This material is based upon work supported by a start-up fund at the University of Minnesota, Twin Cities and an NSF CAREER Award (CMMI-1454293). Parts of this work were carried out in the Characterization Facility at the University of Minnesota, a member of the NSF-funded Materials Research Facilities Network (via the MRSEC program. Portions of this work were conducted in the Minnesota Nano Center, which is supported by the National Science Foundation through the National Nano Coordinated Infrastructure Network (NNCI) under Award Number ECCS-1542202. C. D. acknowledges support from the 3M Science and Technology Fellowship.

CAUTION: Several of the chemicals used in these syntheses are toxic and may cause irritation and severe organ damage when touched or inhaled. Please use appropriate safety equipment and wear personal protective equipment when handling the chemicals.
1. Preparation of Aluminum Oxide and Chromium Protection Layers on a Copper Sacrificial Layer
<ol>
	<li>Using an electron-beam evaporator, deposit 10 nm thick chromium (Cr) and 300 nm thick copper (Cu) layers (sacrificial layer) on the silicon (S...

<ol>
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S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electromechanical+resonators+from+graphene+sheets.">Electromechanical resonators from graphene sheets.</a> Science. 315 (5811), 490-493 (2007).</li><li>Menaa, F., Abdelghani, A., Menaa, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Graphene+nanomaterials+as+biocompatible+and+conductive+scaffolds+for+stem+cells:+impact+for+tissue+engineering+and+regenerative+medicine.">Graphene nanomaterials as biocompatible and conductive scaffolds for stem cells: impact for tissue engineering and regenerative medicine.</a> Journal of Tissue Engineering and Regenerative. 9 (12), 1321-1338 (2015).</li><li>Han, M. Y., &#214;zyilmaz, B., Zhang, Y., Kim, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Energy+band-gap+engineering+of+graphene+nanoribbons.">Energy band-gap engineering of graphene nanoribbons.</a> Physical Review Letters. 98 (20), 206805 (2007).</li><li>Son, Y. W., Cohen, M. L., Louie, S. 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K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Graphene+kirigami.">Graphene kirigami.</a> Nature. 524 (7564), 204-207 (2015).</li><li>Michael Cai, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+instability+driven+self-assembly+and+architecturing+of+2D+materials.">Mechanical instability driven self-assembly and architecturing of 2D materials.</a> 2D Materials. 4 (2), 022002 (2017).</li><li>Shenoy, V. B., Gracias, D. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-folding+thin-film+materials:+From+nanopolyhedra+to+graphene+origami.">Self-folding thin-film materials: From nanopolyhedra to graphene origami.</a> MRS Bulletin. 37 (9), 847-854 (2012).</li><li>Zhu, S., Li, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogenation-Assisted+Graphene+Origami+and+Its+Application+in+Programmable+Molecular+Mass+Uptake,+Storage,+and+Release.">Hydrogenation-Assisted Graphene Origami and Its Application in Programmable Molecular Mass Uptake, Storage, and Release.</a> ACS Nano. 8 (3), 2864-2872 (2014).</li><li>Zhang, L., Zeng, X., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Programmable+hydrogenation+of+graphene+for+novel+nanocages.">Programmable hydrogenation of graphene for novel nanocages.</a> Scientific Reports. 3, 3162 (2013).</li><li>Vickery, J. L., Patil, A. J., Mann, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+Graphene-Polymer+Nanocomposites+With+Higher-Order+Three-Dimensional+Architectures.">Fabrication of Graphene-Polymer Nanocomposites With Higher-Order Three-Dimensional Architectures.</a> Advanced Materials. 21 (21), 2180-2184 (2009).</li><li>Yang, X., Zhu, J., Qiu, L., Li, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioinspired+effective+prevention+of+restacking+in+multilayered+graphene+films:+towards+the+next+generation+of+high-performance+supercapacitors.">Bioinspired effective prevention of restacking in multilayered graphene films: towards the next generation of high-performance supercapacitors.</a> Advanced Materials. 23 (25), 2833-2838 (2011).</li><li>Choi, B. G., Yang, M., Hong, W. H., Choi, J. W., Huh, Y. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+macroporous+graphene+frameworks+for+supercapacitors+with+high+energy+and+power+densities.">3D macroporous graphene frameworks for supercapacitors with high energy and power densities.</a> ACS Nano. 6 (5), 4020-4028 (2012).</li><li>Niu, Z., Chen, J., Hng, H. H., Ma, J., Chen, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+leavening+strategy+to+prepare+reduced+graphene+oxide+foams.">A leavening strategy to prepare reduced graphene oxide foams.</a> Advanced Materials. 24 (30), 4144-4150 (2012).</li><li>Li, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+of+conformal+graphene+cages+on+micrometre-sized+silicon+particles+as+stable+battery+anodes.">Growth of conformal graphene cages on micrometre-sized silicon particles as stable battery anodes.</a> Nature Energy. 1 (2), (2016).</li><li>Cho, J. H., Gracias, D. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-Assembly+of+Lithographically+Patterned+Nanoparticles.">Self-Assembly of Lithographically Patterned Nanoparticles.</a> Nano Letters. 9 (12), 4049-4052 (2009).</li><li>Cho, J. H., Azam, A., Gracias, D. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three+Dimensional+Nanofabrication+Using+Surface+Forces.">Three Dimensional Nanofabrication Using Surface Forces.</a> Langmuir. 26 (21), 16534-16539 (2010).</li><li>Dai, C., Cho, J. 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G., Liu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermal+stability+of+SU-8+fabricated+microstructures+as+a+function+of+photo+initiator+and+exposure+doses.">Thermal stability of SU-8 fabricated microstructures as a function of photo initiator and exposure doses.</a> Proceedings of SPIE. 4980, 209 (2003).</li><li>Winterstein, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SU-8+electrothermal+actuators:+Optimization+of+fabrication+and+excitation+for+long-term+use.">SU-8 electrothermal actuators: Optimization of fabrication and excitation for long-term use.</a> Micromachines. 5 (4), 1310-1322 (2014).</li><li>Syms, R. R. A., Yeatman, E. M., Bright, V. M., Whitesides, G. 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For the cubes fabricated with CVD graphene, because each face of a given cube is designed with an outer frame surrounding a ~160 &#215; 160 &#181;m2 area of free-standing graphene, a single sheet of monolayer graphene does not have the necessary strength to permit parallel processing of the cubes. For this reason, graphene membranes consisting of three layers of CVD graphene monolayer sheets are produced via three separate graphene transfers using multiple PMMA coating/removal steps. On the other hand...

