The discovery that motor proteins not only translate their filaments, but in many cases also rotate them, is rather old, but so far the experimental results were in apparent contradiction with regard to the twirling handedness and an explanation of the twirling mechanism of was lacking. Our model qualitatively and quantitatively explains the emergence of left-handed twirling. As the pitch depends strongly on the ATP concentration, the model also predicts the possibility of a cross-over from left- to right-handed motion, thus providing a reconciliation of previously contradicting results.
COBISS.SI-ID: 22803751
Despite several previously published proposals for artificial cilia, we were the first to successfully produce a working prototype and to prove and measure the pumping of fluid. The measured flow shows a very good agreement with the prediction of the numerical model. We have published the results in the renowned journal PNAS. Nature Physics reported about them in an editorial (news&views). Besides that, we have published a comment on the subject of magnetic swimmers in Physical Review Letters.
COBISS.SI-ID: 23251239
Many biological processes work with an extremely high energetic efficiency, but at first glance this does not hold for ciliary propulsion, reaching about 1%. We have re-examined the problem at the level of a single cilium and an infinite ciliated surface. We numerically determined the optimal shape of the ciliary beating pattern and showed that the optimal collective stroke is remarkably similar to what is observed in microorganisms. For Paramecium we showed that the experimentally measured hydrodynamic efficiency reaches about 50% of the theoretically possible optimum.
COBISS.SI-ID: 25073447
Raziskali smo izkoristek plavalcev, ki se poganjajo z ustvarjanjem tekočinskega toka ob površini in ki delujejo pri nizkem Reynoldsovem številu. Primer takih plavalcev so enoceličarji, ki jih poganjajo migetalke, pa tudi umetni mikroskopski kemoforetski plavalci. Izkaže se, da je energijski strošek površinskega pogona proporcionalen kvadratu hitrosti ob površini, integriranem po celotni površini plavalca. Poiskali smo torej oblike plavalcev ter porazdelitev hitrosti tekočine ob njih na način, da bodo z minimalno disipacijo dosegli določeno hitrost plavanja pri danem volumnu. Rezultat je presenetljiv, saj odvisno od ukrivljenosti površine, ki jo dovolimo, optimalna oblika plavalca vključuje izrastke vzdolž simetrijske osi. Izračunane oblike optimalnih plavalcev pa kažejo tudi precejšnjo podobnost z različnimi oblikami mikroorganizmov, ki jih najdemo v naravi.
COBISS.SI-ID: 26105639
In this article we describe a multipole expansion of the fluid velocity field around a beating cilium. For reasons of symmetry, a small number of terms is often sufficient. The shape of the velocity field therefore becomes independent of the details of the ciliary beating pattern in the far-field approximation. The formalism developed in this publication is applicable to natural, as well as artificial (biomimetic) cilia.
COBISS.SI-ID: 26016551