共查询到20条相似文献,搜索用时 31 毫秒
1.
A. PatrascioiuM. Duocastella J.M. Fernández-PradasJ.L. Morenza P. Serra 《Applied Surface Science》2011,257(12):5190-5194
Laser-induced forward transfer (LIFT) is a high resolution microprinting technique in which small amounts of material are transferred from a previously prepared donor thin film to a receptor substrate. The application of LIFT to liquid donor films allows depositing complex and fragile materials in solution or suspension without compromising the integrity of the deposited material. However, the main drawback of LIFT is the preparation of the donor material in thin film form, being difficult to obtain reproducible thin films with thickness uniformity and good stability.In this work we present a laser microprinting technique that is able to overcome the drawbacks associated with the preparation of the liquid film, allowing the deposition of well-defined uniform microdroplets with high reproducibility and resolution. The droplet transfer mechanism relies on the highly localized absorption of strongly focused femtosecond laser pulses underneath the free surface of the liquid contained in a reservoir.An analysis of the influence of laser pulse energy on the morphology of the printed droplets is carried out, revealing a clear correlation between the printed droplet dimensions and the laser pulse energy. Such correlation is interpreted in terms of the dynamics of the liquid displaced by a laser-generated cavitation bubble close to the free surface of the liquid. Finally, the feasibility of the technique for the production of miniaturized biosensors is tested. 相似文献
2.
M. Duocastella A. Patrascioiu J. M. Fernández-Pradas J. L. Morenza P. Serra 《Applied Physics A: Materials Science & Processing》2012,109(1):5-14
The analysis of the morphology of droplets printed through laser-induced forward transfer (LIFT) of liquid films shows that: (i)?the droplet volume is linearly related with the energy of the laser pulse that originated it, (ii)?the liquid ejection process is activated by an energy density threshold?F 0, and (iii)?the droplet volume can be correlated with a dimensional parameter of the laser beam through an oversimple model that states that the amount of printed liquid equals the liquid contained in the cylindrical portion of an irradiated film whose base corresponds to the cross-sectional area of the beam with energy density higher than?F 0. Although these issues seem to describe correctly the LIFT process, some problematic instances arise from them. Thus, the linear relation between droplet volume and laser pulse energy seems to be inconsistent with the existence of the threshold?F 0. On the other hand, the compatibility between the model and the aforementioned linear relation requires to be explained. Finally, the model is based on the idea that transfer takes place in a way analogous to the LIFT of solid films, but time-resolved imaging studies have demonstrated that liquid ejection follows a dynamics which seems quite unsuited with that idea. In this work previous results are re-analyzed and new experiments are performed in an attempt to clarify these questions. It is then shown that the inconsistencies pointed out are only apparent, and that the validity of the model is limited to irradiation conditions where the beam dimensions are significantly larger than the thickness of the liquid film. Furthermore, an explanation is provided for the dependence of the success and failure of the model on those irradiation conditions in terms of the diverse liquid ejection dynamics taking place. 相似文献
3.
Jet formation in the laser forward transfer of liquids 总被引:1,自引:0,他引:1
M. Duocastella J. M. Fernández-Pradas P. Serra J. L. Morenza 《Applied Physics A: Materials Science & Processing》2008,93(2):453-456
The dynamics of the laser-induced forward transfer (LIFT) of an aqueous solution is investigated through time-resolved imaging.
The experiment is carried out at conditions under which droplets are deposited on a receptor substrate. The obtained images
reveal that after an initial balloon-like stage, a uniform jet with a very long length and high aspect ratio is formed, which
advances at constant speed until it finally becomes unstable and breaks into several droplets. This dynamics demonstrates
that the deposition process of well-defined droplets through LIFT results from the contact of the liquid jet with the receptor
substrate, and not from a flying droplet. 相似文献
4.
Randall T. Imaoka William A. Sirignano 《Proceedings of the Combustion Institute》2005,30(2):1981-1989
The quasi-steady vaporization and combustion of multiple-droplet arrays is studied numerically. Utilizing the Shvab–Zeldovich formulation, a transformation of the governing equations to a three-dimensional Laplace’s equation is performed, and the solution to Laplace’s equation is obtained numerically to find the effects of droplet interactions in symmetric, multiple-droplet arrays. Vaporization rates, flame surface shapes, and flame locations are found for different droplet array configurations and fuels. The number of droplets, the droplet arrangement within the arrays, and the droplet spacing within the arrays are varied to determine the effects of these parameters. Computations are performed for uniformly spaced three-dimensional arrays of up to 216 droplets, with center-to-center spacing ranging from 3 to 25 droplet radii. As a result of the droplet interactions, the number of droplets and relative droplet spacing significantly affect the vaporization rate of individual droplets within the array, and consequently the flame shape and location. For small droplet spacing, the individual droplet vaporization rate decreases below that obtained for an isolated droplet by several orders of magnitude. A similarity parameter which correlates vaporization rates with array size and spacing is identified. Individual droplet flames, internal group combustion, and external group combustion can be observed depending on the droplet geometry and boundary conditions. 相似文献
5.
