printer readable sliced file.</li>
		<li>Click on the Preview button once the pop-up menu appears and navigate through the sliced layers using the scroll bar on the right-hand side. Take careful note of the layer numbers for the last base layer (layer 29 in this case) and the surface pattern layer (30 in this case). 
		NOTE: The first printed layer is &#34;layer 0&#34; not &#34;layer 1&#34;.</li>
		<li>In the right-hand panel, select Single-layer settings, then expand the drop-down menu.</li>
		<li>Change the &#34;Exposure Time (s)&#34; for only the surface layer (layer 30) to 180 s, leaving all other layer exposure times as the default value.</li>
		<li>Click on Save button in the top left corner to save the sliced file to a USB.</li>
	</ol>
	</li>
	<li>Prepare the 3D printer.
	<ol>
		<li>Insert the USB containing the sliced file into the 3D printer (see Table of Materials).</li>
		<li>Before 3D printing, level the build stage and calibrate the z-axis position to the z = 0 by following the specific 3D printer method (manual or automatic calibration following the 3D printer manual).</li>
		<li>Inspect the film of the 3D printer vat to ensure a smooth and clean surface free of defects.</li>
		<li>If the vat film appears damaged, replace it according to the manufacturer&#39;s protocol.</li>
	</ol>
	</li>
</ol>
2. Preparation of resins
NOTE: Resins are categorized as &#34;Bulk Resin&#34; for the resin used to 3D print the original material (base substrate) and &#34;Surface Resin&#34; for the solution used to perform the surface functionalization (surface pattern).
<ol>
	<li>Prepare the Bulk Resin.
	<ol>
		<li>For preparing the bulk resin, weigh 0.36 g of 2-(n-butylthiocarbonothioylthio) propanoic acid (BTPA) into a clean 50 mL amber vial.</li>
		<li>Add 13.63 mL of poly (ethylene glycol) diacrylate average Mn 250 (PEGDA) to the amber vial using a micropipette.</li>
		<li>Add 14.94 mL of N, N-dimethylacrylamide (DMAm) to the amber vial using a micropipette.</li>
		<li>In a separate 20 mL clean glass vial covered with aluminum foil, add 0.53 g of diphenyl (2,4,6-trimethyl benzoyl) phosphine oxide (TPO).</li>
		<li>Using a micropipette, add 10 mL of DMAm to the 20 mL glass vial containing the TPO and seal the vial using the cap.</li>
		<li>Thoroughly homogenize the solution of TPO and DMAm by mixing using a vortex mixer for 10 s and then using a standard laboratory sonic bath (~40 kHz) to sonicate the mixture for 1 min at room temperature (Figure 1C, left).</li>
		<li>Using a glass pipette and rubber pipette bulb, transfer the solution from the 20 mL glass vial to the 50 mL amber vial and seal the vial with a cap and moldable plastic film.</li>
		<li>Gently shake the 50 mL amber vial and then place the vial in a sonic bath for 2 min at room temperature to ensure the mixture is homogeneous (Figure 1C, second from left).</li>
		<li>Place the sealed amber vial filled with the bulk resin in a fume hood for later use.</li>
	</ol>
	</li>
	<li>Prepare the Surface Resin.
	<ol>
		<li>For preparing the surface resin, weigh 0.50 g of TPO into a clean 50 mL amber vial.</li>
		<li>Using a micropipette, add 3.56 mL of DMAm and 11.98 mL of N, N-dimethylformamide (DMF) to the 50 mL amber vial and seal the vial with a cap moldable plastic film.</li>
		<li>Gently shake the sealed amber vial and sonicate for 1 min at room temperature using a standard laboratory sonic bath (~40 kHz).</li>
		<li>To a clean 20 mL vial covered with foil, add 0.29 g 1-pyrenemethyl methacrylate (PyMMA).</li>
		<li>Add 10 mL of DMF to the 20 mL vial and seal the vial with a cap using a micropipette.</li>
		<li>Gently shake the 20 mL glass vial and sonicate in increments of 1 min at room temperature using a standard laboratory sonic bath, visually inspecting between cycles until the PyMMA appears to be dissolved entirely (Figure 1C, third and fourth from left).</li>
		<li>Using a glass pipette and rubber pipette bulb, transfer the solution from the 20 mL glass vial to the 50 mL amber vial.</li>
		<li>Gently shake the 50 mL amber vial and then place the vial in a sonic bath for 2 min at room temperature to ensure the mixture is homogeneous (Figure 1C, right and second from right).</li>
		<li>Place the sealed amber vial filled with the bulk resin in a fume hood for later use. 
		&#8203;CAUTION: Some chemicals used in this protocol may cause severe skin and eye irritation and other toxicity to humans and the environment. Ensure safety protocols are followed in line with the safety data sheet and local regulations.</li>
	</ol>
	</li>
</ol>
3. 3D printing and surface functionalization
<ol>
	<li>Perform 3D printing of the base substrate following the steps below.
	<ol>
