Stick-slip squirmers: slip asymmetry can qualitatively change self-swimming characteristics of squirmers

A slip asymmetry can break the fore–aft symmetry of local hydrodynamic force distribution on surface an otherwise no-slip or uniform-slip particle. Here, we use Lorentz reciprocal theorem to demonstrate that such asymmetry, even in a fractional amount, qualitatively alter swimming characteristics self-propelled spherical squirmer, markedly different from those squirmers. Unlike usual tangential squirming by thrust-providing B 1 mode and type-determining 2 mode, discover two unique features for stick-slip squirmer. First, squirmer acquire velocity U without but simply symmetric extensile/contractile which is able reverse direction Second, stresslet $\boldsymbol{\mathsf{S}}$ also be induced unidirectional capable inverting squirmer's extensile type contractile vice versa change puller pusher manner. We further show modes reinforce compete with each other enhance diminish due interplays between asymmetric forces stick faces. phase diagram established categorize variety newly emerging states, as enhanced/degraded puller/pusher backward puller/pusher, depending relative strength β = / , polarity degree disparity. As result cooperative competitive natures, swim more less efficiently than ones. These distinctive arising disparity not only made geometrically tuneable steering motion provide new means making efficient artificial microswimmers using amphiphilic Janus particles.