KR20060003001A - Microfluidic device with ultraphobic surfaces - Google Patents

Abstract

A microfluidic device having durable ultraphobic fluid contact surfaces in the fluid flow channels of the device. The ultraphobic surface generally includes a substrate portion with a multiplicity of projecting regularly shaped microscale or nanoscale asperities disposed in a regular array so that the surface has a predetermined contact line density equal to or greater than a critical contact line density, and so that the ratio of the cross-sectional dimension of the asperities to the spacing dimension of the asperities is less than or equal to 0.1.

Description

Microfluidic Devices with Ultra-Fobic Surfaces {MICROFLUIDIC DEVICE WITH ULTRAPHOBIC SURFACES}

Related Applications

This application claims the advantages of US Provisional Patent Application 60/462963, entitled "Ultraforbic Surface for High Pressure Liquids," filed April 15, 2003, which is incorporated herein by reference in its entirety. This application further claims the benefit of US Utility Patent Application No. 10 / 454,742, entitled "Fluid Treatment Component with Ultrafobic Surface," filed June 3, 2003, which is also fully incorporated herein by reference. Are merged. The present application further claims the benefit of US Utility Patent Application No. 10 / 652,586, entitled "Microfluidic Device with Ultrapobic Surface," filed August 29, 2003.

The present invention relates generally to microfludic devices and, more particularly, to microfluidic devices having an ultrapobic fluid contact surface.

Efforts and interests in using and developing microfluidic devices have been very recent. Microfluidic devices have already found useful applications in printing devices and so-called "wrap on a chip" devices, where complex chemical and biochemical reactions are carried out in the microfluidic device. The very small volume of liquid required for the reaction in such a system allows for increased reaction response time, small sample volume, and reduced reagent cost. Many other applications are expected to become apparent as the technology is developed and developed.

An important factor in the design of the microfluidic device is the resistance to fluid motion imposed by the contact of the fluid with the surface in the microchannel of the device. To overcome this resistance, higher fluid pressure is required in the device. In contrast, the rate of fluid flow through the device may be limited by the amount of pressure that the device can support or the processing it supports. Moreover, the pressure loss through the micro flow channel can vary greatly due to the surface properties in the flow channel.

What is needed in this industry is microfluidic devices with fluid flow channels with predictable and optimal levels of resistance to fluid flow.

The present invention satisfies the need for oxidative conditions for microfluidic devices with fluid flow channels with predictable and optimal levels of fluid flow resistance. In the present invention, all or any portion of the fluid flow channel of any microfluidic device is provided as a durable ultrapobic fluid contact surface. Ultrapobic surfaces are typically arranged in a variety of microscales in which the surfaces are arranged in regular arrays with measured predetermined contact line densities of contact lines expressed in meters per square meter of surface area above a contact line density value "Λ _L ", determined according to the following equation: Or a portion of the substrate having irregularities protruding in a regular form of nanoscale.

Where P is a predetermined maximum expected for the fluid pressure value in the fluid flow channel, γ is the surface tension of the liquid, and θ _{a, 0} are the experimentally measured true propagating contact of the liquid on the asperity material in degrees Is an angle, ω is an uneven rising angle, and the ratio of the cross-sectional dimension of the unevenness to the spacing dimension of the unevenness is 0.1 or less.

The unevenness may be formed in or on the substrate material itself or in one or more layers of material disposed on the surface of the substrate. The unevenness may be a three dimensional solid or cavity of any regular or irregular shape, or may be arranged in any regular geometric pattern.

The present invention includes a method of manufacturing a microfluidic device comprising forming at least one microfluidic flow channel in a body and disposing a plurality of substantially uniformly formed irregularities in a substantially uniform pattern on the fluid contact surface. And the fluid flow channel has a fluid contact surface. Each unevenness may have an uneven elevation angle and a cross-sectional dimension with respect to the fluid contact surface. The concavities and convexities are positioned so that the surfaces have measured contact line densities of contact lines in meters per square meter of surface area that are greater than the critical contact line density value "Λ _L ", which is determined according to the equation have.

Where P is a predetermined maximum expected for the fluid pressure value in the fluid flow channel, γ is the surface tension of the liquid, and θ _{a, 0} are the experimentally measured true propagating contact of the liquid on the asperity material in degrees Angle, and ω is an uneven rising angle. The ratio of the cross-sectional dimension of the unevenness to the spacing dimension of the unevenness is 0.1 or less and most preferably 0.01 or less.

