Micro-Transfer-Printing (µTP)

This short animated video presentation shows you the basics
as to how our technology works.

Micro-Transfer-Printing (μTP) is a promising new technology for deterministically assembling and integrating arrays of microscale, high-performance devices onto non-native substrates. In its simplest embodiment, (μTP) is analogous to using a rubber stamp to transfer liquid-based inks from an ink-pad onto paper. However, in (μTP) the “inks” are actually composed of high-performance solid-state semiconductor devices and the “paper” can be many things, including plastics and other semiconductors. The (μTP) process, which was invented by Professor John Rogers and co-workers at the University of Illinois, Urbana-Champaign [1, 2], leverages engineered elastomer stamps coupled with high-precision motion controlled print-heads to selectively pick-up and print large arrays of microscale devices onto non-native destination substrates.

At the heart of the process is the ability to selectively tune the adhesion between the elastomer stamp and the printable element by varying the speed of the print-head [2]. This rate dependent adhesion is a consequence of the viscoelastic nature of the elastomer used to construct the stamp. The Adhesion versus Elastomer Stamp Speed graph illustrates how the rate dependent adhesion between the elastomer and the solid elements (line shown in blue) allows for transferring of the elements.  When the stamp is moved quickly away from a bonded interface, the adhesion is large enough to “pick” the printable elements away from their native substrates, and conversely, when the stamp is moved slowly away from a bonded interface the adhesion is low enough to “let go” or “print” the element onto a foreign surface.

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Another key aspect of the (μTP) technology are the strategies and processes for making the printable device elements. In simplest terms, the strategy is to utilize growth and microfabrication methods that allow for thin sacrificial layers to be introduced and subsequently removed from underneath the devices. Microfabricated structures are utilized to tether the undercut device to the native substrate prior to transfer-printing.  The tethers are designed such that they release or fracture during the pick-up portion of the transfer process.  These strategies have been employed to make a wide variety of printable microscale devices, including lasers [3], LEDs [4, 5], solar cells [6], pixel-driver integrated circuits [7] and high-speed flexible transistors [8]. Many important materials systems are compatible with (μTP) including Gallium Arsenide [3, 4 and 6], Indium Phosphide, Gallium Nitride [5, 8], thin-film Diamond [6] and Silicon [1] and Silicon-based integrated circuits [7, 9].

References

[1] E. Menard, K.J. Lee, D.-Y. Khang, R. G. Nuzzo and J.A. Rogers, “A printable form of silicon for high performance thin film transistors on plastic substrates,” Applied Physics Letters, 84(26), 5398-5400 (2004).

[2] M.A. Meitl, Z.-T. Zhu, V. Kumar, K.J. Lee, X. Feng, Y.Y. Huang, I. Adesida, R.G. Nuzzo and J.A. Rogers, “Transfer Printing by Kinetic Control of Adhesion to an Elastomeric Stamp,” Nature Materials 5, 33-38 (2006).

[3] J. Justice, C. A. Bower et al., “Wafer scale integration of III-V lasers on silicon using transfer printing of epitaxial layers,” Nature Photonics, 6, 612-616 (2012).

[4] S.-I. Park, Y. Xiong, R.-H. Kim, P. Elvikis, M. Meitl, D.-H. Kim, J. Wu, J. Yoon, C.-J. Yu, Z. Liu, Y. Huang, K.-C. Hwang, P. Ferreira, X. Li, K. Choquette and J.A. Rogers, “Printed Assemblies of Inorganic Light-Emitting Diodes for Deformable and Semitransparent Displays,” Science 325, 977-981 (2009).

[5] H. Kim, E. Brueckner, J. Song, Y. Li, S. Kim, C. Lu, J. Sulking, K. Choquette, Y. Huang, R.G. Nuzzo and J.A. Rogers, “Unusual Strategies for Using Indium Gallium Nitride Grown on Silicon (111) for Solid-State Lighting,” Proceedings of the National Academy of Sciences USA 108(25), 10072-10077 (2011).

[6] J. Yoon, S. Jo, I.S. Chun, I. Jung, H.-S. Kim, M. Meitl, E. Menard, X. Li, J.J. Coleman, U. Paik and J.A. Rogers, “GaAs Photovoltaics and Optoelectronics Using Releasable Multilayer Epitaxial Assemblies,” Nature 465, 329-333 (2010).

[7] Bower et al., “Transfer-printed microscale integrated circuits for high performance display backplanes,” IEEE Trans. Compon. Pack. Manufac. Technol. 1, 1916–1922 (2011).

[8] K.J. Lee, M.A. Meitl, J.-H. Ahn, J.A. Rogers, R.G. Nuzzo, V. Kumar and I. Adesida, “Bendable GaN High Electron Mobility Transistors on Plastic Substrates,” Journal of Applied Physics 100, 124507 (2006).

[9] H.-J. Chung, T.-I. Kim, H.-S. Kim, S.A. Wells, S. Jo, N. Ahmed, Y.H. Jung, S.M. Won, C.A. Bower and J.A. Rogers, “Fabrication of Releasable Single-Crystal Silicon-Metal Oxide Field-Effect Devices and Their Deterministic Assembly on Foreign Substrates,” Advanced Functional Materials 21, 3029-3036 (2011).