Swimming force characterizations of multistaged bi-helical microswimmer and 3D vortex trap manipulation

Abstract

Vortex trap manipulation of microscopic objects in three-dimensions by helical microswimmers has a great potential towards non-contact biological cell manipulation or microassembly. However, in the current state-of-the-art, it has been limited in 2D manipulation due to the conflicting characteristics of optimizing the trapping force and propulsion force. In this paper, we propose a new design of the helical microswimmers enabling purely non-contact, selective and 3D vortex trap micromanipulation. The proposed helical microswimmers are fabricated by 3D nanoprinting technology based on two-photon laser absorption. The vertically standing helical mirostructures on top of the supporting micropillars allows uniform coating of ferromagnetic metal layer with minimum shadow area during metallization by sputtering. Furthermore this reduces the risk of damaging or losing materials during micromanipulation process for releasing them after fabrication which allows propulsion force characterizations and optimization. We characterized to reveal their propulsion force and this proved the propulsion force was recovered back to even higher than the single helical microswimmers. We consider that the proposed helical microswimmers with 3D manipulation could have a great impact to non-contact biological cell manipulation.