Unevenness may be photolithography or nanomachining, microstamping, microcontact printing, self-assembled metal colloidal monolayers, atomic force microscopy nanomachining, sol-gel molding, self-assembled monolayer orientation patterning, chemical etching, sol-gel It may also be formed using stamping, printing with colloidal ink, and depositing a layer of parallel carbon nanotubes on the substrate. The method further includes determining a critical uneven height value "Z _C " expressed in meters according to the following equation.

Here, d is the distance between adjacent irregularities expressed in metric units, θ _{α, 0} is the true traveling contact angle of the liquid on the surface expressed in angular units, and ω is the uneven raised angle expressed in angular units.

Fluid flow channels in microfluidic devices with ultrapobic fluid contacting surfaces exhibit greatly reduced storage for fluid flow, and are expected to result in significantly improved device efficiency, lower internal pressure and improved fluid flow throughput. Ultrapobic surfaces can exhibit predictable ultrapobic properties and are durable under fluid pressure up to the maximum designed pressure.

1 is an enlarged perspective view of an ultrapobic surface according to the present invention.

1A is a schematic representation of a liquid slug in a flow channel.

1B is an exploded view of a microfluidic device according to the present invention.

1C is a cross-sectional view of an alternative embodiment of the microfluidic device according to the present invention.

2 is a top plan view of a portion of the surface of FIG.

3 is a side cross-sectional view of the surface portion shown in FIG.

4 is a partial top plan view of an alternative embodiment of an ultrapobic surface according to the present invention with irregularities arranged in a hexagonal array.

5 is a side cross-sectional view of the alternative embodiment.

Fig. 6 is a side sectional view showing the deflection of liquid suspended between irregularities.

Fig. 7 is a side sectional view showing the amount of liquid formed on top of the unevenness.

Fig. 8 is a side sectional view showing a liquid in contact with the bottom of the interdentations.

Figure 9 is a side cross-sectional view of a single unevenness of an alternative embodiment of the ultrapobic surface according to the present invention with an uneven elevation angle.

Figure 10 is a side cross-sectional view of a single unevenness of an alternative embodiment of the ultrapobic surface according to the present invention wherein the unevenness elevation angle is an obtuse angle.

Figure 11 is a partial top plan view of an alternative embodiment of an ultrapobic surface according to the present invention in which the irregularities are cylindrical and arranged in a rectangular array.

12 is a side cross-sectional view of an alternative embodiment of FIG.

FIG. 13 is a table listing the linear portion of contact and contact linear density for various uneven shapes and arrangements.

Figure 14 is a side cross-sectional view of an alternate embodiment of an ultrapobic surface in accordance with the present invention.

15 is a top plan view of an alternative embodiment of FIG.

Figure 16 is a top plan view of a single unevenness of an alternative embodiment of the ultrapobic surface according to the present invention.

FIG. 17 is a graphical representation of a liquid and certain ultrapobic surfaces in a relationship between maximum pressure P and uneven spacing y for various values of x / y ratio.

For the purposes of the present application, the term "microfluidic device" broadly means a part or any other device that can be used to contact, manipulate, transport, contain, process, or transport a fluid, wherein the fluid is one or more of microminiature dimensions. Flow through the fluid flow channel. For the purposes of the present invention, the term "miniature" means a dimension of 500 μm or less. "Fluid flow channel" broadly means any channel, conduit, pipe, tube, chamber, or other enclosed space of any cross-sectional shape used to manipulate, transport, contain, or transport a fluid. The term "fluid contact surface" means any or any surface of a fluid flow channel that can be in wide contact with a fluid.

It is known that the physical properties of the fluid contact surface of a fluid handling part affect the friction of the part and the fluid. In general, for example, smooth surfaces reduce friction, while rough surfaces increase friction. In addition, surfaces formed of wet resistant materials such as PTFE or other engineering polymers exhibit relatively low fluid friction. Wet resistant surfaces by liquids are referred to as "fobic" surfaces. Such surfaces may be known as hydrophobic and lyophobic to other liquids when the liquid is water. If the surface is wet resistant such that small droplets of water or other liquids exhibit a very high static contact angle with the surface (greater than about 120 degrees), if the surface tends to be significantly reduced to retain the liquid droplets, or if the liquid If the gas-solid interface is present on its surface when fully submerged in the liquid, the surface may be referred to as "superhydrophobic" or "superfluid". For the purposes of the present application, the term "ultraphobic" is generally used to refer to both superhydrophobic and microliquid surfaces.