		<li>Pour the previously prepared bulk resin (step 2.1) into the 3D printer vat (see Table of Materials), ensuring that the solution completely covers the bottom film in the vat without any air bubbles or other inhomogeneities, and then close the 3D printer case.</li>
		<li>Navigate the USB using the 3D printer screen and select the sliced model file by clicking on the triangle Play button to begin the 3D printing process.</li>
		<li>By watching the 3D printer screen, take careful note of the number of layers printed, and pause the printing program by pressing the two vertical lines Pause button during 3D printing of the last layer of the base substrate (layer 29 in this case).</li>
		<li>Remove the entire build stage and gently rinse the build stage and printed material with undenatured 100% ethanol from a wash bottle for 10 s to remove residual bulk resin from the 3D printed material and the build stage.</li>
		<li>Using compressed air, gently dry the 3D printed material and build stage to remove residual ethanol and then reinsert the build stage into the 3D printer.</li>
		<li>Remove the vat from the 3D printer and pour the remaining bulk resin into an amber vial. Store the vial in a cool dark place.</li>
		<li>Using undenatured 100% ethanol from a wash bottle, carefully rinse the vat to remove any residual bulk resin.</li>
		<li>Dry the vat using a stream of compressed air to remove any residual ethanol and reinsert the vat into the 3D printer.</li>
	</ol>
	</li>
	<li>Perform surface functionalization.
	<ol>
		<li>Pour the previously prepared surface resin (step 2.2) into the 3D printer vat, ensuring that the solution completely covers the bottom film without any air bubbles or other inhomogeneities, and then close the 3D printer case.</li>
		<li>Resume the 3D printing program by clicking on the triangle Play button to allow the predetermined surface patterning to occur.</li>
		<li>Once the printing program has been completed, remove the build stage from the 3D printer and wash for 10 s with undenatured 100% ethanol using a wash bottle to remove residual surface resin from the 3D printed material and the build stage.</li>
		<li>Using compressed air (flow rate, 30 L/min), gently dry the 3D printed material and build stage to remove residual ethanol.</li>
		<li>While still attached to the build stage, post-cure the material by inverting the entire build stage and placing it under 405 nm light for 15 min.</li>
		<li>Gently remove the surface-functionalized 3D printed material from the build stage using a thin metal plate or paint scraper.</li>
		<li>Without further adjustments, analyze the material&#39;s mechanical and surface properties.</li>
	</ol>
	</li>
</ol>
4. Analysis of 3D printed samples
<ol>
	<li>Perform the fluorescence analysis.
	<ol>
		<li>Place the 3D printed, surface-functionalized material under a 312 nm UV gas discharge lamp (see Table of Materials) in a dark place, ensuring the surface-functionalized layer is facing up.</li>
		<li>Turn the lamp on to continuously irradiate the surface layer with 312 nm light and observe the fluorescent pattern. Take photographs if required. 
		NOTE: This is a visual inspection step; time cannot be specified. Irradiation is continuous while observation is occurring.</li>
		<li>Place the 3D printed, surface-functionalized material into a Fluorescence imager. Using the provided software, capture digital fluorescence images of the top and bottom surfaces using the Trans-UV (302 nm) gas discharge source (see Table of Materials).</li>
	</ol>
	</li>
	<li>Perform the tensile property analysis.
	<ol>
		<li>Measure the gauge with and thickness of the dog-bone specimens (in millimeters).</li>
		<li>Place the dog-bone-shaped specimens between the grips of a tensile testing machine, ensuring the 3D printed material is equally placed at a distance specified by the standards document, in this case, 50.3 mm.</li>
		<li>Set the tensile test program; in this case, the lift speed was set to 1.1 mm/min, the number of samples was set at 10 per second.</li>
		<li>Start the program to acquire force (N) vs. travel (mm) data.</li>
		<li>Once the sample gets prepared, stop the machine, and save the data as column-separated data with a .CSV file extension.</li>
		<li>Convert the force (N) data to stress (MPa) by dividing each point of the force column by the gauge area (mm2, obtained by multiplying the gauge width by the gauge thickness).</li>
		<li>Convert the travel data to strain (%) by diving the travel data by the gauge length (50.3 mm) at every point and multiplying each result by 100.</li>
		<li>Calculate toughness (MJ/m3) using the trapezoidal rule to calculate the area under the stress-strain curve.</li>
		<li>Calculate Young&#39;s modulus (MPa) by taking the gradient of the stress (MPa) vs. strain (%) curve in the elastic region, in this work from 1%-2% elongation27.</li>
	</ol>
	</li>
</ol>

