Optics and microsystems for in vitro fertilization

There are various difficulties which reduce the percentage of success in human in vitro fertilization (IVF). One of them concerns the choice of the oocyte to be fertilized. Up to now, the selection of the mature cell to be employed essentially relies on subjective criteria. Most biologists visually estimate the morphological properties of the oocyte. Some of the microsystems we are currently developing in our laboratory propose a solution to the objective determination of some of the oocyte properties, with the ulterior motive of grouping the microsystems in a single Lab-On-Chip (LOC). In this paper, we present these microsystems or techniques (microfluidic platform, microoptics, micromechanics, and image processing) together with the first experimental results that have been achieved. To conclude, we would like to say that the systems we describe are unique and that the results we have obtained up to now cannot be achieved using any other IVF techniques. Also, these studies have been approved by the local ethics committee.     

The Quantum Measurement Problem and Cluster Separability

A modified Beltrametti-Cassinelli-Lahti model of the measurement apparatus that satisfies both the probability reproducibility condition and the objectification requirement is constructed. Only measurements on microsystems are considered. The cluster separability forms a basis for the first working hypothesis: the current version of quantum mechanics leaves open what happens to systems when they change their separation status. New rules that close this gap can therefore be added without disturbing the logic of quantum mechanics. The second working hypothesis is that registration apparatuses for microsystems must contain detectors and that their readings are signals from detectors. This implies that the separation status of a microsystem changes during both preparation and registration. A new rule that specifies what happens when these changes occur and that guarantees the objectification is formulated and discussed. A part of our result has certain similarities with ‘collapse of the wave function’.     

First quantum correction to the radial distribution function and to the thermodynamic properties for a fluid of hard spheres

Dealing with the positions and orientations of the molecules as independent stochastic processes, the authors investigate the influence of translational and rotational fluctuations of anisotropically polarizable microsystems on the evolution in time of the second-order intensity correlation tensor of Rayleigh scattered light as well as on its spectral density. The notion of second-order depolarization is introduced and is shown to be a useful quantity for obtaining information on the translational and rotational motions of microsystems and their optical anisotropy.     

Slow-light enhanced light–matter interactions with applications to gas sensing

Optical gas detection in microsystems is limited by the short micron scale optical path length available. Recently, the concept of slow-light enhanced absorption has been proposed as a route to compensate for the short path length in miniaturized absorption cells. We extend the previous perturbation theory to the case of a Bragg stack infiltrated by a spectrally strongly dispersive gas with a narrow and distinct absorption peak. We show that considerable signal enhancement is possible. As an example, we consider a Bragg stack consisting of PMMA infiltrated by O₂. Here, the required optical path length for visible to near-infrared detection (760 nm) can be reduced by at least a factor of 10², making a path length of 1 mm feasible. By using this technique, optical gas detection can potentially be made possible in microsystems.     

Integrated Genetic Analysis Microsystems

The advent of integrated microsystems for genetic analysis allows the acquisition of information at unprecedented length and time scales. The convergence of molecular biology, chemistry, physics, and materials science is required for their design and construction. The utility of the microsystems originates from increased analysis speed, lower analysis cost, and higher parallelism leading to increased assay throughput. In addition, when fully integrated, this technology will enable portable systems for high-speed in situ analyses, permitting a new standard in disciplines such as clinical chemistry, personalized medicine, forensics, biowarfare detection, and epidemiology. This article presents an overview of the recent history of integrated genetic analysis microsystems with an emphasis on materials aspects, and provides a perspective on current developments and future prospects.     

Spatiotemporal resonances in mixing of open viscous fluids

In this Letter, we reveal a new dynamical phenomenon, called "spatiotemporal resonance," which is expected to take place in a broad range of viscous, periodically forced, open systems. The observation originates from a numerical and theoretical analysis of a micromixer, and is supported by preliminary experimental observations. The theoretical model nicely matches the numerical results, which again is supported by the experiment. Because of the general nature of the phenomenon, this phenomenon is not limited to microsystems. Because of the resonances, a slight tuning of the control parameters makes the mixer enhance the mixing, or suppress it, enhancing interfacial diffusion instead.     

The space-time structure of quantum systems in external fields

An axiomatic foundation of a quantum theory for microsystems in the presence of external fields is developed. The space-time structure is introduced by considering the invariance of the theory under a kinematic invariance group. The formalism is illustrated by the example of charged particles in electromagnetic potentials. In the example, gauge invariance is discussed.     