The friction between the liquid and the surface can be significantly lower for the ultrapobic surface as opposed to the conventional surface. As a result, ultrapobic surfaces are highly desirable to reduce resistance to fluid flow due to surface resistivity, especially in microfluidic applications.

It is already well known that surface roughness has a significant effect on the degree of wetness. In general, in some atmospheres, roughness may cause the liquid to adhere more strongly to the surface than the corresponding smooth surface. However, in other atmospheres, roughness may cause the liquid to adhere less strongly to rough surfaces than to smooth surfaces. In some atmospheres, the surface may be ultrapobic. Such ultrapobic surfaces generally take the form of a substrate member having a plurality of microscale to nanoscale protrusions or cavities referred to herein as "unevenness".

In general, the pressure ΔP _total for moving the liquid slug through the horizontal flow channel at a predetermined speed may be divided into components of viscosity, surface force and gravity (head) as follows.

(1)

(One)

Horizontally oriented cylindrical flow channel 110 is shown in cross section in FIG. 1A. Cylindrical flow channel 110 is defined by channel wall 115 with fluid contact surface 120. Liquid slug 100 is shown in flow channel 110. Liquid slug 100 has a front interface 130 with fluid 132 and a rear interface 140 with fluid 142. Fluid 132 and fluid 142 may be in gas or liquid form. In the case of the horizontally oriented cylindrical flow channel 110, the general relationship given in Equation 1 can be expressed in particular as follows.

Where μ is the viscosity of the liquid, L is the length of the liquid slug 100, ν is the speed at which the liquid slug 100 moves, R is the cross section radius of the cylindrical flow channel 110, and γ is the liquid slug (100) is the surface tension of the liquid, θ _r is the true retracted contact angle of the surface 120 of the flow channel 110 and the rear interface 140 of the liquid slug 100, θa is the flow channel 110 Is the actual forward contact angle of the surface 120 and the front interface 130 of the liquid slug 100. Similar specific formulas are described in the prior art for flow channels of non-cylindrical flow channels.

In liquid slug 100 with one or more interfaces 130, 140 contacting surface 120 in microfluidic flow channel 110, surface forces prevail due to the small dimensions of liquid slug 100. The viscous component of the force can be absolutely ignored. Accordingly, the pressure ΔP for effectively moving the liquid slug 100 through the horizontal microcylindrical flow channel 110 is as follows.

(3)

(3)

By minimizing this surface force through the use of the ultrapobic flow channel surface according to the invention, a significant reduction in pressure for moving the liquid slug through the flow channel can be achieved.

The microfluidic device 10 according to the present invention is shown in the generally enlarged and exploded view of FIG. 1B. Apparatus 10 generally includes a body 11 having a rectangular flow channel 12 formed therein. The main body 11 generally includes a main portion 13 and a cover portion 14. The flow channel 12 is defined on three sides by the opposite surface 15 inwardly on the main portion 13 and on the fourth side by the opposite surface 16 inwardly on the cover portion 14. Surface 15 and surface 16 together define channel wall 16a. According to the present invention, all or any desired portion of the channel wall 16a may be provided to the ultrapobic fluid contact surface 20. Although the shape of two pieces with square flow channels is shown in FIG. 1B, the microfluidic device 10 may include any one piece body 11 having a cylindrical, polygonal, or irregularly shaped flow channel formed therein. It is readily understood that it can be formed in other shapes and in virtually any other flow channel shape or configuration.

An alternative embodiment of the microfluidic device is shown in cross section in FIG. 1C. In this embodiment, the body 200 is formed of an integral piece. Cylindrical flow channel 202 is defined within body 200 and has a channel wall 204 that represents the ultrapobic fluid contact surface 20 facing into flow channel 202.

A greatly enlarged view of the ultrapobic fluid contact surface 20 according to the present invention is shown in FIG. The surface generally includes a substrate 22 having a plurality of protruding irregularities 24. As further described herein, the substrate 22 may be part of the body 11 or may be a separate layer of material on the body 11. Unevenness 24 is typically formed from substrate 22 as further described herein. Each concave-convex 24 has a plurality of side surfaces 26 and an upper portion 28. Each unevenness 24 has a width dimension indicated by "x" in the figure and a height dimension indicated by "z" in the figure.

As shown in Figs. 1 to 3, the unevenness 24 is arranged in a regular rectangular array, and each unevenness is spaced from adjacent unevenness by a gap dimension indicated by "y" in the figure. The angle faced by the upper edge 30 of the unevenness 24 is represented by φ, and the rising angle of the side surface 24 of the unevenness 24 relative to the substrate 22 is represented by ω. The sum of the angles φ and ω is 180 degrees.

