A new technology for studying multicomponent liquids using a quartz crystal resonator: Theory and applications

A new technique for analyzing multicomponent liquids is suggested. It is based on recording “electronic autographs” of liquids and thereby allows one to identify and certify them. In this technique, information comes from the dynamics of the complex process of self-organization in drying drops, this dynamics being dependent on the composition and structure of the liquid. Detecting the self-organization dynamics as acoustomechanical impedance, one can reveal quantitative distinctions between liquids and thereby test their quality by comparing with a reference.     

Structural evolution of drying drops of biological fluids

Qualitative analysis of experimental data for the mechanisms of structuring in drying drops of biological fluids is carried out. It is shown that the structural evolution of the drying drops is a complex process in which two stages can be separated out by convention: events occurring during evaporation of free water and structuring due to evaporation of film water. Consideration of the structural evolution of drying drops on the basis of the physical chemistry of solutions, physics of polymers, mechanics, and materials science makes it possible to explain the phenomenology of the process in terms of well-known physical phenomena.     

Thermographic investigation of the temperature field dynamics at the liquid-air interface in drops of water solutions drying on a glass substrate

The temperature field distribution at the liquid-air interface in drops of water and water solutions drying on a glass substrate is studied with thermal imaging means. It is shown that irrespective of the liquid composition, the circumferential temperature of the drops (along the boundary line) is always higher than the temperature on the top. The temperature field on the surface of the drops is nonstationary and varies chaotically during water evaporation. It is found that the dynamics of histograms for albumin-containing and albumin-free liquids differ. Mechanisms behind the origination of thermocapillary liquid flows and their directivity in the drying drops are discussed.     

Nucleation and growth on a superhydrophobic grooved surface

The growth dynamics of water drops condensed on a superhydrophobic geometrically patterned surface were studied. Drop size evolution at early and intermediate times is self-similar. Drop growth laws do not differ for a flat surface because of a reduction of both drop and substrate dimensionality. A striking observation is the instantaneous drying of the top surface of grooves at a point in time due to coalescence of the drops with a completely filled channel. At late times, only a few large drops grow connected to the channels, in a mixed Wenzel-penetration regime.     

The acoustical input impedance of excised human lungs--measurements and model matching

The input impedance at primary bronchi of excised human lungs was measured in the frequency range from 2-5000 Hz. For the measurements, a self-developed acoustic impedance head and a narrow-band measuring system with sinusoidal excitation were used. The lungs were inflated and deflated by using an arrangement called respiratory state controller. The impedances were thus measured at different states of lung inflation. An already existing mathematical model was developed further to cover not only fairly inflated lungs, but also deflated ones. The parameter sensitivity of this model is investigated. The acoustomechanical parameters of the model were fitted to match the impedances measured. It turns out that some of these parameters are hardly calculable. The values given in this paper were chosen to agree with the measurements and to be physically reasonable. Although the measurements were performed at primary bronchi, the model is able to predict also impedances at the top end of the trachea (at different respiratory states). This impedance is useful for speech signal processing applications. The model prediction of the trachea impedances agrees well with previous results of other authors.     

Drops of biological fluids drying on a hard substrate: Variation of the morphology,weight, temperature,and mechanical properties

The time variation of the morphology, weight, temperature, and integral mechanical properties of drying drops of biological fluids are investigated with the aim of defining more exactly the mechanism of self-organization in the drops. Test fluids in experiments are distilled water, a physiological salt solution (0.9 wt. % NaCl), a solution of bovine serum albumin (BSA) in water, and a solution of BSA (7 wt. %) in the physiological solution. It is shown that the variation of the weight of the drying drops can be described by a sloping straight line with two slightly nonlinear portions at the beginning and at the end of the drying process. The earlier nonlinear portion correlates with a more rapid fall of the temperature, which slows down and stabilizes as a saturated vapor layer forms over the drop. The later nonlinear portion in the drop weight variation is associated with the retardation of water diffusion through the solidifying medium. The temperature variation of the drops is a superposition of endothermal (water evaporation) and exothermal (salt crystallization and gelation) phase transitions. Phase transitions may change the mechanical properties of the drying drops, which can be detected by the method of acoustic impedancemetry.     

