The work was supported by the National Natural Science Foundation of China (Grant Nos. 11002139 and 81327803) and the Fundamental Research Funds for the Central Universities. We thank Zachary J. Smith of the University of Science and Technology for providing the audio voiceover.

1. Preparing materials for 3D printing
NOTE: Our optical phantom production line uses a variety of printing materials to simulate the structural and functional heterogeneities of biological tissue. The selection of the printing materials also depends on the manufacturing processes.
<ol>
	<li>Material preparation for spin coating printing
	<ol>
		<li>Add 100 mg of titanium dioxide (TiO2) powder into a beaker containing 100 mL of stereolithography (SLA) photopolymer resin.</li>
		<li>Stir the mixture in the beaker for 30 min on a magnetic stirrer.</li>
		<li>Seal the beaker with tinfoil and sonicate it in an ultrasonic machine for 15 min.</li>
		<li>Vacuum the material for 10 min and load it into the storage syringe of the device.</li>
	</ol>
	</li>
	<li>Material preparation for polyjet printing
	<ol>
		<li>Add 17.56 g of 2-hydroxy-2-methylpropiophenone (1-hydroxycyclohexyl phenyl ketone) into the beaker containing 80 g of triethylene glycol dimethacrylate to get 18% (w/w) material.</li>
		<li>Seal the beaker with tinfoil and sonicate it in an ultrasonic machine for 15 min.</li>
		<li>Take out 20 mL of the mixture and add 5 mg of the oil-soluble Chinese red dye into it. Repeat step 1.2.2.</li>
		<li>Vacuum all the materials, load the solution with dye into the cartridges for the Y (Yellow) channel, and load the pure solution into the cartridges for the K (Black) channel.</li>
	</ol>
	</li>
	<li>Material preparation for FDM printing
	<ol>
		<li>Load 200 g of gel wax into each of three beakers and then heat them to 60 &#176;C on a magnetic stirrer.</li>
		<li>Add 600 mg TiO2 powder into the first beaker. Add 80 mg of graphite powder into the second one.</li>
		<li>Stir the gel wax mixed with TiO2 and gel wax mixed with graphite powder in different beakers for 30 min on the magnetic stirrer.</li>
		<li>Vacuum the three different materials for 2 min and load them into the extruder of the hybrid-three-nozzle module before solidification.</li>
	</ol>
	</li>
</ol>
2. Preparing computer models for multimodal 3D printing
NOTE: The heterogeneous skin tissue is simplified into three layers: epidermis, dermis, and subcutaneous tissue. The epidermis layer is produced by spin coating using the material introduced in step 1.1. The dermis layer is produced by polyjet printing using the photosensitive polymer introduced in step 1.2. The subcutaneous tissue layer is produced by FDM using the material introduced in step 1.3. A prototype computer aided design (CAD) file of different printing parameters is generated to guide the aforementioned fabrication processes.
<ol>
	<li>Design of a digital optical phantom for skin
	<ol>
		<li>Design the skin phantom with the following three layers: an epidermis layer of 100 &#181;m thick, a dermis layer of 400 &#181;m thick, and a subcutaneous tissue of 1 cm thick.</li>
		<li>Draw a tumor model using a 3D modeling software package (e.g., Solidworks) (Figure 5A).</li>
	</ol>
	</li>
	<li>Parameter setting for spin coating
	<ol>
		<li>Set the parameters of rotating speed and duration in the control software of the printing device. The first-stage spin coating speed used in this demonstration is 200 revolutions per min (rpm), the spin coating time is 20 s, the speed in the second-stage spin coating is 1,000 rpm, and the spin coating time is 40 s.</li>
		<li>Set the amount of spin coating material as 3 mL and the time of light-curing as 180 s in the control software.</li>
	</ol>
	</li>
	<li>Preparation of the source file for polyjet printing
	<ol>
		<li>Import the blood vessel image to be printed into the AcroRIP Color software package and set the parameters (printing position and inkjet amount) according to the relationship between the optical parameters of the printed phantoms and the image properties. In this printed blood vessel picture, the K channel is loaded with a transparent photocurable material, and the Y channel is loaded with a photocurable material mixed with Chinese red dye.</li>
		<li>Generate a &#34;.prn&#34; file with parameters defined for 3D printing.</li>
	</ol>
	</li>
	<li>Preparation of G code for FDM printing
	<ol>
		<li>Draw a frustum model with a 3D mapping software package (e.g., Solidworks) to simulate a tumor.</li>
		<li>Import the &#34;.stl&#34; file of the tumor model into a Cura software package installed with an all-in-one nozzle slicing script.</li>
		<li>Slice the model to generate the G code required for printing.</li>
	</ol>
	</li>
	<li>Loading of the documents to the printing control software
	<ol>
		<li>Click the &#34;File&#34; menu item in the menu bar, select the &#34;Import UV Print File&#34; submenu item, and load the UV printing &#34;.prn&#34; files introduced in step 2.3.</li>
		<li>Load the G code generated in step 2.4 into the print control software as in step 2.5.1.</li>
		<li>Click the Start Printing button to start the automated 3D printing procedure.</li>
	</ol>
	</li>
</ol>
3. Printing the skin epidermis layer phantom component by spin coating
NOTE: The spin coating module is mainly comprised of three parts: 1) a spin coater; 2) a glue dispenser; and 3) a UV lamp.