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The authors declare no conflicts of interest.

The present protocol demonstrates a process for 3D printing of polymer materials with independently tunable bulk and interfacial properties. The procedure is performed via a two-step method by 3D printing the base substrate and subsequently modifying the surface layer of the 3D printed object using a different functional resin but using the same 3D printing hardware. While the 3D printers used in this work are designed to print crosslinked materials in a layer-by-layer fashion, the surface functionalization can ...

Additive manufacturing and 3D printing have revolutionized material manufacturing by providing more efficient and facile routes for the fabrication of geometrically complex materials1. Apart from the enhanced design freedoms in 3D printing, these technologies produce less waste than traditional subtractive manufacturing processes via the judicious use of precursor materials in a layer-by-layer manufacturing process. Since the 1980s, a wide range of different 3D printing techniques has been developed to fabricate polymeric, metal, and ceramic components1. The most commonly employed methods include extrusion-based 3D printing such as fused filament fabrication and direct ink writing techniques2, sintering techniques such as selective laser sintering3, as well as resin-based photoinduced 3D printing techniques such as laser and projection-based stereolithography and masked digital light processing techniques4. Among the many 3D printing techniques in existence today, photoinduced 3D printing techniques provide some advantages compared to other methods, including higher resolution and faster printing speeds, as well as the ability to perform solidification of the liquid resin at room temperature, which opens the possibility to advanced biomaterial 3D printing4,5,6,7,8,9.
While these advantages have allowed the widespread adoption of 3D printing in many fields, the limited ability to independently tailor the 3D printed material properties restricts future applications10. In particular, the inability to easily tailor the bulk mechanical properties independently of the interfacial properties limits applications such as implants, which require finely tailored biocompatible surfaces and often vastly differing bulk properties, as well as antifouling and antibacterial surfaces, sensor materials, and other smart materials11,12,13. Researchers have proposed surface modification of 3D printed materials to overcome these issues to provide more independently tailorable bulk and interfacial properties10,14,15.
Recently, our group developed a photoinduced 3D printing process that exploits reversible addition-fragmentation chain transfer (RAFT) polymerization to mediate network polymer synthesis15,16. RAFT polymerization is a type of reversible deactivation radical polymerization that provides a high degree of control over the polymerization process and allows for the production of macromolecular materials with finely tuned molecular weights and topologies, and broad chemical scope17,18,19. Notably, the thiocarbonylthio compounds, or RAFT agents, used during RAFT polymerization are retained after polymerization. They can thus be reactivated to modify further the chemical and physical properties of the macromolecular material. Thus, after 3D printing, these dormant RAFT agents on the surfaces of the 3D printed material can be reactivated in the presence of functional monomers to provide tailored material surfaces20,21,22,23,24,25,26. The secondary surface polymerization dictates the interfacial material properties and can be performed in a spatially controlled fashion via photochemical initiation.
