Bio-hybrid micro-swimmers propelled by flagella isolated from C. reinhardtii

Abstract

Bio-hybrid micro-swimmers, composed of biological entities integrated with synthetic constructs, actively transport cargo by converting chemical energy into mechanical work. Here, using isolated and demembranated flagella from green algae \textit{Chlamydomonas...

Flagellum-driven cargoes: Influence of cargo size and the flagellum-cargo attachment geometry

“…The static component of the axonemal curvature leads to a curved swimming trajectory of the micro-swimmer (see Fig 1D) [18][19][20][21]. In comparison, when the static curvature is strongly reduced, a micro-swimmer swims along an essentially straight path [14,[22][23][24]. Importantly, the static curvature of axonemes is highly dependent on the calcium concentration.…”

“…Autonomous flagella-driven motility of various biological species, mainly E. coli and sperm, are utilized as bio-actuators to provide an efficient cargo transport [7][8][9][10][11][12][13]. More recently, in the experiments by Ahmad et al [14], axonemally-driven cargoes are fabricated by integration of isolated and demembranated flagella from C. reinhardtii (known as axonemes) with micron-sized beads (see Fig 1 and S1-S2 Videos). These ATPreactivated axonemes, with a length of approximately 10 μm, beat with an ATP-dependent frequency [15][16][17] and have an asymmetric waveform that can best be described as a base-to-tip traveling wave component superimposed on a circular arc with mean curvature of about -0.2 μm −1 .…”

“…Importantly, the static curvature of axonemes is highly dependent on the calcium concentration. Namely, increasing the calcium concentration beyond 0.05 mM reduces the static curvature of axonemes by one order of magnitude [14,23,24], thereby inducing a transition from circular to straight swimming trajectories of axonemally-propelled beads. In addition to the flagellar waveform, the axoneme-bead attachment geometry also plays a critical role in the cargo propulsion speed.…”

“…As emphasized in Ref. [14], axonemes can attach to the bead symmetrically, with their tangent vector at the contact point passing through the bead center, or asymmetrically. Due to the limitations of 2D microscopy in Ref.…”

“…Due to the limitations of 2D microscopy in Ref. [14], it was not experimentally possible to distinguish between these two types of bead-axoneme attachment and 3D microscopy techniques [25] are required to quantify the effect of attachment geometry on the propulsion speed. This symmetric versus asymmetric attachment has consequences on cargo propulsion dynamics and investigating this effect theoretically and numerically is the main focus of the present work.…”