<ol>
	<li>Move the substrate on the loading station to the sample stage of the spin coater with a mechanical hand. Start the vacuum pump to fix the substrate by adsorption.</li>
	<li>The glue dispenser controls the syringe to drip the material introduced in step 2.2.2 at the center of the substrate.</li>
	<li>The spin coater starts to work following the set speed and time parameters.</li>
	<li>Put down the UV lamp (wavelength: 395 nm) and turn it on for 180 s.</li>
	<li>Lift the UV lamp, turn off the spin-coater, and print the skin epidermis layer.</li>
</ol>
4. Printing the skin dermis layer phantom component by polyjetting
NOTE: The polyjet printing module consists of a piezoelectric inkjet nozzle, a three-dimensional mobile platform, a control panel, and a UV lamp (mercury lamp). The solvent-based photocurable material, absorption material, and scattering material are used as a matrix. Different optical parameters are obtained by spraying materials in different proportions in different regions. Finally, the dermis layer phantom is printed and cured layer-by-layer.
<ol>
	<li>Move the substrate to the 3D mobile platform and open the suction valve to adsorb the substrate on the platform.</li>
	<li>The 3D mobile platform holds the substrate to the initial position of the UV printer.</li>
	<li>Push the inkjet printer to the working position by the cylinder, and the inkjet printer works the time specified in the &#34;.prn&#34; file sent by the host computer. Here, the paper feed signal of the inkjet printer is used to drive the movement of the Y-axis mobile platform.</li>
	<li>The inkjet printer prints the layer designed in step 2.5.1 and the cylinder pushes the inkjet printer back to the original position. The Y-axis of the 3D moving platform placed with the substrate is initialized by moving to its initial position.</li>
	<li>The substrate moves 50 mm in the positive direction of the Y-axis. The UV lamp is pushed down by the cylinder (10 mm above the substrate).</li>
	<li>Turn on the UV lamp for 180 s according to the curing time setting.</li>
	<li>Push the UV lamp to the initial position with the cylinder. The Y-axis of the 3D mobile platform placed with the substrate is initialized and returned to its initial position.</li>
	<li>Move the 3D mobile platform placed with substrate down by 0.1 mm along the Z-axis.</li>
	<li>Repeat steps 4.1&#8211;4.8 to print the next layer until the multilayer printing is completed.</li>
</ol>
5. Printing the subcutaneous tissue phantom component by FDM
NOTE: The FDM module is comprised of a hybrid-three-head module, a single-head module, and a 3D mobile platform. The gel wax, the absorbing material, and the scattering material are used as raw materials to prepare a phantom simulating subcutaneous tissue/tumor. The gel wax is heated and melted in the feeder. Uniformly stirred by the extrusion head, it is extruded to print the final phantoms with the desired optical parameters.
<ol>
	<li>Turn on the heating power of the nozzle module and set the temperature to 60 &#176;C.</li>
	<li>Move the mixing nozzle to the working position by pushing the cylinder.</li>
	<li>The FDM module receives the G code commands sent by the host computer, and the mixing nozzle is heated up to 68 &#176;C.</li>
	<li>Turn on the agitation motor and mix the materials well.</li>
	<li>Initialize the 3D mobile platform and the XYZ axes move to the initial position.</li>
	<li>The printing process is executed following the G code commands. In a layer-by-layer printing procedure, the materials are extruded in proportion to the mixing ratio that determine the optical parameters of the phantom in each layer. The printing continues until the subcutaneous tissue portion or the tumor portion is fully printed.</li>
	<li>Move the mixing nozzle module to the initial position by pushing the cylinder. 
	CAUTION: Because graphite powder has strong light absorption, it needs to be mixed as uniformly as possible to avoid changes in the optical parameters induced by aggregation. TiO2 powder of large particle size easily precipitates and affects material placement accuracy, so it is necessary to fully mix it. TiO2 should be replaced if stored for a long time.</li>
</ol>
6. Moving the substrate back to the loading station
<ol>
	<li>Initialize the 3D mobile platform and move the XYZ axis to the initial position. Move the 3D mobile platform to the handover location.</li>
	<li>Move the mechanical hand to the position above the substrate by pushing the cylinder.</li>
	<li>Pick up the substrate and move it over the loading station with the mechanical hand. Place the substrate on the loading station and complete the automated printing.</li>
</ol>
7. Casting the subcutaneous tissue layer phantom component by molding
NOTE: If the tumor model for the phantom is designed, it will be necessary to cast the entire phantom by pouring the polydimethylsiloxane (PDMS) outside the tumor. Steps 7.1&#8211;7.3 are not required for the FDM module to print subcutaneous tissue layer without a tumor.
<ol>
	<li>Press on a substrate with a 3D printed rectangular mold.</li>
	<li>Pour liquid PDMS into the mold.</li>
	<li>Place the substrate in an incubator and store at 60 &#176;C for 2 h.</li>
	<li>Remove the phantom from the substrate.</li>
</ol>