The present protocol describes a method for 3D printing polymeric materials via a photoinduced RAFT polymerization process and the subsequent in situ surface modification to modulate the interfacial properties independently of the bulk material mechanical properties. Compared to previous 3D printing and surface modification approaches, the current protocol does not require deoxygenation or other stringent conditions and is thus highly accessible for non-specialists. Furthermore, the use of 3D printing hardware to perform both the initial material fabrication and the surface post-functionalization provides spatial control over the material properties and can be performed without the tedious alignment of several different photomasks to make complex patterns.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1-pyrenemethyl methacrylate</td>
			<td>Sigma-Aldrich</td>
			<td>765120</td>
			<td></td>
		</tr>
		<tr>
			<td>2-(n-butylthiocarbonothioylthio) propanoic acid</td>
			<td>Boron Molecular</td>
			<td>BM1640</td>
			<td></td>
		</tr>
		<tr>
			<td>3D Printer</td>
			<td>Photon</td>
			<td>Mono S</td>
			<td>light intensity at digital mask surface = 0.81 mW cm-2</td>
		</tr>
		<tr>
			<td>3D Printing Slicing Software</td>
			<td>Photon</td>
			<td>Photon Workshop V2.1.19</td>
			<td></td>
		</tr>
		<tr>
			<td>40 kHz Ultrasonic Bath</td>
			<td>Thermoline</td>
			<td>UB-410</td>
			<td></td>
		</tr>
		<tr>
			<td>Compressed Air</td>
			<td>Coregas</td>
			<td>230142</td>
			<td>Tank operating at 130 kPa</td>
		</tr>
		<tr>
			<td>Computer Assisted Design Program</td>
			<td>SpaceClaim</td>
			<td>SpaceClaim Design Manager V19.1</td>
			<td></td>
		</tr>
		<tr>
			<td>Diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide</td>
			<td>Sigma-Aldrich</td>
			<td>415952</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol Undenatured 100% AR</td>
			<td>ChemSupply</td>
			<td>EL043-2.5L-P</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol Wash bottle</td>
			<td>Rowe Scientific</td>
			<td>AZLWGF541P</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescence Imager</td>
			<td>Bio-Rad</td>
			<td>Gel Doc XR+</td>
			<td>Uses a 302 nm gas discharge lamp as emission source</td>
		</tr>
		<tr>
			<td>Light intensity power meter</td>
			<td>Newport</td>
			<td>843-R</td>
			<td></td>
		</tr>
		<tr>
			<td>Mechanical Tester</td>
			<td>Mark&#8211;10</td>
			<td>ESM303</td>
			<td>1 kN force gauge M5&#8211;200</td>
		</tr>
		<tr>
			<td>Moldable plastic film</td>
			<td>Parafilm</td>
			<td>PM992</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N-dimethlacrylamide</td>
			<td>Sigma-Aldrich</td>
			<td>274135</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N-Dimethylformamide HPLC</td>
			<td>ChemSupply</td>
			<td>LC1051-G4L</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly(ethylene glycol) diacrylate average Mn 250</td>
			<td>Sigma-Aldrich</td>
			<td>475629</td>
			<td></td>
		</tr>
		<tr>
			<td>Post Cure Lamp</td>
			<td>Leoway</td>
			<td>&#8206;B0869BY79P</td>
			<td>60 W 405 nm</td>
		</tr>
		<tr>
			<td>Standards document</td>
			<td>ASTM</td>
			<td>ASTM Standard D638-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Tensile testing machine</td>
			<td>Mark-10</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>UV Light</td>
			<td>Fisher Scientific</td>
			<td>11-982-30</td>
			<td>6 W Spectroline E-Series, Gas discharge lamp</td>
		</tr>
		<tr>
			<td>Vortex Mixer IKA Vortex 3</td>
			<td>LabTek</td>
			<td>3340000I</td>
			<td></td>
		</tr>
	</tbody>
</table>

3d printing and in situ surface modification via type i photoinitiated reversible addition-fragmentation chain transfer polymerization

