The creation of 3D micro-and nanoobjects with well-defined and reproducible functionalities remains a key challenge in nanotechnology. A promising approach consists in shaping multifunctional nanomembranes into advanced 3D micro- and nanoarchitectures.1 Planar nanomembranes can be defined with unrivalled precision by well-established thin film technologies and lateral patterning techniques on a substrate surface. After deposition and structuring, the nanomembranes will shape themselves if sufficient built-in strain is present during release from the substrate .
If this strain is homogeneously distributed over the thickness of the nanomembrane, it then forms into a network of well defined and ordered wrinkles,2,3 which show potential for highly integrative nanofluidic systems with ultra high-speed electronic and photonic read-out.4
Of particular interest are nanomembranes which curl themselves into rolled-up micro-/nanotubes driven by a built-in stress gradient across the layer thickness (Fig. 1(a)). The technology of creating micro-/nanotubes directly on a chip is entirely disruptive and has no counterpart anywhere else. The approach is fully integrative with existing technologies since - by definition - the tubes are fabricated at a well-defined position on a chip.
The tubes are scalable in size from millimeters to nanometers and the diameter of the tubes are only dependent on layer thicknesses, differential stress, and elasticity of the materials. This directly implies that the tube size is decoupled from the lithographic resolution used to define the 2D sheet to be rolled-up. The choice in materials and its combinations are universal and they can be deposited as a 2D layer.
While the roll-up of stressed metal films on substrates is a phenomenon known for more than 100 years,5 it is only a decade ago that the great potential of this observation was recognized as a major breakthrough in interdisciplinary nanotechnologies.6 By now, we are able to create micro-/nanotubes out of practically any material combination, including Si, C, Fe, Au, ZnO, Ag, Pt, SiO2 and combinations thereof. Naturally, this leads to a manifold of different applications and concepts, including lab-in-a-tube systems,7 meta-material fiber optics,8 optofluidic components9 and multifunctional micro-/nanojet engines.10,11
Figure 1 (b,c) shows a jet engine made from a rolled-up multifunctional nanomembrane, which self-propels in H2O/H2O2. The inner surface of the tube consists of platinum, which induces a catalytic reaction leading to oxygen bubble formation inside the tube body. The bubbles are thrusted out of the tube opening and the engine moves into the opposite direction by repulsion.
Since we included a Fe layer as a ferromagnetic material into the tube wall, the direction of the moving jet engine can be controlled by an externally applied magnetic field (Fig. 2). Such obejcts can be used for drug delivery and cargo transportation in lab-on-a chip systems or maybe in the far future in human bodies for desease curing.
1. O. G. Schmidt, N. Schmarje, C. Deneke, C. Müller, and N.-Y. Jin-Phillipp, "Three-dimensional Nano-objects evolving from a two-dimensional layer technolog.", Advanced Materials 13, 756 (2001)
2. Y. F. Mei, D. J. Thurmer, F. Cavallo, S. Kiravittaya, O. G. Schmidt, "Semiconductor sub-micro-/ nanochannel networks by deterministic layer wrinkling", Advanced Materials 19, 2124 (2007)
3. A. Malachias, Y. F. Mei, R. K. Annabattula, Ch. Deneke, P. R. Onck, O. G. Schmidt, "Wrinkled-up nanochannel networks: Long-range ordering, scalability, and X-ray investigation", ACS Nano 2, 1715 (2008)
4. Y. F. Mei, S. Kiravittaya, M. Benyoucef, D. J. Thurmer, T. Zander, C. Deneke, F. Cavallo, A. Rastelli, O. G. Schmidt, "Optical properties of a wrinkled nanomembrane with embeded quantum well", Nano Letters 7, 1676 (2007)
5. G. G. Stoney, "The Tension of Metallic Films Deposited by Electrolysis" Proc. R. Soc. Lond. A 82, 172-175 (1909).
6. O. G. Schmidt and K. Eberl, "Thin solid films roll up into nanotubes", Nature 410, 168 (2001)
7. G. S. Huang, Y. F. Mei, D. J. Thurmer, E. Coric, O. G. Schmidt," Rolled-up transparent microtubes as two-dimensionally confined culture scaffolds of individual yeast cells", Lab on a Chip 9, 263 (2009)
8. E. J. Smith, Z. Liu, Y. F. Mei, O. G. Schmidt, "Combined surface plasmon and classical waveguiding through metamaterial fiber design", Nano Letters 10, 1 (2010)
9. A. Bernardi, S. Kiravittaya, A. Rastelli, R. Songmuang, D. J. Thurmer, M. Benyoucef, O. G. Schmidt, "On-chip Si/SiOx microtube refractometer", Applied Physics Letters 93, 094106 (2008)
10. Y. F. Mei, G. S. Huang, A. A. Solovev, E. Bermúdez Ureña, I. Moench, F. Ding, T. Reindl, R. K. Y. Fu, P. K. Chu, O. G. Schmidt,"Versatile approach for integrative and functionalized tubes by strain engineering of nanomembranes on polymers", Advanced Materials 20, 4085 (2008)
11. A. A. Solovev, Y. F. Mei, E. Bermúdez Ureña, G. S. Huang, O. G. Schmidt," Catalytic microtubular jet engines self-propelled by accumulated gas bubbles", small 5, 1688 (2009).
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