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The authors have nothing to disclose.

In the fabrication of the multilayered phantom, the material used for spin coating is a kind of light-curable material instead of PDMS. The intermediate layer is printed with the polyjet printing method, which uses the light-curable resin as raw material. Although thin PDMS phantoms can be made by spin coating after adding tert-butyl alcohol, a PDMS layer cannot effectively bind to the light-curable material during polyjet printing. Therefore, we chose the light-curable resin for spin coating.
<p class="jove_content"...

Biomedical optical imaging represents a family of medical imaging tools that detect diseases and tissue anomalies based on light interactions with biological tissue. In comparison with other imaging modalities, such as magnetic resonance imaging (MRI) and computed tomography (CT), biomedical optical imaging takes the advantage of noninvasive measurement of tissue structural, functional, and molecular characteristics using low-cost and portable devices1,2,3,4. However, despite its superiority in cost and portability, optical imaging has not been widely accepted for clinical diagnosis and therapeutic guidance, partially due to its poor reproducibility and lack of quantitative mapping between optical and biological parameters. The main reason for this limitation is the lack of traceable standards for quantitative calibration and validation of biomedical optical imaging devices.
In the past, a variety of tissue-simulating phantoms were developed for biomedical optical imaging research in various tissue types, such as brain5,6,7, skin8,9,10,11,12, bladder13, and breast tissues14,15,16,17. These phantoms are primarily produced by one of the following fabrication processes: 1) spin coating10,18 (for simulating homogenous and thin-layered tissue); 2) molding19 (for simulating bulky tissue with geometric features); and 3) three-dimensional (3D) printing20,21,22 (for simulating multilayered heterogeneous tissue). Skin phantoms produced by molding are able to mimic the bulk optical properties of skin tissue but cannot simulate the lateral optical heterogeneities19. Bentz et al. used a two-channel FDM 3D printing method to mimic different optical properties of biological tissue23. However, using two materials cannot sufficiently simulate tissue optical heterogeneity and anisotropy. Lurie et al. created a bladder phantom for optical coherence tomography (OCT) and cystoscopy by combining 3D printing and spin coating13. However, heterogeneous features of the phantom, such as blood vessels, had to be hand painted.
Among the above phantom fabrication processes, 3D printing provides the most flexibility for simulating the structural and functional heterogeneities of biological tissue. However, many biological tissue types, such as skin tissue, consist of multilayered and multiscaled components that cannot be effectively duplicated by a single 3D printing process. Therefore, integration of multiple manufacturing processes is necessary. We propose a 3D printing production line that integrates multiple manufacturing processes for automatic production of multilayered and