Two-dimensional (2D) graphene sheets possess extraordinary optical, electronic, and mechanical properties, making them model systems for the observation of novel quantum phenomena for next-generation electronic, optoelectronic, electrochemical, electromechanical, and biomedical applications1,2,3,4,5,6. Apart from the as-produced 2D layered structure of graphene, recently, various modification approaches have been investigated to observe new functionalities of graphene and seek new application opportunities. For example, modulating (or tuning) its physical properties (i.e.,&#160;doping level and/or band gap) by tailoring the shapes or patterning of the 2D structure to a one-dimensional (1D) or zero-dimensional (0D) structure (e.g., graphene nanoribbon or graphene quantum dots) has been studied to obtain new physical phenomena including quantum confinement effects, localized plasmonic modes, localized electron distribution, and spin-polarized edge states7,8,9,10,11,12. In addition, varying the texture of 2D graphene by crumpling (often called kirigami), delamination, buckling, twisting, or stacking of multiple layers, or changing the graphene surface shape by transferring 2D graphene on top of a 3D feature (substrate) has been shown to change the graphene&#39;s wettability, mechanical characteristics, and optical properties13,14.
Beyond changing the surface morphology and layered structure of 2D graphene, assembly of 2D graphene into functionalized, well-defined, three-dimensional (3D) polyhedrons has been of great interest recently in the graphene community to obtain new physical and chemical phenomena15. In theory, the elastic, electrostatic, and van der Waals energies of 2D graphene-based structures can be leveraged to transform the 2D graphene into various 3D graphene-origami configurations16,17. Based on this concept, theoretical modeling studies have investigated 3D graphene structure designs, formed from nanoscale 2D graphene membranes, with possible uses in drug delivery and general molecular storage16,17.&#160;Yet, the experimental progress of this approach is still far from realizing these applications. On the other hand, a number of chemical synthetic methods have been developed to achieve 3D structures via template-assisted assembly, flow-directed assembly, leavening assembly, and conformal growth methods18,19,20,21,22. However, these methods are currently limited in that they cannot produce a 3D, hollow, enclosed structure without losing the intrinsic properties of the graphene sheets.
Here, a strategy for building 3D, hollow, graphene-based microcubes (overall dimension of ~200 &#181;m) by using origami-like self-folding is outlined; overcoming the foremost challenges in the construction of free-standing, hollow, 3D, polyhedral, graphene-based materials. In origami-like, hands-free self-folding techniques, 2D lithographically patterned planar features (i.e.,&#160;graphene-based membranes) are connected with hinges (i.e.,&#160;thermal-sensitive polymer, photoresist) at various joints, thereby forming 2D nets which fold up when the hinges are heated to melting temperature23,24,25,26. The graphene-based cubes are realized with window membrane components composed of a few layers of chemical vapor deposition (CVD) grown graphene or graphene oxide (GO) membranes; both with the use of polymer frames and hinges. The fabrication of the 3D graphene-based cubes involves: (i) preparation of protection layers, (ii) graphene-membrane transfer and patterning, (iii) metal surface patterning on graphene-membranes, (iv) frame and hinges patterning and deposition, (v) self-folding, and (vi) removal of the protection layers (Figure 1). This article focuses mostly on the self-folding aspects of the 3D graphene-based cubes fabrication. Details on physical and optical properties of the 3D graphene-based cubes can be found in our other recent publications27,28.