6.
The transient convective burning of n-octane droplets interacting within single-layer arrays in a hot gas flow perpendicular to the layer is studied numerically, with considerations of droplet surface regression, deceleration due to the drag of the droplets, internal liquid motion, variable properties, non-uniform liquid temperature and surface tension. Infinite periodic arrays, semi-infinite periodic arrays with one row of droplets (linear array) or two rows of droplets, and finite arrays with nine droplets with centers in a plane are investigated. All arrays are aligned orthogonal to the free stream direction. This paper compares the behavior of semi-infinite periodic arrays and finite arrays with the behavior of previously studied infinite periodic arrays. Furthermore, it identifies the critical values of the initial Damköhler number for bifurcations in flame behavior at various initial droplet spacing for all these arrays. The initial flame shape is either an envelope flame or a wake flame as determined by the initial Damköhler number, the array configuration and the initial droplet spacing. The critical initial Damköhler number separating initial wake flames from initial envelope flames decreases with increasing interaction amongst droplets at intermediate droplet spacing (when the number of rows in the array increases or the initial droplet spacing decreases for a specific number of rows in the array). In the transient process, an initial wake flame has a tendency to develop from a wake flame to an envelope flame, with the moment of wake-to-envelope transition advanced for the increasing interaction amongst droplets at intermediate droplet spacing. For the array with nine droplets with centers in a plane, the droplets at different types of positions have different critical initial Damköhler number and different wake-to-envelope transition time for initial wake flame. 相似文献
7.
M. DuocastellaA. Patrascioiu V. Dinca J.M. Fernández-PradasJ.L. Morenza P. Serra 《Applied Surface Science》2011,257(12):5255-5258
Laser-induced forward transfer (LIFT) is a direct-writing technique which can be used to successfully print various complex and sensitive materials with a high degree of spatial resolution. However, the optimization of its performances requires a deep understanding of the LIFT dynamics. Such understanding should allow correlating the phenomena underlying the liquid transfer process with the morphology of the obtained deposits. To this end, in this work it is presented a study related to two aspects: first, the correlation of the morphological characteristics of the transferred droplets with the variation of the film thickness combined with laser fluence; and second, a correlation of the dependences observed with the dynamics of the transfer process. The work is focused on the understanding of the observed dependences for which the information provided by time-resolved analysis on liquid transfer dynamics has proved to be crucial. 相似文献
8.
M. Duocastella M. Colina J.M. Fernández-Pradas P. Serra J.L. Morenza 《Applied Surface Science》2007,253(19):7855-7859
Laser-induced forward transfer (LIFT) is a direct-writing technique that allows printing patterns of diverse materials with a high degree of spatial resolution. In conventional LIFT a small fraction of a solid thin film is vaporized by means of a laser pulse focused on the film through its transparent holder, and the resulting material recondenses on the receptor substrate. It has been recently shown that LIFT can also be used to transfer materials from liquid films. This widened its field of application to biosensors manufacturing, where small amounts of biomolecules-containing solutions have to be deposited with high precision on the sensing elements. However, there is still little knowledge on the physical processes and parameters determining the characteristics of the transfers.In this work, different parameters and their effects upon the transferred material were studied. It was found that the deposited material corresponds to liquid droplets which volume depends linearly on the laser pulse energy, and that a minimum threshold energy has to be overcome for transfer to occur. The liquid film thickness was varied and droplets as small as 10 μm in diameter were obtained. Finally, the effects of the variation of the film to substrate distance were also studied and it was found that there exists a wide range of distances where the morphology of the transferred droplets is independent of this parameter, what provides LIFT with a high degree of flexibility. 相似文献
9.
10.
P. V. Dolganov V. K. Dolganov P. Cluzeau 《Journal of Experimental and Theoretical Physics》2009,109(1):169-175
Cholesteric droplets in ferroelectric free-standing films with tunable anchoring on the droplet boundary are investigated.
A droplet and satellite topological defect(s) form a topological dipole. We obtained droplets with different angles α between
two radial lines from the droplet center to −1/2 topological defects. Droplets with parallel dipoles form linear chains in
which the interparticle distances decrease with increasing the defect angle α. For the first time, the dependence of the interparticle
distance on the angle between topological defects was measured. We can adjust the magnitude and orientation of topological
dipoles formed by the droplets. For the first time, the droplets with antiparallel topological dipoles were prepared in a
smectic film. Interaction of the droplets with parallel and antiparallel dipoles differs drastically. Formation of antiparallel
dipoles leads to a decomposition of the droplet pairs and chains of droplets. Our observations may be used to change the magnitude,
anisotropy of the interparticle interaction, and structures of inclusions in liquid crystal media.