multiscaled tissue simulating phantoms as a traceable standard for biomedical optical imaging (Figure 1). Although spin coating, polyjet printing, and FDM are automated in our 3D printing production line, each modality retains the same functional characteristics as the established processes. Therefore, this paper provides a general guideline for producing multiscaled, multilayered, and heterogeneous tissue-simulation phantoms without the need for physical integration of multiple processes in a single apparatus.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/60563/60563fig1.jpg" /> 
Figure 1: The CAD diagram of the 3D printing production line. (A) The 3D printing production line with the top shell removed. (B) The schematic of the spin coating module and the mechanical hand module. (C) The schematic of the polyjet printing module. (D) The schematic of the FDM printing module (the UV lamp belongs to the polyjet printing module). <a href="https://www.jove.com/files/ftp_upload/60563/60563fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>2-Hydroxy-2-methylpropiophenone</td>
			<td>aladdin</td>
			<td>H110280-500g</td>
			<td>Light initiator 
			<a href="http://www.aladdin-e.com/" target="_blank">http://www.aladdin-e.com/</a></td>
		</tr>
		<tr>
			<td>3D printing control system</td>
			<td>USTC</td>
			<td>USTC-3DPrinter_control1.0</td>
			<td>custom-made 
			github: 
			<a href="https://github.com/macanzhen/3D_printing_control_system_of_USTC" target="_blank">https://github.com/macanzhen/</a></td>
		</tr>
		<tr>
			<td>3D printing system</td>
			<td>USTC</td>
			<td>USTC-3DPrinter1.0</td>
			<td>custom-made</td>
		</tr>
		<tr>
			<td>AcroRip color</td>
			<td>Human Plus</td>
			<td>AcroRip v8.2.6</td>
			<td></td>
		</tr>
		<tr>
			<td>All-in-one nozzle slicing script</td>
			<td>Shenzhen CBD Technology Co.,Ltd.</td>
			<td></td>
			<td>github: 
			<a href="https://github.com/macanzhen/3D_printing_Cura_all-in-one-nozzle-slicing-script" target="_blank">https://github.com/macanzhen/</a></td>
		</tr>
		<tr>
			<td>Chinese Red Dye</td>
			<td>Juents</td>
			<td></td>
			<td>Oil-soluble</td>
		</tr>
		<tr>
			<td>Cura</td>
			<td>Ultimaker</td>
			<td>Cura_15.04.6</td>
			<td></td>
		</tr>
		<tr>
			<td>Gel Wax</td>
			<td>Shanghai Lida Industry Co.,ltd.</td>
			<td>LP</td>
			<td>melting point: 56 &#176;C</td>
		</tr>
		<tr>
			<td>Graphite</td>
			<td>aladdin</td>
			<td>G103922-100g</td>
			<td>Change object optical absorption parameters 
			<a href="http://www.aladdin-e.com/" target="_blank">http://www.aladdin-e.com/</a></td>
		</tr>
		<tr>
			<td>PDMS</td>
			<td>Dow Corning</td>
			<td>184</td>
			<td></td>
		</tr>
		<tr>
			<td>Titanium dioxide</td>
			<td>ALDRICH</td>
			<td>24858-100G</td>
			<td>347 nm</td>
		</tr>
		<tr>
			<td>Triethylene glycol dimethacrylate</td>
			<td>aladdin</td>
			<td>T101642-250ml</td>
			<td>Photocured monomer 
			<a href="http://www.aladdin-e.com/" target="_blank">http://www.aladdin-e.com/</a></td>
		</tr>
		<tr>
			<td>UV ink SLA Photopolymer Resin</td>
			<td>time80s</td>
			<td>RESIN-A</td>
			<td><a href="http://www.time80s.com/zlxz" target="_blank">http://www.time80s.com/zlxz</a></td>
		</tr>
	</tbody>
</table>