In general, the ultrapobic fluid contact surface 20 will exhibit ultrapobic properties when the liquid-solid-gas interface is maintained at the surface. As shown in FIG. 7, if the liquid 32 contacts only the upper portion 28 and a portion of the side 26 adjacent the upper edge 30 of the unevenness 24, the space 34 between the unevennesses is either air or Leaving it filled with other gases, there is an essential liquid-solid-gas interface. The liquid may be said to be "suspended" on top of and between the upper edge 30 of the unevenness 24.

As disclosed below, the formation of the liquid-solid-gas interface depends on certain interrelated geometrical parameters of the unevenness 24, the properties of the liquid and the interaction of the liquid with the solid surface. According to the present invention, the geometrical characteristics of the unevenness 24 may be selected such that the surface 20 exhibits ultrapobic properties at any desired liquid pressure.

Referring to the rectangular arrays of FIGS. 1-3, the surface 20 may be divided into uniform regions 36 shown bordered by dashed lines surrounding the unevenness 24. The area density δ of the irregularities of each of the four uneven regions 36 may be described by the following equation.

(4)

(4)

Here, y is a gap between the irregularities expressed in metric units.

In the case of unevenness 24 having a square cross section as shown in FIGS. 1 to 3, the length of the perimeter p of the upper portion 28 at the upper edge 30 is

(5)

(5)

Where x is an uneven width expressed in meters.

The perimeter p is referred to as the "contact line" which forms the location of the liquid-solid-gas interface. The contact line density Λ, which is the length of the contact line per unit area of the surface, is the product of the area density δ of the unevenness and the perimeter p.

(6)

(6)

In the case of the rectangular array of square irregularities shown in Figs.

(7)

(7)

If the force F due to gravity acting on the liquid is less than the surface force f on the contact line with the unevenness, a large amount of liquid will be suspended at the top of the unevenness. The fitness force F associated with gravity is determined according to the following equation.

(8)

(8)

Where (P) is the density of the liquid, ( g ) is the acceleration due to gravity, and ( h ) is the depth of the liquid. Thus, for example, in the case of a 10 meter column of water having a density of approximately 1000 kg / m ³ , the stamina F is

F = (1000㎏ / m ³ ) (9.8m / s ² ) (10m) = 9.8 x 10 ⁴ kg / m ² -s

The surface force (f) is the surface tension (γ) of the liquid, the apparent contact angle ( θ _s ) with the side surface 26 of the unevenness 24 with respect to the vertical, the contact linear density (Λ) of the unevenness, and the apparent contact of the liquid. Depends on the area A.

(9)

(9)

True propagation contact angle of the liquid in a given solid phase ( θ _{α, 0} ) Is defined as the largest stopping angle measured by experimentation of liquid on the surface of a material that does not necessarily have irregularities. The true advancing contact angle can be easily measured by techniques well known in the art.

Drops suspended on a surface with an uneven surface may have its true traveling contact angle value ( θ _{α, 0} at the side of the uneven surface). ). The contact angle with respect to the vertical at the side of the unevenness (θ _s) is true, proceed by the contact angle φ or ω as follows (θ _{α, 0} ).

(10)

10

By equalizing F and f and subtracting for contact linear density Λ, the critical linear density parameter Λ _L may be determined to predict the ultrapobic characteristics of the surface.

(11)

(11)

Where g is the density (ρ) of the liquid, ( g ) is the acceleration due to gravity, ( h ) is the depth of the liquid, (γ) is the surface tension of the liquid, and ω is the angle The angle of elevation of the side of the unevenness with respect to (θ _{α, 0} ) is the experimentally measured true advancing contact angle of the liquid on the uneven material in angular units.

If Λ> Λ _L , the liquid will be suspended on top of the unevenness 24, creating an ultrapobic surface. Further, if Λ <Λ _L, the liquid contact interface at the top surface collapse and unevenness will be alone liquid / solid without ultra pobik characteristics.

By substituting the appropriate value of the molecule of the given equation, the value of the critical contact linear density may be determined to design a surface that retains ultrapobic properties at any desired amount of pressure. The equation may be generalized as follows.

