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Fluidic self-assembly for MicroLED displays by controlled viscosity


Displays in which arrays of microscopic ‘particles’, or chiplets, of inorganic light-emitting diodes (LEDs) constitute the pixels, termed MicroLED displays, have received considerable attention1,2 because they can potentially outperform commercially available displays based on organic LEDs3,4 in terms of power consumption, colour saturation, brightness and stability and without image burn-in issues1,2,5,6,7. To manufacture these displays, LED chiplets must be epitaxially grown on separate wafers for maximum device performance and then transferred onto the display substrate. Given that the number of LEDs needed for transfer is tremendous—for example, more than 24 million chiplets smaller than 100 μm are required for a 50-inch, ultra-high-definition display—a technique capable of assembling tens of millions of individual LEDs at low cost and high throughput is needed to commercialize MicroLED displays. Here we demonstrate a MicroLED lighting panel consisting of more than 19,000 disk-shaped GaN chiplets, 45 μm in diameter and 5 μm in thickness, assembled in 60 s by a simple agitation-based, surface-tension-driven fluidic self-assembly (FSA) technique with a yield of 99.88%. The creation of this level of large-scale, high-yield FSA of sub-100-μm chiplets was considered a significant challenge because of the low inertia of the chiplets. Our key finding in overcoming this difficulty is that the addition of a small amount of poloxamer to the assembly solution increases its viscosity which, in turn, increases liquid-to-chiplet momentum transfer. Our results represent significant progress towards the ultimate goal of low-cost, high-throughput manufacture of full-colour MicroLED displays by FSA.

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Fig. 1: Fabrication of a MicroLED lighting panel by FSA.
Fig. 2: Difference in assembly mechanism between large and small chiplets and its effect on assembly yield.
Fig. 3: MicroLED lighting panel manufactured by a simple agitation-based FSA process.
Fig. 4: FR of agitation-based FSA processes versus chiplet mass.

Data availability

The data that support the findings of this study are available from the corresponding authors on request.

Code availability

The code used to determine the alignment errors of the assembled chiplets is available from the corresponding authors on request.


  1. Templier, F. GaN-based emissive microdisplays: a very promising technology for compact, ultra-high brightness display systems. J. Soc. Inf. Disp. 24, 669–675 (2016).

    Article  CAS  Google Scholar 

  2. Wu, T. et al. Mini-LED and micro-LED: promising candidates for the next generation display technology. Appl. Sci. 8, 1557 (2018).

    Article  Google Scholar 

  3. Tang, C. W. & VanSlyke, S. A. Organic electroluminescent diodes. Appl. Phys. Lett. 51, 913–915 (1987).

    Article  ADS  CAS  Google Scholar 

  4. Baldo, M. A. et al. Highly efficient phosphorescent emission from organic electroluminescent devices. Nature 395, 151–154 (1998).

    Article  ADS  CAS  Google Scholar 

  5. Scholz, S., Kondakov, D., Lussem, B. & Leo, K. Degradation mechanisms and reactions in organic light-emitting devices. Chem. Rev. 115, 8449–8503 (2015).

    Article  CAS  PubMed  Google Scholar 

  6. Laaperi, A. OLED lifetime issues from a mobile-phone-industry point of view. J. Soc. Inf. Disp. 16, 1125–1130 (2008).

    Article  Google Scholar 

  7. Zhang, K., Peng, D., Lau, K. M. & Liu, Z. Fully-integrated active matrix programmable UV and blue micro-LED display system-on-panel (SoP). J. Soc. Inf. Disp. 25, 240–248 (2017).

    Article  CAS  Google Scholar 

  8. Zhang, Y., Chen, B., Liu, X. & Sun, Y. Autonomous robotic pick-and-place of microobjects. IEEE Trans. Robot. 26, 200–207 (2010).

    Article  CAS  Google Scholar 

  9. Gauthier, M. & Régnier, S. Robotic Microassembly (John Wiley & Sons, 2011).

  10. Carlson, A., Bowen, A. M., Huang, Y., Nuzzo, R. G. & Rogers, J. A. Transfer printing techniques for materials assembly and micro/nanodevice fabrication. Adv. Mater. 24, 5284–5318 (2012).

