The research was supported by R-397-000-204-133 (National University of Singapore Young Investigator Award).

Note: All the soft pneumatic grippers were fabricated by casting silicone-based elastomeric mixtures into customized 3D-printed molds, which followed a fabrication process comprising three steps: molding gripper-arm components with embedded pneumatic channels, molding chamber component connected to the pneumatic channels, and sealing the chamber component filled with air.
1. Preparation of Elastomers
<ol>
	<li>Place a container for mixer on a weighing scale and tare it. Pour parts A and B of the silicone-based elastomer in the container with a 1:1 weight ratio.</li>
	<li>Cover the container and measure the total weight.</li>
	<li>Place the container and material into a centrifugal mixer. Adjust the weight balance on the mixer to the weight measured in step 1.2.</li>
	<li>Set the mixing and de-aeration modes to 2,000 rpm and 2,200 rpm respectively for 30 sec. Mix the elastomer components thoroughly to achieve uniform curing.</li>
</ol>
2. Mold Design and Production
Note: The geometry of the mold will vary depending on the specific requirements for different applications. The following steps illustrate general key steps in CAD software that are required to create the chamber and gripper component of the mold.
<ol>
	<li>Design the molds and sealing mold using computer-aided design (CAD) software. See Figure 1 for the geometry and specific dimensions of the molds used in this manuscript.
	<ol>
		<li>Design of the outer boundary box
		<ol>
			<li>Right-click on the top plane and click on &#34;Normal to&#34; button to normalize to the top plane.</li>
			<li>Click on &#34;Sketch&#34; on the top left corner to open a &#34;Sketch&#34; window. Then, click on the &#34;Sketch&#34; button on the top left corner of the toolbar to draw a rectangular base of chamber component.</li>
			<li>Click on the &#34;Smart Dimension&#34; feature, which is located beside the &#34;Sketch&#34; button, to define sketch dimensions. Ensure that the sketch is fully defined (i.e., all drawing lines become black) and exit the sketch when done.</li>
			<li>Click on the &#34;Features&#34; window. Then, click on &#34;Extruded Boss/Base&#34; feature to extrude selected contours in the Y-direction.</li>
			<li>Click on the top surface of the model to preselect the sketch plane. Sketch a rectangle and define the dimensions as described in 2.1.1.2 and 2.1.1.3.</li>
			<li>Click on the &#34;Features&#34; window. Then, click on &#34;Extruded Cut&#34; feature to extrude cut a cavity for casting elastomers (Figure 2A). Ensure that the wall thickness is 2.5 mm.</li>
		</ol>
		</li>
		<li>Design of the inner chamber
		<ol>
			<li>Right-click on the surface on the Y-direction of the opening area. Then, click on &#34;Normal to&#34; to normalize to that surface.</li>
			<li>Next, click on the &#34;Sketch&#34; window to draw a rectangle for chamber component as described in steps 2.1.1.2 and 2.1.1.3.</li>
			<li>Click on the &#34;Features&#34; window. Then, click on &#34;Extruded Boss/Base&#34; feature to extrude the chamber component in the Y-direction (Figure 2B). 
			Note: The depth of the cut in step 2.1.1.6 is 2.5 mm larger than this extruded base.</li>
		</ol>
		</li>
		<li>Design of the gripper component
		<ol>
			<li>Click on the surface of the model in negative X-direction to preselect the sketch plane for gripper component. Create a rectangle in the &#34;Sketch&#34; window as described in steps 2.1.1.2 and 2.1.1.3.</li>
			<li>Click on the &#34;Features&#34; window. Then, click on &#34;Extruded Boss/Base&#34; feature to extrude the selected contour in the negative X-direction.</li>
			<li>Click on the top surface of the gripper component to preselect the sketch plane. Create a shape of gripper in the &#34;Sketch&#34; window (Figure 2C) and exit the sketch when the dimensions is fully defined as described in steps 2.1.1.2 and 2.1.1.3.</li>
			<li>Click on the &#34;Features&#34; window. Then, click on &#34;Extruded Cut&#34; to cut a cavity for casting elastomers in the gripper component. Ensure that the wall thickness is 2.5 mm.</li>
		</ol>
		</li>
		<li>Design of the connection between chamber and gripper
		<ol>
			<li>Create a rectangle in the &#34;Sketch&#34; window on the top surface of the chamber piece as described in 2.1.1.2 and 2.1.1.3.</li>
			<li>Click on the &#34;Features&#34; window. Then, click on &#34;Extruded Cut&#34; to create a connection between chamber and gripper components (Figure 2D).</li>
		</ol>
		</li>
		<li>Design of the pneumatic channels
		<ol>
			<li>Create 1.5 mm diameter circles on the surface of the chamber piece in the positive X-direction as described in steps 2.1.1.2 and 2.1.1.3.</li>
			<li>Click on the &#34;Features&#34; window. Then, click on &#34;Extruded Cut&#34; to create channels for wire rods insertion (Figure 2E). Ensure the holes are not cut through the gripper component.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>In a separate CAD file, draw a sealing mold with a cavity of length and width that are 1 mm larger than the outer dimensions of the chamber component of the gripper. Note: The wall thickness is 2.5 mm.
	<ol>
		<li>Click on the &#34;Sketch&#34; window to create a rectangle on the top plane as described steps 2.1.1.2 and 2.1.1.3.</li>
		<li>Click on the &#34;Features&#34; window. Then, click on &#34;Extruded Boss/Base&#34; feature to extrude selected contours in the Y-direction.</li>
		<li>Click on the top face of the model to preselect the sketch plane. Sketch a rectangle and define the dimensions as described in steps 2.1.1.2 and 2.1.1.3).</li>
