A droplet actuation technique for a lab-on-chip device using partial wetting surface without external force.

Highlights • A droplet actuation and manipulation mechanism using freely available surface energy is demonstrated without using external force. • The presented technique can avoid unwanted secondary effects due to external actuation. • Droplet transportation using experimental selective painting surface is validated with lattice Boltzmann model. • A new approach to design lab-on-chip using micro-pillar surface is discussed in LBM framework. Abstract In the digital microfluidic systems, the droplet actuation and control in a chip is an important requirement. Usually, to actuate any droplet operation, an external energy needs to be supplied. We have demonstrated the utilization of the freely available surface energy by the suitable design of partial wetting surfaces to actuate and perform various droplet operations like splitting, transportation and merging. This approach would help us to realize on-chip droplet operations without applying external force like pressure, electric field or magnetic field with required control. The partial wetting surface and interface are synthesized using a selective painting technique and basic operations such as impingement, spreading and transportation are demonstrated. These dynamic properties of the droplet are modelled and analyzed with a multiphase lattice Boltzmann method (LBM). The partial wetting study of droplet dynamics is demonstrated using chemical gradient and structural gradient. The modelling results show good agreement with the experimental study, thus LBM can be used as tool for analyzing such chip designs. Further a microfluidic chip is designed with partial wetting surfaces chemically and by the placement of micro-pillars and basic on-chip operations such as splitting, merging and transportation are illustrated using LBM. [ABSTRACT FROM AUTHOR]