Design and Fabrication of a Novel Microfluidic Nanoprobe

Moldovan, N.; Kim, Keun-Ho; Espinosa, Horacio D.

doi:10.1109/jmems.2005.863701

Cited by 55 publications

(46 citation statements)

References 24 publications

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“…The technique has many industrial applications, including the printing industry and dispensing of glue for packaging. Most recently, it has been adapted for a variety of novel uses at small scales, such as direct scanning probe lithography (Ginger et al 2004), micromachined fountain-pen techniques (Deladi et al 2004;Moldovan et al 2006) and in the formation of micro-arrays of biological materials (Müller & Nicolau 2004). Despite the simplicity of the operation, the exact control of the dispensing drop size is complicated by several factors, such as the syringe geometry, the dispensing speed, the liquid properties and the surface wettability.…”

Section: Introductionmentioning

confidence: 99%

The motion, stability and breakup of a stretching liquid bridge with a receding contact line

Qian

Breuer

2011

J. Fluid Mech.

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The complex behavior of drop deposition on a hydrophobic surface is considered by looking at a model problem in which the evolution of a constant-volume liquid bridge is studied as the bridge is stretched. The bridge is pinned with a fixed diameter at the upper contact point, but the contact line at the lower attachment point is free to move on a smooth substrate. Experiments indicate that initially, as the bridge is stretched, the lower contact line slowly retreats inwards. However at a critical radius, the bridge becomes unstable, and the contact line accelerates dramatically, moving inwards very quickly. The bridge subsequently pinches off, and a small droplet is left on the substrate.A quasi-static analysis, using the Young-Laplace equation, is used to accurately predict the shape of the bridge during the initial bridge evolution, including the initial onset of the slow contact line retraction. A stability analysis is used to predict the onset of pinch-off, and a one-dimensional dynamical equation, coupled with a Tanner-law for the dynamic contact angle, is used to model the rapid pinch-off behavior. Excellent agreement between numerical predictions and experiments is found throughout the bridge evolution, and the importance of the dynamic contact line model is demonstrated. † Current address:

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Section: Introductionmentioning

confidence: 99%

The motion, stability and breakup of a stretching liquid bridge with a receding contact line

Qian

Breuer

2011

J. Fluid Mech.

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“…Results from nonlinear numerical simulations agree well with the experiments, although the accuracy of the predictions is limited by inadequate models for the behavior of the dynamic contact angle. Contact dispensing methods of fluids are widely used in a variety of applications including direct scanning probe lithography [1], micromachined fountain-pen techniques [2,3], electrowetting-assisted drop deposition [4] and biofluid dispensing applications [5,6]. The process is, at first glance, straightforward and is initiated by the formation of a liquid bridge between the substrate and a dispensing syringe.…”

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confidence: 99%

Micron-Scale Droplet Deposition on a Hydrophobic Surface Using a Retreating Syringe

et al. 2009

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Droplet deposition onto a hydrophobic surface is studied experimentally and numerically. A wide range of droplet sizes can result from the same syringe, depending strongly on the needle retraction speed. Three regimes are identified according to the motion of the contact line. In Region I, at slow retraction speeds, the contact line expands and large droplets can be achieved. In Region II, at moderate needle speeds, a quasi-cylindrical liquid bridge forms resulting in drops approximately the size of the needle. Finally, at high speeds (Region III), the contact line retracts and droplets much smaller than the syringe diameter are observed. Scaling arguments are presented identifying the dominant mechanisms in each regime. Results from nonlinear numerical simulations agree well with the experiments, although the accuracy of the predictions is limited by inadequate models for the behavior of the dynamic contact angle. [5,6]. The process is, at first glance, straightforward and is initiated by the formation of a liquid bridge between the substrate and a dispensing syringe. As the syringe retreats, the liquid bridge stretches, grows and breaks, leaving a drop on the substrate. A seemingly simple question can be askedhow does the drop size depend on the syringe geometry, speed and the fluid properties? A comprehensive answer must consider the stability of the liquid bridge and the physics of the moving contact line at the liquid-air-solid interface -both difficult problems. Theoretical studies of liquid bridge stability date back to Rayleigh [7], and have been extended to include gravity and non-cylindrical geometries [8,9]. In addition, the nonlinear dynamics have been solved numerically, using both 2-D (axisymmetric) [10] and 1-D (slender-jet) [11,12] models. Previous work has concentrated on geometries in which the contact line is pinned at both ends of the liquid bridge [12,13], and there are only a few results that couple the liquid bridge with a moving contact line [14,15]. A possible reason for this is the difficulty in solving the flow near the contact line where the continuum equations are invalid [16,17] and a microscopic description must be imposed (e.g. [18]). In this letter, we focus on the physics of drop dispensing on a flat, smooth, hydrophobic substrate in which the contact line is free to move and is inherently coupled with the liquid bridge stability. Experiments and numerical simulations are used to identify a range of complex flow phenomena which enable the deposited drop size to vary by two orders of magnitude as the syringe retraction speed is changed.In our experiment, a stainless steel syringe (typical radius, R = 200µm) is mounted vertically on a computercontrolled stage. The syringe is connected by a small tube to a 10cc barrel mounted on the same stage. This configuration maintains a constant hydrostatic head, H, at the syringe tip (H ∼ 4cm). The fluid (a 85-15 mixture by volume of glycerol and water) has viscosity µ = 84 cP and surface tension γ = 0.063 N/m. The fluid exhibits a static co...