(12)

(12)

Where P is the maximum pressure at which the surface must exhibit ultra-pobic properties expressed in kilograms per square meter, γ is the surface tension of the liquid expressed in Newtons per meter, and θ _{α, 0} is an uneven material expressed in degrees Is the experimentally measured true advancing contact angle of the liquid in the phase, and ω is the uneven elevation angle expressed in degrees.

It is expected that the surface 20 formed according to this relationship will reach the value of P used in the equation (9) and exhibit ultrapobic properties under any liquid pressure value including it. Ultraphobic properties will depend on whether the surface is submerged, treated with jets or liquid jets, or collided with individual droplets.

Once the value of the critical contact linear density is determined, the remaining details of the irregularities geometry may be determined according to the relationship of x and y given in the equation for contact linear density. That is, the geometry of the surface may be determined by selecting the value of x or y of the contact line equation and calculating it for other variables.

The tendency of the ultrapobic surface 20 to resist the droplet of liquid to keep the droplet on the surface at a very high contact angle can be best expressed by the contact angle hysteresis (Δθ), which is advanced to the liquid droplet on the surface. Is the difference between and retracting contact angles. In general, lower values of contact angle hysteresis correspond to relatively large repulsion properties of the surface. The contact angle hysteresis with respect to the surface can be determined according to the following equation.

Δθ = λ _p (Δθ ₀ + ω) (13)

Where (λp) is the contact linear portion along the unevenness, (Δθ ₀ ) is the difference between the actual forward contact angle (θ _a , ₀ ) and the true receding contact angle (θ _r , ₀ ) for the surface material, (ω ) Is the rising angle of the unevenness. In the case of a rectangular array of square irregularities,

λ _p = x / y (14)

An equation for determining a surface with a different shape is given in FIG. In the case of droplets of liquid on the surface, the true advancing contact angle of the surface can be determined according to the following equation.

(15)

(15)

The true retraction contact angle can be determined according to the following equation.

(16)

(16)

Relatively low values of λ _p , ω, x / y and Λ result in a relatively improved rebound to the surface, and each relatively high value of the same factor results in a relatively improved performance of the surface to suspend the column of liquid. It is easily understood by experimenting with the relationships described above. As a result, if a surface with good rebound and suspension properties is desired, it is generally necessary to select and balance values for these factors.

The equation can also be used to show the relationship to the desired liquid properties between the uneven space y and the maximum pressure P for various values of x / y. 17, i.e., the example shown in Figure 17, can serve as a useful design tool, as demonstrated by the examples given below.

The liquid interface deflects downwards between adjacent irregularities by the amount D ₁ , as shown in FIG. 6. If the amount D ₁ is greater than the height z of the unevenness 24, the liquid contacts the substrate 22 at the point between the unevenness 24. If this occurs, the liquid is attracted into the space 34 and squeezed against the unevenness, destroying the ultrapobic properties of the surface. The numerical value of D ₁ represents a critical uneven height and can be determined according to the following equation.

(17)

(17)

Where (d) is the shortest distance between adjacent concavities and convexities in the contact line, ω is the concave-convex elevation angle, and θ _{a, 0} is the experimentally measured true advancing contact angle of the liquid on the concave-convex material. The height z of the unevenness 24 should be at least equal to the critical uneven height Zc, and is preferably larger than that.

Although the uneven | corrugated rising angle (omega) is 90 degrees in FIGS. 1-3, other uneven | corrugated shape is possible. For example, ω may be an acute angle as shown in FIG. 9 or an obtuse angle as shown in FIG. In general, ω is preferably between 80 and 130 degrees.

In addition, a wide variety of irregularities and arrangements are possible within the scope of the present invention. For example, the unevenness may be a polyhedron, cylindrical, cylindrical, or any other suitable three dimensional shape as shown in FIGS. 11 and 12. Moreover, various methods can be used to optimize the contact line density of the irregularities. As shown in Figs. 14 and 15, the uneven 24 may be formed of the base 38 and the head portion 40. The larger boundary of the head portion 40 at the upper edge 30 increases the contact linear density of the surface. Also, features such as recess 42 can be formed in the uneven 24 as shown in FIG. 16 to increase the boundary at the upper edge 30, thereby increasing the contact linear density. The unevenness may also be a cavity formed in the substrate.

The unevenness may be arranged in a rectangular array as described above in a polygonal array or a circular or egg-like arrangement, such as the hexagonal array shown in FIGS. 4 and 5. Unevenness may also be distributed randomly if the critical contact linear density is maintained, but such random arrangements may have less predictable ultrapobic properties and are therefore less desirable. In this random arrangement of irregularities, the critical contact linear density and other related factors can be considered as the mean for the surface. In the table of FIG. 13, equations for calculating the contact linear density for various other irregularities and arrangements are listed.