		<li>Click on the &#34;Features&#34; window. Then, click on &#34;Extruded Cut&#34; feature to extrude cut a cavity for casting elastomers. Ensure that the wall thickness is 2.5 mm.</li>
	</ol>
	</li>
	<li>Save each mold piece as a .STL file for 3D printing.</li>
	<li>Load the .STL file into the 3D printer with resolution of 30 &#181;m and print the mold pieces9.</li>
	<li>Remove any support material on the mold pieces and wash the mold pieces with water.</li>
</ol>
3. Soft Single/Double-actuatable Arm Pneumatic Grippers
<ol>
	<li>Molding gripper-arm components with embedded pneumatic channels
	<ol>
		<li>Insert two 3D-printed chamber-blocks on the left and right side of the chamber component (Figure 3A) in order to generate a sealed chamber with pneumatic channels connected to it.</li>
		<li>Insert two 1.5 mm-diameter titanium wire rods through the chamber, keeping a 2 mm distance from the gripper tips to create the pneumatic channels (Figure 3A). Note: Use one wire rod for the single-actuatable-arm gripper.</li>
		<li>Pour the elastomeric mixture into the mold to fully fill the gripper component.</li>
		<li>Ensure there is no visible air bubbles present.</li>
		<li>Place the mold into oven for curing at 60 &#176;C for 10 min. Once elastomer is cured, remove the mold from the oven.</li>
	</ol>
	</li>
	<li>Molding chamber component connected to the pneumatic channels
	<ol>
		<li>Pull the wire rods and the two chamber-blocks out from the mold.</li>
		<li>Place a 3D-printed gripper-block on top of the gripper component in order to create the chamber (Figure 3B). Insert the wire rods to block the holes in the wall of the mold.</li>
		<li>Pour the elastomeric mixture into the mold to fill the remaining part of chamber component and ensure there is no visible air bubbles trapped in the mold.</li>
		<li>Cure the part at a temperature of 60 &#176;C for 10 min. Remove the mold from the oven once elastomer is cured.</li>
		<li>Remove the gripper-block and demold the fully cured gripper with chamber structure.</li>
	</ol>
	</li>
	<li>Sealing the chamber component filled with air
	<ol>
		<li>Pour the elastomeric mixture into the sealing mold and cure it at 60 &#176;C for 10 min.</li>
		<li>Brush a layer of elastomeric material on the cured 2.5 mm sealing layer. Place the cured gripper with chamber structure on top of the coated sealing layer and bond the two pieces together (Figure 3C).</li>
		<li>Subsequently, cure the entire structure fully at 60 &#176;C for 15 min.</li>
		<li>Demold the fully cured soft robotic gripper device.</li>
	</ol>
	</li>
</ol>
4. Insertion of Soft Robotic Pneumatic Gripper Device into Handling Tool
<ol>
	<li>Design the handling tools as described in the Supplemental file 1 using CAD software and save it in .STL file. See Figures 4 and 5 for the dimensions of the tools.</li>
	<li>Load the .STL file in the 3D printer and print the mold pieces9. 
	Note: All printing steps for manual control handling tool, rectangular cap, and movable piston (Figure 4) can be completed within 3 hr 48 min. The printing time for fabricating the robotic control handling tool and rectangular cap (Figure 5) is 1 hr 56 min. See Supplemental file 2 for 3D printer operation instructions.</li>
	<li>Peel off any support material on the tools after the printing is completed. Then, wash the tools with water.</li>
	<li>Insert the gripper into the manual control handling tool (Figure 4A) and cover the opening area with a movable rectangular cap (Figure 4B).</li>
	<li>Insert a movable piston (Figure 4C) to facilitate chamber compression.</li>
	<li>Insert the gripper and linear actuator into the robotic control handling tool (Figure 5A). Note: The linear actuator replaces the movable piston in manual control mode for chamber compression.</li>
	<li>Cover the opening area with a movable rectangular cap (Figure 5B).</li>
</ol>
5. Evaluations and Grip Compressive Test
<ol>
	<li>Evaluate the functionality of the soft gripper by performing gripping tests with a jumper wire.
	<ol>
		<li>Place a jumper wire on the table.</li>
		<li>Adjust the gripper so that the wire is in between of the two gripper arms.</li>
		<li>Move the movable piston to compress the chamber in order to actuate the gripper arms to hold the wire. 
		Note: Only the manual control handling tool is used in the gripping demonstration.</li>
		<li>Hold and move the wire to a box located at 20 cm away from wire&#39;s original location.</li>
	</ol>
	</li>
	<li>Place a calibrated force sensing resistor between the two jaws of the gripper. Ensure the gripper jaws grip on the sensing area. Note: The diameter of the sensing area is 14.7 mm.</li>
	<li>Compress the chamber to actuate the gripper arms to grip on the force sensing resistor.</li>
	<li>Measure the maximum grip compressive forces that the soft single-actuatable-arm and double-actuatable-arm pneumatic grippers could generate as described in 10. 
	Note: The readout values will be displayed on a laptop. The maximum grip compressive forces are measured at the point of maximum pressure that the pneumatic channels can withstand.</li>
	<li>Cut out the individual elastomeric gripping jaws from a soft double-actuatable-arm pneumatic gripper.</li>
	<li>Insert the forceps tips into the pneumatic channels of the elastomeric gripping jaws.</li>
	<li>Place a calibrated force sensing resistor between the two jaws of the forceps.</li>
	<li>Measure the compressive forces10 generated by elastomer-coated forceps and forceps during a simulated nerve surgery conducted by a neurosurgeon. 
	Note: The neurosurgeon applies a force that is similar to what he normally applies during actual surgery on the force sensing resistor.</li>
	<li>Average the data obtained from five trials in each test.</li>
</ol>