<table border="0" cellpadding="0" cellspacing="0" style="width:1315px;" width="1313">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Acetone</td>
			<td style="width:295px;">Fisher Chemical</td>
			<td style="width:199px;">A18P-4</td>
			<td style="width:511px;">N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Aluminium oxide</td>
			<td style="width:295px;">Kurt J. Lesker Company</td>
			<td style="width:199px;">EVMALO-1-2.5</td>
			<td>99.99% Pure</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">APS Copper Etchant 100</td>
			<td style="width:295px;">Transene Company, Inc.</td>
			<td style="width:199px;">N/A</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Camera (for 3D image)</td>
			<td style="width:295px;">Nikon</td>
			<td style="width:199px;">D5100</td>
			<td>1080p Full HD, Effective pixels: 16.2 million, Sensorsize: 23.6 mm x 15.6 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">CE-5 M Chromium Mask Etchant</td>
			<td style="width:295px;">Transene Company, Inc.</td>
			<td style="width:199px;">N/A</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Chemical deposition growth (CVD) system</td>
			<td style="width:295px;">Customized</td>
			<td style="width:199px;">N/A</td>
			<td>Lindberg/Blue Tube Furnace</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Chromium</td>
			<td style="width:295px;">Kurt J. Lesker Company</td>
			<td style="width:199px;">EVMCR35J</td>
			<td>99.95% pure</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Chromium Etchant 473</td>
			<td style="width:295px;">Transene Company, Inc.</td>
			<td style="width:199px;">N/A</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Copper</td>
			<td style="width:295px;">Kurt J. Lesker Company</td>
			<td style="width:199px;">EVMCU40QXQJ</td>
			<td>99.99% pure</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Developer-1 (MF319 developer)</td>
			<td style="width:295px;">Microposit</td>
			<td style="width:199px;">10018042</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Developer-2 (AZ developer)</td>
			<td style="width:295px;">Merck performance Materials Corp.</td>
			<td style="width:199px;">1005422496</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Developer-3 (SU-8 developer)</td>
			<td>MicroChem</td>
			<td style="width:199px;">NC9901158</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Digital Hot Plate</td>
			<td style="width:295px;">Thermo Scientific</td>
			<td style="width:199px;">HP131725</td>
			<td>Super-Nuvoa series, maximum temperature: 370 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">E-Beam Evaporator System</td>
			<td style="width:295px;">Rocky Mountain Vacuum Tech.</td>
			<td style="width:199px;">N/A</td>
			<td>RME-2000</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Graphene oxide</td>
			<td style="width:295px;">Goographene</td>
			<td style="width:199px;">N/A</td>
			<td>Purity: ~ 99%; Single layer ratio: ~99%;&#160; 0.7-1.2 nm in thickness.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Isopropyl Alcohol</td>
			<td style="width:295px;">Fisher Chemical</td>
			<td style="width:199px;">A416-4</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Mask Aligner</td>
			<td style="width:295px;">Midas</td>
			<td style="width:199px;">MDA-400LJ</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Microscope</td>
			<td style="width:295px;">Omax</td>
			<td style="width:199px;">NJF-120A</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">multiple polymethyl methacrylate (PMMA)</td>
			<td style="width:295px;">MicroChem</td>
			<td style="width:199px;">950 PMMA A9</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Oxygen plasma&#160;</td>
			<td style="width:295px;">Technics Inc.</td>
			<td style="width:199px;">SERIES 800</td>
			<td>Microscale reactive ion etching (RIE)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Photoresist-1 (S1813 Photoresist)</td>
			<td style="width:295px;">Microposit</td>
			<td style="width:199px;">10018348</td>
			<td>N/A</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Photoresist-2 (SPR220 Photoresist)</td>
			<td style="width:295px;">MicroChem</td>
			<td style="width:199px;">SPR00220-7G</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Photoresist-3 (SU-8 Photoresist)</td>
			<td>MicroChem</td>
			<td style="width:199px;">SU-8-2010</td>
			<td>N/A</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Profilometer</td>
			<td style="width:295px;">Tencor Instruments</td>
			<td style="width:199px;">N/A</td>
			<td>Alpha-Step 200</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Raman</td>
			<td style="width:295px;">WITec Instruments Corp.</td>
			<td style="width:199px;">Alpha300R</td>
			<td>Confocal Raman Microscope</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Silicon Wafer</td>
			<td style="width:295px;">Siltronic AG</td>
			<td style="width:199px;">N/A</td>
			<td>100mm diameter, N-type, one-side polish, resitivity: 560-840 &#937;&#8226;cm</td>
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			<td height="21" style="height:21px;width:311px;">Spinner</td>
			<td style="width:295px;">Best Tools</td>
			<td style="width:199px;">S0114031123</td>
			<td>SMART COATER 100</td>
		</tr>
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			<td height="21" style="height:21px;width:311px;">Titanium</td>
			<td style="width:295px;">Kurt J. Lesker Company</td>
			<td>EVMTI45QXQA</td>
			<td>99.99% Pure</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Ultrasonic Cleaner</td>
			<td style="width:295px;">Crest Ultrasonics</td>
			<td style="width:199px;">N/A</td>
			<td>Powersonic series</td>
		</tr>
	</tbody>
</table>

