Programmable metachronal motion of closely packed magnetic artificial cilia.

Despite recent advances in artificial cilia technologies, the application of metachrony, which is the collective wavelike motion by cilia moving out-of-phase, has been severely hampered by difficulties in controlling closely packed artificial cilia at micrometer length scales. Moreover, there has been no direct experimental proof yet that a metachronal wave in combination with fully reciprocal ciliary motion can generate significant microfluidic flow on a micrometer scale as theoretically predicted. In this study, using an in-house developed precise micro-molding technique, we have fabricated closely packed magnetic artificial cilia that can generate well-controlled metachronal waves.

Measuring the average cell size and width of its distribution in cellular tissues using Fourier transform.

We present an in-depth investigation of a fully automated Fourier-based analysis to determine the cell size and the width of its distribution in 3D biological tissues. The results are thoroughly tested using generated images, and we offer valuable criteria for image acquisition settings to optimize accuracy. We demonstrate that the most important parameter is the number of cells in the field of view, and we show that accurate measurements can already be made on volume only containing [Formula: see text] cells.

MorphoScript: a dedicated analysis to assess the morphology and contractile structures of cardiomyocytes derived from stem cells.

Motivation: Cardiomyocytes derived from stem cells are closely followed, notably since the discovery in 2007 of human induced pluripotent stem cells (hiPSC). Cardiomyocytes (hiPSC-CM) derived from hiPSC are indeed more and more used to study specific cardiac diseases as well as for developing novel applications such as drug safety experiments. Robust dedicated tools to characterize hiPSC-CM are now required.

Forces encountered by a sphere during impact into sand.

We describe direct measurements of the acceleration of an object impacting on a loosely packed granular bed under various pressures, using an instrumented sphere. The sphere acts as a noninvasive probe that measures and continuously transmits the acceleration as it penetrates into the sand, using a radio signal. The time-resolved acceleration of the sphere reveals the detailed dynamics during the impact that cannot be resolved from the position information alone.

Collapsing granular beds: the role of interstitial air.

A prefluidized sand bed consisting of fine particles compactifies when it is subjected to a shock. We observe that the response depends on both the shock strength and the ambient pressure, where, counterintuitively, at high ambient pressure the compaction is larger, which we connect to a decrease of the static friction inside the bed. We find that the interstitial air is trapped inside the bed during and long after compaction.

Cell shape dynamics: from waves to migration.

We observe and quantify wave-like characteristics of amoeboid migration. Using the amoeba Dictyostelium discoideum, a model system for the study of chemotaxis, we demonstrate that cell shape changes in a wave-like manner. Cells have regions of high boundary curvature that propagate from the leading edge toward the back, usually along alternating sides of the cell.