Modeling and Swimming Property Characterizations of Scaled-Up Helical Microswimmers.

International audienceMicro- and nanorobots capable of controlled propulsion at low Reynolds number are foreseen to change many aspects of medicine by enabling targeted diagnosis and therapy, and minimally invasive surgery. Several kinds of helical swimmers with different heads actuated by a rotating magnetic field have been proposed in prior works. Beyond these proofs of concepts, this paper aims to obtain an optimized design of the helical swimmers adapted to low Reynolds numbers. For this, we designed an experimental setup and scaled-up helical nanobelt swimmers with different head and tail coatings to compare their rotational propulsion characteristics.We found in this paper that the head shape of a helical swimmer does not influence the shape of the rotational propulsion characteristics curve, but it influences the cutoff frequency values.The rotational propulsion characteristics of the helical swimmers with a magnetic head or a magnetic tail are different. The helical swimmers with uniformly coated magnetic tails do not show a cutoff frequency, whereas the ones with a magnetic head exhibit a saturation of frequency

The rotational propulsion characteristics of scaled-up helical microswimmers with different heads and magnetic positioning.

International audienceMicro and nanorobots capable of controlled propulsion at low Reynolds number are foreseen to change many aspects of medicine by enabling targeted diagnosis and therapy, and minimally invasive surgery. Several kinds of helical swimmers with different heads actuated by a rotating magnetic field have been proposed in prior works. Beyond these proofs of concepts, this paper aims to study behaviours of helical swimmers with different head and magnetic positing adapted to low Reynolds number liquids. For this, we designed an experimental setup and scaled-up helical nanobelt swimmers with different heads and tail coatings to compare their rotational propulsion characteristics. We found in this paper that the head shape of a helical swimmer does not influence on the shape of the rotational propulsion characteristics curve, but it influences on the values of the cut-off frequency. The rotational propulsion characteristics of helical swimmers with a magnetic head or a magnetic tail are much different. The helical swimmer with uniformly coated magnetic tail does not show a cut-off frequency but a saturation of frequency

First experiments on MagPieR: a planar wireless magnetic and piezoelectric microrobot.

International audienceThe paper documents the principle and experiments of the "2mm dash" winner at NIST IEEE Mobile Microrobotics Challenge held at ICRA2010 in Alaska [1]. Submission is made for the special session "ICRA Robot Challenge: Advancing Research Through Competitions". The new MagPieR microrobot was specially designed for breaking the speed record, providing a planar magnetic actuation with an optimised coils setup and a subsequent piezoelectric actuation for improved sliding condition. The paper describes the principle of actuation, the microrobot manufacturing flowchart and the assembly setup. Some simulations are provided with a first series of experimental data and conclusions

Using breakdown phenomenon as mobile magnetic field sensor in microfluidics

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Swimming property characterizations of Magnetic Polarizable microrobots

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On-chip mobile microrobotic transducer for high-temporal resolution sensing using dynamics analysis

International audienceUntethered mobile magnetic microrobots in liquids are under increased investigation with the intended goal to obtain in vivo transducing applications, mostly for micromanipulation or cargo transport. Using them as wireless sensors is less common though it offers a highly controllable and mobile sensing capability at micrometric scale with the capability to provide information about their dynamics and interaction with their environment. Here a system is proposed which is fully controllable by calibrated external magnetic fields and high temporal resolution (>5000FPS) visual feedback. With the targeted applications being in microscale fluids, a mobile magnetic microrobot is integrated into an optically transparent microfluidic chip which demonstrates sensing capabilities. In these experiments, physical sensing is quantified through microrobot dynamics analysis of its elementary planar motions (rotary and translational) and these results are related to local viscosity of fluid and friction from the interfaces. These results also allow for the characterization of swimming performances, magnetization and thus help to improve the design of the microrobotic system. An analysis of transition dynamics also provides complementary measurement on the microrobot hydrodynamics and the interaction with its substrate. The proposed on-chip mobile microrobotic system provides an advantageous testing platform to further investigate the visual servo automation control towards their in-vitro or in-vivo applications

The Rotation of Microrobot Simplifies 3D Control Inside Microchannels

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On-chip multimodal vortex trap micro-manipulator with multistage bi-helical micro-swimmer

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Visual Servo Control for Path Following Based on 3D Steering of Scaled-up Helical Microwimmers.

International audienceHelical microswimmers capable of propulsion at low Reynolds numbers have great potential for numerous applications.Several kinds of artificial magnetic actuated helical microswimmers have been designed by researchers. However, they are primarily open-loop controlled. This paper aims to investigate methods of closed-loop control of a magnetic actuated helical swimmer at low Reynolds number by using visual feedback.For many in-vitro applications, helical swimmers should pass through a defined path, for example along channels, without any prerequisite on the velocity profile along the path. Therefore, the main objective of this paper is to achieve a velocity-independent planar path following task. Since the planar path following is based on 3D steering control of the helical swimmer, a 3D pose estimation of a helical swimmer is introduced based on the realtime visual tracking with a stereo vision system. The contribution of this paper is in two parts: the 3D steering of a helical swimmer is demonstrated by visual servo control; and the path following of a straight line with visual servo control is achieved, then compared to open-loop control. We further expect that with this visual servo control method, the helical swimmers will be able to follow reference paths at the microscale