fabrication of three-dimensional graphene-based polyhedrons via origami-like self-folding

The assembly of two-dimensional (2D) graphene into three-dimensional (3D) polyhedral structures while preserving the graphene's excellent inherent properties has been of great interest for the development of novel device applications. Here, fabrication of 3D, microscale, hollow polyhedrons (cubes) consisting of a few layers of 2D graphene or graphene oxide sheets via an origami-like self-folding process is described. This method involves the use of polymer frames and hinges, and aluminum oxide/chromium protection layers that reduce tensile, spatial, and surface tension stresses on the graphene-based membranes when the 2D nets are transformed into 3D cubes. The process offers control of the size and shape of the structures as well as parallel production. In addition, this approach allows the creation of surface modifications by metal patterning on each face of the 3D cubes. Raman spectroscopy studies show the method allows the preservation of the intrinsic properties of the graphene-based membranes, demonstrating the robustness of our method.

Figure 2&#160;displays optical images of the lithographic processes of the 2D graphene and GO net structures and subsequent self-folding process. The self-folding process is monitored in real-time via a high-resolution microscope. Both types of 3D graphene-based cubes are folded at ~80 &#176;C. Figure 3 lays out video captured sequences showing the self-folding of 3D graphene-based cubes in a parallel manner. Under an op...

Watch this Scientific Journal Video about Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding at JoVE.com

Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding

Here, we present a protocol for fabrication of 3D graphene-based polyhedrons via origami-like self-folding.

Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding

The assembly of two-dimensional (2D) graphene into three-dimensional (3D) polyhedral structures while preserving the graphene's excellent inherent ...

