Laser filament bottom-up growth sintering for multi-planar diffraction-limit printing and its application to ultra-transparent wearable thermo-electronics

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2018, Vol.6 (29), p.7759-7766
• Main Authors: Kwon, Seung-Gab, Back, Seunghyun, Park, Jong Eun, Kang, Bongchul
• Format: Article
• Language: English
• Subjects: Clustering; Conductors; Crystallization; Diffraction; Electrodes; Elongation; Eyewear; Laser sintering; Lasers; Low cost; Organic chemistry; Precursors; Sintering; Slopes; Solid electrodes; Visible spectrum; Wearable technology
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/C8TC01915K

We report a novel cost-effective digital fabrication method for the production of high resolution electrodes of 1 μm-grade width on multiple planes connected at an angle using an affordable light source. This was achieved by the laser filament growth sintering of nanoseed/organometallic hybrid precursors, which were reformulated from a low-cost, particle-free, ionic organometallic solution. Growth sintering of the hybrid precursor, which creates solid electrodes through the sequential thermo-chemical interactions of nucleation, clustering, thermal growth, and aggregation, improves the conductivity and resolution of the electrodes via bottom-up thermal crystallization and stable chemical transition processes. The laser filament with a Bessel profile, which was modulated from a conventional low-cost laser with a Gaussian profile, localizes the growth sintering interaction within a transversely elongated focusing area close to the diffraction limit, unlike the very narrow focusing area in typical laser optics. As a result, this method enabled the fabrication of an ultra-transparent conductor with a transmittance of more than 97% in the visible spectrum. The electrodes were completely invisible to the naked eye, even when viewed at close range. A transparent micro-heater for humidity-free smart glasses was successfully fabricated to demonstrate the potential of one-step manufacturing of functional wearable devices.