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“…69 In a concept known as "Nano-fountain probe" or "liquid nanodispensing", material is delivered a nanochannel through the AFM tip. [70][71][72] This approach has demonstrated versatility through the printing of gold colloids, 73 DNA 74 , and proteins. 75 The design has allowed for some unique applications, for example, the injection of single cells with nanoparticles ( Figure 6C).…”

Section: Scanning Probe Lithographymentioning

confidence: 99%

Nano-bioelectronics via dip-pen nanolithography

et al. 2015

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The emerging field of nano-biology is borne from advances in our ability to control the structure of materials on finer and finer length-scales, coupled with an increased appreciation of the sensitivity of living cells to nanoscale topographical, chemical and mechanical cues. As we envisage and prototype nanostructured bioelectronic devices there is a crucial need to understand how cells feel and respond to nanoscale materials, particularly as material properties (surface energy, conductivity etc.) can be very different at the nanoscale than at the bulk. However, the patterning of organic bioelectronic materials is often not achievable using conventional fabrication techniques, especially on soft, biocompatible substrates. Nonconventional nanofabrication strategies are required. Dip-pen nanolithography is a nanofabrication technique which uses the nanoscale tip of an atomic force microscope to direct-write functional inks. Over the past decade, the technique has evolved as uniquely capable in the realm of bio-nanofabrication, with the capability to deposit both biomolecules and electrode materials. This review highlights this new tool for fabricating nanoscale bioelectronic devices, and for enabling heretofore unrealised experiments in the response of living cells to tailored nano-environments. We firstly introduce bioelectronics, followed by a survey of different lithography methods and their use to achieve paradigmic bioelectronic architectures. We then focus on dip-pen nanolithography, highlighting the range of bioelectronic materials and biomolecules which can be deposited using the technique, as well as its demonstrated use as a lithography tool in nano-biology. We discuss the progress made towards upscaling the DPN technology towards larger areas, in particular via the polymer pen approach. The emerging field of nano-biology is borne from advances in our ability to control the structure of materials on finer and finer length-scales, coupled with an increased appreciation of the sensitivity of living cells to nanoscale topographical, chemical and mechanical cues. As we envisage and prototype nanostructured bioelectronic devices there is a crucial need to understand how cells feel and respond to nanoscale materials, particularly as material properties (surface energy, conductivity etc.) can be very different at the nanoscale than at the bulk. However, the patterning of organic bioelectronic materials is often not achievable using conventional fabrication techniques, especially on soft, biocompatible substrates. Nonconventional nanofabrication strategies are required. Dip-pen nanolithography is a nanofabrication technique which uses the nanoscale tip of an atomic force microscope to direct-write functional inks. Over the past decade, the technique has evolved as uniquely capable in the realm of bio-nanofabrication, with the capability to deposit both biomolecules and electrode materials. This review highlights this new tool for fabricating nanoscale bioelectronic devices, and for enabling heretofore u...

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Design and Fabrication of a Novel Microfluidic Nanoprobe

Cited by 55 publications

References 24 publications

The motion, stability and breakup of a stretching liquid bridge with a receding contact line

The motion, stability and breakup of a stretching liquid bridge with a receding contact line

Micron-Scale Droplet Deposition on a Hydrophobic Surface Using a Retreating Syringe

Nano-bioelectronics via dip-pen nanolithography

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