Printing
technologies that integrate wearable components onto flexible
and stretchable substrates are crucial for the development of miniaturized
wearable electronics. In this study, we developed all-printed paper-based
flexible micro-supercapacitors based on water-based additive-free
oxidized single-walled carbon nanotube pastes. The use of a modified
Brodie’s method with mild oxidants and minimum usage of strong
acids enabled the production of highly conductive and printable oxidized
single-walled carbon nanotube pastes. Pseudo-plastic pastes were obtained
because of the numerous hydrogen bonds between the oxidized single-walled
carbon nanotubes. By photothermal treatment with intense pulsed light
irradiation, a microporous structure was developed in the interdigitated
energy storage electrodes to facilitate the infiltration of electrolytes.
The paper-based flexible micro-supercapacitor exhibited a high energy
density of 0.51 μW h cm–2 at a power density
of 0.59 mW cm–2 and a superior capacity retention
of 85% after 10,000 bending cycles with a bending radius of 3 mm.
The all-printed flexible micro-supercapacitor array with a total capacitance
of 0.1 mF charged to 4.0 V successfully powered a commercial digital
clock for approximately 40 s. The micro-supercapacitor array operated
properly under both tensile and compressive strains. These results
demonstrate that the water-based additive-free oxidized single-walled
carbon nanotube pastes are promising printable materials for the construction
of flexible micro-supercapacitors.
Intense pulsed light (IPL)‐induced photothermal heating is relatively effective at reducing the annealing or sintering time of metal particle‐based conductive patterns in the manufacturing of printed electronics. However, defects such as cavities, delamination, and inhomogeneous shrinkage within the sintered patterns are a well‐known problem in IPL sintering. These defects are considerably influenced by undesired temperature gradients induced inside samples during IPL sintering. To solve this undesired temperature gradient problem, we propose a bidirectional IPL (B‐IPL) sintering approach using front‐ and back‐elliptical reflectors on both sides of the printed pattern. The effects of the B‐IPL energy density and number of shots on the electrical and mechanical properties of the printed patterns were systematically investigated using noncontact spectroscopic temperature sensing techniques with a µs‐timescale infrared temperature sensor system. Cross‐sectional field emission scanning electron microscopy images indicate that B‐IPL sintering significantly enhances the densification level and sintering uniformity of printed patterns compared to conventional IPL.
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