Name: bioinspired soft robot with incorporated microelectrodes
Uploaded: 2020-02-28T13:00:00
Description: Watch this Scientific Journal Video about Bioinspired Soft Robot with Incorporated Microelectrodes at JoVE.com

This paper was funded by the National Institutes of Health (R01AR074234, R21EB026824, R01 AR073822-01), the Brigham Research Institute Stepping Strong Innovator Award, and AHA Innovative Project Award (19IPLOI34660079).

This study was carried out in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. The protocol was approved by the institutional Animal Care and Use Committee (IACUC) of Brigham and Women&#39;s Hospital.
1. GelMA synthesis
<ol>
	<li>Dissolve 10 g of gelatin in 100 mL of Dulbecco&#39;s phosphate-buffered saline (DPBS) using a magnetic stirrer at 50 &#176;C.</li>
	<li>Add 8 mL of methacrylic anhydride slowly w...

<ol>
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Using this method, we were able to successfully fabricate a batoid fish-like bioinspired soft robot with an integrated self-actuating cardiac tissue on a multilayer structured scaffold that is controlled by embedded Au microelectrodes. Due to two distinct micropatterned hydrogel layers made of PEGDA and CNT&#8211;GelMA hydrogels, the bioinspired scaffold showed good mechanical stability and ideal cell alignment and maturation. The PEGDA pattern layer, which serves as a cartilage joint of the skeletal architecture in a st...

