Directed self-propulsion of droplets on surfaces absent of gradients for cargo transport

Ssu Wei Hu, Kuan Yu Chen, Yu Jane Sheng, Heng Kwong Tsao

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Hypothesis: Manipulating droplet transportation without inputting work is desired and important in microfluidic systems. Although the creation of wettability gradient on surfaces has been employed to achieve this goal, the transport distance is very limited, hindering its applications in long-term operations. Experiments: Here, we show that programming long-ranged transport of droplets on surfaces can be achieved by the addition of trisiloxane surfactants and the creation of deep grooves. The former provides Marangoni stress to actuate the droplet motion and also reduces the inherent contact line pinning. The latter acts as a railing to guide the motion of surfactant-laden droplets to follow various layouts with geometric features of roads. Findings: It is found that the droplets with microliters can move over 20 cm. This work-free method is applicable to a variety of substrate materials and liquids. By using self-running shuttles, a convenient platform for liquid cargos transport is developed and demonstrated. Moreover, the coalescence of cargos carried by different shuttles is accomplished in a three-branch layout, revealing new droplet microreactors.

Original languageEnglish
Pages (from-to)469-478
Number of pages10
JournalJournal of Colloid and Interface Science
StatePublished - 15 Mar 2021


  • Creation of deep grooves
  • Long-ranged transport
  • Manipulated self-propulsion of liquid droplets
  • Marangoni stress
  • Transport of liquid cargo
  • Ultra-low contact angle hysteresis


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