In general, the substrate material may be any material from which micro or nano scale irregularities can be appropriately formed. The unevenness may be formed directly into the substrate material itself or into one or more other layers of material deposited on the substrate material by photolithography or any of a variety of suitable methods. Direct extrusion can be used to form irregularities in the shape of parallel ridges. This parallel ridge is most preferably directed transverse to the fluid flow direction. Photolithographic methods that may be suitable for forming micro / nanoscale irregularities are disclosed in PCT Patent Application Publication WO 02/084340, which is fully incorporated herein by reference.

Methods that may be suitable for forming the irregularities of the desired shape and separation distance include nanomachining disclosed in US Patent Application Publication No. 2002/00334879, microstamping disclosed in US Pat. No. 5,725,788, microcontact printing disclosed in US Pat. No. 5,900,160. , Self-assembled metal colloid monolayer disclosed in US Pat. No. 5,609,907, microstamping disclosed in US Pat. No. 6,444,254, nuclear microscopy nanomachining disclosed in US Pat. Sol-gel molding disclosed in US Pat. No. 6,530,554, self-assembled monolayer oriented patterning of surfaces disclosed in US Pat. No. 6,518,168, chemical etching disclosed in US Pat. No. 6,541,389, or sol disclosed in US Patent Application Publication 2003/0047822. Gel stamping, all of which are fully incorporated herein by reference Are merged. Carbon nanotube structures can also be used to form the desired uneven shape. Examples of carbon nanotube structures are disclosed in US Patent Application Publication Nos. 2002/0098135 and 2002/0136683, which are also incorporated herein by reference. In addition, suitable concave-convex structures can be formed using known methods for printing with colloidal inks. Of course, it is contemplated that any other method by which micro / nanoscale irregularities can be formed accurately can also be used.

In general, it is most desirable to optimize the repellent properties of the ultrapobic flow channel surface to minimize the contact of liquid slugs with the flow channel surface, thereby minimizing the final surface force. As described above, the surface repulsion properties can be optimized by selecting relatively low values for λ _p , ω, x / y and Λ, but the surface has ultrapobic properties at the maximum pressure expected to meet in the flow channel. To ensure that the surface has a sufficient critical contact linear density figure Λ _L. For best flow channel performance, the x / y ratio to the uneven shape should be less than about 0.1 and most preferably less than about 0.01.

A method for optimizing the microfluidic flow channel for the repulsion characteristic can be illustrated by the following example.

Example 1:

Cylindrical microfluidic channels are formed in the silicon body to form the microfluidic device. Ultrapobic surfaces are provided on the inwardly facing walls of the microfluidic flow channel according to the invention. The ultrapobic surface consists of an array of square posts (ω = 90 °) arranged in the wall of the channel. The channel walls are also coated with organosilanes so that the channels have the following dimensions and properties.

R = 1 μm

θ _{a, 0} = 110 °

θ _{r, 0} = 90 °

Water slugs in the flow channel have the following dimensions and properties.

γ = 0.073 N / m

L = 0.1mm

v = 0.1mm / s

If slug (θ _a , If the flow channel has a smooth fluid contact surface such that the actual forward and backward contact angle of θ _r ) is substantially the same as the actual forward and backward contact angle for the fluid contact surface material, the pressure required to move the liquid slug through the smooth flow channel is calculated as follows: do.

The repulsion of the fluid contacting surface is optimized by selecting a small x / y ratio to increase the actual forward and backward contact angles of the water at the fluidic contacting surface.

x / y = λ _p = 0.01

therefore,

And,

The pressure for moving the liquid slug through the flow channel with the ultrapobic fluid contacting surface is

The residual geometric details of the surface can be determined as follows using the relationship given above.

Of the relationship between the maximum pressure (P) and the uneven spacing (y) for various values of x / y with values of θ _{a, 0} and θ _{r, 0} that match the water and organosilane coated silicone material as a liquid Referring to FIG. 17, which is a plot, y can be determined at a rate of about 1 × 10 ⁻⁵ m or 10 μm and 0.01 / x for a maximum pressure of 100 Pa. therefore,

x = 0.01 (y) = 0.01 (1x10 ^-5 m) = 1x10 ^-7 m or 100nm

Next, we calculate for Z _c ,

Thus, if square irregularities are located on the fluid contact surface of the flow channel in a rectangular arrangement, they should have a cross-sectional dimension of about 100 nm, spaced about 10 μm apart, and at least 0.9 μm high.