Optofluidic Microsystems for Chemical and Biological Analysis

Optofluidics - the synergistic integration of photonics and microfluidics - has recently emerged as a new analytical field that provides a number of unique characteristics for enhanced sensing performance and simplification of microsystems. In this review, we describe various optofluidic architectures developed in the past five years, emphasize the mechanisms by which optofluidics enhances bio/chemical analysis capabilities, including sensing and the precise control of biological micro/nanoparticles, and envision new research directions to which optofluidics leads.     

Manipulation with sound and vibration: A review on the micromanipulation system based on sub-MHz acoustic waves

Manipulation of micro-objects have been playing an essential role in biochemical analysis or clinical diagnostics. Among the diverse technologies for micromanipulation, acoustic methods show the advantages of good biocompatibility, wide tunability, a label-free and contactless manner. Thus, acoustic micromanipulations have been widely exploited in micro-analysis systems. In this article, we reviewed the acoustic micromanipulation systems that were actuated by sub-MHz acoustic waves. In contrast to the high-frequency range, the acoustic microsystems operating at sub-MHz acoustic frequency are more accessible, whose acoustic sources are at low cost and even available from daily acoustic devices (e.g. buzzers, speakers, piezoelectric plates). The broad availability, with the addition of the advantages of acoustic micromanipulation, make sub-MHz microsystems promising for a variety of biomedical applications. Here, we review recent progresses in sub-MHz acoustic micromanipulation technologies, focusing on their applications in biomedical fields. These technologies are based on the basic acoustic phenomenon, such as cavitation, acoustic radiation force, and acoustic streaming. And categorized by their applications, we introduce these systems for mixing, pumping and droplet generation, separation and enrichment, patterning, rotation, propulsion and actuation. The diverse applications of these systems hold great promise for a wide range of enhancements in biomedicines and attract increasing interest for further investigation.     

Calcul de la force diélectrophorétique dans les microsystèmes biologiques: comparaison du modèle dipolaire avec le modèle du tenseur de Maxwell

The validity of the point-dipole approach, frequently used to estimate the dielectrophoretic force applied upon biological cells in microsystems, is examined. Forces given by this approach are compared to those obtained by the Maxwell stress tensor method. In a needle-plate electrode configuration, results provided by finite element method show that the point-dipole approach is unsatisfactory when cells size is comparable to the gap distance. When subjected to a uniform electric field, cell-to-cell interaction is studied. In that case, the point-dipole approach is very accurate provided that cell-to-cell distance is larger than their radius R.     

Electrical manipulation of electrolytes with conductivity gradients in microsystems

Fluid manipulation is of capital importance for the lab-on-a-chip (LOC) technology. We analyse numerically the electrical manipulation of an electrolyte with a steep gradient in saline concentration by a microelectrode array subjected to ac voltages. The results show that the fluid with higher conductivity tends to replace the liquid with lower conductivity in the vicinity of the microelectrodes. This results in the deflection of the interface between the two regions with different saline concentration. We compute the induced velocity as a function of applied voltage and conductivity difference. Only several volts are required to deflect the interface in microsystems.     

利用飞秒激光直写实现透明介电材料中三维维微微纳结构的制备与集成

本文综述了利用飞秒激光三维直写技术,在玻璃和晶体等透明介电材料中实现微流体、微光学、微电子学等一系列功能性微纳结构,并进一步构筑新型微纳光子器件的原理、技术与应用。     

Multimode interference devices for focusing in microfluidic channels

Low-cost, compact, automated optical microsystems for chemical analysis, such as microflow cytometers for identification of individual biological cells, require monolithically integrated microlenses for focusing in microfluidic channels, to enable high-resolution scattering and fluorescence measurements. The multimode interference device (MMI), which makes use of self-imaging in multimode waveguides, is shown to be a simple and effective alternative to the microlens for microflow cytometry. The MMIs have been designed, realized, and integrated with microfluidic channels in a silica-based glass waveguide material system. Focal spot sizes of 2.4 μm for MMIs have been measured at foci as far as 43.7 μm into the microfluidic channel.     