3D printing provides facile access to geometrically complex materials. However, these materials have intrinsically linked bulk and interfacial properties dependent on the chemical composition of the resin. In the current work, 3D printed materials are post-functionalized using the 3D printer hardware via a secondary surface-initiated polymerization process, thus providing independent control over the bulk and interfacial material properties. This process begins with preparing liquid resins, which contain a monofunctional monomer, a crosslinking multifunctional monomer, a photochemically labile species that enables initiation of polymerization, and critically, a thiocarbonylthio compound which facilitates reversible addition-fragmentation chain transfer (RAFT) polymerization. The thiocarbonylthio compound, known commonly as a RAFT agent, mediates the chain growth polymerization process and provides polymeric materials with more homogeneous network structures. The liquid resin is cured in a layer-by-layer fashion using a commercially available digital light processing 3D printer to give three-dimensional materials having spatially controlled geometries. The initial resin is removed and replaced with a new mixture containing functional monomers and photoinitiating species. The 3D printed material is then exposed to light from the 3D printer in the presence of the new functional monomer mixture. This allows photoinduced surface-initiated polymerization to occur from the latent RAFT agent groups on the surface of the 3D printed material. Given the chemical flexibility of both resins, this process allows a wide range of 3D printed materials to be produced with tailorable bulk and interfacial properties.

The general procedure for 3D printing and surface functionalization is shown in Figure 1. In this protocol, a network polymer is initially synthesized via a photoinduced RAFT polymerization process15, using a 3D printer to fabricate an object in a layer-by-layer process (Figure 1A). The bulk resin used to form the polymer network contains a photolabile initiating species (TPO), which generates radicals upon exposure to 405 nm lig...

Watch this Scientific Journal Video about 3D Printing and In Situ Surface Modification via Type I Photoinitiated Reversible Addition-Fragmentation Chain Transfer Polymerization at JoVE.com

3D Printing and In Situ Surface Modification via Type I Photoinitiated Reversible Addition-Fragmentation Chain Transfer Polymerization

The present protocol describes the digital light processing-based 3D printing of polymeric materials using type I photoinitiated reversible addition-fragmentation chain transfer polymerization and the subsequent in situ material post-functionalization via surface-mediated polymerization. Photoinduced 3D printing provides materials with independently tailored and spatially controlled bulk and interfacial properties.

3D Printing and In Situ Surface Modification via Type I Photoinitiated Reversible Addition-Fragmentation Chain Transfer Polymerization

3D printing provides facile access to geometrically complex materials. However, these materials have intrinsically linked bulk and interfacial properties ...

3d-printing-situ-surface-modification-via-type-i-photoinitiated

Research

JoVE Journal

Chemistry

3.3K Views.  University of New South Wales. The present protocol describes the digital light processing-based 3D printing of polymeric materials using type I photoinitiated reversible addition-fragmentation chain transfer polymerization and the subsequent in situ material post-functionalization via surface-mediated polymerization. Photoinduced 3D printing provides materials with independently tailored and spatially controlled bulk and interfacial properties.

Video: 3D Printing and In Situ Surface Modification via Type I Photoinitiated Reversible Addition-Fragmentation Chain Transfer Polymerization

Facile and Efficient Preparation of Tri-component Fluorescent Glycopolymers via RAFT-controlled Polymerization

Synthetic glycopolymers are instrumental and versatile tools used in various biochemical and biomedical research fields. An example of a facile and efficient synthesis of well-controlled fluorescent statistical glycopolymers using reversible addition-fragmentation chain-transfer (RAFT)-based polymerization is demonstrated. The synthesis starts with the preparation of &#946;-galactose-containing glycomonomer 2-lactobionamidoethyl methacrylamide obtained by reaction of lactobionolactone and N-(2-aminoethyl) methacrylamide (AEMA). 2-Gluconamidoethyl methacrylamide (GAEMA) is used as a structural analog lacking a terminal &#946;-galactoside. The following RAFT-mediated copolymerization reaction involves three different monomers: N-(2-hydroxyethyl) acrylamide as spacer, AEMA as target for further fluorescence labeling, and the glycomonomers. Tolerant of aqueous systems, the RAFT agent used in the reaction is (4-cyanopentanoic acid)-4-dithiobenzoate. Low dispersities (&#8804;1.32), predictable copolymer compositions, and high reproducibility of the polymerizations were observed among the products. Fluorescent polymers are obtained by modifying the glycopolymers with carboxyfluorescein succinimidyl ester targeting the primary amine functional groups on AEMA. Lectin-binding specificities of the resulting glycopolymers are verified by testing with corresponding agarose beads coated with specific glycoepitope recognizing lectins. Because of the ease of the synthesis, the tight control of the product compositions and the good reproducibility of the reaction, this protocol can be translated towards preparation of other RAFT-based glycopolymers with specific structures and compositions, as desired.