Modern state-of-the-art soft robots can mimic the hierarchical structures and muscle dynamics of many living organisms, such as the jellyfish1,2, sting ray2, octopus3, bacteria4, and sperm5. Mimicking the dynamics and architecture of natural systems offers higher performances in terms of both energetic and structural efficiency6. This is intrinsically related to the soft nature of natural tissue (e.g., skin or muscle tissue with a Young&#39;s modulus between 104&#8722;109 Pa) which allows for higher degrees of freedom and superior deformation and adaptability when compared with standard engineered actuators (e.g., a Young's modulus usually between 109&#8722;1012 Pa)6. Cardiac muscle-based soft-actuators, especially, show superior energy efficiency due to their self-actuation as well as their potential for autorepair and regeneration when compared to a mechanically based robotic system7. However, the fabrication of soft robots is challenging due to the necessity of integrating different components with different physical, biological, and mechanical properties into the one system. For example, engineered synthetic systems need to be integrated with living biological systems, not only providing them with structural support but also influencing and modulating their actuation behavior. In addition, many microfabrication methods require harsh/cytotoxic processes and chemicals that decrease the viability and function of any living components. Therefore, new approaches are necessary to enhance the functionality of the soft robots and to control and modulate their behavior.
To successfully integrate living components with good viability, a hydrogel-based scaffold is an excellent material to create the body of a soft robot. A hydrogel's physical and mechanical properties can easily be tuned to create microenvironments for living components such as muscle tissues8,9. Also, it can easily adopt various microfabrication techniques, resulting in the creation of hierarchical structures with high fidelity1,2,10. Flexible electronic devices can be incorporated into the soft robot to control its behavior with electrical stimulation. For example, optogenetic techniques to engineer electrogenic cells (e.g., cardiomyocytes), which show a light-dependent electrophysiological activation, have been used to develop a polydimethylsiloxane (PDMS)-based soft robotic sting ray guided by light that was able to recreate the undulatory movement of the fish in vitro2. Although optogenetic techniques have shown excellent controllability, the work presented uses electrical stimulation, a conventional and traditional simulation method. This is because electrical stimulation via flexible microelectrodes is easy and simple compared to optogenetic techniques, which require extensive development processes11. The use of flexible electronic devices can allow for long-term stimulation and standard/simple fabrication processes as well as tunable biocompatibility and physical and mechanical properties12,13.
Here, we present an innovative method to fabricate a bioinspired soft robot, actuated by the beating of engineered cardiac muscle tissue and controlled by electrical stimulation through embedded flexible Au microelectrodes. The soft robot is designed to mimic the muscle and cartilage structure of the sting ray. The sting ray is an organism with a relatively easy to mimic structure and movement compared to other swimming species. The muscles are recreated in vitro by seeding cardiomyocytes on an electrically conductive hydrogel micropattern. As previously reported, incorporating electrically conductive nanoparticles such as CNT in the GelMA hydrogel not only improves the electrical coupling of the cardiac tissue, but also induces an excellent in vitro tissue architecture and arrangement8,9. The cartilage joints are then mimicked using a mechanically robust PEGDA hydrogel pattern that acts as the mechanically robust substrate of the whole system. Flexible Au microelectrodes with a serpentine pattern are embedded in the PEGDA pattern to locally and electrically stimulate the cardiac tissue.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>250 mL Beaker</td>
			<td>PYREX</td>
			<td>1000-250CNEa</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Hydroxy-4&#39;-(2-hydroxyethoxy)-2-methylpropiophenone</td>
			<td>Sigma-Aldrich</td>
			<td>410896</td>
			<td></td>
		</tr>
		<tr>
			<td>3-(Trimethoxysilyl)propyl methacrylate</td>
			<td>Milipore</td>
			<td>M6514</td>
			<td></td>
		</tr>
		<tr>
			<td>37&#176; Water bath</td>
			<td>VWR</td>
			<td>W6M</td>
			<td></td>
		</tr>
		<tr>
			<td>4&#39;,6-diamidino-2-phenylindole (DAPI)</td>
			<td>Sigma-Aldrich</td>
			<td>D9542</td>
			<td></td>
		</tr>
		<tr>
			<td>50mL Conical Centrifuge Tubes</td>
			<td>Falcon</td>
			<td>14-959-49A</td>
			<td></td>
		</tr>
		<tr>
			<td>70 &#181;m Cell Strainer</td>
			<td>Falcon</td>
			<td>352350</td>
			<td></td>
		</tr>
		<tr>
			<td>80&#176; incubator</td>
			<td>VWR</td>
			<td>1370GM</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor 488 goat anti-mouse IgG (H+L)</td>
			<td>Invitrogen</td>
			<td>A11029</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor 594 goat anti-rabbit IgG (H+L)</td>
			<td>Invitrogen</td>
			<td>A11037</td>
			<td></td>
		</tr>
		<tr>
			<td>Alexa Fluor 488 Phalloidin</td>
			<td>Invitrogen</td>
			<td>A12379</td>
			<td></td>
		</tr>
		<tr>
			<td>Antibiotic/Antimycotic solution</td>
			<td>ThermoFisher Scientific</td>
			<td>15240062</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Connexin 43/GJAI antibody</td>
			<td>Abcam</td>
			<td>ab11370</td>
			<td>Rabbit polyclonal</td>
		</tr>
		<tr>
			<td>Anti-Sarcomeric &#945;-actinin</td>
			<td>Abcam</td>
			<td>ab9465</td>
			<td>Mouse monoclonal</td>
		</tr>
		<tr>
			<td>Benchtop Freeze Dryers</td>
			<td>Labconco</td>
			<td>77500-00 K</td>
			<td></td>
		</tr>
		<tr>
			<td>Biosafety cabinet</td>
			<td>Sterilgard</td>
			<td>A/B3</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbon rod electrodes</td>
			<td>SGL Carbon Group</td>
			<td>6971105</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Eppendorf</td>
			<td>5804</td>
			<td></td>
		</tr>
		<tr>
			<td>CO2 incubator</td>
			<td>Forma Scientific</td>
			<td>3110</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase, Type II, Powder</td>
			<td>Gibco</td>
			<td>17-101-015</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal Microscope</td>
			<td>Zeiss</td>
			<td>LSM 880</td>
			<td></td>
		</tr>
		<tr>
			<td>COOH Functionalized Carbon Nanotubes</td>
			<td>NanoLab</td>
			<td>PD30L5-20-COOH</td>
			<td></td>
		</tr>
		<tr>
			<td>Dicing saw machine</td>
			<td>Giorgio Technology</td>
			<td>DAD-321</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM, High Glucose</td>
			<td>Gibco</td>
			<td>11-965-118</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS without Calcium and Magnesium</td>
			<td>Gibco</td>
			<td>14-190-144</td>
			<td></td>
		</tr>
		<tr>
			<td>E-beam evaporator</td>
			<td>CHA</td>
			<td>57367</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>Gibco</td>
			<td>10-437-028</td>
			<td></td>
		</tr>
		<tr>
			<td>Gelatin</td>
			<td>Sigma-Aldrich</td>
			<td>G9391</td>
			<td>Type B, 300 bloom from porcine skin</td>
		</tr>
		<tr>
			<td>Glass slide</td>
			<td>VWR</td>
			<td>48382-180</td>
			<td></td>
		</tr>
		<tr>
			<td>HBSS without Calcium, Magnesium or Phenol Red</td>
			<td>Gibco</td>
			<td>14-175-079</td>
			<td></td>
		</tr>
		<tr>
			<td>Inverted optical microscope</td>
			<td>Olympus</td>
			<td>CK40</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic hotplate</td>
			<td>Corning</td>
			<td>PC-420</td>
			<td></td>
		</tr>
		<tr>
			<td>methacrylic anhydride</td>
			<td>Sigma-Aldrich</td>
			<td>276695</td>
			<td>Contains 2,000ppm topanol A as inhibitor</td>
		</tr>
		<tr>
			<td>Nunc EasYFlask 175cm2</td>
			<td>ThermoFisher Scientific</td>
			<td>159910</td>
			<td></td>
		</tr>
		<tr>
			<td>Olicscope</td>
			<td>Siglent</td>
			<td>SDS1052DL+</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde Aqueous Solution -16%</td>
			<td>Electron Microscopy Sciences</td>
			<td>15710</td>
			<td></td>
		</tr>
		<tr>
			<td>PDMS SYLGARD 184</td>
			<td>Sigma-Aldrich</td>
			<td>761036</td>
			<td></td>
		</tr>
		<tr>
			<td>Photomask</td>
			<td>Mini micro stencil inc</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Platinum wire</td>
			<td>Alfa Aesar</td>
			<td>AA43014BU</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyethylene glycol dimethcrylate</td>
			<td>Polysciences Inc.</td>
			<td>15178-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Regenerated Cellulose Dialysis Tubing</td>
			<td>Fisherbrand</td>
			<td>21-152-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Silver Epoxy Adhesive</td>
			<td>MG Chemicals</td>
			<td>8330S</td>
			<td></td>
		</tr>
		<tr>
			<td>Stericup Quick Release-GP Sterile Vacuum Filtration System</td>
			<td>Millipore</td>
			<td>S2GPU02RE</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultra sonicator</td>
			<td>Qsonica</td>
			<td>Q500</td>
			<td></td>
		</tr>
		<tr>
			<td>UV Curing System</td>
			<td>OmniCure</td>
			<td>S2000</td>
			<td></td>
		</tr>
		<tr>
			<td>Vortex mixer</td>
			<td>Scientific Industry</td>
			<td>SI-0246A</td>
			<td></td>
		</tr>
		<tr>
			<td>Waveform generator</td>
			<td>Agilent</td>
			<td>33500B</td>
			<td></td>
		</tr>
		<tr>
			<td>Wrap Aluminium foil</td>
			<td>Reynolds</td>
			<td>N/A</td>
			<td></td>
		</tr>
	</tbody>
</table>

