Synchronization of Coupled Boolean Phase Oscillators

We design, characterize, and couple Boolean phase oscillators that include state-dependent feedback delay. The state-dependent delay allows us to realize an adjustable coupling strength, even though only Boolean signals are exchanged. Specifically, increasing the coupling strength via the range of state-dependent delay leads to larger locking ranges in uni- and bi-directional coupling of oscillators in both experiment and numerical simulation with a piecewise switching model. In the unidirectional coupling scheme, we unveil asymmetric triangular-shaped locking regions (Arnold tongues) that appear at multiples of the natural frequency of the oscillators. This extends observations of a single locking region reported in previous studies. In the bidirectional coupling scheme, we map out a symmetric locking region in the parameter space of frequency detuning and coupling strength. Because of large scalability of our setup, our observations constitute a first step towards realizing large-scale networks of coupled oscillators to address fundamental questions on the dynamical properties of networks in a new experimental setting.Comment: 8 pages, 8 figure

Small-Signal Amplification of Period-Doubling Bifurcations in Smooth Iterated Maps

Various authors have shown that, near the onset of a period-doubling bifurcation, small perturbations in the control parameter may result in much larger disturbances in the response of the dynamical system. Such amplification of small signals can be measured by a gain defined as the magnitude of the disturbance in the response divided by the perturbation amplitude. In this paper, the perturbed response is studied using normal forms based on the most general assumptions of iterated maps. Such an analysis provides a theoretical footing for previous experimental and numerical observations, such as the failure of linear analysis and the saturation of the gain. Qualitative as well as quantitative features of the gain are exhibited using selected models of cardiac dynamics.Comment: 12 pages, 7 figure

Robotic Micro-assembly of microparts using a piezogripper.

International audienceThis paper deals with robotic micro-assembly of silicon micro-objects whose sizes are tens of micrometers. This production means is one of a more promising approach to realize 3D and/or hybrid microsystems. Current works in robotic micro-assembly are focused on the assembly of microobjects on a large substrate. We are focusing in the study of micro-parts assembly to build microscopic subsystems usable in larger products. This approach requires specific functionalities like a ‘micro-vise' required to block the first object during assembly. Original strategies are proposed and applied on an experimental robotic structure composed of micropositionning stages, videomicroscopes, piezogripper, and silicon endeffectors. Some experimental teleoperated micro-assemblies has validated the proposed methods and the reliability of the principles. Future works will be focused on micro-assembly automation

Ultra-Fast Physical Generation of Random Numbers Using Hybrid Boolean Networks

We describe a high-speed physical random number generator based on a hybrid Boolean network with autonomous and clocked logic gates, realized on a reconfigurable chip. The autonomous logic gates are arranged in a bidirectional ring topology and generate broadband chaos. The clocked logic gates receive input from the autonomous logic gates so that random numbers are generated physically that pass standard randomness tests without further post-processing. The large number of logic gates on reconfigurable chips allows for parallel generation of random numbers, as demonstrated by our implementation of 128 physical random number generators that achieve a real-time bit rate of 12.8 Gbit/s.Comment: 5 pages, 3 figures, accepted in Phys. Rev. E as a Rapid Communicatio

Spectral-phase interferometry for direct electric-field reconstruction applied to seeded extreme-ultraviolet free-electron lasers

We present a setup for complete characterization of femtosecond pulses generated by seeded free-electron lasers (FEL's) in the extreme-ultraviolet spectral region. Two delayed and spectrally shifted replicas are produced and used for spectral phase interferometry for direct electric field reconstruction (SPIDER). We show that it can be achieved by a simple arrangement of the seed laser. Temporal shape and phase obtained in FEL simulations are well retrieved by the SPIDER reconstruction, allowing to foresee the implementation of this diagnostic on existing and future sources. This will be a significant step towards an experimental investigation and control of FEL spectral phase

Micro-manipulation of silicate micro-sized particles for biological applications.

International audienceThere are great challenges in biological research to study mechanical or chemical interactions between biological objects and artificial parts, to analyse the biocompatibility of artificial materials and/or to increase knowledge about biological cells. Some interaction studies between cells and artificial objects require to positioning very small objects whose typical size is comparable with cell's size (typically 5-20 micrometers). This paper presents design, building and testing of a new micro-manipulation station able to grasp, transport and release ten micrometers objects. Devoted to an existing piezoelectric microgripper, innovative end-effectors in silicon have been designed after several mechanical studies. They have been built with microfabrication processes (DRIE1) in SOI 2 wafers. For the application, the positioning of silicate crystals which contain iron close to E-Coli bacteria, new end-effectors were glued on the piezoelectric microgripper. Mounted on a three axis micropositioning stage under a videomicroscope, this innovative microgripper is able to grasp a silicate crystal of 15 micrometers in the aire and release it in the bacteria liquid medium

A novel integrated micro-force measurement system for plane-plane contact research.

International audienceThe evaluation of plane-plane contact force has become a big issue in micro/nano research, for example in micro-assembly. However with the lack of effective experimental equipments, the research on plane-plane contact has been limited to theoretical formulations or virtual simulation. In this paper, a micro-force sensor and precision parallel robot integrated system is proposed for the micro-force measurement of plane-plane contact. In the proposed system, the two objects are fixed on the parallel robot end-platform and the micro-force sensor probe tip, respectively, and the high precision robot system is employed to provide six degree-of-freedoms motion between both objects. So it is convenient for the micro-force measurement between the planar objects with different orientations. As a significant application, the proposed system is utilized for measurements of pull-off force between planar objects, in which the validation of the system is demonstrated in practice. The proposed micro-force measurement system is generic, which can be extended to a variety of micro-force measurements in plane-plane contact