An efficient, three-step synthesis of RAFT-based fluorescent glycopolymers, consisting of glycomonomer preparation, copolymerization, and post-modification, is demonstrated. This protocol can be used to prepare RAFT-based statistical glycopolymers with desired structures.

Synthetic glycopolymers are instrumental and versatile tools used in various biochemical and biomedical research fields. An example of a facile and ...

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

We demonstrate a method for high-throughput catalyst screening using a parallel pressure reactor starting from the initial synthesis of a nickel &#945;-diimine ethylene polymerization catalyst. Initial polymerizations with the catalyst lead to optimized reaction conditions, including catalyst concentration, ethylene pressure and reaction time. Using gas-uptake data for these reactions, a procedure to calculate the initial rate of propagation (kp) is presented. Using the optimized conditions, the ability of the nickel &#945;-diimine polymerization catalyst to undergo chain transfer with diethylzinc (ZnEt2) during ethylene polymerization was investigated. A procedure to assess the ability of the catalyst to undergo chain transfer (from molecular weight and 13C NMR data), calculate the degree of chain transfer, and calculate chain transfer rates (ke) is presented.

A protocol for the high-throughput analysis of polymerization catalyst, chain transfer polymerizations, polyethylene characterization, and reaction kinetic analysis is presented.

We demonstrate a method for high-throughput catalyst screening using a parallel pressure reactor starting from the initial synthesis of a nickel ...

Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis

Boron doped diamond (BDD) electrodes have shown considerable promise as an electrode material where many of their reported properties such as extended solvent window, low background currents, corrosion resistance, etc., arise from the catalytically inert nature of the surface. However, if during the growth process, non-diamond-carbon (NDC) becomes incorporated into the electrode matrix, the electrochemical properties will change as the surface becomes more catalytically active. As such it is important that the electrochemist is aware of the quality and resulting key electrochemical properties of the BDD electrode prior to use. This paper describes a series of characterization steps, including Raman microscopy, capacitance, solvent window and redox electrochemistry, to ascertain whether the BDD electrode contains negligible NDC i.e. negligible sp2 carbon. One application is highlighted which takes advantage of the catalytically inert and corrosion resistant nature of an NDC-free surface i.e. stable and quantifiable local proton and hydroxide production due to water electrolysis at a BDD electrode. An approach to measuring the local pH change induced by water electrolysis using iridium oxide coated BDD electrodes is also described in detail.

Assessment of Boron Doped Diamond Electrode Quality and Application to In Situ Modification of Local pH by Water Electrolysis

A protocol is described for the characterization of the key electrochemical parameters of a boron doped diamond (BDD) electrode and subsequent application for in situ pH generation experiments.

Boron doped diamond (BDD) electrodes have shown considerable promise as an electrode material where many of their reported properties such as extended ...

A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where interfacial tension is a dominant force. A variety of methods exist for controlling the interfacial tension of aqueous and organic liquids on this scale; however, these techniques have limited utility for liquid metals due to their large interfacial tension.
Liquid metals can form soft, stretchable, and shape-reconfigurable components in electronic and electromagnetic devices. Although it is possible to manipulate these fluids via mechanical methods (e.g., pumping), electrical methods are easier to miniaturize, control, and implement. However, most electrical techniques have their own constraints: electrowetting-on-dielectric requires large (kV) potentials for modest actuation, electrocapillarity can affect relatively small changes in the interfacial tension, and continuous electrowetting is limited to plugs of the liquid metal in capillaries.
Here, we present a method for actuating gallium and gallium-based liquid metal alloys via an electrochemical surface reaction. Controlling the electrochemical potential on the surface of the liquid metal in electrolyte rapidly and reversibly changes the interfacial tension by over two orders of magnitude ( &#820;500 mN/m to near zero). Furthermore, this method requires only a very modest potential (&#60; 1 V) applied relative to a counter electrode. The resulting change in tension is due primarily to the electrochemical deposition of a surface oxide layer, which acts as a surfactant; removal of the oxide increases the interfacial tension, and vice versa. This technique can be applied in a wide variety of electrolytes and is independent of the substrate on which it rests.