The article is published in the original. 相似文献
11.
Hiroshi Nomura Hiroshi Iwasaki Yusuke Suganuma Masato Mikami Masao Kikuchi 《Proceedings of the Combustion Institute》2011,33(2):2013-2020
Combustion experiments of fuel droplet array in fuel vapor-air mixture were performed at microgravities to investigate growth mechanism of group combustion of fuel droplets. A 10-droplet array was inserted into the test section filled with a saturated fuel vapor-air mixture as a simple model of prevaporized sprays. Gas equivalence ratio of the fuel vapor-air mixture was regulated by the test section temperature. n-Decane droplets of 0.8 mm in the initial diameter were suspended at the crossing points of 10 sets of X-shaped suspenders. The first droplet was ignited by a hot wire to initiate flame spread along a fuel droplet array. Flame spread speed was obtained from the history of the leading edge position of a spreading flame. Effects of droplet spacing and gas equivalence ratio on the flame spreading behavior and the flame spread speed were examined. The droplet spacing and the gas equivalence ratio were varied from 1.6 to 10.2 mm and from 0.2 to 0.7, respectively. The gas equivalence ratio has little effect on the relationship between the flame spreading behavior and the droplet spacing. The flame spread speed increases as the increase in the gas equivalence ratio at all droplet spacings. The influence of the gas equivalence ratio on the flame spread speed becomes strong as the increase in the droplet spacings. The flame spread speed increases as the increase in the droplet spacing, and then decreases. The maximum flame spread speed appears in the range from 2.4 to 3 mm at all gas equivalence ratios. 相似文献
12.
13.
Quan-Yuan Zeng 《中国物理 B》2022,31(4):46801-046801
The impact of droplets on the liquid film is widely involved in industrial and agricultural fields. In recent years, plenty of works are limited to dry walls or stationary liquid films, and the research of multi-droplet impact dynamic films is not sufficient. Based on this, this paper employs a coupled level set and volume of fluid (CLSVOF) method to numerically simulate two-droplet impingement on a dynamic liquid film. In our work, the dynamic film thickness, horizontal central distance between the droplets, droplets' initial impact speed, and simultaneously the flow velocity of the moving film are analyzed. The evolution phenomenon and mechanism caused by the collision are analyzed in detail. We find that within a certain period of time, the droplet spacing does not affect the peripheral crown height; when the droplet spacing decreases or the initial impact velocity increases, the height of the peripheral crown increases at the beginning, and then, because the crown splashed under Rayleigh-Plateau instability, this results in the reduction of the crown height. At the same time, it is found that when the initial impact velocity increases, the angle between the upstream peripheral jet and the dynamic film becomes larger. The more obvious the horizontal movement characteristics, the more restrained the crown height; the spread length increases with the increase of the dynamic film speed, droplet spacing and the initial impact velocity. When the liquid film is thicker, more fluid enters the crown, due to the crown being unstable, the surface tension is not enough to overcome the weight of the rim at the end of the crown, resulting in droplets falling off. 相似文献
14.
Keiji Kataoka 《Optical Review》2008,15(4):196-203
In the slant scanning method of multiple beams a misalignment of the slant angle causes a beam spacing error and pitch irregularities
of scan lines called “banding”. This paper evaluates the pitch irregularities and tries to clarify the allowable beam spacing
error. The following results are obtained: (1) The maximum spacing error of print lines is proportional to m/(dpi), where m is the number of multiple beams and dpi print dot density. (2) The noticeable limit of periodic variations of print density
at low spatial frequency was presumed to be a visibility between 1 and 2% in experiments. (3) The allowable beam spacing error
was calculated introducing the human eye spatial frequency response. (4) The banding simulation experiments by laser recording
on the photographic paper on the XY stage showed good coincidence with the theoretical evaluations. 相似文献
15.
Shunsuke Suzuki Akira Nakajima Kouichi Tanaka Ayako Hashimoto Yoshikazu Kameshima Kiyoshi Okada 《Applied Surface Science》2008,254(6):1797-1805
We prepared line-patterned hydrophobic surfaces using fluoroalkylsilane (FAS) and octadecyltrimethoxysilane (ODS) then investigated the effect of line direction on sliding behavior of water droplets by direct observation of the actual droplet motion during sliding. Water droplets slide down with a periodic large deformation of the contact line and sliding velocity fluctuation that occurred when they crossed over the 500-μm ODS line regions in FAS regions on a Si surface tilted at 35°. These behaviors are less marked for motion on a 100-μm line surface, or on lines oriented parallel to the slope direction. Smaller droplets slide down with greater displacement in the line direction on 500-μm line patterning when the lines were rotated at 13° in-plane for the slope direction. This sliding behavior depended on the droplet size and rotation angle, and is accountable by the balance between gravitational and retentive forces. 相似文献
16.