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M., Shafighi, M., Gurunluoqlu, R., Wechselberger, G., Piza-Katzer, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microsurgical+repair+of+the+sural+nerve+after+nerve+biopsy+to+avoid+associated+sensory+morbidity:+a+preliminary+report.">Microsurgical repair of the sural nerve after nerve biopsy to avoid associated sensory morbidity: a preliminary report.</a> Neurosurgery. 54 (4), 897-900 (2004).</li><li>Bamberg, R., Jones, B., Murray, L., Sagstetter, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Laparoscopic grasper for minimally invasive laparoscopic surgery. , (2006).</li><li>Ducic, I., Hill, L., Maher, P., Al-Attar, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perioperative+complications+in+patients+undergoing+peripheral+nerve+surgery.">Perioperative complications in patients undergoing peripheral nerve surgery.</a> Ann Plast Surg. 66 (1), 69-72 (2011).</li><li>Shepherd, R. 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The authors have nothing to disclose.

We have successfully demonstrated that the soft robotic pneumatic gripper devices allowed compliant gripping of objects, which exerted much lower compressive forces on the gripped object than the elastomer-coated forceps tips and forceps exerted. Forceps is an essential tool for nerves manipulation during peripheral nerve repair surgeries11, 12. However, its metallic structure required extreme caution in usage from the surgeons in order to prevent nerve damage caused by excessive gripping forces and the incide...