This protocol uses origami-like self-folding methods to create 3D graphene-based polyhedrons. Two-dimensional graphene sheets possess extraordinary optical, electronic, and mechanical properties. By tailoring the shape of two-dimensional graphene, its physical, chemical, and optical properties can be tuned, which can introduce new material behaviors, allowing new application opportunities.In this regard, integrating 2D graphene into the structures of functionalized, well-defined, three-dimensional polyhedrons has been of great interest recently in the graphene community. 3D graphene polyhedrons may be beneficial for many applications. Examples include gas and water-protected containers, molecular storage, delivery systems, encapsulation of liquid-based materials, for easy to observation in electron microscopy, functional optoelectronic devices, and matter materials.A number of chemical routes for the production of 3D graphene-based structures have been introduced. However, these methods typically require strong chemical reactions, which affect the intrinsic properties of the graphene and present challenges in the construction of free-standing, hollow, 3D graphene polyhedrons. To overcome these limitations, this study shows a methodology for realizing multi-faced 3D microcubes with 2D graphene and graphene oxide by using origami-like self-folding.To help give context to the overall fabrication process of the 3D graphene-based cubes, a simplified six-step overview will now be introduced prior to the detailed protocol. First, prepare the protection layers. Then, perform graphene-membrane transfer in patterning onto the protection layers.Then, create metal surface patterning on the graphene membranes. Next, define polymer frames and hinges. Then, transform the 2D nets into 3D cubes via self-folding.Lastly, remove the protection layers. Using an electron beam evaporator, deposit 10 nanometer-thick chromium and 300 nanometer-thick copper layers on the silicon substrate. Spin coat photoresist at 2500 RPM followed by baking at 115 degrees Celsius for 60 seconds.Expose the designed 2D net areas to UV light on a contact mask aligner for 15 seconds and then develop for 60 seconds in developer. Rinse the sample with deionized water and blow-dry with an air gun. Deposit a 10 nanometer-thick chromium layer and lift off the remaining photoresist in acetone.Rinse the sample with deionized water and blow-dry with an air gun. To pattern 2D nets with six-square aluminum oxide and chromium protection layers on the nets, spin coat photoresist at 2, 500 RPM followed by baking at 115 degrees Celsius for 60 seconds. Expose the designed six-square protection layers to UV light on a contact mask aligner for 15 seconds and develop for 60 seconds in developer.Rinse the sample with deionized water and blow-dry with an airgun. Deposit a 100 nanometer-thick aluminum oxide layer in a 10 nanometer-thick chromium layer. Remove the remaining photoresist in acetone.Rinse the sample with deionized water and blow-dry with an airgun. Starting with the 15 millimeter square piece of graphene adhered on copper foil, spin coat a thin PMMA layer at 3000 RPM on the surface of the graphene. Bake at 180 degrees Celsius for 10 minutes.Place the PMMA graphene in copper foil-layered sheet, floating copper-side down in copper etchant for 24 hours to etch away the copper foil. After the copper foil is completely dissolved, leaving PMMA in graphene, transfer the floating PMMA-coated graphene onto the surface of a pool of deionized water using a microscope slide glass to remove any copper etchant residue. Repeat the transfer of the PMMA-coated graphene onto new deionized water pools several times to adequately rinse.Transfer the floating PMMA-coated graphene onto another piece of graphene adhered on copper foil to obtain a bilayer graphene membrane. Thermally treat the double-layer graphene on copper foil on a hot plate at 100 degrees Celsius for 10 minutes. Remove the PMMA on top of the double-layer graphene on the copper foil in an acetone bath, leaving a graphene, graphene, and copper foil layer stack, followed by transferring to deionized water.Repeat the graphene transfer one more time to get three stacked layers of graphene membranes. Place the PMMA, graphene, graphene, graphene, and copper foil layered sheet, floating copper side down in copper etchant for 24 hours to etch away the copper foil. Transfer the PMMA-coated three layers of graphene membranes onto the pre-fabricated aluminum oxide and chromium protection layers.After transfer of the graphene, remove the PMMA with acetone. Then, dip the sample in deionized water and dry in air. Thermally treat the multi-layer graphene on the substrate on a hot plate at 100 degrees Celsius for one hour.Spin coat photoresist at 2500 RPM and bake at 115 degrees Celsius for 60 seconds. UV expose the regions of photoresist directly above the square protection layer areas using a contact mask aligner for 15 seconds. Then develop for 60 seconds.Remove the newly-uncovered unwanted graphene areas via an oxygen plasma treatment for 15 seconds. Remove the leftover photoresist in acetone. Rinse the sample with deionized water and dry in air.Spin coat photoresist at 1700 RPM for 60 seconds on top of the previously fabricated aluminum oxide and chromium protection layers to obtain a 10 micrometer thick layer. Bake the photoresist at 115 degrees Celsius for 60 seconds and then wait for three hours. With the same mask used for patterning the aluminum oxide and chromium layers, UV expose the sample on a contact mask aligner for 80 seconds and develop for 90 seconds.Rinse the sample with deionized water and blow-dry with an air gun. Perform a UV flood exposure of the entire sample without a mask for 80 seconds. Spin coat the prepared graphene oxide and water mixture on the sample at 1000 RPM for 60 seconds.Perform the spin coating a total of three times. Dip the sample in developer to allow lift-off of unwanted graphene oxide. The lift-off process under a microscope is shown here with the footage accelerated.Rinse the sample with deionized water and carefully blow-dry the sample with an air gun. Thermally treat the sample on a hot plate at 100 degrees Celsius for one hour. Create 20 nanometer-thick titanium patterns on top of the patterned graphene-based membranes.Thermally treat the sample on a hot plate at 100 degrees Celsius for one hour. On top of the graphene-based membranes with titanium surface patterns, spin coat photoresist at 2500 RPM for 60 seconds to form a five micrometer-thick layer and bake at 90 degrees Celsius for two minutes. UV-expose the samples for 20 seconds, bake at 90 degrees Celsius for three minutes, and develop for 90 seconds.Rinse the sample with deionized water and isopropyl alcohol, and carefully blow-dry the sample with an air gun. Post-bake the samples at 200 degrees Celsius for 15 minutes to enhance the mechanical stiffness of frames. To make the hinge pattern, spin coat photoresist at 1000 RPM for 60 seconds to form a 10 micrometer-thick film on top of the prefabricated substrate.Bake at 115 degrees Celsius for 60 seconds and wait for three hours. UV-expose the sample on a contact mask aligner for 80 seconds and develop for 90 seconds. Rinse the sample with deionized water and carefully blow-dry the sample with an air gun.To release the 2D structures, dissolve the copper sacrificial layer under the 2D nets in a copper etchant. Carefully transfer the released structures into a deionized water bath by using a pipette and rinse a few times to remove the residual copper etchant. Place the 2D structures in deionized water, heated above the melting point of the polymer hinges.Monitor the self-folding in real time via optical microscopy and remove from the heat source upon successful assembly into closed cubes. After self-folding, remove the aluminum oxide and chromium protection layers with chromium etchant. Gently transfer the cubes into a deionized water bath and carefully rinse.The optical images show the lithographic processes of the 2D graphene and graphene oxide net structures and the subsequent self-folding process. The self-folding process is monitored in real time via a high-resolution microscope. Both types of 3D graphene-based cubes are folded at about 80 degrees Celsius.The figures lay out video-captured sequences showing the self-folding of 3D graphene-based cubes in a parallel manner. Under an optimized process, this approach shows a highest yield of approximately 90 percent. The figures show optical images of the 3D assembled graphene and graphene oxide-based cubes with and without surface patterns.The overall size of the self-folded cubes is 200 micrometers wide by 200 micrometers long by 200 micrometers high. 20 nanometer-thick titanium-patterned features and UMN lettering are defined on each face of the 3D graphene-based cubes. The figures include Raman spectroscopy of 2D graphene-based nets and 3D graphene-based cubes.The results show no noticeable changes in Raman peak position and intensity for both graphene and graphene oxide membranes after the self-folding. However, when protection layers are not used, noticeable changes in relative peak intensities were observed, indicating changes or damage to the properties of the graphene during the self-folding. This method allows the development of biomedical, electronic, and optical devices, including sensors and electric circuits using the numerous advantages of 3D configurations.Furthermore, since the process uses an early image to only graphene-based materials, this method may be applied to other two-dimensional material, such as tren-ja-men-a ai chai-hus knives and black passports, thereby allowing this opportunity to be used in developing next-generation 3D configurations of 2D materials.

