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Indexed by:期刊论文

Date of Publication:2018-10-01

Journal:INTERNATIONAL JOURNAL OF ADHESION AND ADHESIVES

Included Journals:SCIE

Volume:85

Page Number:23-28

ISSN No.:0143-7496

Key Words:Contact dispensing; High-viscosity adhesive; Liquid-bridge breakup; Microfluidics

Abstract:In contact dispensing process including the extruding, stretching, and liquid-bridge breakup, the initial distance d(n-s)(ini) between the needle tip and the substrate has great influence on the dispensed adhesive volume. Herein, the effect of on the dispensing process in nano-liter level is studied for high-viscosity adhesive. Complete contact dispensing process is simulated using computational fluid dynamic technique. Moreover, the experimental platform including heating device, dispenser, and imaging unit etc. is built up to investigate the dispensing process. According to the results, with the increase of d(n-s)(ini), the variation of extruded adhesive volume can be divided into three regimes that are respectively dominated by different factors. As d(n-s)(ini) is in the range of 45-75 mu m, due to the spatial flow resistance decreasing, the extruded volume sharply increases. Then, when d(n-s)(ini) is in the range of 75-115 mu m, owing to the contact area s(a-s) between the extruded adhesive and the substrate continuing to decrease, the increase of extruded volume becomes slow. Once d(n-s)(ini) reaches 115 mu m, comparing to the decrease of s(a-s), the contribution of spatial flow resistance can be neglected, thus the extruded volume will decrease until s(a-s) approaches to zero. Additionally, the following transfer process based on the liquid-bridge breakup is studied too. The variation of absolute transferred volume is consistent with that of the extruded volume. However, since s(a-s) continuously decreases with the increasing of d(n-s)(ini), the transfer ratio gradually decreases. The presented results can improve the precise contact dispensing process and other related techniques.