    Article  CAS  PubMed  Google Scholar 

  11. Meitl, M. A. et al. Transfer printing by kinetic control of adhesion to an elastomeric stamp. Nat. Mater. 5, 33–38 (2005).

    Article  ADS  Google Scholar 

  12. Yeh, H.-J. & Smith, J. S. Fluidic self-assembly for the integration of GaAs light-emitting diodes on Si substrates. IEEE Photonics Technol. Lett. 6, 706–708 (1994).

    Article  ADS  Google Scholar 

  13. Mastrangeli, M., Zhou, Q., Sariola, V. & Lambert, P. Surface tension-driven self-alignment. Soft Matter 13, 304–327 (2017).

    Article  ADS  CAS  PubMed  Google Scholar 

  14. Jacobs, H. O., Tao, A. R., Schwartz, A., Gracias, D. H. & Whitesides, G. M. Fabrication of a cylindrical display by patterned assembly. Science 296, 323–325 (2002).

    Article  ADS  CAS  PubMed  Google Scholar 

  15. Zheng, W., Buhlmann, P. & Jacobs, H. O. Sequential shape-and-solder-directed self-assembly of functional microsystems. Proc. Natl Acad. Sci. USA 101, 12814–12817 (2004).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  16. Morris, C. J. & Parviz, B. A. Micro-scale metal contacts for capillary force-driven self-assembly. J. Micromech. Microeng. 18, 015022 (2007).

    Article  Google Scholar 

  17. Saeedi, E., Kim, S. & Parviz, B. A. Self-assembled crystalline semiconductor optoelectronics on glass and plastic. J. Micromech. Microeng. 18, 075019 (2008).

    Article  ADS  Google Scholar 

  18. Park, S.-C. et al. A first implementation of an automated reel-to-reel fluidic self-assembly machine. Adv. Mater. 26, 5942–5949 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  19. Gengel, G. W. Integrated circuit packages assembled utilizing fluidic self-assembly. Google Patents (2002).

  20. Knuesel, R. J. & Jacobs, H. O. Self-assembly of microscopic chiplets at a liquid-liquid-solid interface forming a flexible segmented monocrystalline solar cell. Proc. Natl Acad. Sci. USA 107, 993–998 (2010).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  21. Knuesel, R. J. & Jacobs, H. O. Self-tiling monocrystalline silicon; a process to produce electrically connected domains of Si and microconcentrator solar cell modules on plastic supports. Adv. Mater. 23, 2727–2733 (2011).

    Article  CAS  PubMed  Google Scholar 

  22. Stauth, S. A. & Parviz, B. A. Self-assembled single-crystal silicon circuits on plastic. Proc. Natl Acad. Sci. USA 103, 13922–13927 (2006).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  23. Rao, M., Lusth, J. C. & Burkett, S. L. Analysis of a dip-solder process for self-assembly. J. Vac. Sci. Technol. B 29, 042003 (2011).

    Article  Google Scholar 

  24. Tien, J., Terfort, A. & Whitesides, G. M. Microfabrication through electrostatic self-assembly. Langmuir 13, 5349–5355 (1997).

    Article  CAS  Google Scholar 

  25. Whitesides, G. M. & Grzybowski, B Self-assembly at all scales. Science 295, 2418–2421 (2002).

    Article  ADS  CAS  PubMed  Google Scholar 

  26. Bird, R. B., Stewart, W. E. & Lightfoot, E. N.Transport Phenomena (John Wiley, 2007).

  27. Thomas, D. K. & Charlesby, A. Viscosity relationship in solutions of polyethylene glycols. J. Polym. Sci. 42, 195–202 (1960).

    Article  ADS  CAS  Google Scholar 

  28. Fox, T. G. & Flory, P. J. Second-order transition temperatures and related properties of polystyrene. i. Influence of molecular weight. J. Appl. Phys. 21, 581–591 (1950).