bioinspired soft robot with incorporated microelectrodes

Bioinspired soft robotic systems that mimic living organisms using engineered muscle tissue and biomaterials are revolutionizing the current biorobotics paradigm, especially in biomedical research. Recreating artificial life-like actuation dynamics is crucial for a soft-robotic system. However, the precise control and tuning of actuation behavior still represents one of the main challenges of modern soft robotic systems. This method describes a low-cost, highly scalable, and easy-to-use procedure to fabricate an electrically controllable soft robot with life-like movements that is activated and controlled by the contraction of cardiac muscle tissue on a micropatterned sting ray-like hydrogel scaffold. The use of soft photolithography methods makes it possible to successfully integrate multiple components in the soft robotic system, including micropatterned hydrogel-based scaffolds with carbon nanotubes (CNTs) embedded gelatin methacryloyl (CNT-GelMA), poly(ethylene glycol) diacrylate (PEGDA), flexible gold (Au) microelectrodes, and cardiac muscle tissue. In particular, the hydrogels alignment and micropattern are designed to mimic the muscle and cartilage structure of the sting ray. The electrically conductive CNT-GelMA hydrogel acts as a cell scaffold that improves the maturation and contraction behavior of cardiomyocytes, while the mechanically robust PEGDA hydrogel provides structural cartilage-like support to the whole soft robot. To overcome the hard and brittle nature of metal-based microelectrodes, we designed a serpentine pattern that has high flexibility and can avoid hampering the beating dynamics of cardiomyocytes. The incorporated flexible Au microelectrodes provide electrical stimulation across the soft robot, making it easier to control the contraction behavior of cardiac tissue.

Flow diagram of the steps for developing the Au microelectrode-incorporated bioinspired soft robot 
The aim of the soft robot design was to build a membrane capable of actuating a swimming movement with minimal complexity. The structure must be able to sustain strong flexions repeatedly over time (about 1 Hz) and be able to keep its shape while achieving a strong beating. By selectively photo crosslinking the polymer using photomasks, we fabricated a hierarchically structured scaffold comprised of a...

Watch this Scientific Journal Video about Bioinspired Soft Robot with Incorporated Microelectrodes at JoVE.com

Bioinspired Soft Robot with Incorporated Microelectrodes

A bioinspired scaffold is fabricated by a soft photolithography technique using mechanically robust and electrically conductive hydrogels. The micropatterned hydrogels provide directional cardiomyocyte cell alignment, resulting in a tailored direction of actuation. Flexible microelectrodes are also integrated into the scaffold to bring electrical controllability for a self-actuating cardiac tissue.

Bioinspired soft robotic systems that mimic living organisms using engineered muscle tissue and biomaterials are revolutionizing the current biorobotics ...

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