News Column

Patent Issued for Reconfigurable Lithographic Structures

May 6, 2014



By a News Reporter-Staff News Editor at Journal of Technology -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Gracias, David Hugo (Baltimore, MD); Leong, Timothy Gar-Ming (Baltimore, MD), filed on March 6, 2009, was published online on April 22, 2014.

The assignee for this patent, patent number 8703073, is The Johns Hopkins University (Baltimore, MD).

Reporters obtained the following quote from the background information supplied by the inventors: "The current invention relates to lithographically produced structures, and more particularly to reconfigurable lithographically produced structures.

"Lithography, the workhorse of the microelectronics industry, is routinely used to fabricate micro and nanostructures in a highly monodisperse manner, with high accuracy and precision. However, one of the central limitations of this technology is that it is inherently two-dimensional (2D) as a result of the wafer based fabrication paradigm. It is extremely challenging to fabricate three-dimensional (3D) patterned structures, let alone complex structures containing encapsulated objects, on the sub-mm scale. Thus, the parallel fabrication of such structures remains a major challenge that needs to be addressed.

"Some solutions have emerged that enable sub-mm scale lithographic fabrication in 3D; these include techniques such as wafer stacking (N. Miki, X. Zhang, R. Khanna, A. A. Ayon, D. Ward, S. M. Spearing, Sens. Actuators, A 2003, 103, 194-201), micromachining (S. Kawata, H. B. Sun, T. Tanaka, K. Takada, Nature 2001, 412, 697-698), molding (L. T. Romankiw, Electrochim. Acta 1997, 42, 2985-3005; L. Weber, W. Ehrfeld, H. Freimuth, M. Lacher, H. Lehr, B. Pech, presented at Micromachining and Microfabrication Process Technology II, Austin, Tex., USA, October 1996), and self-assembly (G. M. Whitesides, B. Grzybowski, Science 2002, 295, 2418-2421). Self-assembly, or self-folding, of 2D lithographically patterned templates is one attractive strategy for fabricating 3D patterned, sub-mm scale structures. There are numerous methods that enable self-folding, such as surface tension-based assembly (R. R. A, Syms, E. Yeatman, V. M. Bright, G. M. Whitesides, J. Microelectromech. Syst. 2003, 12, 387-417; T. G. Leong, P. A. Lester, T. L. Koh, E. K. Call, D. H. Gracias, Langmuir 2007, 23, 8747-8751), electroactive polymer actuation (E. W. H. Jager, E. Smela, O. Inganas, Science 2000, 290, 1540-1545), electric actuation (K. Suzuki, I. Shimoyama, H. Miura, J. Microelectromech. Syst. 1994, 3, 4-9; K. Suzuki, H. Yamada, H. Miura, H, Takanobu, Microsyst. Technol. 2007, 13, 1047-1053), thermal and shape memory alloy actuation (J. K. Luo, J, H, He, Y. Q. Fu, A, J. Hewitt, S. M. Spearing, N. A. Fleck, W. I. Milne, J. Micromech. Microeng. 2005, 15, 1406-1413; J. K. Luo, R. Huang, J. H. He, Y. Q. Fu, A. J. Flewitt, S. M. Spearing, N. A. Fleck, W. I. Milne, Sens. Actuators, A 2006, 132, 346-353; A. P. Lee, D. R. Ciarlo, P. A. Krulevitch, S. Lehew, J. Trevino, M. A. Northrup, Sens. Actuators, A 1996, 54, 755-759), and stress-driven actuation (W. J. Arora, A. J. Nichol, H. I. Smith, G. Barbastathis, Appl. Phys. Lett. 2006, 88, 053108; C. L. Chua, D. K. Fork, K. Van Schuylenbergh, J.-P. Lu, J. Microelectromech. Syst. 2003, 12, 989-995; E. Moiseeva, Y. M. Senousy, S. McNamara, C. K. Harnett, J. Micromech. Microeng. 2007, 17, N63-N68; O. G. Schmidt, K. Eberl, Nature 2001, 410, 168). However, most previous demonstrations of lithographically patterned, self-folding microstructures are assembled tethered to substrates. Additional limitations include high temperature assembly incompatible with aqueous media or spontaneous assembly once the underlying support layer is dissolved. Thus, versatile on-demand encapsulation of objects within self-assembled structures remains even more of a challenge and has not been previously demonstrated.

"Our research group has demonstrated a process that utilized an electrodeposited solder as a hinge for the self-assembly of lithographically structured microcontainers (T. G. Leong, P. A. Lester, T. L. Koh, E. K. Call, D. H. Gracias, Langmuir 2007, 23, 8747-8751). However, the assembly could only be carried out at high temperature (188.degree. C.), in the presence of soldering flux, and in high boiling point (non-aqueous) media. These microcontainers could only be loaded after assembly. Lower temperature assembly has been demonstrated in aqueous media using a low melting point solder (mp 47.degree. C.) (M, Boncheva, G. M. Whitesides, Adv. Mater. 2005, 17, 553-557); however, the structures fabricated were on the millimeter to centimeter scale, and the templates were fabricated by hand in a serial manner. Also, since the low melting point solder used is a stoichiometrically complex bismuth alloy that is deposited by dip-coating; low temperature, parallel, wafer scale self-folding of smaller microstructures has remained a challenge.

"Therefore, there remains a need for improved reconfigurable, lithographically produced structures."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "A lithographically structured device according to some embodiments of the current invention have an actuation layer and a control layer operatively connected to the actuation layer. The actuation layer includes a stress layer and a neutral layer that is constructed of materials and with a structure such that it stores torsional energy upon being constructed. The control layer is constructed to maintain the actuation layer substantially in a first configuration in a local environmental condition and is responsive to a change in the local environmental condition such that it permits a release of stored torsional energy to cause a change in a structural configuration of the lithographically structured device to a second configuration, the control layer thereby providing a trigger mechanism. The lithographically structured device has a maximum dimension that is less than about 10 mm when it is in the second configuration.

"A method of producing a plurality of devices includes forming a plurality of device structures on a substrate and releasing the plurality of device structures from the substrate. Each device structure of the plurality of device structures includes an actuation layer and a control layer operatively connected to the actuation layer. The actuation layer is constructed of a material and with a structure such that it stores torsional energy upon being constructed, and the control layer is constructed to maintain the actuation layer substantially in a first configuration in a local environmental condition and is responsive to a change in the local environmental condition such that it permits a release of stored torsional energy to cause a change in a structural configuration of the device structure to a second configuration.

"A method encapsulating or gripping a sub-millimeter size object includes disposing a lithographically structured device proximate the sub-millimeter size object, the lithographically structured device having a first structural configuration; and changing an environmental condition proximate the lithographically structured device to cause the lithographically structured device to change to a second structural configuration to thereby encapsulate or grip the object. The lithographically structured device has a maximum dimension in the second structural configuration that is less than about 10 mm."

For more information, see this patent: Gracias, David Hugo; Leong, Timothy Gar-Ming. Reconfigurable Lithographic Structures. U.S. Patent Number 8703073, filed March 6, 2009, and published online on April 22, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=98&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=4894&f=G&l=50&co1=AND&d=PTXT&s1=20140422.PD.&OS=ISD/20140422&RS=ISD/20140422

Keywords for this news article include: Technology, The Johns Hopkins University.

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Source: Journal of Technology


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