    Article  ADS  CAS  Google Scholar 

  29. Franck, A. ARES-G2: a new generation of separate motor and transducer rheometers. Appl. Rheol. 18, 44–47 (2008).

    Article  Google Scholar 

  30. Raza, M. Q., Kumar, N. & Raj, R. Surfactants for bubble removal against buoyancy. Sci. Rep. 6, 19113 (2016).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  31. Gowda, A., Seo, J., Ranaweera, C. K. & Babu, S. Cleaning solutions for removal of 30 nm ceria particles from proline and citric acid containing slurries deposited on silicon dioxide and silicon nitride surfaces. ECS J. Solid State Sci. Technol. 9, 044013 (2020).

    Article  ADS  CAS  Google Scholar 

  32. Fang, J. & Böhringer, K. F. Parallel micro component-to-substrate assembly with controlled poses and high surface coverage. J. J. Micromech. Microeng. 16, 721–730 (2006).

    Article  ADS  Google Scholar 

  33. Hoo, J. H., Park, K. S., Baskaran, R. & Böhringer, K. F. Template-based self-assembly for silicon chips and 01005 surface-mount components. J. Micromech. Microeng. 24, 045018 (2014).

    Article  ADS  CAS  Google Scholar 

  34. Sun, F., Leblebici, Y. & Brunschwiler, T. Surface-tension-driven multi-chip self-alignment techniques for heterogeneous 3D integration. In Proc. 2011 IEEE 61st Electronic Components and Technology Conference (ECTC) 1153–1159 (IEEE, 2011);

  35. Löthman, P. A. et al. A thermodynamic description of turbulence as a source of stochastic kinetic energy for 3D self-assembly. Adv. Mater. Interfaces 7, 1900963 (2020).

    Article  Google Scholar 

  36. Kaltwasser, M. et al. Fluidic self-assembly on electroplated multilayer solder bumps with tailored transformation imprinted melting points. Sci. Rep. 9, 11325 (2019).

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This research was supported by LG Electronics Research Project no. 0534-20140020, Global Research Development Center Program no. 2015K1A4A3047345, grants from the National Research Foundation of Korea funded by the Ministry of Science and ICT (no. NRF-2020R1A3B3079653) and the Ministry of Education (nos. NRF-2019R1I1A1A01059219 and 2020R1I1A1A01075042), the BK21 Plus Program (Creative Research Engineer Development for IT, Seoul National University, 2019–2020) and the BK21 FOUR Program (Education and Research Program for Future ICT Pioneers, Seoul National University, 2021–2023).

Author information

Authors and Affiliations



S.K. conceived the original idea. D.L., S.C. and Cheolheon Park performed all experiments except for the fabrication of LED chiplets and characterization of MicroLED panels. Changseo Park, K.J., H.Y., W.C., C.H.L., T.K., Y.H.M., M.J., Y.-H.C., J.S.L. and K.R.P. manufactured LED chiplets and performed electrode fabrication. J.L. performed characterization of MicroLED panels. D.L., S.C., Cheolheon Park and K.R.P. fabricated the chiplets used in the study of the assembly mechanism. K.A. and J.N. provided help with viscosity measurements and analysed fluid and chiplet dynamics. D.L., S.C., Cheolheon Park, C.K. and S.K. analysed experimental results. C.K. and S.K. supervised the project. D.L., S.C., Cheolheon Park, J.L., S.K. and C.K. wrote the manuscript.

Corresponding authors

Correspondence to Changsoon Kim or Sunghoon Kwon.

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The authors declare no competing interests.