multimodal 3d printing of phantoms to simulate biological tissue

Biomedical optical imaging is playing an important role in diagnosis and treatment of various diseases. However, the accuracy and the reproducibility of an optical imaging device are greatly affected by the performance characteristics of its components, the test environment, and the operations. Therefore, it is necessary to calibrate these devices by traceable phantom standards. However, most of the currently available phantoms are homogeneous phantoms that cannot simulate multimodal and dynamic characteristics of biological tissue. Here, we show the fabrication of heterogeneous tissue-simulating phantoms using a production line integrating a spin coating module, a polyjet module, a fused deposition modeling (FDM) module, and an automatic control framework. The structural information and the optical parameters of a &#34;digital optical phantom&#34; are defined in a prototype file, imported to the production line, and fabricated layer-by-layer with sequential switch between different printing modalities. Technical capability of such a production line is exemplified by the automatic printing of skin-simulating phantoms that comprise the epidermis, dermis, subcutaneous tissue, and an embedded tumor.

Phantom fabricated by spin coating 
The spin coating evenly distributes the droplets on the substrate by rotating the turntable, and a single layer of the original body is fabricated after curing. The rotational speed of the substrate and the time of rotation not only affect the surface quality of the phantom, but also determine the thickness of each layer of the phantom. Phantoms of different thicknesses can be fabricated by repetitive spin coating layer-by-layer. The optical parameters of the phan...

Watch this Scientific Journal Video about Multimodal 3D Printing of Phantoms to Simulate Biological Tissue at JoVE.com

Multimodal 3D Printing of Phantoms to Simulate Biological Tissue

Spin coating, polyjet printing, and fused deposition modeling are integrated to produce multilayered heterogeneous phantoms that simulate structural and functional properties of biological tissue.

Biomedical optical imaging is playing an important role in diagnosis and treatment of various diseases. However, the accuracy and the reproducibility of ...

multimodal-3d-printing-of-phantoms-to-simulate-biological-tissue

Research

JoVE Journal

Engineering

7.3K Views.  University of Science and Technology of China. Spin coating, polyjet printing, and fused deposition modeling are integrated to produce multilayered heterogeneous phantoms that simulate structural and functional properties of biological tissue.

Video: Multimodal 3D Printing of Phantoms to Simulate Biological Tissue

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

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

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

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

High-resolution, High-speed, Three-dimensional Video Imaging with Digital Fringe Projection Techniques

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses triangulation between matching points in two views of the same scene at different angles to compute depth.&#160;However, unlike a stereo-based method, DFP uses a digital video projector to replace one of the cameras1. The projector rapidly projects a known sinusoidal pattern onto the subject, and the surface of the subject distorts these patterns in the camera&#8217;s field of view. Three distorted patterns (fringe images) from the camera can be used to compute the depth using triangulation.
Unlike other 3D measurement methods, DFP techniques lead to systems that tend to be faster, lower in equipment cost, more flexible, and easier to develop.&#160;DFP systems can also achieve the same measurement resolution as the camera.&#160;For this reason, DFP and other digital structured light techniques have recently been the focus of intense research (as summarized in1-5). Taking advantage of DFP, the graphics processing unit, and optimized algorithms, we have developed a system capable of 30&#160;Hz 3D video data acquisition, reconstruction, and display for over 300,000 measurement points per frame6,7.&#160;Binary defocusing DFP methods can achieve even greater speeds8.
Diverse applications can benefit from DFP techniques. Our collaborators have used our systems for facial function analysis9, facial animation10, cardiac mechanics studies11, and fluid surface measurements, but many other potential applications exist.&#160;This video will teach the fundamentals of DFP techniques and illustrate the design and operation of a binary defocusing DFP system.

This video describes the fundamentals of digital fringe projection techniques, which provide dense 3D measurements of dynamically changing surfaces.&#160;It also demonstrates the design and operation of a high-speed binary defocusing system based on these techniques.

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses ...