fabrication-three-dimensional-graphene-based-polyhedrons-via-origami

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8.8K Aufrufe.  University of Minnesota, Minneapolis, United States. Dieses Protokoll verwendet origami-ähnliche Selbstfaltungsmethoden, um 3D-Graphen-basierte Polyeder zu erstellen. Zweidimensionale Graphenplatten besitzen außergewöhnliche optische, elektronische und mechanische Eigenschaften. Durch die Anpassung der Form von zweidimensionalem Graphen können seine physikalischen, chemischen und optischen Eigenschaften optimiert werden, was neue Materialverhalten einleiten kann, was neue Anwendungsmöglichkeiten ermöglicht.In dieser Hinsicht war di...

Serie: Fabrication of Three-Dimensional Graphene-Based Polyhedrons via Origami-Like Self-Folding

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 ...

Process of Making Three-dimensional Microstructures using Vaporization of a Sacrificial Component

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material fabrication techniques are able to mimic the complexity of these structures while maintaining scalability. The Vaporization of a Sacrificial Component (VaSC) process is able to do so. This process uses sacrificial fibers as a template to form hollow, cylindrical microchannels embedded within a matrix. Tin (II) oxalate (SnOx) is embedded within poly(lactic) acid (PLA) fibers which facilitates the use of this process. The SnOx catalyzes the depolymerization of the PLA fibers at lower temperatures. The lactic acid monomers are gaseous at these temperatures and can be removed from the embedded matrix at temperatures that do not damage the matrix. Here we show a method for aligning these fibers using micromachined plates and a tensioning device to create complex patterns of three-dimensionally arrayed microchannels. The process allows the exploration of virtually any arrangement of fiber topologies and structures.

The Vaporization of a Sacrificial Component (VaSC) process is used to fabricate microvascular structures. This procedure uses sacrificial poly(lactic) acid fibers to form hollow microchannels with precise 3D geometric positioning provided by laser micromachined guide plates.

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material ...

Fabrication of Spatially Confined Complex Oxides

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from the inherent strong electron correlations that reside within them. These materials can also possess electronic phase separation in which regions of vastly different resistive and magnetic behavior can coexist within a single crystal alloy material. By reducing the scale of these materials to length scales at and below the inherent size of the electronic domains, novel behaviors can be exposed. Because of this and the fact that spin-charge-lattice-orbital order parameters each involve correlation lengths, spatially reducing these materials for transport measurements is a critical step in understanding the fundamental physics that drives complex behaviors. These materials also offer great potential to become the next generation of electronic devices 1-3. Thus, the fabrication of low dimensional nano- or micro-structures is extremely important to achieve new functionality. This involves multiple controllable processes from high quality thin film growth to accurate electronic property characterization. Here, we present fabrication protocols of high quality microstructures for complex oxide manganite devices. Detailed descriptions and required equipment of thin film growth, photo-lithography, and wire-bonding are presented.