The production of small fluid droplets relies on an instability of solutions to the Young-Laplace equation. We ask whether smaller droplets can be produced by changing the shape of the nozzle. At a given critical pressure, the circular nozzle actually produces the largest droplet. The droplet volume can be decreased by up to 18% using a triangular nozzle with stretched corners. 相似文献
17.
Droplet wetting on two parallel filaments may assume a barrel-shaped morphology or a liquid bridge depending upon the filament diameter and spacing, droplet volume, and contact angle. This paper is aimed to examine the dependency of droplet wetting length upon the above parameters. In the process, morphology of either a barrel-shaped droplet or a liquid bridge sitting on two parallel filaments is determined numerically by using surface finite element method (SFEM). Variation of wetting length with contact angle is examined at varying droplet volume, filament spacing, and droplet morphology. It is found that the droplet wetting length increases with decreasing filament spacing ratio as well as contact angle while it also increases with the growth of droplet volume. The dependency of wetting length upon contact angle behaves sensitive to filament spacing in the case of stable liquid bridges, while it exhibits nearly constant sensitivity to the contact angle in the case of barrel-shaped droplets. The quantitative relations yielded in this study can be considered as characteristic curves applicable for a variety of droplet-on-filament systems, particularly useful to wetting property characterization of filaments, micro liquid delivery, biological cell manipulation, etc. 相似文献
18.
Mathieu Sellier Volker Nock Cécile Gaubert Claude Verdier 《The European physical journal. Special topics》2013,219(1):131-141
This paper considers the interaction between two droplets placed on a substrate in immediate vicinity. We show here that when the two droplets are of different fluids and especially when one of the droplet is highly volatile, a wealth of fascinating phenomena can be observed. In particular, the interaction may result in the actuation of the droplet system, i.e. its displacement over a finite length. In order to control this displacement, we consider droplets confined on a hydrophilic stripe created by plasma-treating a PDMS substrate. This controlled actuation opens up unexplored opportunities in the field of microfluidics. In order to explain the observed actuation phenomenon, we propose a simple phenomenological model based on Newton’s second law and a simple balance between the driving force arising from surface energy gradients and the viscous resistive force. This simple model is able to reproduce qualitatively and quantitatively the observed droplet dynamics. 相似文献
19.
T. Gilet D. Terwagne N. Vandewalle 《The European physical journal. E, Soft matter》2010,31(3):253-262
We present the results of a combined experimental and theoretical investigation of oil droplets sliding on fibres. First,
both the axisymmetric shape and the motion of a droplet on a vertical fibre are described. The motion is shown to result from
a balance between the droplet weight and the viscous stresses. On a long-term range, the droplet loses some mass through coating
the fibre, which decreases its velocity. In a second time, we rationalize the behaviour of a droplet that encounters a junction
between vertical and horizontal fibres. Depending on its size, the droplet may cross the junction or remain blocked. The transition
is well described by an ordinary differential equation equivalent to a damped harmonic oscillator truncated to the neighbourhood
of the horizontal fibre. This simple system is the basic element for more complex fiber networks that would be useful in microfluidic
applications involving droplets. 相似文献
20.
Crystal morphology variation in inkjet-printed organic materials 总被引:1,自引:0,他引:1
Andrew C. IhnenAnne M. Petrock Tsengming ChouPhillip J. Samuels Brian E. FuchsWoo Y. Lee 《Applied Surface Science》2011,258(2):827-833
The recent commercialization of piezoelectric-based drop-on-demand inkjet printers provides an additive processing platform for producing and micropatterning organic crystal structures. We report an inkjet printing approach where macro- and nano-scale energetic composites composed of cyclotrimethylenetrinitramine (RDX) crystals dispersed in a cellulose acetate butyrate (CAB) matrix are produced by direct phase transformation from organic solvent-based all-liquid inks. The characterization of printed composites illustrates distinct morphological changes dependent on ink deposition parameters. When 10 pL ink droplets rapidly formed a liquid pool, a coffee ring structure containing dendritic RDX crystals was produced. By increasing the substrate temperature, and consequently the evaporation rate of the pooled ink, the coffee ring structure was mitigated and shorter dendrites from up to ∼1 to 0.2 mm with closer arm spacing from ∼15 to 1 μm were produced. When the nucleation and growth of RDX and CAB were confined within the evaporating droplets, a granular structure containing nanoscale RDX crystals was produced. The results suggest that evaporation rate and microfluidic droplet confinement can effectively be used to tailor the morphology of inkjet-printed energetic composites. 相似文献