Mobile microrobots can be used as on-chip remote micromanipulation tools to handle with delicate samples, such as cells and biological tissues. Many efforts have been made to improve microrobots actuation, controllability and power consumption. However, stiction phenomena occurring between the robot and the substrate on which it is moving are still a big issue to deal with. In this paper stiction problem is addressed with a new approach. To begin, the two contact surfaces are coated with low friction materials combination (Al2O3/Si3N4) and different roughnesses are taken into account, in order to find the best combination and to ensure uniform sample conditions. Tests have been made, proving that a rough bottom surface of microrobots moving on a Si3N4coated glass substrate minimizes stiction events. Starting from this surface combination, the powering algorithm of the electromagnetic field generation system is changed: oscillations perpendicular to the robot trajectory are added to the standard actuation power to overcome static friction while parallel ones are used to avoid dynamic friction, which speeds down the robot. The new powering algorithm is adapted in realtime by visually tracked position and speed of the microrobots. Both the fabrication process flow and the powering algorithm are fully described in the paper. Coatings and adaptive powering show promising results: they manage to reach a long time closed-loop position control stability of the microrobot and they can be applied to find the smoothest path between two points after having performed a surface scanning to map the in-plane stiction distributions. Enhanced position control accuracy and the demonstrated robustness in long term motion control through the proposed approaches could be an important asset to on-chip microrobots toward their biological or micromanufacturing applications.

Magnetically actuated micro/nano robots are promising to various biological and medical applications in wet environments. In order to improve robots control, robustness and efficiency, real time 3D topographical surface analysis are essential especially for their navigation under such wet and confined environments. In this paper we propose a swimmer from the Roll-To-Swim (RTS) family capable of detecting and characterizing its surrounding topography thanks to 2D optical feedback. This RTS detects the presence of an obstacle (6.5μm height) by detecting perturbations in its horizontal rolling motion. Then we reconstruct a 2D probabilistic map of obstacles presence. To further characterize the surface topography, we developed the spintop motion where the RTS stands vertically while rotating. We provide a speed characterization of this new motion and demonstrate its maneuverability by integrating it in a closed-loop path following control. In this motion, RTS can be trapped by a targeted obstacle. The amount of power needed to escape is used to characterize the height of the obstacle from 2.5 to 6.5μm with a precision of 2μm. This wireless topographical detection by RTS can be a promising tool to choose an efficient pathway and an appropriate motion adapted to the surrounding environment as well as a surface topography analyzer.

In-vivo and in-vitro micro-interventions by mobile robotic agents require their precise control. Numerous types of microrobotic swimmers have been developed, assuming different peculiar applications, but often suffering from a lack of mobility and robustness, due to their unique propulsion mode. Hence we present in this paper the multi-flagella helical microswimmers that combine complementary propulsion modes for covering different motions and applications. The numerous possibilities of motions make the robots capable of moving rapidly, on long distances and in hard conditions, as expected in biological organisms. Besides, our microswimmers prove to be able of precise targeted binding, reversible binding, and multi-scale cargo transport moving particles from 5 to 30 μm large. Thus the demonstrated skillful multi-flagella helical microswimmers are very promising for future interventions in microfluidic chips and biological organisms, such as cell manipulation, precise drug delivery, minimally invasive surgery.

Helical microswimmers that are 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 with no 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 3-D steering control of the helical swimmer, a 3-D pose estimation of a helical swimmer is introduced based on the real-time visual tracking with a stereo vision system. The contribution of this paper is in two parts: The 3-D 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 with 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.

Helical microswimmers capable of propulsion at low Reynolds numbers have been proposed for many applications. However, closed-loop controlled helical swimmers are still challenging because of the limits of optical tracking, and a lack of control parameters lying on the swimming characteristics of both linear propulsion and steering. Although the linear propulsion characteristics of helical swimmers were extensively studied, the steering characteristics have not yet been clearly shown. Helical microswimmers are efficient in propulsion, whereas their high surface-to-volume ratio limits the steering performances. In this paper, we characterized both the direction and inclination steering using a real-time visual tracking of orientation. The direction steering efficiency could be increased in terms of response time with a higher inclination angle both in floating conditions and on a sticky substrate. We thus developed a 3D steering strategy by combining direction and inclination steering to improve the steering performance. We further expect that the characterization of steering performance can contribute to defining the control parameters for future closed-loop control.

Helical microstructures present large force and deformation range that give them good potential to become mechanical force sensors at the microscale. Various materials and processes have been proposed but their real life applications especially in wet/air environments are still very few mainly due to their mechanical robustness and non-linearity. Polymer microhelical devices are promising to overcome such mechanical limitations. Three-dimensional laser lithography allows fabrications of polymer helical microdevices with different geometries and designs but their mechanical properties were not yet known. In this paper, we present the fabrication of polymer microhelical device and in-situ scanning electron microscope micromanipulations for their mechanical property characterizations. It reachs mean stiffness up to 0.82 N/m (91.3 times higher than self-scrolling semiconductor microhelical devices which is 0.009 N/m), 68 % of elongation range and 12 μN of application force. The linearity of their mechanics can also reach up to 39 % of their elongation. Thanks to their excellent large range force/displacement mechanics and linearity, polymer micro-helical devices can further be applied as force sensors for measuring mechanical properties of deformable biological objects or soft nanostructures.