We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where ...

Atom Transfer Radical Polymerization of Functionalized Vinyl Monomers Using Perylene as a Visible Light Photocatalyst

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The procedure is performed under an inert atmosphere using air- and water-exclusion techniques. The outcome of the polymerization is affected by the ratios of monomer, initiator, and catalyst used as well as the reaction concentration, solvent, and nature of the light source. Temporal control over the polymerization can be exercised by turning the visible light source off and on. Low dispersities of the resultant polymers as well as the ability to chain-extend to form block copolymers suggest control over the polymerization, while chain end-group analysis provides evidence supporting an atom-transfer radical polymerization mechanism.

A method for the atom transfer radical polymerization of functionalized vinyl monomers using perylene as a visible-light photocatalyst is described.

A standardized technique for atom transfer radical polymerization of vinyl monomers using perylene as a visible-light photocatalyst is presented. The ...

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the development of antibody drug conjugates (ADCs) and nanomedicine, fluorescent microscopy and systems chemistry. For many of these applications, specificity of the bioconjugation method used is of prime concern. The Michael addition of maleimides with cysteine(s) on the target proteins is highly selective and proceeds rapidly under mild conditions, making it one of the most popular methods for protein bioconjugation.
We demonstrate here the modification of the only surface-accessible cysteine residue on yeast cytochrome c with a ruthenium(II) bisterpyridine maleimide. The protein bioconjugation is verified by gel electrophoresis and purified by aqueous-based fast protein liquid chromatography in 27% yield of isolated protein material. Structural characterization with MALDI-TOF MS and UV-Vis is then used to verify that the bioconjugation is successful. The protocol shown here is easily applicable to other cysteine - maleimide coupling of proteins to other proteins, dyes, drugs or polymers.

Synthesis of Protein Bioconjugates via Cysteine-maleimide Chemistry

This protocol details the important steps required for the bioconjugation of a cysteine containing protein to a maleimide, including reagent purification, reaction conditions, bioconjugate purification and bioconjugate characterization.

The chemical linking or bioconjugation of proteins to fluorescent dyes, drugs, polymers and other proteins has a broad range of applications, such as the ...

Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2&#215;1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods.

This work details the procedures for the growth and characterization of crystalline SrTiO3 directly on germanium substrates by atomic layer deposition. The procedure illustrates the ability of an all-chemical growth method to integrate oxides monolithically onto semiconductors for metal-oxide semiconductor devices.

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and ...

Microfluidic Dry-spinning and Characterization of Regenerated Silk Fibroin Fibers

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables the silk proteins to be compact and ordered by shearing and elongation forces. Here, a biomimetic microfluidic channel was designed to mimic the specific geometry of the spinning duct of the silkworm. Regenerated silk fibroin (RSF) spinning doped with high concentration, was extruded through the microchannel to dry-spin fibers at ambient temperature and pressure. In the post-treated process, the as-spun fibers were drawn and stored in ethanol aqueous solution. Synchrotron radiation wide-angle X-ray diffraction (SR-WAXD) technology was used to investigate the microstructure of single RSF fibers, which were fixed to a sample holder with the RSF fiber axis normal to the microbeam of the X-ray. The crystallinity, crystallite size, and crystalline orientation of the fiber were calculated from the WAXD data. The diffraction arcs near the equator of the two-dimensional WAXD pattern indicate that the post-treated RSF fiber has a high orientation degree.

A protocol for the microfluidic spinning and microstructure characterization of regenerated silk fibroin monofilament is presented.

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables ...

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a ...

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.

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. ...