ABSTRACT
Multi-photon reduction (MPR) based on femtosecond laser makes rapid prototyping and molding in micro-nano scale feasible, but is limited in material selectivity due to lack of the understanding of the reaction mechanism in MPR process. In this paper, additively manufacturing of complex silver-based patterns through MPR is demonstrated. The effects of laser parameters, including laser pulse energies and scanning speeds, on the structural and chemical characteristics of the printed structures are systematically investigated. The results show that the geometric size of printed cubes deviates from the designed size further by increasing laser pulse energy or decreasing scanning speed. The reaction mechanism of MPR is revealed by studying the elemental composition and chemical structures of printed cubes. The evolution of Raman spectra upon the laser processing parameters suggests that the MPR process mainly includes two processes: reduction and decomposition. In the MPR process, silver ions are reduced and grow into particles by accepting the electrons from ethonal molecules; meanwhile carboxyl groups in polyvinylpyrrolidone are decomposed and form amorphous carbon that is attached on the surface of silver particles. The conductivity of silver wires fabricated by MPR reaches 2 × 105S m-1and stays relatively constant as varying their cross section area, suggesting excellent electrical conduction. The understanding of the MPR process would accelerate the development of MPR technology and the implementation of MPR in micro-electromechanical systems could therefore be envisioned.
ABSTRACT
Government public support is an important policy tool to support enterprises in carrying out innovation and R&D in China. However, there is a lack of systematic research on the effect of direct and indirect government support on the innovation ability of Chinese high-tech enterprises, especially the relatively weak SMEs. This paper aims to explore the impact of public support on sustainable innovation by SMEs in China and identify the differences, if any, between direct and indirect support. By using the survey data of 2600 Chinese SMEs, we found that government support significantly and positively impacts both innovation input and output. In particular, we found that R&D intensity acts as a mediator between direct government support and innovation output; however, indirect support did not exhibit a significant mediating effect. Additionally, it was found that innovative sales can promote innovation investment by alleviating financial constraints; this is known as sustainable innovation.