Soft robots have sparked great research interest within the robotics community and they have been used in different functional tasks such as undulatory locomotion in unstructured environments1 and gripping2. They are mainly composed of soft elastomeric materials and controlled by different actuation techniques through the use of different materials such as electroactive polymer (EAP), shape memory alloy (SMA), or compressed fluid3. EAPs function based on a differential voltage that induces electrostatic forces to produce active strains and thereby generates actuation. The peculiar shape memory effect of the SMAs is deployed to generate the desired actuation based on the force generation during phase transformations upon the change in temperature. Lastly, compressed fluid actuation technique facilitates a simple design strategy to induce stiffness difference in the soft actuators, such that the more compliant regions will inflate upon pressurization. Soft robots are designed to broaden the applications of traditional hard robots, especially in applications where delicate objects are involved. Particularly, in this paper, we present our unique approach in developing soft robotic grippers for delicate surgical manipulation.
Surgical gripping is an important aspect involved in many surgical procedures such as hepatic, gynecological, urological, and nerve repair surgeries4, 5. It is typically performed by rigid, steel tissue gripping tools such as the forceps and laparoscopic graspers for the purpose of facilitating observation, excision, anastomosis procedures, etc. However, extreme caution is required as the conventional gripping tools are made of metal that may cause high stress concentration areas in the soft tissue at the points of contact6. Depending on the severity of the tissue damages, various complications, such as pain, pathological scar tissue formation, and even permanent disability, may result. A prior study reported that the complication rate in peripheral nerve surgery was 3%7. Therefore, the concept of soft gripping that can provide safe compliant grip can be a promising candidate for delicate surgical manipulation.
Here, we present a combination of 3D-printing and modified soft lithography techniques, which adopted a rod-based approach, to fabricate customizable soft robotic pneumatic grippers. Traditional fabrication technique of soft robots based on compressed fluid actuation requires a mold with pneumatic channels printed on it and a sealing process to seal the channels8. However, it is not feasible for miniaturized soft robots which need small pneumatic channels where occlusion of channels can easily happen in the sealing process. The traditional technique requires the sealing of the pneumatic channels to be done by bonding a coated sealing layer to it. Hence, the layer of elastomeric material which initially serves as a bonding layer may spill into the tiny channels and occlude those channels. It is also not possible to position the pneumatic channels at the middle of the structure and connect to a chamber component using conventional techniques. The proposed approach allows the creation of miniaturized pneumatic channels connected to an air-filled chamber using rods and does not require sealing of the tiny channels. In addition, the chamber connected to the pneumatic channels serve as an air source which does not require external air sources for compressed fluid actuation. It allows both the manual and robotic control modes by facilitating the chamber compression to actuate the gripping component, thereby providing users the option of controlling the amount of force that they are applying through the gripper. This approach is highly customizable and can be used to fabricate various types of soft gripper designs such as grippers with single or multiple actuatable arms.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Weighing Scale</td>
			<td>Severin</td>
			<td>KW3667</td>
			<td>(Step: Preparation of elastomers)</td>
		</tr>
		<tr>
			<td>Ecoflex Supersoft 0030 Elastomer</td>
			<td>Smooth-On</td>
			<td>EF0030</td>
			<td>(Step: Preparation of elastomers)</td>
		</tr>
		<tr>
			<td>Planetary Centrifugal Mixer and Containers</td>
			<td>THINKY USA Inc.</td>
			<td>ARE-310</td>
			<td>(Step: Preparation of elastomers)</td>
		</tr>
		<tr>
			<td>Solidworks CAD</td>
			<td>Dassault Syst&#232;mes&#160;</td>
			<td>Solidworks Research Subscription</td>
			<td>(Step: Soft single/double-actuatable arm pneumatic grippers)</td>
		</tr>
		<tr>
			<td>Objet 3D Printer</td>
			<td>Stratasys</td>
			<td>260 Connex2</td>
			<td>(Step: Soft single/double-actuatable arm pneumatic grippers)</td>
		</tr>
		<tr>
			<td>Titanium Wire Rods</td>
			<td>Titan Engineering</td>
			<td>N/A</td>
			<td>(Step: Soft single/double-actuatable arm pneumatic grippers)</td>
		</tr>
		<tr>
			<td>Natural Convection Oven with Timer</td>
			<td>Thermo Fisher Scientific</td>
			<td>BIN#ED53</td>
			<td>(Step: Soft single/double-actuatable arm pneumatic grippers)</td>
		</tr>
		<tr>
			<td>Linear Actuator</td>
			<td>Firgelli Technologies</td>
			<td>L12</td>
			<td>(Step: Insertion of soft robotic pneumatic gripper device into handling tool)</td>
		</tr>
		<tr>
			<td>Jumper Wire</td>
			<td>sgbotic</td>
			<td>CAB-01146</td>
			<td>(Step: Evaluations and grip compressive test)</td>
		</tr>
		<tr>
			<td>Force Sensing Resistor</td>
			<td>Interlink Electronics</td>
			<td>FSR402</td>
			<td>(Step: Evaluations and grip compressive test)</td>
		</tr>
	</tbody>
</table>

rod-based fabrication of customizable soft robotic pneumatic gripper devices for delicate tissue manipulation

Soft compliant gripping is essential in delicate surgical manipulation for minimizing the risk of tissue grip damage caused by high stress concentrations at the point of contact. It can be achieved by complementing traditional rigid grippers with soft robotic pneumatic gripper devices. This manuscript describes a rod-based approach that combined both 3D-printing and a modified soft lithography technique to fabricate the soft pneumatic gripper. In brief, the pneumatic featureless mold with chamber component is 3D-printed and the rods were used to create the pneumatic channels that connect to the chamber. This protocol eliminates the risk of channels occluding during the sealing process and the need for external air source or related control circuit. The soft gripper consists of a chamber filled with air, and one or more gripper arms with a pneumatic channel in each arm connected to the chamber. The pneumatic channel is positioned close to the outer wall to create different stiffness in the gripper arm. Upon compression of the chamber which generates pressure on the pneumatic channel, the gripper arm will bend inward to form a close grip posture because the outer wall area is more compliant. The soft gripper can be inserted into a 3D-printed handling tool with two different control modes for chamber compression: manual gripper mode with a movable piston, and robotic gripper mode with a linear actuator. The double-arm gripper with two actuatable arms was able to pick up objects of sizes up to 2 mm and yet generate lower compressive forces as compared to elastomer-coated and non-coated rigid grippers. The feasibility of having other designs, such as single-arm or hook gripper, was also demonstrated, which further highlighted the customizability of the soft gripper device, and it's potential to be used in delicate surgical manipulation to reduce the risk of tissue grip damage.