We describe the use of pulsed laser deposition (PLD), photolithography and wire-bonding techniques to create micrometer scale complex oxides devices. The PLD is utilized to grow epitaxial thin films. Photolithography and wire-bonding techniques are introduced to create practical devices for measurement purposes.

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from ...

Fabrication of Uniform Nanoscale Cavities via Silicon Direct Wafer Bonding

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned and bonded silicon wafers. Unlike confinements in porous materials often used for these types of experiments3, bonded wafers provide predesigned uniform spaces for confinement. The geometry of each cell is well known, which removes a large source of ambiguity in the interpretation of data.
Exceptionally flat, 5 cm diameter, 375 &#181;m thick Si wafers with about 1 &#181;m variation over the entire wafer can be obtained commercially (from Semiconductor Processing Company, for example). Thermal oxide is grown on the wafers to define the confinement dimension in the z-direction. A pattern is then etched in the oxide using lithographic techniques so as to create a desired enclosure upon bonding. A hole is drilled in one of the wafers (the top) to allow for the introduction of the liquid to be measured. The wafers are cleaned2 in RCA solutions and then put in a microclean chamber where they are rinsed with deionized water4. The wafers are bonded at RT and then annealed at ~1,100 &#176;C. This forms a strong and permanent bond. This process can be used to make uniform enclosures for measuring thermal and hydrodynamic properties of confined liquids from the nanometer to the micrometer scale.

A method for permanently bonding two silicon wafers so as to realize a uniform enclosure is described. This includes wafer preparation, cleaning, RT bonding, and annealing processes. The resulting bonded wafers (cells) have uniformity of enclosure ~1%1,2. The resulting geometry allows for measurements of confined liquids and gasses.

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned ...

Fabrication and Testing of Microfluidic Optomechanical Oscillators

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including microresonators. However, because of the increased acoustic radiative losses during direct liquid immersion of optomechanical devices, almost all published optomechanical experiments have been performed in solid phase. This paper discusses a recently introduced hollow microfluidic optomechanical resonator. Detailed methodology is provided to fabricate these ultra-high-Q microfluidic resonators, perform optomechanical testing, and measure radiation pressure-driven breathing mode and SBS-driven whispering gallery mode parametric vibrations. By confining liquids inside the capillary resonator, high mechanical- and optical- quality factors are simultaneously maintained.

Parametric optomechanical excitations have recently been experimentally demonstrated in microfluidic optomechanical resonators by means of optical radiation pressure and stimulated Brillouin scattering. This paper describes the fabrication of these microfluidic resonators along with methodologies for generating and verifying optomechanical oscillations.

Cavity optomechanics experiments that parametrically couple the phonon modes and photon modes have been investigated in various optical systems including ...

Patterning via Optical Saturable Transitions - Fabrication and Characterization

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical Saturable Transitions (POST). In this technique the chemical properties of organic photochromic molecules that undergo single-photon reactions are exploited, enabling rapid top-down nanopatterning over large areas at low light intensities, thereby, allowing for the circumvention of the far-field diffraction barrier.4 Simple, cost-effective, high throughput and resolution alternatives to nanopatterning are being explored, such as, two-photon polymerization5,6, beam pen lithography (BPL)7, scanning electron beam lithography (SEBL), and focused ion beam (FIB) patterning. However, multi-photon approaches require high light intensities, which limit their potential for high throughput and offer low image contrast. Although, electron and ion beam lithographic processes offer increased resolution, the serial nature of the process is limited to slow writing speeds, which also prevents patterning of features over large areas. Beam-pen lithography is an approach towards parallel near-field optical lithography. However, the gap between the source of the beam and the surface of the photoresist needs to be controlled extremely precisely for good pattern uniformity and this is very challenging to accomplish for large arrays of beams. Patterning via Optical Saturable Transitions (POST) is an alternative optical nanopatterning technique for patterning sub-wavelength features1-3. Since this technique uses single photons instead of electrons, it is extremely fast and does not require high light intensities1-3, opening the door to massive parallelization.

We report that the diffraction limit of conventional optical lithography can be overcome by exploiting the transitions of organic photochromic derivatives induced by their photoisomerization at low light intensities.1-3 This paper outlines our fabrication technique and two locking mechanisms, namely: dissolution of one photoisomer and electrochemical oxidation.

This protocol describes the fabrication and characterization of nanostructures using a novel nanolithographic technique called Patterning via Optical ...