Example 2:

Assume a cylindrical micro flow channel in a PFA plastic with the following dimensions and characteristics.

R = 10㎛

θ _{a, 0} = 110 °

θ _{r, 0} = 90 °

Also assume water slug in the flow channel.

γ = 0.073 N / m

L = 1mm

v = 0.1mm / s

v = 0.1mm / s

Again, if slugs (θ _a , If the flow channel has a smooth fluid contact surface such that the actual forward and backward contact angle of θ _r ) is substantially the same as the actual forward and backward contact angle for the fluid contact surface material, the pressure required to move the liquid slug through the smooth flow channel is Is calculated.

An array of square posts (ω = 90 °) is arranged on the fluid contact surface of the flow channel to form an ultrapobic surface.

x / y = λ _p = 0.01

therefore,

And,

The pressure for moving the liquid slug through the flow channel with the ultrapobic fluid contacting surface is as follows.

The residual geometric details of the surface can be determined as follows using the relationship described above.

Figure 17 is a plot of the relationship between the maximum pressure (P) and the uneven spacing (y) for various values of x / y, with values of θ _{a, 0} and θ _{r, 0} corresponding to water and PFA materials as liquids. For reference, y can be determined at an x / y ratio of about 1 × 10 ⁻⁵ m or 10 μm and 0.01 for a maximum pressure of 100 Pa. therefore,

x = 0.01 (y) = 0.1 (10μm) = 1μm

Next, we calculate for Z _c ,

Thus, if square irregularities are located on the fluid contact surface of the flow channel in a rectangular arrangement, they should have a cross-sectional dimension of about 1 μm, spaced about 10 μm, and be at least 0.8 μm high.

It is readily understood by those skilled in the art that the method described above can be used to determine the optimal uneven spacing and shape for the ultrapobic fluid contact surfaces in the microfluidic flow channel for any shaped liquid and flow channel surface material.

Additional objects, advantages and novel features of the invention will be set forth in part in the description, and will be apparent to one skilled in the art upon examination of the following or by the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the combinations and teachings particularly pointed out in the appended claims.

Claims (26)

A body having at least one microfluidic fluid flow channel therein, the microfluidic fluid flow channel being defined by a channel wall having a fluidic contact surface portion, the fluidic contact surface portion being substantially uniformly shaped and dimensioned thereon A substrate having unevenness, wherein the unevenness is arranged in a substantially uniform pattern, each unevenness having an uneven elevation angle and cross-sectional dimension with respect to the substrate, and the unevenness has a critical contact linear density value whose surface is determined by the following equation Positioned to have a measured contact line density of the contact line expressed in meters per square meter of surface area equal to or greater than "Λ _L " and spaced apart from each other by a substantially uniform separation distance dimension,

Where P is a predetermined maximum value expected for the fluid pressure value in the fluid flow channel, γ is the surface tension of the liquid, θ _{a, 0} are the experimentally measured true advancing contact angles of the liquid on the uneven material in degrees, ω is the uneven elevation angle, wherein the ratio of the cross-sectional dimension of the unevenness to the spacing dimension of the unevenness is 0.1 or less. The microfluidic device of claim 1, wherein the unevenness is a protrusion. The microfluidic device of claim 2, wherein the unevenness is in the form of a polyhedron. 3. A microfluidic device according to claim 2, wherein each unevenness generally has a square cross section. The microfluidic device of claim 2, wherein the unevenness is cylindrical or cylindrical. The microfluidic device of claim 1, wherein the unevenness is a cavity formed in a substrate. The microfluidic device of claim 1, wherein the unevenness is a parallel ridge. 8. The microfluidic device of claim 7, wherein the parallel ridges are disposed transverse to the direction of fluid flow. The method of claim 1, wherein the unevenness has a substantially uniform uneven height with respect to the substrate portion, the uneven height is greater than the critical uneven height value "Z _C " expressed in meters determined by the following equation,

