A micro-needle induced strategy for preparation of monodisperse liquid metal droplets in glass capillary microfluidics
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Monodisperse micro-sized liquid metal droplets have received considerable attention for developing flexible electronics, microfluidics actuators and reconfigurable devices. Herein we report an innovative and efficient strategy for large-scale preparation of Galinstan liquid metal microdroplets with controllable sizes using a micro-needle induced glass capillary microfluidic device. By inserting a stainless steel micro-needle into the inner liquid metal phase in the glass capillary, the hydrodynamic instability of the liquid metal stream is significantly suppressed to guarantee steady fluid flow before the liquid metal is pinched off by the outer phase flow, giving rise to a stable generation of monodisperse liquid metal microdroplets. The microdroplet size dependence on the flow ratio of the continuous and dispersed-phase is investigated experimentally. A theoretical framework based on the Plateau–Rayleigh instability is proposed to explain the advantage of the micro-needle induced strategy. This strategy has great potential for the generation of high interfacial tension liquid metal emulsions.
KeywordsMicro-needle induced Liquid metal Glass capillary microfluidic Hydrodynamic instability Plateau–Rayleigh instability
This work was supported by the National Natural Science Foundation of China (Grant nos. 11672095, 11802078, 11702035 and 11572335), the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (Grant no. 51521003), the CAS Key Research Program of Frontier Sciences (QYZDB-SSW-JSC036), the CAS Strategic Priority Research Program (XDB22040403), and University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province (Grant no. UNPYSCT-2018104).
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