Three-Dimensional Droplet Manipulation Using a Pnipam-Coated Mechanical Gripper

Abstract

The three-dimensional manipulation of droplets has crucial applications in nanomaterials synthesis, lab-on-a-chip, medical inspection, etc. Unfortunately, few investigations have been conducted on the three-dimensional manipulation of droplets. In this work, a thermoresponsive PNIPAM film was created by electrospinning. By bonding this film to a homemade mechanical gripper, the droplet was manipulated three-dimensionally. The experimental results demonstrated that the mechanical gripper could easily grasp droplets of different volumes at a low temperature (20 ℃ e.g.) and transport them to other three-dimensional target locations. After that, the mechanical gripper was heated to a specific temperature (38 ℃), allowing the droplet to slide off when the mechanical gripper was opened. Further experimental findings indicated that the aforementioned droplet manipulation did not produce droplet loss or evident damage to the droplet interior. Moreover, three-dimensional droplet manipulation was achieved due to the alteration in hysteresis force generated by the hydrophilic property of the PNIPAM surface at different temperatures. The findings of this work would support the automated procedure of droplet manipulation and the continuing development of related fields.

Keywords: Lossless droplet manipulation, Low damage droplet manipulation, Three-dimensional droplet manipulation, Mechanical gripper, PNIPAM.