The soft robotic pneumatic gripper devices were capable of picking up objects with dimensions of up to 1.2 mm in diameter (Figure 6). The maximum grip compressive force generated by the single- actuatable-arm, and double- actuatable-arm soft gripper devices were 0.27 &#177; 0.07 N and 0.79 &#177; 0.14 N respectively, as compared to 1.71 &#177; 0.16 N and 2.61 &#177; 0.22 N compressive forces in simulated surgery by the elastomer-coated forceps and by uncoated forceps (<st...

Watch this Scientific Journal Video about Rod-based Fabrication of Customizable Soft Robotic Pneumatic Gripper Devices for Delicate Tissue Manipulation at JoVE.com

Rod-based Fabrication of Customizable Soft Robotic Pneumatic Gripper Devices for Delicate Tissue Manipulation

This protocol describes a rod-based approach, combining 3D-printing and soft lithography techniques for fabricating the soft gripper devices. This approach eliminates the need for an external air source by incorporating a chamber component and reduces the chance of occlusion during the sealing process, particularly for miniaturized pneumatic channels.

Soft compliant gripping is essential in delicate surgical manipulation for minimizing the risk of tissue grip damage caused by high stress concentrations ...

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8.7K Views.  National University of Singapore. This protocol describes a rod-based approach, combining 3D-printing and soft lithography techniques for fabricating the soft gripper devices. This approach eliminates the need for an external air source by incorporating a chamber component and reduces the chance of occlusion during the sealing process, particularly for miniaturized pneumatic channels.

Video: Rod-based Fabrication of Customizable Soft Robotic Pneumatic Gripper Devices for Delicate Tissue Manipulation

Fabrication of Biologically Derived Injectable Materials for Myocardial Tissue Engineering

This protocol provides methods for the preparation of an injectable extracellular matrix (ECM) gel for myocardial tissue engineering applications. Briefly, decellularized tissue is lyophilized, milled, enzymatically digested, and then brought to physiological pH. The lyophilization removes all water content from the tissue, resulting in dry ECM that can be ground into a fine powder with a small mill. After milling, the ECM powder is digested with pepsin to form an injectable matrix. After adjustment to pH 7.4, the liquid matrix material can be injected into the myocardium. Results of previous characterization assays have shown that matrix gels produced from decellularized pericardial and myocardial tissue retain native ECM components, including diverse proteins, peptides and glycosaminoglycans. Given the use of this material for tissue engineering, in vivo characterization is especially useful; here, a method for performing an intramural injection into the left ventricular (LV) free wall is presented as a means of analyzing the host response to the matrix gel in a small animal model. Access to the chest cavity is gained through the diaphragm and the injection is made slightly above the apex in the LV free wall. The biologically derived scaffold can be visualized by biotin-labeling before injection and then staining tissue sections with a horse radish peroxidase-conjugated neutravidin and visualizing via diaminobenzidine (DAB) staining. Analysis of the injection region can also be done with histological and immunohistochemical staining. In this way, the previously examined pericardial and myocardial matrix gels were shown to form fibrous, porous networks and promote vessel formation within the injection region.

Methods for preparing an injectable matrix gel from decellularized tissue and injecting it into rat myocardium in vivo are described.

This protocol provides methods for the preparation of an injectable extracellular matrix (ECM) gel for myocardial tissue engineering applications.  ...

Engineering Skeletal Muscle Tissues from Murine Myoblast Progenitor Cells and Application of Electrical Stimulation

Engineered muscle tissues can be used for several different purposes, which include the production of tissues for use as a disease model in vitro, e.g. to study pressure ulcers, for regenerative medicine and as a meat alternative 1. The first reported 3D muscle constructs have been made many years ago and pioneers in the field are Vandenburgh and colleagues 2,3. Advances made in muscle tissue engineering are not only the result from the vast gain in knowledge of biochemical factors, stem cells and progenitor cells, but are in particular based on insights gained by researchers that physical factors play essential roles in the control of cell behavior and tissue development. State-of-the-art engineered muscle constructs currently consist of cell-populated hydrogel constructs. In our lab these generally consist of murine myoblast progenitor cells, isolated from murine hind limb muscles or a murine myoblast cell line C2C12, mixed with a mixture of collagen/Matrigel and plated between two anchoring points, mimicking the muscle ligaments. Other cells may be considered as well, e.g. alternative cell lines such as L6 rat myoblasts 4, neonatal muscle derived progenitor cells 5, cells derived from adult muscle tissues from other species such as human 6 or even induced pluripotent stem cells (iPS cells) 7. Cell contractility causes alignment of the cells along the long axis of the construct 8,9 and differentiation of the muscle progenitor cells after approximately one week of culture. Moreover, the application of electrical stimulation can enhance the process of differentiation to some extent 8. Because of its limited size (8 x 2 x 0.5 mm) the complete tissue can be analyzed using confocal microscopy to monitor e.g. viability, differentiation and cell alignment. Depending on the specific application the requirements for the engineered muscle tissue will vary; e.g. use for regenerative medicine requires the up scaling of tissue size and vascularization, while to serve as a meat alternative translation to other species is necessary.