Beyond Millikan: the dynamics of charging events on individual colloidal particles

By measuring the stable charge on oil drops in air, Millikan demonstrated the discrete nature of electric charge. We extend his approach to the charge on solid-liquid interfaces, and focus on the dynamics of the discrete fluctuations. Our measurements are accurate and fast enough to observe changes of one elementary charge. Experiments over thousands of seconds yield information about the fast dynamics of electrochemical reactions, relevant for physicochemical and biological systems. As an example, we study (dis)charging processes on colloidal particles in a nonpolar liquid.     

Low-Coherence interference microscopy of the internal structure of crystallized blood plasma

The possibility of using full-field low-coherence (white light) interferometry to investigate the surface profile and the internal spatial structure of crystallized drops of blood plasma and to study plasma structuring in real time is discussed. The experimental microtomograms of the central and peripheral regions of a plasma drop are presented. A method is proposed to estimate the contact angle using two-dimensional cross sections of the drop optical structure in the peripheral region.     

Effect of ultrasound “Preinsonification” of solutions on the structuring of dried microdrop trails

The effect of ultrasound preinsonification of a solution on the kinetics and end result of the drying (evaporation) of a microdrop of this solution on a substrate was examined. The results of experiments with salt solution (NaCl) of albumin drops and of an alkaline (NaOH) solution drops are presented. It is shown that the morphology of the dried microdrop residual trail of a preinsonified solution differs noticeably compared to the microdrop trail of a solution that has not been insonified. The main reasons for the revealed effects are analyzed.     

Protein and salt: Spatiotemporal dynamics of events in a drying drop

Technical Physics - Self-organization processes in biological fluids and aqueous solutions containing protein and salt in various ratios have been studied in drops drying on the surface of a solid...     

A change in the physical state of a nonequilibrium blood plasma protein film in patients with carcinoma

Pronounced changes in the physical phase and in the phase transition dynamics of proteins in drying blood plasma are observed. The morphologies (topologies) of these nonequilibrium films in donors and in patients with various types of metastatic carcinoma qualitatively differ by the process of protein film self-assembly and by symmetry type. New types of defects and solid crystals appear, liquid crystals persist for a long time, etc. The microscopic examination of the drying protein plasma topology can be used for diagnosing metastatic carcinoma.     

Drying and advancing droplets of polymer solutions

In this paper, we report on the competition between evaporation and hydrodynamics for advancing drops of polymer solutions. We thus study advancing drops which are allowed to evaporate. Drying drives the accumulation of polymer at the contact line, whereas the advancing motion tends to homogenize the drop. At high velocity, we experimentally verify classical hydrodynamics predictions. At intermediate velocities, drying dominates and the contact line becomes more viscous than the bulk droplet. In the limiting case of very low velocities, the contact line can be partially pinned on the substrate because of the formation of a glassy defect at the contact line.     

Crystallization of solutes from droplets

Experiments on crystallization of thiourea and sodium hydroxide from an aqueous solution in a microvolume of 10⁻¹⁰ 1 (100 pl) are described. The phenomenon of dehydration self-organization in such tiny droplets of solution is studied for the first time. The effect of different factors, such as solution concentration, ratio of the components mentioned above in one solution, and substrate properties on the size, structure, and properties of crystals grown. Analysis of the experimental data is performed, and the drying rate of the drops and the supersaturation of the solution are estimated. Insight into the self-organization of solute molecules in a micro-or nanovolume of the drying solution may be of great applied and fundamental value, giving rise to new techniques in micro-and nanotechnology and new classes of problems in the physics of fractals and strongly nonstationary dissipative processes.     