Stroboscopic digital speckle pattern interferometry for vibration analysis of microsystem

In this paper, vibration measurement and analysis of microsystems, such as micro-electro-mechanical systems (MEMS) by using stroboscopic digital speckle pattern interferometry (DSPI) is presented. Because of the speckle interferometry, the technique is suited for samples which have a rough surface or whose surfaces can be sprayed into a scattering surface. A laser speckle microinterferometer incorporated with optoelectronic devices for a stroboscopic illumination and a synchronization of the signals between excitation and stroboscopic illumination is described and demonstrated. The system can measure both out-of-plane and in-plane displacement under either a static or dynamic loading. The fundamental is explained and some applications are demonstrated.     

Current-controlled curvature of coated micromirrors

Precise control of micromirror curvature is critical in many optical microsystems. Micromirrors with current-controlled curvature are demonstrated. The working principle is that resistive heating changes the temperature of the micromirrors and thermal expansion induces a controlled curvature whose magnitude is determined by coating design. For example, for wide focal-length tuning, the radius of curvature of a gold-coated mirror was tuned from 2.5 to 8.2 mm over a current-induced temperature range from 22 degrees to 72 degrees C. For fine focal-length tuning, the radius of curvature of a dielectric-coated (SiO2/Y2O3 lambda/4 pairs) mirror was tuned from -0.68 to -0.64 mm over a current-induced temperature range from 22 to 84 degrees C. These results should be readily extendable to mirror flattening or real-time adaptive shape control.     

Characteristics of combustion in a narrow channel with a temperature gradient

Characteristics of premixed combustion in a heated channel with an inner diameter smaller than the conventional quenching distance of the employed mixture were investigated experimentally, analytically, and numerically. A cylindrical quartz tube with an inner diameter of 2 mm was used as a model channel. The downstream part of the tube was heated by an external heat source, and hence the temperature gradient in the axial direction was formed in the middle of the tube. Flat and stationary conventional premixed flames were stabilized at a point in this temperature gradient. In addition to these flames, various other flames that exhibit dynamic behaviors such as cyclic oscillatory motions, and repetitive ignition and extinction were also observed experimentally. These flames with large amplitude oscillatory motion might be utilized as a heat source with high speed temporal temperature variations in microsystems for future application. Another stable flame region in extremely low speed criteria at a mixture velocity of 2–3 cm/s was also experimentally confirmed. This flame was inferred to be an example of mild combustion, and it might also be used as a mild heat source for microdevices. The overall stability criteria of these flame regimes were analytically examined, and the detailed structure of each flame on the stable solution branches was numerically examined by employing 1D computation with detailed chemistry. The two results qualitatively agreed with each other and clarified the mechanism of the present various flames and their dynamic characteristics.     

Magnetization and magnetostriction studies of TbFeCo/YFeCo multilayers

Exchange-spring TbFeCo/YFeCo multilayers exhibit interesting magnetic and magnetostrictive properties that are rather promising for application in microsystems. In this paper, we present a study of the effect of the exchange coupling on the magnetic properties of these magnetostrictive multilayers. An exchange bias phenomenon, revealed by a shift of the minor hysteresis loop along the applied field axis, is found as the result of the creation of interfacial domain walls. This effect strongly depends on the magnetic properties of the soft YFeCo layer, and becomes more pronounced at low temperatures due to the enhancement of the magnitude of the exchange coupling between the layers.     

On some peculiarities of quantum mechanics

General regularities related toLagrangian andHamiltonian equations are revealed. Probability distributions for functions ofHamiltonian random variables are considered. It is shown that all probability distributions of this kind are fully determined by the probability distributions for the random variables satisfying the corresponding Lagrangian equations. Some formulas related tocanonically conjugate operators are given. The similarity of these formulas to those related to Hamiltonian random variables is demonstrated. The quantum approach to the treatment of Hamiltonian random variables is discussed, and the origin of some peculiarities related to this approach is elucidated; it is explained, in particular, why it is impossible to form the joint probability density for canonically conjugate random variables when using this approach. The peculiarities revealed prove to be common for any objects possessing Hamiltonian random variables, irrespective of the nature of the objects, and coincide, therefore, with those in quantum mechanics. The existence of joint probability distributions for canonically conjugate random variables in the general case is demonstrated through the calculation of the corresponding joint mathematical expectations in an illustrative example. This proves, in particular, that joint probability distributions for canonically conjugate coordinates and momenta exist indeed in the case of mechanical microsystems. The results obtained prove once again that the pecularities of quantum mechanics are not related to the specificity of the measurements of physical quantities for microsystems.