Engineered muscle tissue has great potential in regenerative medicine, as disease model and also as an alternative source for meat. Here we describe the engineering of a muscle construct, in this case from mouse myoblast progenitor cells, and the stimulation by electrical pulses.

Engineered muscle tissues can be used for several different purposes, which include the production of tissues for use as a disease model in vitro, e.g. to ...

Density Gradient Multilayered Polymerization (DGMP): A Novel Technique for Creating Multi-compartment, Customizable Scaffolds for Tissue Engineering

Complex tissue culture matrices, in which types and concentrations of biological stimuli (e.g. growth factors, inhibitors, or small molecules) or matrix structure (e.g. composition, concentration, or stiffness of the matrix) vary over space, would enable a wide range of investigations concerning how these variables affect cell differentiation, migration, and other phenomena. The major challenge in creating layered matrices is maintaining the structural integrity of layer interfaces without diffusion of individual components from each layer1. Current methodologies to achieve this include photopatterning2-3, lithography4, sequential functionalization5, freeze drying6, microfluidics7, or centrifugation8, many of which require sophisticated instrumentation and technical skills. Others rely on sequential attachment of individual layers, which may lead to delamination of layers9. 
DGMP overcomes these issues by using an inert density modifier such as iodixanol to create layers of varying densities10. Since the density modifier can be mixed with any prepolymer or bioactive molecule, DGMP allows each scaffold layer to be customized. Simply varying the concentration of the density modifier prevents mixing of adjacent layers while they remain aqueous. Subsequent single step polymerization gives rise to a structurally continuous multilayered scaffold, in which each layer has distinct chemical and mechanical properties. The density modifier can be easily removed with sufficient rinsing without perturbation of the individual layers or their components. This technique is therefore well suited for creating hydrogels of various sizes, shapes, and materials.
A protocol for fabricating a 2D-polyethylene glycol (PEG) gel, in which alternating layers incorporate RGDS-350, is outlined below. We use PEG because it is biocompatible and inert. RGDS, a cell adhesion peptide11, is used to demonstrate spatial restriction of a biological cue, and the conjugation of a fluorophore (Alexa Fluor 350) enables us to visually distinguish various layers. This procedure can be adapted for other materials (e.g. collagen, hyaluronan, etc.) and can be extended to fabricate 3D gels with some modifications10.

Density Gradient Multilayered Polymerization DGMP: A Novel Technique for Creating Multi-compartment, Customizable Scaffolds for Tissue Engineering

Here we describe a unique strategy for creating biocompatible, layered matrices with continuous interfaces between distinct layers for tissue engineering. Such a scaffold could provide an ideal customizable environment to modulate cell behavior by various biological, chemical or mechanical cues

Complex tissue culture matrices, in which types and concentrations of biological stimuli (e.g. growth factors, inhibitors, or small molecules) or matrix ...

Human Cartilage Tissue Fabrication Using Three-dimensional Inkjet Printing Technology

Bioprinting, which is based on thermal inkjet printing, is one of the most attractive enabling technologies in the field of tissue engineering and regenerative medicine. With digital control&#160;cells, scaffolds, and growth factors can be precisely deposited to the desired two-dimensional (2D) and three-dimensional (3D) locations rapidly. Therefore, this technology is an ideal approach to fabricate tissues mimicking their native anatomic structures. In order to engineer cartilage with native zonal organization, extracellular matrix composition (ECM), and mechanical properties, we developed a bioprinting platform using a commercial inkjet printer with simultaneous photopolymerization capable for 3D cartilage tissue engineering. Human chondrocytes suspended in poly(ethylene glycol) diacrylate (PEGDA) were printed for 3D neocartilage construction via layer-by-layer assembly. The printed cells were fixed at their original deposited positions, supported by the surrounding scaffold in simultaneous photopolymerization. The mechanical properties of the printed tissue were similar to the native cartilage. Compared to conventional tissue fabrication, which requires longer UV exposure, the viability of the printed cells with simultaneous photopolymerization was significantly higher. Printed neocartilage demonstrated excellent glycosaminoglycan (GAG) and collagen type II production, which was consistent with gene expression. Therefore, this platform is ideal for accurate cell distribution and arrangement for anatomic tissue engineering.