Preparation and 3D Tracking of Catalytic Swimming Devices

We report a method to prepare catalytically active Janus colloids that "swim" in fluids and describe how to determine their 3D motion using fluorescence microscopy. One commonly deployed method for catalytically active colloids to produce enhanced motion is via an asymmetrical distribution of catalyst. Here this is achieved by spin coating a dispersed layer of fluorescent polymeric colloids onto a flat planar substrate, and then using directional platinum vapor deposition to half coat the exposed colloid surface, making a two faced "Janus" structure. The Janus colloids are then re-suspended from the planar substrate into an aqueous solution containing hydrogen peroxide. Hydrogen peroxide serves as a fuel for the platinum catalyst, which is decomposed into water and oxygen, but only on one side of the colloid. The asymmetry results in gradients that produce enhanced motion, or "swimming". A fluorescence microscope, together with a video camera is used to record the motion of individual colloids. The center of the fluorescent emission is found using image analysis to provide an x and y coordinate for each frame of the video. While keeping the microscope focal position fixed, the fluorescence emission from the colloid produces a characteristic concentric ring pattern which is subject to image analysis to determine the particles relative z position. In this way 3D trajectories for the swimming colloid are obtained, allowing swimming velocity to be accurately measured, and physical phenomena such as gravitaxis, which may bias the colloids motion to be detected.

A method to prepare catalytically active Janus colloids that can "swim" in fluids and determine their 3D trajectories is presented.

We report a method to prepare catalytically active Janus colloids that "swim" in fluids and describe how to determine their 3D motion using fluorescence ...

3D Printing of Biomolecular Models for Research and Pedagogy

The construction of physical three-dimensional (3D) models of biomolecules can uniquely contribute to the study of the structure-function relationship. 3D structures are most often perceived using the two-dimensional and exclusively visual medium of the computer screen. Converting digital 3D molecular data into real objects enables information to be perceived through an expanded range of human senses, including direct stereoscopic vision, touch, and interaction. Such tangible models facilitate new insights, enable hypothesis testing, and serve as psychological or sensory anchors for conceptual information about the functions of biomolecules. Recent advances in consumer 3D printing technology enable, for the first time, the cost-effective fabrication of high-quality and scientifically accurate models of biomolecules in a variety of molecular representations. However, the optimization of the virtual model and its printing parameters is difficult and time consuming without detailed guidance. Here, we provide a guide on the digital design and physical fabrication of biomolecule models for research and pedagogy using open source or low-cost software and low-cost 3D printers that use fused filament fabrication technology.

Physical models of biomolecules can facilitate an understanding of their structure-function for the researcher, aid in communication between researchers, and serve as an educational tool in pedagogical endeavors. Here, we provide detailed guidance for the 3D printing of accurate models of biomolecules using fused filament fabrication desktop 3D printers.

The construction of physical three-dimensional (3D) models of biomolecules can uniquely contribute to the study of the structure-function relationship. 3D ...

Multi-material Ceramic-Based Components &#8211; Additive Manufacturing of Black-and-white Zirconia Components by Thermoplastic 3D-Printing (CerAM - T3DP)

To combine the benefits of Additive Manufacturing (AM) with the benefits of Functionally Graded Materials (FGM) to ceramic-based 4D components (three dimensions for the geometry and one degree of freedom concerning the material properties at each position) the Thermoplastic 3D-Printing (CerAM -&#160;T3DP) was developed. It is a direct AM technology which allows the AM of multi-material components. To demonstrate the advantages of this technology black-and-white zirconia components were additively manufactured and co-sintered defect-free.
Two different pairs of black and white zirconia powders were used to prepare different thermoplastic suspensions. Appropriate dispensing parameters were investigated to manufacture single-material test components and adjusted for the additive manufacturing of multi-color zirconia components.

Multi-material Ceramic-Based Components &amp;#8211; Additive Manufacturing of Black-and-white Zirconia Components by Thermoplastic 3D-Printing (CerAM - T3DP)

Here we describe a protocol for additively manufacturing black-and-white zirconia components by Thermoplastic 3D-Printing (CerAM -&#160;T3DP) and co-sintering defect-free.

To combine the benefits of Additive Manufacturing (AM) with the benefits of Functionally Graded Materials (FGM) to ceramic-based 4D components (three ...

