Abstract
Direct laser-writing techniques have attracted attention for their use in two- and three-dimensional printing technologies. In this article, we report on a micropatterning process that uses femtosecond laser reductive sintering of mixed CuO/NiO nanoparticles. The writing speed, laser fluence, and incident total energy were varied to investigate the influence of heat accumulation on the micropatterns formed by these materials. Heat accumulation and the thermal history of the laser irradiation process significantly affected the material composition and the thermoelectric properties of the fabricated micropatterns. Short laser irradiation durations and high laser fluences decrease the amount of metal oxide in the micropatterns. Selective fabrication of p-type and n-type thermoelectric micropatterns was demonstrated to be possible with control of the reduction and reoxidization reactions through the control of writing speed and total irradiation energy.
Highlights
Direct laser-writing techniques have attracted attention in printing technologies
We have developed a process for femtosecond laser reductive sintering of metal oxide NPs [12,13,14]
This article reports our investigation of the effects of heat accumulation on micropatterns formed through femtosecond laser reductive sintering of CuO/NiO mixed NPs
Summary
Direct laser-writing techniques have attracted attention in printing technologies. For example, three-dimensional (3D) printing, which is known as additive manufacturing, has been used in the fabrication of 3D bulk metal structures. Metal oxide NP solutions with NPs of CuO, Cu2O, and NiO, a reducing agent, and a dispersant, have been used for laser reductive sintering [8,9,10,11]. Cu-rich and Cu2O-rich micropatterns can be formed selectively by controlling laser irradiation conditions such as the writing speed [12]. We have used this process to fabricate Cu/Cu2O composite micro-thermistors. This article reports our investigation of the effects of heat accumulation on micropatterns formed through femtosecond laser reductive sintering of CuO/NiO mixed NPs. The details of the patterning properties were evaluated at writing speeds including below 1 mm/s. We fabricated thermocouples to demonstrate the process’s effectiveness for precisely fabricating fine micropatterns with controllable thermoelectric properties
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