The methods described in this paper show how to convert a commercial inkjet printer into a bioprinter with simultaneous UV polymerization. The printer is capable of constructing 3D tissue structure with cells and biomaterials. The study demonstrated here constructed a 3D neocartilage.

Bioprinting, which is based on thermal inkjet printing, is one of the most attractive enabling technologies in the field of tissue engineering and ...

Cultivation of Mammalian Cells Using a Single-use Pneumatic Bioreactor System

Recent advances in mammalian, insect, and stem cell cultivation and scale-up have created tremendous opportunities for new therapeutics and personalized medicine innovations. However, translating these advances into therapeutic applications will require in vitro systems that allow for robust, flexible, and cost effective bioreactor systems. There are several bioreactor systems currently utilized in research and commercial settings; however, many of these systems are not optimal for establishing, expanding, and monitoring the growth of different cell types. The culture parameters most challenging to control in these systems include, minimizing hydrodynamic shear, preventing nutrient gradient formation, establishing uniform culture medium aeration, preventing microbial contamination, and monitoring and adjusting culture conditions in real-time. Using a pneumatic single-use bioreactor system, we demonstrate the assembly and operation of this novel bioreactor for mammalian cells grown on micro-carriers. This bioreactor system eliminates many of the challenges associated with currently available systems by minimizing hydrodynamic shear and nutrient gradient formation, and allowing for uniform culture medium aeration. Moreover, the bioreactor&#8217;s software allows for remote real-time monitoring and adjusting of the bioreactor run parameters. This bioreactor system also has tremendous potential for scale-up of adherent and suspension mammalian cells for production of a variety therapeutic proteins, monoclonal antibodies, stem cells, biosimilars, and vaccines.

Using a pneumatic bioreactor, we demonstrate the assembly, operation, and performance of this single-use bioreactor system for the growth of mammalian cells.

Recent advances in mammalian, insect, and stem cell cultivation and scale-up have created tremendous opportunities for new therapeutics and personalized ...

Design and Fabrication of an Elastomeric Unit for Soft Modular Robots in Minimally Invasive Surgery

In recent years, soft robotics technologies have aroused increasing interest in the medical field due to their intrinsically safe interaction in unstructured environments. At the same time, new procedures and techniques have been developed to reduce the invasiveness of surgical operations. Minimally Invasive Surgery (MIS) has been successfully employed for abdominal interventions, however standard MIS procedures are mainly based on rigid or semi-rigid tools that limit the dexterity of the clinician. This paper presents a soft and high dexterous manipulator for MIS. The manipulator was inspired by the biological capabilities of the octopus arm, and is designed with a modular approach. Each module presents the same functional characteristics, thus achieving high dexterity and versatility when more modules are integrated. The paper details the design, fabrication process and the materials necessary for the development of a single unit, which is fabricated by casting silicone inside specific molds. The result consists in an elastomeric cylinder including three flexible pneumatic actuators that enable elongation and omni-directional bending of the unit. An external braided sheath improves the motion of the module. In the center of each module a granular jamming-based mechanism varies the stiffness of the structure during the tasks. Tests demonstrate that the module is able to bend up to 120&#176; and to elongate up to 66% of the initial length. The module generates a maximum force of 47 N, and its stiffness can increase up to 36%.

This paper describes the design and fabrication of a soft unit for surgical manipulators. The base module includes three flexible fluidic actuators to achieve omnidirectional bending and elongation, and a granular jamming-based mechanism to enable stiffness control. A complete mechanical characterization is also reported.

In recent years, soft robotics technologies have aroused increasing interest in the medical field due to their intrinsically safe interaction in ...

Automated Robotic Liquid Handling Assembly of Modular DNA Devices

Recent advances in modular DNA assembly techniques have enabled synthetic biologists to test significantly more of the available &#34;design space&#34; represented by &#34;devices&#34; created as combinations of individual genetic components. However, manual assembly of such large numbers of devices is time-intensive, error-prone, and costly. The increasing sophistication and scale of synthetic biology research necessitates an efficient, reproducible way to accommodate large-scale, complex, and high throughput device construction.
Here, a DNA assembly protocol using the Type-IIS restriction endonuclease based Modular Cloning (MoClo) technique is automated on two liquid-handling robotic platforms. Automated liquid-handling robots require careful, often times tedious optimization of pipetting parameters for liquids of different viscosities (e.g. enzymes, DNA, water, buffers), as well as explicit programming to ensure correct aspiration and dispensing of DNA parts and reagents. This makes manual script writing for complex assemblies just as problematic as manual DNA assembly, and necessitates a software tool that can automate script generation. To this end, we have developed a web-based software tool, http://mocloassembly.com, for generating combinatorial DNA device libraries from basic DNA parts uploaded as Genbank files. We provide access to the tool, and an export file from our liquid handler software which includes optimized liquid classes, labware parameters, and deck layout. All DNA parts used are available through Addgene, and their digital maps can be accessed via the Boston University BDC ICE Registry. Together, these elements provide a foundation for other organizations to automate modular cloning experiments and similar protocols.
The automated DNA assembly workflow presented here enables the repeatable, automated, high-throughput production of DNA devices, and reduces the risk of human error arising from repetitive manual pipetting. Sequencing data show the automated DNA assembly reactions generated from this workflow are ~95% correct and require as little as 4% as much hands-on time, compared to manual reaction preparation.

