Optically-Directed Bubble Printing of MXenes on Flexible Substrates toward MXene-Enabled Wearable Electronics and Strain Sensors

Abstract

This study presents the use of laser-driven microbubbles for micropatterning Ti₃C₂T_X MXenes on flexible polyethylene terephthalate films, yielding conductive micropatterns without the need for pre- or postprocessing. Characterization of the electrical properties under varying strain conditions revealed distinct responses; resistance decreased under compressive strain and increased under tensile strain, demonstrating their potential as strain sensors. The patterns maintained functional integrity over 1000 cycles of bending, with a significant increase in resistance observed under tensile strain (61.6%) compared to compressive strain (11.3%). In addition, narrower MXene lines exhibited greater strain sensitivity, while broader lines were more robust. This work underscores the potential of bubble printing as an effective approach for printing conductive micropatterns and emphasizes its potential for substantial advances in wearable technology, flexible electronics, and strain sensing technologies.

Keywords: MXene patterning; directed assembly; flexible electronics; laser printing; nanoparticle assembly; strain sensing.

Figure 1

(a) UV–vis spectrum of synthesized Ti₃C₂T_X MXene, with a TEM image of a MXene flake inset; (b) Scheme of the optical setup used for bubble printing; (c) Scheme of the process of bubble printing; (d) Microscope images of bubble printing of a MXene line: (1) laser on, (2) movement to the right, (3) movement to the left, (4) final printed pattern. A typical example corresponding to (d) is shown in Video S1.

Figure 2

Scanning electron micrographs of bubble printed MXene patterns (a) without applied strain and (b) after 1000 applied to cycles of bending to 60.3° under tensile strain, showing microcracks and flaking damage. The white arrow in (b) indicates the extent of a microcrack. Additional images are given in Figure S2.

Figure 3

(a) Photograph of the bubble printed MXene pattern on PET film unbent (top) and bent (bottom); (b) Photograph of the custom-built bending setup; IV curves of MXene patterns at different bending angles for applied (c) compressive and (d) tensile strain. A zoom of (c) can be found in Figure S4.

Figure 4

Cycle stability of bubble printed MXene lines under repeated cycles of bending from 0° to 60.3° to apply (a) compressive and (b) tensile strain. (c) Average change in resistance for samples shown in (a) and (b) over 1000 cycles in both bending directions. (d) Average change in resistance within a single cycle of bending to 60.3° after 999 cycles.