Structure and dynamics of liquid crystalline pattern formation in drying droplets of DNA

We investigate the formation of ringlike deposits in drying drops of DNA. In analogy with the colloidal "coffee rings," DNA is transported to the perimeter by the capillary flow. At the droplet edge, however, DNA forms a lyotropic liquid crystal (LC) with concentric chain orientations to minimize the LC elastic energy. During the final stages of drying, the contact line retracts, and the radial stress causes undulations at the rim that propagate inward through the LC and form a periodic zigzag structure. We examine the phenomenon in terms of a simple model based on LC elasticity.     

Segregation in desiccated sessile drops of biological fluids

It is shown here that concurrence between advection and diffusion in a drying sessile drop of a biological fluid can produce spatial redistribution of albumen and salt. The result gives an explanation for the patterns observed in the dried drops of the biological fluids.     

透明液体中激光致声特性

研究透明液体的特性阻抗、激光声的传播距离和激光焦斑半径对激光声信号的影响.通过实验和数值计算发现,在一定范围内,随着特性阻抗的增加,声波的峰值声压、主频和声能也相应增加;随着激光声传播距离的增加,激光声的主频从急速下降变为相对稳定;在保证光击穿的条件下,选择较大的激光焦斑半径,可提高光声能量转换效率.     

Dynamics of concentrated colloidal suspensions during drying --aging,rejuvenation and overaging

We report on the slow dynamics of concentrated colloidal suspensions during drying and rewetting under conditions of reversible concentration changes without coalescence or aggregation. We used multispeckle diffusing-wave spectroscopy to monitor the slow dynamics of particles. We found that the relaxation of the suspensions exhibits successively slowing-down, acceleration and a stationary regime during drying at constant rates. Under rewetting conditions, we observed slowing-down and a stationary regime. The characteristic time of the stationary regime is inversely proportional to the rate of concentration change and identical for both drying and rewetting. We explain these regimes as aging (overaging), rejuvenation and plastic flow of the suspensions induced by a deviatoric stress (a combination of compressive and elongational stresses) which is induced by the uniaxial compressive strain generated by evaporation.Received: 3 June 2004, Published online: 3 August 2004PACS: 82.70.Dd Colloids - 47.55.Mh Flows through porous media - 42.25.Dd Wave propagation in random media     

Spreading of liquid drops on Agar gels

We study the spreading of pure water drops or water drops with surfactine (surfactant produced by bacteria Bacillus Subtilis) on gels (Agar/Water gel). We find that, surprisingly, the drops do not spread indefinitely, but remain in a state of partial wetting. Eventually the liquid diffuses into the gel on a time scale short with respect to evaporation times. The drops containing surfactant show a complex dynamics: at first the spreading velocity decreases, until the front stops and starts receding at about constant velocity. Concurrently, a second front detaches from the rim of the drop if the agar concentration is sufficiently low, and continues to move outwards.     

Chaotic dynamics of driven flux drops: a superconducting "dripping faucet"

When a current is applied to a type-I superconducting strip containing a narrow channel across its width, magnetic flux spots nucleate at the edge and are then driven along the channel by the current. These flux "drops" are reminiscent of water drops dripping from a faucet, a model system for studying low-dimensional chaos. We use a novel high-bandwidth Hall probe to detect in real time the motion of individual flux spots moving along the channel. Analyzing the time series consisting of the intervals between successive flux drops, we find distinct regions of chaotic behavior characterized by positive Lyapunov exponents, indicating that there is a close analogy between the dynamics of the superconducting and water drop systems.     

Thermodynamics predicts how confinement modifies the dynamics of the equilibrium hard-sphere fluid

We study how confining the equilibrium hard-sphere fluid to restrictive one- and two-dimensional channels with smooth interacting walls modifies its structure, dynamics, and entropy using molecular dynamics and transition-matrix Monte Carlo simulations. Although confinement strongly affects local structuring, the relationships between self-diffusivity, excess entropy, and average fluid density are, to an excellent approximation, independent of channel width or particle-wall interactions. Thus, thermodynamics can be used to predict how confinement impacts dynamics.