Here, an automated workflow to perform modular DNA &#34;device&#34; assembly using a modular cloning DNA assembly method on liquid-handling robots is presented. The protocol uses an intuitive software tool for generating liquid handler picklists for combinatorial DNA device library generation, which we demonstrate using two liquid handling platforms.

Recent advances in modular DNA assembly techniques have enabled synthetic biologists to test significantly more of the available &#34;design space&#34; ...

Fabrication of Three-dimensional Paper-based Microfluidic Devices for Immunoassays

Paper wicks fluids autonomously due to capillary action. By patterning paper with hydrophobic barriers, the transport of fluids can be controlled and directed within a layer of paper. Moreover, stacking multiple layers of patterned paper creates sophisticated three-dimensional microfluidic networks that can support the development of analytical and bioanalytical assays. Paper-based microfluidic devices are inexpensive, portable, easy to use, and require no external equipment to operate. As a result, they hold great promise as a platform for point-of-care diagnostics. In order to properly evaluate the utility and analytical performance of paper-based devices, suitable methods must be developed to ensure their manufacture is reproducible and at a scale that is appropriate for laboratory settings. In this manuscript, a method to fabricate a general device architecture that can be used for paper-based immunoassays is described. We use a form of additive manufacturing (multi-layer lamination) to prepare devices that comprise multiple layers of patterned paper and patterned adhesive. In addition to demonstrating the proper use of these three-dimensional paper-based microfluidic devices with an immunoassay for human chorionic gonadotropin (hCG), errors in the manufacturing process that may result in device failures are discussed. We expect this approach to manufacturing paper-based devices will find broad utility in the development of analytical applications designed specifically for limited-resource settings.

We detail a method to fabricate three-dimensional paper-based microfluidic devices for use in the development of immunoassays. Our approach to device assembly is a type of multilayer, additive manufacturing. We demonstrate a sandwich immunoassay to provide representative results for these types of paper-based devices.

Paper wicks fluids autonomously due to capillary action. By patterning paper with hydrophobic barriers, the transport of fluids can be controlled and ...

A Simple and Scalable Fabrication Method for Organic Electronic Devices on Textiles

Today, wearable electronics devices combine a large variety of functional, stretchable, and flexible technologies. However, in many cases, these devices cannot be worn under everyday conditions. Therefore, textiles are commonly considered the best substrate to accommodate electronic devices in wearable use. In this paper, we describe how to selectively pattern organic electroactive materials on textiles from a solution in an easy and scalable manner. This versatile deposition technique enables the fabrication of wearable organic electronic devices on clothes.

In this paper, we present a protocol to selectively deposit organic materials on textiles, which allows for the direct integration of organic electronic devices with wearables. The fabricated devices can be fully integrated in textiles, respecting their mechanical appearance and enabling sensing capabilities.

Today, wearable electronics devices combine a large variety of functional, stretchable, and flexible technologies. However, in many cases, these devices ...

Soft Lithographic Procedure for Producing Plastic Microfluidic Devices with View-ports Transparent to Visible and Infrared Light

Infrared (IR) spectro-microscopy of living biological samples is hampered by the absorption of water in the mid-IR range and by the lack of suitable microfluidic devices. Here, a protocol for the fabrication of plastic microfluidic devices is demonstrated, where soft lithographic techniques are used to embed transparent Calcium Fluoride (CaF2) view-ports in connection with observation chamber(s). The method is based on a replica casting approach, where a polydimethylsiloxane (PDMS) mold is produced through standard lithographic procedures and then used as the template to produce a plastic device. The plastic device features ultraviolet/visible/infrared (UV/Vis/IR) -transparent windows made of CaF2 to allow for direct observation with visible and IR light. The advantages of the proposed method include: a reduced need for accessing a clean room micro-fabrication facility, multiple view-ports, an easy and versatile connection to an external pumping system through the plastic body, flexibility of the design, e.g., open/closed channels configuration, and the possibility to add sophisticated features such as nanoporous membranes.

A protocol for the fabrication of plastic microfluidic devices with transparent view-ports for visible and infrared light imaging is described.

Infrared (IR) spectro-microscopy of living biological samples is hampered by the absorption of water in the mid-IR range and by the lack of suitable ...