Research ArticleMATERIALS SCIENCE

A general ink formulation of 2D crystals for wafer-scale inkjet printing

See allHide authors and affiliations

Science Advances  12 Aug 2020:
Vol. 6, no. 33, eaba5029
DOI: 10.1126/sciadv.aba5029
  • Fig. 1 Coffee-ring effect.

    Inverted optical micrographs of dried inkjet-printed droplets on clean glass: (A to C) common solution-processed 2D crystal dispersions (sections S1 and S2). (D to H) Formulated inks via solvent exchange in IPA or binary solvents of IPA/ethanol (10 volume %), IPA/2-butanol (10 and 20 volume %), and IPA/t-butanol (10 volume %). Scale bar, 50 μm. The brightness and contrast are optimized for clarity. MoS2 is the 2D crystal example. Substrate is Si/SiO2 at 60°C. (I) Schematic drying process showing CRE formation (8).

  • Fig. 2 Solutal Marangoni effect.

    (A) Optical micrographs of a drying droplet of IPA/2-butanol (10 volume %) with tracer particles on glass from droplet impact (0.007 tf), to maximum spreading (0.36 tf), to when the edge recedes close to the particle periphery (0.58 tf), and at the end of drying (tf). Scale bar, 50 μm. The brightness and contrast are optimized for clarity. (B) Particle trajectories at 0.04 tf to 0.05 tf, with red arrows showing the trajectory end, and (C) the corresponding velocity maps averaged over two time intervals: For IPA, IPA/ethanol, and IPA/t-butanol, the particles nearest to the pinned contact lines display largest velocities and increase from ∼0.3 to ∼0.6 mm s−1; for IPA/2-butanol, the contact line and the near particle first advance at ∼0.5 mm s−1. The droplet then ceases to expand, and the particle velocities greatly decrease. Polystyrene nanoparticles (diameter ~755 nm) are used as tracer particles as 2D crystals are too small to visualize. Stationary particles adhering to substrates are excluded from analysis. (D) Contact diameter (D) of droplets without tracer particles as a function of time. The time is normalized by tf and D by the diameter just after (1 ms) inertial droplet impact (D0). (E) Reconstructed height profiles of an IPA/2-butanol droplet at various times (movies S6 and S8). Solid line at 0.004 tf and 0.13 tf is circular fit. (F) Schematic depicting the solutal Marangoni effect.

  • Fig. 3 Inkjet printing of 2D crystals.

    (A) Ink examples and corresponding optical micrographs of printed single lines on Si/SiO2. Scale bar, 100 μm. The inks are diluted for clarity. Brightness and contrast of the lines are enhanced to reflect the distribution of printed flakes. TMD, transition metal dichalcogenide; h-BN, hexagonal boron nitride. (B) Printed patterns on PET: (1 to 13) individual patterns and (14) gradient printing. Scale bar, 1 cm. Inset shows 3, 11, 12, and 14 with a dark background. Corresponding (C) optical micrographs of selected areas in 1, 2, 3, and 5. Scale bar, 500 μm. (D and E) SEM in 9 and 13. Scale bars, 100 μm. Photo credit: Guohua Hu, University of Cambridge and The Chinese University of Hong Kong.

  • Fig. 4 Inkjet-printed patterns with identical print-to-print functional features.

    (A) Schematic of ultrafast fiber laser cavity showing integration of an array of 4 × 8 inkjet-printed 2H-MoS2 SAs. (B) Spectrogram plots illustrating the evolution of ultrashort laser pulse generation. (C) Gaussian fitting of the measured pulse duration τ of randomly selected 16 SA devices. (D to F) Fully inkjet-printed rGO/α-Fe2O3 5 × 10 sensor array on PET. Scale bars, 100 μm. Photo credit: Guohua Hu, University of Cambridge and The Chinese University of Hong Kong. (G) Gaussian fitting of the measured responsivity (Rgas, the change in the device resistance) of at 1 part per million NO2. Three short-circuited devices are excluded from fitting. (H) Photograph of 100 × 45 inkjet-printed MoS2 photodetector array on a 3-inch wafer (diameter 76 mm), where the uniformly printed 2H-MoS2 over interdigitated gold electrodes acts as the active layer. Photo credit: Yubo Wang, University of Cambridge and Zhejiang University. (I) Photograph of >300 devices, showing visually identical printed MoS2 array. Scale bar, 2 mm. (J) Optical micrograph of a single photodetector. Scale bar, 100 μm. (K) SEM micrograph showing even flake distribution over the false-colored interdigitated electrodes. Scale bar, 10 μm. (L) Gaussian fitting of the measured responsivity Rphoto of a randomly selected 50-device array under 40-μW illumination at 635 nm, 5 V. Six devices are short-circuited and excluded from the fitting.

Supplementary Materials

  • Supplementary Materials

    A general ink formulation of 2D crystals for wafer-scale inkjet printing

    Guohua Hu, Lisong Yang, Zongyin Yang, Yubo Wang, Xinxin Jin, Jie Dai, Qing Wu, Shouhu Liu, Xiaoxi Zhu, Xiaoshan Wang, Tien-Chun Wu, Richard C. T. Howe, Tom Albrow-Owen, Leonard W. T. Ng, Qing Yang, Luigi G. Occhipinti, Robert I. Woodward, Edmund J. R. Kelleher, Zhipei Sun, Xiao Huang, Meng Zhang, Colin D. Bain, Tawfique Hasan

    Download Supplement

    The PDF file includes:

    • Sections S1 to S9
    • Figs. S1 to S15
    • Table S1

    Other Supplementary Material for this manuscript includes the following:

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article