Near Surface Effects on the Flagellar Propulsion of Soft Robotic Sperms

Abstract

In this work, we investigate the near surface effects on the flagellar propulsion of externally actuated soft robotic sperms. A group of $\pmb{250}-\mu \text{m}$ -long robotic sperms are fabricated using electrospinning, and the influence of a nearby wall on their flagellar propulsion is modeled and characterized inside a fluidic chip with channels of varying width. Our experimental results show that the swimming speed of the robotic sperm decreases by a factor of 2 when its distance to a nearby surface is decreased by 50%, at frequency and precision angle of 5 Hz and 15°, respectively. We also show that the reduction in swimming speed can be mitigated by adapting the beating frequency and the precision angle of the tail and head of the robotic sperm during flagellar propulsion. We also demonstrate point-to-point closed-loop control along a reference trajectory inside a channel of varying width and achieve maximum steady-state error of $\pmb{5.6}\mu \text{m}$ t,