Using Flexible Gold-Titanium Reaction Cells to Simulate Pressure-Dependent Microbial Activity in the Context of Subsurface Biomining

Laboratory studies investigating subsurface microbial processes, such as metal leaching in deep ore deposits (biomining), share common and challenging obstacles, including the special environmental conditions that need to be replicated, e.g., high pressure and in some cases acidic solutions. The former requires an experimental setup suitable for pressurization up to 100 bar, while the latter demands a fluid container with high chemical resistance against corrosion and unwanted chemical reactions with the container wall. To meet these conditions for an application in the field of in situ biomining, a special flexible gold-titanium reaction cell inside a rocking high-pressure reactor was used in this study. The described system allowed simulation of in situ biomining through sulfur-driven microbial iron reduction in an anoxic, pressure-controlled, highly chemically inert experimental environment. The flexible gold-titanium reaction cell can accommodate up to 100 mL of sample solution, which can be sampled at any given time point while the system maintains the desired pressure. Experiments can be performed on timescales ranging from hours to months. Assembling the high-pressure reactor system is fairly time consuming. Nevertheless, when complex and challenging (microbiological) processes occurring in the earth&#39;s deep subsurface in chemically aggressive fluids have to be investigated in the laboratory, the advantages of this system outweigh the disadvantages. The results found that even at high pressure the microbial consortium is active, but at significantly lower metabolic rates.

This protocol describes microbial experiments under elevated pressures to study in situ biomining processes. The experimental approach employs a rocking high-pressure reactor equipped with a gold-titanium reaction cell containing a microbial culture in an acidic, iron-rich medium.

Laboratory studies investigating subsurface microbial processes, such as metal leaching in deep ore deposits (biomining), share common and challenging ...

3D Printing - Evaluating Particle Emissions of a 3D Printing Pen

Three-dimensional (3D) printing as a type of additive manufacturing shows continuing increase in application and consumer popularity. The fused filament fabrication (FFF) is an inexpensive method used most frequently by consumers. Studies with 3D printers have shown that during the printing process particulate and volatile substances are released. Handheld 3D printing pens also use the FFF method but the consumer&#8217;s proximity to the 3D pens gives reason to higher exposure compared to a 3D printer. At the same time, 3D printing pens are often marketed for children who could be more sensitive to the printing emission. The aim of this study was to implement a low cost method to analyze the emissions of 3D printing pens. Polylactide (PLA) and acrylonitrile butadiene styrene (ABS) filaments of different colors were tested. In addition, filaments containing metal and carbon nanotubes (CNTs) were analyzed. An 18.5 L chamber and sampling close to the emission source was used to characterize emissions and concentrations near the breathing zone of the user.
Particle emissions and particle size distributions were measured and the potential release of metal particles and CNTs investigated. Particle number concentrations were found in a range of 105 - 106 particles/cm3, which is comparable to previous reports from 3D printers. Transmission electron microscopy (TEM) analysis showed nanoparticles of the different thermoplastic materials as well as of metal particles and CNTs. High contents of metal were observed by inductively coupled plasma mass spectrometry (ICP-MS).
These results call for a cautious use of 3D pens due to potential risk to the consumers.

This protocol presents a method to analyze the emission of 3D printing pens. Particle concentration and particle size distribution of the released particle is measured. Released particles are further analyzed with transmission electron microscopy (TEM). Metal content in filaments is quantified by inductively coupled plasma mass spectrometry (ICP-MS).

Three-dimensional (3D) printing as a type of additive manufacturing shows continuing increase in application and consumer popularity. The fused filament ...

