Microfluidics and Nanofluidics

, Volume 16, Issue 4, pp 667–675 | Cite as

A facile on-demand droplet microfluidic system for lab-on-a-chip applications

  • Hongbo Zhou
  • Shuhuai YaoEmail author
Research Paper


We present a facile microfluidic droplet-on-demand (DOD) system in which a pulsed pressure generated by a high-speed solenoid valve is used to control the formation and movement of water-in-oil emulsion droplets in a T-junction microchannel. We investigated the working principle of the DOD system and established a scaling model for the droplet volume in terms of the amplitude and duration of the pulse and the hydraulic resistance of the injection channel. The droplet formation was characterized in three designs at various pressure pulses. The experimental results support our scaling model very well. In the DOD system we developed, nanoliter-volume droplets with a throughput of a few droplets per second were on-demand generated. Moreover, we examined the applicable scope of the DOD system. As examples of practical applications of the DOD system, we demonstrated a digital display module to show droplets formed at a prescribed time and a droplet array with a concentration gradient to show droplets formed with a precise volume. We expect our work can provide design guidelines for a robust DOD system and improve the capabilities of droplet-based microfluidics in ‘lab-on-a-chip’ systems.


Droplet on demand Pressure control Solenoid valve Microfluidics 



This work was supported by the Direct Allocation Grant (No. DAG12EG07-13) from HKUST and the National Science Foundation of China (No. 61006086). The authors would like to thank Dr. Gang Li in SIMIT for his valuable suggestion.

Supplementary material

10404_2013_1268_MOESM1_ESM.doc (1011 kb)
Online Resource 1 about the detail scaling model for the DOD process. (DOC 1,011 kb)
10404_2013_1268_MOESM2_ESM.mpg (1006 kb)
Online Resource 2: effect of the DOD system. (MPG 1,006 kb)

Online Resource 3: the digital character ‘5’ displaying process. (MPG 584 kb)

Online Resource 4: the DOD droplets trapping process. (MPG 1,352 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringThe Hong Kong University of Science and TechnologyHong KongChina
  2. 2.State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information TechnologyChinese Academy of ScienceShanghaiChina

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