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Nature thanks Massimo Mastrangeli and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data

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Extended data figures and tables

Extended Data Fig. 1 Reduction of assembly yield due to the reduced mass of GaN chiplets in conventional agitation-based FSA.

a, The width (WCh) and depth (DCh) of the chiplets are 20 and 40 μm, respectively. The binding sites with a width (WB) of 20 μm and a depth (DB) of 40 μm are arranged with horizontal (PH) and vertical (PV) periods of 120 and 360 μm, respectively. b, WCh = 30 μm, DCh = 30 μm, WB = 30 μm, DB = 30 μm, PH = 120 μm, PV = 360 μm. c, WCh = 20 μm, DCh = 40 μm, WB = 30 μm, DB = 30 μm, PH = 80 μm, PV = 80 μm. d, WCh = 30 μm, DCh = 30 μm, WB = 30 μm, DB = 30 μm, PH = 80 μm, PV = 80 μm. In all cases, the thickness of the chiplets is 5 μm, and the assembly yields are smaller than 5%; scale bars in a and b, 500 μm; scale bars in c and d, 300 μm.

Extended Data Fig. 2 Dependence of the assembly yield on the concentration of high molecular weight poloxamer in the assembly solution.

The uses of rectangular-cuboid-shaped (width, 20 μm; depth, 40 μm; height, 5 μm) GaN chiplets and square shaped (30 × 30 μm2) binding sites resulted in random rotational orientations, which was not of concern because these experiments were performed only to find the optimized concentration of the poloxamer. a, poloxamer concentration: 0.2 wt%, assembly yield < 40%. b, poloxamer concentration: 1 wt%, assembly yield < 80%. c, poloxamer concentration: 2 wt%, assembly yield > 97%. d, poloxamer concentration: 4 wt%, assembly yield < 15%; scale bars, 400 μm.

Extended Data Fig. 3 Yield versus viscosity characteristics.

To investigate the dependence of the assembly yield on viscosity while ruling out other chemical effects from poloxamer, we used a water/glycerol mixture (red) as the assembly solution, where the viscosity was varied by adjusting the glycerol concentration. The yield versus viscosity curve for this system is found to be similar to that for the water/poloxamer system (green).

Extended Data Fig. 4 Three major forces exerted on chiplets.

For model descriptions see Methods, ‘Mechanical analysis of a single chiplet travelling in a vigorously agitated liquid’.

Extended Data Fig. 5 Effect of the size of the binding sites on the assembly quality.

a, Three or more Si chiplets (width, 150 μm; depth, 150 μm; height: 150 μm) were assembled at a single binding site (200 × 200 μm2). b, Two or more GaN chiplets (width, 30 μm; depth, 30 μm; height, 5 μm) were assembled at a single binding site (30 × 30 μm2). In both experiments, the entire bottom surface of the chiplets were coated with Au; scale bars, 100 μm.

Extended Data Fig. 6 Schematic of MicroLED chiplet fabrication.

a, 5-μm-thick multilayer for InGaN/GaN-based blue LEDs epitaxially grown on a sapphire substrate is patterned by photolithography followed by inductively coupled plasma etch. b, Au layer deposited using an electron-beam evaporator is patterned by a lift-off process. c, SiO2 deposited by plasma-enhanced chemical vapor deposition is patterned by photolithography followed by dry etch. d, Photoresist layer, which later serves as a sacrificial release layer, is patterned by photolithography, onto which an adhesive film is attached. e, Chiplets are separated from the sapphire wafer by laser lift-off (LLO). f, Ti and SiO2 layers are sequentially deposited. g, Chiplets are released from the adhesive film by immersion into a solvent.

Extended Data Fig. 7 Images of the elements of a MicroLED array panel assembled by using an assembly solution with high molecular weight poloxamers (2 wt%).

a, Optical microscope image of the assembled MicroLED lighting panel; scale bar, 500 μm. b, Scanning electron microscope (SEM) image of disk-shaped GaN chiplets (diameter: 45 μm, thickness: 5 μm) before assembly; scale bar, 80 μm. c, Cross sectional SEM image of an assembled chiplet; scale bar, 10 μm.

Extended Data Table 1 Yields of 10 FSA experiments with addition of 2 wt% poloxamer

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Lee, D., Cho, S., Park, C. et al. Fluidic self-assembly for MicroLED displays by controlled viscosity. Nature 619, 755–760 (2023).

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