Where d is the shortest distance between adjacent unevenness in meters, θ _{α, 0} is the experimentally measured true traveling contact angle of the liquid on the uneven material in angular units, and ω is unevenness in degrees Microfluidic device with rising angle. Method of manufacturing microfluidic devices, The method includes forming at least one microfluidic flow channel in a body; Disposing a plurality of substantially uniformly formed irregularities in a substantially uniform pattern on the fluid contact surface portion, The fluid flow channel defined by the channel wall has a fluid contact surface portion, each unevenness has an uneven elevation angle and a cross-sectional dimension with respect to the fluid contact surface, and the unevenness has a critical contact linear density value "ΛL whose surface is determined by the following equation. "Are positioned to have a measured contact line density of the contact line expressed in meters per square meter of surface area greater than and spaced apart from each other by a substantially uniform spacing dimension, Where P is a predetermined maximum value expected for the fluid pressure value in the fluid flow channel, γ is the surface tension of the liquid, θ _{a, 0} are the experimentally measured true advancing contact angles of the liquid on the uneven material in degrees, [omega] is the uneven elevation angle, wherein the ratio of the cross-sectional dimension of the unevenness to the separation dimension of the unevenness is 0.1 or less. The method of manufacturing a microfluidic device according to claim 10, wherein the ratio of the cross-sectional dimension of the unevenness to the spaced apart dimension of the unevenness is 0.01 or less. The method of claim 10, wherein the unevenness is nanomachining, microstamping, microcontact printing, self-assembled metal colloidal monolayer, nuclear microscopy nanomachining, sol-gel molding, self-assembled monolayer orientation patterning, chemical etching, sol-gel A method of making a microfluidic device formed by a process selected from the group consisting of stamping, printing with colloidal ink, and deposition of layers of parallel carbon nanotubes on a substrate. The method of claim 10, wherein the irregularities are formed by extrusion. The method of claim 10, further comprising selecting a geometry for the unevenness. The method of manufacturing a microfluidic device according to claim 10, further comprising selecting an array pattern for irregularities. The method of claim 10, further comprising selecting at least one dimension for the unevenness and determining at least one other dimension for the unevenness using an equation for contact linear density. The method of claim 10, further comprising determining a critical uneven height value “Z _c ” in meters according to the following equation,

Wherein d is the shortest distance in meters between adjacent unevenness, θ _{a, o} is the true advancing contact angle of the liquid on the surface in angular units, and ω is the uneven elevation angle in degrees. A microfluidic fluid flow system having at least one microfluidic device, A body having at least one microfluidic fluid flow channel therein, the microfluidic fluid flow channel being defined by a channel wall having a fluidic contact surface portion, the fluidic contact surface portion being substantially uniformly shaped and dimensioned thereon A substrate having irregularities, wherein the irregularities are arranged in a substantially uniform pattern, each irregularity having an uneven elevation angle and a cross-sectional dimension with respect to the substrate, and the unevenness is a critical contact linear density value whose fluid contact surface portion is determined according to the following equation: Positioned to have a measured contact line density of the contact line expressed in meters per square meter of surface area equal to or greater than "Λ _L " and spaced apart from each other by a substantially uniform separation distance dimension,

Where P is a predetermined maximum value expected for the fluid pressure value in the fluid flow channel, γ is the surface tension of the liquid, θ _{a, 0} are the experimentally measured true advancing contact angles of the liquid on the uneven material in degrees, ω is an uneven elevation angle, wherein the ratio of the cross-sectional dimension of the unevenness to the unevenness dimension of the unevenness is at least 0.1 microfluidic fluid flow system with at least one microfluidic device. 19. The microfluidic fluid flow system of claim 18, wherein the irregularities are protrusions. 20. The microfluidic fluid flow system of claim 19, wherein the irregularities are polyhedral in shape and have at least one microfluidic device. 20. The microfluidic fluid flow system of claim 19, wherein each unevenness has at least one microfluidic device having a generally square cross section. 20. The microfluidic fluid flow system of claim 19, wherein the unevenness is at least one microfluidic device that is cylindrical or cylindrical in shape. 19. The microfluidic fluid flow system of claim 18, wherein the unevenness is at least one microfluidic device formed in a substrate. 19. The microfluidic fluid flow system of claim 18, wherein the unevenness is at least one microfluidic device that is a parallel ridge. 25. The microfluidic fluid flow system of claim 24, wherein the parallel ridge has at least one microfluidic device disposed transverse to the fluid flow direction. The method of claim 18, wherein the unevenness has a substantially uniform uneven height with respect to the substrate portion, the uneven height is greater than the critical uneven height value "Z _c " in meters determined by the following equation,

Where d is the shortest distance in meters between adjacent unevenness, θ _{a, o} is the experimentally measured true advancing contact angle of the liquid on the uneven material in angular units, and ω is at least one fine that is the uneven rising angle in angular units Microfluidic fluid flow system with flowable device.

Images