Fig. 1. Generation of ultrafast laser and its mechanism of interaction with material. (a) Schematic diagram of ultrafast laser chirped pulse amplification technology^[25]; (b) time scales of various mechanisms in laser-material interaction (green bars indicate the range of durations for different carrier density)^[22]

Fig. 2. Overview of ultrafast laser techniques for flexible electronics field

Fig. 3. Ultrafast laser-induced modification for graphene device fabrication. (a) Mechanism of interaction between ultraviolet high-frequency ultrafast laser and wood cells; (b) images of the flexible temperature sensor fabicated by FsLIG on leaves; (c) response test curve of the flexible temperature sensor fabricated by FsLIG on leaves^[31]; (d) manufacturing process of the highly flexible flexible sensor constructed based on wood material using FsLIG technology and the final prepared scanning electron microscope (SEM) image of the flexible LIG thermistor cross-section^[35]

Fig. 4. Ultrafast laser-induced modification for rGO device fabrication. (a) Mechanism of laser-induced graphene oxide reduction^[40]; (b) manufacturing process of ultrafast laser direct writing rGO-ZnO hybrid-based photodetector^[41]

Fig. 5. Ultrafast fabrication of LIG/MnO₂ micro-supercapacitors by spatially shaped femtosecond laser and its mechanism schematic^[42]

Fig. 6. Temporally and spatially shaped femtosecond laser (TSSF) for MXene device fabrication. (a) Schematic diagram of MXene/1T-MoS₂ MCS prepared by TSSF^[43]; (b) schematic diagram of MXene quantum dots (MQD)/rGO MCS prepared by TSSF^[44]

Fig. 7. Fabrication of flexible inorganic thin film devices by ultrafast laser transfer technology. (a) Schematic diagram of the ultrafast laser transfer functional device^[50]; (b) images of the roughness of the separation surface of the transfer device under different laser scanning speeds^[53]; (c) schematic diagram of the UV picosecond laser transfer strategy; (d) images of the patterned flexible GaN LEDs fabricated by UV picosecond laser transfer strategy and the luminescence curves under different bending states^[54]

Fig. 8. Ultrafast laser transfer of two-dimensional materials, organic thin films, and metal nano-structures. (a) Schematic diagram of the ultrafast laser-induced forward transfer; (b) ultrafast laser transfer fabrication of GO microresonators; (c) ultrafast laser transfer fabrication of PPV structure^[55]; (d) ultrafast laser-induced forward transfer fabrication of patterned metal nano-structures on flexible substrates; (e) schematic of ultrafast laser polarization modulated transfer of patterned metal nano-structures; (f) pre-patterned arrays of metal nano-structures to be transferred; (g) electric field distribution in the E_zdirection at 45° polarization; (h) image of metal nano-structures transferred by ultrafast laser^[56]

Fig. 9. Ultrafast laser micro/nano joining for flexible electronics fabrication. (a) Simulation of electric field intensity around Ag nanowires at different angles under ultrafast laser irradiation^[65]; (b) overall morphology of Ag-CNF heterogeneous interface formed under femtosecond laser irradiation; (c) HRTEM image of Ag-CNF heterogeneous interface; (d) (e) flexible stress sensor with Ag-CNF heterogeneous connection; (f) comparison of the relative resistance value versus strain curves of Ag-CNF hybrid nanowire sensor and CNF nanowire sensor^[69]

Fig. 10. Ultrafast laser high-resolution patterned etching for fabricating flexible electronics. (a) Schematic diagram of the femtosecond laser Bessel beam fabrication of graphene nanoscale supercapacitor; (b) scanning electron microscopy image of the GNSC array with 500 nm electrode gap (scale bar: 30 μm) [inset: the electrode gap (scale bar: 1 μm)]; (c) capacitance retention of GNSC during 10000 charge-discharge cycles (inset: specific areal capacitance of graphene supercapacitors with diverse electrode gap widths at a scan rate of 5 mV·s^-1[73]); (d) photograph of the laser-ablated OTFT arrays [insets: microscopy images of 5 × 5 OTFT arrays (down) and a single OTFT (up), scale bars are 100 µm (down) and 20 µm (up), respectively]; (e) statistical distribution of on-off current ratio (I_ON/I_OFF) , threshold voltage (V_TH), subthreshold swing (|SS|), and mobility of laser-ablated OTFT devices with a laser intensity of 11.64 kW·cm^-2; (f) I_ON/I_OFF, V_TH, |SS|, and mobility of laser-ablated OTFT devices under different bending cycles^[74]

Fig. 11. Ultrafast laser etching of stretchable structures for flexible electronics fabrication. (a) Schematic of the fabrication process of stretchable OLEDs^[75]; (b) schematic of ultrafast laser-prepare Kirigami sensor; (c) ultrafast laser-prepared Kirigami sensor worn at the knee for strain measurement^[77]

Fig. 12. Ultrafast laser etching of micro/nano composite structures for flexible electronic device fabrication. (a) Ultrafast laser etching process for the direct fabrication of flexible pressure sensors; (b) SEM image of the surface topography of PDMS after ultrafast laser etching; (c) SEM image of PDMS covered with Ag nanowires after etching; (d) arrayed flexible pressure sensors for pressure distribution monitoring^[78]; (e) ultrafast laser etching process for the indirect fabrication of flexible piezoresistive sensors (inset: the structure of the sensor device); (f) SEM image of microhole structure prepared by femtosecond laser on a silicon wafer and microcone structure formed by PDMS inversion moulding; (g) flexible piezoresistive sensor for blood pressure pulse monitoring^[79]

Fig. 13. Superdiffraction processing techniques of ultrafast laser. (a) Microsphere-assisted femtosecond laser superdiffraction processing^[83]; (b) superdiffraction processing based on O-FIB^[84]; (c) 2D micro-nano hybrid structures prepared by MLOP-NL^[85]