Magnetically actuated helical nanoswimmers have various potential applications from in-vitro microfluidics to invivo less invasive surgery. However these applications provide more challenging environments for the helical nanoswimmers by often limiting their mobility robustness from their limited motion dexterity. That is why we propose in this paper a multimodal Roll-to-Swim motion transition of helical nanoswimmers. The proposed Roll-to-Swim is a robust swimmer that takes advantages of both a rolling motion and a cork-screw swimming. The Roll-to-Swim can switch between these two different propulsion modes by simply controlling the direction and the frequency of the rotating magnetic field. We also show that the proposed system can be controlled either manually or by a closed loop with microscopic visual feedback. The system proved to be used for cargo transport of micro scale particles. Thanks to the demonstrated multi-motion transition and the cargo transport capabilities, Roll-to-Swimmers can be very promising and useful tools toward in-vitro microfluidics or in-vivo applications.

The development of new mobile microrobotic swimmers, limited by low Reynolds dynamics and stiction effects in confined environments, should aim for efficient propulsion mechanisms in wet confined environments and more elaborated manipulation strategies. We first introduced a novel type of microrobots called MagPol (Magnetic Polarizable) integrated in a microfluidic chip controlled through magnetic waves. We developed a simple method analyzing rotational dynamics to characterize swimming performances inside microfluidic environments and provide experimental criteria to improve hydrodynamics of future designs. Magpols demonstrated their in-plane mobilities, with a maximum speed up-to 566 millimeters per second (1390 body lengths per second), and the completions of sophisticated trajectory through the microchannels, forward or backward. In addition to their enhanced planar mobilities, we newly demonstrated a backward towing technique by reversing intrinsic magnetic moment.

Sensing magnetization and enhancing dynamics performances is essential while studying wireless magnetic mobile robots. Sensing physical parameters in microfluidic environments has strongly been demanded in various lab-on-a-chip applications as well. In this paper, we propose mobile microrobots as mobile sensor in microfluidics. We develop an original environment for highresolution dynamic tracking and analysis in microfluidic chips. Studying robot dynamics in low Reynolds fluid with no magnetic sensor in the chip is challenging as the field distribution and robot magnetization are not well known. Our intended goal is to explore intrinsic magneto-fluidic sensing capacities to collect more information on the microsystem. We successfully integrate our robot into a transparent microfluidic chip for high-temporal resolution analysis of dynamics. We develop an electromagnetic setup allowing complete remote control (at low power) of rotational behaviour. We study a breakdown phenomenon up to 1kHz signal and develop a scalar method analyzing rotational dynamics to enhance their sensing capacity.

Micro and nanorobots can change many aspects of medicine by enabling targeted diagnosis and therapy, and minimal invasive surgery. A helical nanobelt with a magnetic head was proposed as a microrobot driven by rotating magnetic field in prior works. Magnetically coated tails were already shown in some works. However the control of such surface magnetic tails is not clearly realized yet. This paper aims to obtain control parameters for the modeling and simulation of the influence of surface magnets onto the swimming performances. For this, we created scaled-up helical nanobelts and the experimental testbed to get the control parameters and to prepare future closed-loop control.

The 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.

In this article, a nanorobotic manipulation system under Scanning Electron Microscope (SEM) is developed for mechanical property characterization of ultra flexible nano-structures. Frequency modulated quartz tuning fork is proposed as gradient force sensing. Helical Nanobelts (HNB) were used as example to demonstrate the capabilities of the proposed system. The stiffness of HNBs were obtained in full tensile elongation experiments, ranging from 0.009 N/m at rest position to 0.297 N/m at full elongation before breaking with a resolution of 0.0031 N/m. The non-linear behavior of the HNB's measured stiffness is clearly revealed for the first time in full range. Furthermore, the stiffness could be transformed into force measurement that ranges from 14.5 nN to 2.96 μN.

This paper presents the nanorobotic resistance spot welding (RSW) of ultra-thin film three-dimensional helical nanobelts(HNBs) for the assembly of nanoelectromechanical systems (NEMS) from as-fabricated building blocks. Three-dimensional HNBs with metal pads firstly placed onto as-fabricated micropipette electrode. using nanorobotic manipulation, then fixed with RSW. The spot-welded structures are then electro-mechanically characterized to show the ohmic conductivity and electromechanical stability. Experiments show that RSW can enable stable ohmic contacts with sufficient mechanical strength for constructing devices such as force sensors from HNBs.

This paper proposes human-robot cooperative tele-micromanipulation system with novel single-master (PHANToM haptic device) multi-slaves (6 D.O.F parallel manipulator). The different kinematical configuration and the different D.O.F between the master and the slave introduces a mapping problem which can be serious for some cooperative manipulations. The position/force virtual mapping method is implemented in the single-master dual-slave tele-micromanipulation system to realize the human-robot cooperative internal force regulation while grasping task. The generated reference trajectories of both manipulators by the virtual mapping method are shared with the cooperative impedance control of multi-slaves to regulate the internal force while grasping an object. Lastly, an improved internal force regulation using the SMMS (single-master multi-slave) tele-micromanipulation system while grasping an object is verified by the pick-and-place experimental results.