Frugal Imaging Technique of Capillary Flow Through Three-Dimensional Polymeric Printing Powders

The development of novel imaging techniques of molecular and colloidal transport, including nanoparticles, is an area of active investigation in microfluidic and millifluidic studies. With the advent of three-dimensional (3D) printing, a new domain of materials has emerged, thereby increasing the demand for novel polymers. Specifically, polymeric powders, with average particle sizes on the order of a micron, are experiencing a growing interest from academic and industrial communities. Controlling material tunability at the mesoscopic to microscopic length scales creates opportunities to develop innovative materials, such as gradient materials. Recently, a need for micron-sized polymeric powders has been growing, as clear applications for the material are developing. Three-dimensional printing provides a high-throughput process with a direct link to new applications, driving investigations into the physio-chemical and transport interactions on a mesoscale. The protocol that is discussed in this article provides a non-invasive technique to image fluid flow in packed powder beds, providing high temporal and spatial resolution while leveraging mobile technology that is readily available from mobile devices, such as smartphones. By utilizing a common mobile device, the imaging costs that would normally be associated with an optical microscope are eliminated, resulting in a frugal-science approach. The proposed protocol has successfully characterized a variety of combinations of fluids and powders, creating a diagnostic platform for quickly imaging and identifying an optimal combination of fluid and powder.

The proposed technique will provide a novel, efficient, frugal, and non-invasive approach for imaging fluidic flow through a packed powder bed, yielding high spatial and temporal resolution.

The development of novel imaging techniques of molecular and colloidal transport, including nanoparticles, is an area of active investigation in ...

Four-Dimensional Printing of Stimuli-Responsive Hydrogel-Based Soft Robots

The present protocol describes the creation of four-dimensional (4D), time-dependent, shape-changeable, stimuli-responsive soft robots using a three-dimensional (3D) bio-printing method. Recently, 4D printing techniques have been extensively proposed as innovative new methods for developing shape-transformable soft robots. In particular, 4D time-dependent shape transformation is an essential factor in soft robotics because it allows effective functions to occur at the right time and place when triggered by external cues, such as heat, pH, and light. In line with this perspective, stimuli-responsive materials, including hydrogels, polymers, and hybrids, can be printed to realize smart shape-transformable soft robotic systems. The current protocol can be used to fabricate thermally responsive soft grippers composed of N-isopropylacrylamide (NIPAM)-based hydrogels, with overall sizes ranging from millimeters to centimeters in length. It is expected that this study will provide new directions for realizing intelligent soft robotic systems for various applications in smart manipulators (e.g., grippers, actuators, and pick-and-place machines), healthcare systems (e.g., drug capsules, biopsy tools, and microsurgeries), and electronics (e.g., wearable sensors and fluidics).

This manuscript describes a 4D printing strategy for fabricating intelligent stimuli-responsive soft robots. This approach can provide the groundwork to facilitate the realization of intelligent shape-transformable soft robotic systems, including smart manipulators, electronics, and healthcare systems.

The present protocol describes the creation of four-dimensional (4D), time-dependent, shape-changeable, stimuli-responsive soft robots using a ...

Visualizing Polymer Dynamics for Optimizing 3D Printing Quality

Real-Time Imaging of Bonding in 3D-Printed Layers

In recent times, 3D printing technology has revolutionized our ability to design and produce products, but optimizing the print quality can be challenging. The process of extrusion 3D printing involves pressuring molten material through a thin nozzle and depositing it onto previously extruded material. This method relies on bonding between the consecutive layers to create a strong and visually appealing final product. This is no easy task, as many parameters, such as the nozzle temperature, layer thickness, and printing speed, must be fine-tuned to achieve optimal results. In this study, a method for visualizing the polymer dynamics during extrusion is presented, giving insight into the layer bonding process. Using laser speckle imaging, the plastic flow and fusion can be resolved non-invasively, internally, and with high spatiotemporal resolution. This measurement, which is easy to perform, provides an in-depth understanding of the underlying mechanics influencing the final print quality. This methodology was tested with a range of cooling fan speeds, and the results showed increased polymer motion with lower fan speeds and, thus, explained the poor printing quality when the cooling fan was turned off. These findings show that this methodology allows for optimizing the printing settings and understanding the material behavior. This information can be used for the development and testing of novel printing materials or advanced slicing procedures. With this approach, a deeper understanding of extrusion can be built to take 3D printing to the next level.

Author Spotlight: Real-Time Imaging of Bonding in 3D-Printed Layers  

With a non-invasive and real-time technique, nanoscopic polymer motion inside a polymer filament is imaged during 3D printing. Fine-tuning this motion is crucial for producing constructs with optimal performance and appearance. This method reaches the core of plastic layer fusion, thus offering insights into optimal printing conditions and material design criteria.