Atomically Traceable Nanostructure Fabrication

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process being used in order to maintain exquisite control over both feature size and feature density. Here, we demonstrate a method for tracking atomically resolved and controlled structures from initial template definition through final nanostructure metrology, opening up a pathway for top-down atomic control over nanofabrication. Hydrogen depassivation lithography is the first step of the nanoscale fabrication process followed by selective atomic layer deposition of up to 2.8 nm of titania to make a nanoscale etch mask. Contrast with the background is shown, indicating different mechanisms for growth on the desired patterns and on the H passivated background. The patterns are then transferred into the bulk using reactive ion etching to form 20 nm tall nanostructures with linewidths down to ~6 nm. To illustrate the limitations of this process, arrays of holes and lines are fabricated. The various nanofabrication process steps are performed at disparate locations, so process integration is discussed. Related issues are discussed including using fiducial marks for finding nanostructures on a macroscopic sample and protecting the chemically reactive patterned Si(100)-H surface against degradation due to atmospheric exposure.

We report a protocol for combining the atomic metrology of the Scanning Tunneling Microscope for surface patterning with selective Atomic Layer Deposition and Reactive Ion Etching. Using a robust process involving numerous atmospheric exposures and transport, 3D nanostructures with atomic metrology are fabricated.

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process ...

Using Synchrotron Radiation Microtomography to Investigate Multi-scale Three-dimensional Microelectronic Packages

Synchrotron radiation micro-tomography (SR&#181;T) is a non-destructive three-dimensional (3D) imaging technique that offers high flux for fast data acquisition times with high spatial resolution. In the electronics industry there is serious interest in performing failure analysis on 3D microelectronic packages, many which contain multiple levels of high-density interconnections. Often in tomography there is a trade-off between image resolution and the volume of a sample that can be imaged. This inverse relationship limits the usefulness of conventional computed tomography (CT) systems since a microelectronic package is often large in cross sectional area 100-3,600 mm2, but has important features on the micron scale. The micro-tomography beamline at the Advanced Light Source (ALS), in Berkeley, CA USA, has a setup which is adaptable and can be tailored to a sample&#39;s properties, i.e., density, thickness, etc., with a maximum allowable cross-section of 36 x 36 mm. This setup also has the option of being either monochromatic in the energy range ~7-43 keV or operating with maximum flux in white light mode using a polychromatic beam. Presented here are details of the experimental steps taken to image an entire 16 x 16 mm system within a package, in order to obtain 3D images of the system with a spatial resolution of 8.7 &#181;m all within a scan time of less than 3 min. Also shown are results from packages scanned in different orientations and a sectioned package for higher resolution imaging. In contrast a conventional CT system would take hours to record data with potentially poorer resolution. Indeed, the ratio of field-of-view to throughput time is much higher when using the synchrotron radiation tomography setup. The description below of the experimental setup can be implemented and adapted for use with many other multi-materials.

For this study synchrotron radiation micro-tomography, a non-destructive three-dimensional imaging technique, is employed to investigate an entire microelectronic package with a cross-sectional area of 16 x 16 mm. Due to the synchrotron&#39;s high flux and brightness the sample was imaged in just 3 min&#160;with an 8.7 &#181;m spatial resolution.

Synchrotron radiation micro-tomography (SR&#181;T) is a non-destructive three-dimensional (3D) imaging technique that offers high flux for fast data ...

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic recording of image sequences. The basic components, features, constraints and optimization tips of a 3D-PTV topology consisting of a high-speed camera with a four-view splitter are described and discussed in this article. The technique is applied to the intermediate flow field (5 &#60;x/d &#60;25) of a circular jet at Re &#8776; 7,000. Lagrangian flow features and turbulence quantities in an Eulerian frame are estimated around ten diameters downstream of the jet origin and at various radial distances from the jet core. Lagrangian properties include trajectory, velocity and acceleration of selected particles as well as curvature of the flow path, which are obtained from the Frenet-Serret equation. Estimation of the 3D velocity and turbulence fields around the jet core axis at a cross-plane located at ten diameters downstream of the jet is compared with literature, and the power spectrum of the large-scale streamwise velocity motions is obtained at various radial distances from the jet core.

A three-dimensional particle tracking velocimetry (3D-PTV) system based on a high-speed camera with a four-view splitter is described here. The technique is applied to a jet flow from a circular pipe in the vicinity of ten diameters downstream at Reynolds number Re &#8776; 7,000.

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic ...

Fabrication and Characterization of Superconducting Resonators

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance.

Superconducting microwave resonators are of interest for detection of light, quantum computing applications and materials characterization. This work presents a detailed procedure for fabrication and characterization of superconducting microwave resonator scattering parameters.

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors ...