| Method of transforming a pre-determined force or pressure pattern -> Monitor Keywords |
|
|
 
Method of transforming a pre-determined force or pressure patternRelated Patent Categories: Pumps, ProcessesMethod of transforming a pre-determined force or pressure pattern description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060204366, Method of transforming a pre-determined force or pressure pattern. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is based on U.S. Provisional Application No. 60/645,613 filed Jan. 24, 2005. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an improved method of and device for tightly and uniformly sealing any type of fluidic structure, in particular to components made from flat, solid, yet flexible, semi-finished parts such as planar lab-on-a-chip structures. [0004] 2. Description of the Prior Art [0005] US 2002/0155337 A1 discloses to convex fuel manifold providing uniform pressure seal to a fuel cell stack. According to this disclosure a reactant gas manifold for a fuel cell stack assembly having a generally planar configuration with two opposing long sides joined together by two opposing short ends, the sides and ends having substantially small surfaces for sealing against a fuel cell stack. The surfaces are manufactured convex. This results when the manifold distorts as a consequence of said short ends being bonded to a fuel cell stack, the sealing surfaces of the long sides will provide substantially uniform sealing pressure throughout the length thereof. [0006] U.S. Pat. No. 6,451,264 B1 is related to a fluid flow control in curved capillary channels. According to this solution a capillary pathway is dimensioned so that the driving force for the movement of liquid through the capillary pathway arises from capillary pressure. A plurality of groups of microstructures affixed in the capillary pathway within discrete segments of the pathway for facilitating the transport of a liquid around curved portions of said pathway. Capillary channels can be coupled between adjacent groups of microstructures to either the inner and outer wall of the capillary pathway. The width of each capillary channel is generally smaller than the capillary pathway to which it is connected can be varied to achieve differences in full initiation. The grouped microstructures are spaced from each other within each group on a nearest neighbour basis by less than that necessary to achieve capillary flow of liquid within each group. Each group of microstructures are spaced from any adjacent group by an inter-group space greater than the width of any adjacent capillary channels connected to the capillary pathway. Generally, the microstructures are centered on centers which are equally spaced from each other and microstructures that are located closer to the inner wall of any curve in the capillary pathway are generally smaller than those microstructures located closer to the outer wall. This combination of structural features causes fluids to flow through the capillary pathway so that the rate of flow is somewhat non-uniform as compared to the fluid traveling around curved portions of the capillary pathway. The meniscus appearing to pass momentarily at each inter-group space, the flow being somewhat smaller near the inner wall of a curved portion as compared to the outer wall. [0007] In almost every case of a micro fluidic device, a more or less complicated channel network structure, located on the surface of a solid, needs to be shut off from the outside world, using a lid or any sort of a top cover, in order to prevent liquid from the inside flowing out at places other than desired to protect users from possible dangerous fluids leaking from the channel network and to prevent the inside from being contaminated with particles, etc.. [0008] Up to date, several different techniques are being used to fulfill the task described above. One way of covering a flat fluidic structure is to use a suitable glue. The glue can be applied using glue dispensers, roll-on techniques, printing techniques or sprays. Care has to be taken that no glue contaminates the often delicate structures within the fluidic network, clogging them or gluing movable parts against each other or to a sort of a carrier chip. Since micro fluidics usually deal with very small channel geometries (often 100 micrometers and way below), application of an exact amount of glue to the exactly right place is often hard to achieve and needs significant expertise of manual workers and/or high precision machines with the ability of ensuring the high quality demands applying to life sciences and health care products. This, however, usually results in high costs for the fabrication of the base-lid connection. Furthermore, contamination of substances used for detection of certain ingredients contained in the fluids flowing through the channels has to be avoided. Since most glues use solvents that more or less rapidly evaporate into the air as well as emigrate into the surrounding material that they have been applied onto, it must be assured sure that these solvents do not interfere with the detection taking place within the channels (such as fluorescence detection, for example). More important, it must be assured that no remnants of any type come in contact with the liquids in the case of re-entering the human body (pharmaceutical application fluidics come up to give an example). [0009] Furthermore, said solvents often remain at least in small quantities within the closed structures for a rather long time, for months or even years. They are therefore not favourable for being used in the above-mentioned fields of application. [0010] Another often-used way of quickly and securely gluing parts together is by using ultraviolet-curable adhesives. Since they remain viscous until exposed to ultraviolet light, the parts can be readjusted and even partly cleaned from excess glue before fixing. The fixation process itself usually takes only a couple of seconds. Adversely, UV radiation sometimes might affect detection substances, such as dyes, located inside the micro fluidic system. Also, not all polymers are transparent to UV light, especially when coloured. [0011] A second way for fulfilling the task in question is thermal bonding, using the capability of globally heating up the bodies to be connected, while melting only the material that forms the contact surfaces. This technique is useful especially when polymeric materials are being used. Melting can be induced by placing an intermediate material sheet between the contact areas that has a melting point significantly below the one of the base and lid material, followed by heating up the complete structure above the softening/melting point of the connection layer, while applying some pressure. Many polymers are available in grades with different melting points, whereas the basic material is kept the same. For example, TOPAS.RTM., a cycloolefin-copolymer from TICONA, is available with glass transition temperatures of 68, 80, 136, 140, 160 and 180.degree. C., respectively. However, the molecular structures of the underlying basic material and the melting layer remain identical. This results in a homogenous material cross section, since no significantly other material has to be used. [0012] On the other hand, the same problems known from using viscous gluing fluids discussed above apply here as well: softened material can flow into the channel structures, movement of parts can be obstructed. Furthermore, many biomedical applications are sensitive to high temperatures within the channels since they comprise temperature damageable substances that are often destroyed by temperatures higher than 40.degree. C.-60.degree. C. Since the whole structure is heated up (e.g., by placing it in an oven), thermal bonding is often inappropriate for connecting parts used in biomedical applications. Last but not least, heating up and cooling down is a time-consuming process, making it not first choice for mass produced parts where short cycle times are essential. [0013] Another way to induce melting is to use laser irradiation that can be very precisely directed to the places where the surfaces should be connected to each other, resulting in locally melting the material only inside the connection surfaces. This not only minimizes the amount of energy (by adjusting the laser power), but also enables a very exact location of the welding seam since lasers can have less than 100 micrometers small focal spots that can be directed very accurately along pre-described paths. By using fast laser scanners or masks, even larger areas can easily and quickly be heated up. It has to be emphasized that heating takes place only at the contact area and not in the depth of the material, depending on the absorption coefficient that indicates the ability of the material to absorb irradiation of a certain wavelength. It also has to be understood that one of the contact partners must be transparent to said wavelength whereas the other has to absorb light of the same wavelength quite well. This, of course, does limit the area of application for said technology since not all materials are available in transparent and non-transparent types nor can they be made to be so. Since diagnostic micro fluidic devices often use some sort of light detection on the embedded sample, the need for one absorbing contact partner might inhibit proper functioning of the device so that usage of laser-induced heating ("laser welding") as a connection technique cannot be used. Also, the usually high initial costs for laser welding systems might keep otherwise potential users from employing this technique. [0014] Where applicable, however, laser welding is a very fast and reliable method to fasten and tightly seal any type of fluidic device (as long as melting material is present at least at the contact surface). Since no additional material for the connection layer is necessary, no further steps than making sure that the proper absorption/transmission is possible have to be taken. [0015] A third and quite simple way of sealing fluidic structures is to mechanically press lid and base against each other. Depending on the pressure inside the channels, the surface quality of the contact surfaces and the available external pressure, it may or may not be necessary to take actions to improve sealing by placing additional sealing layers in between the contact surfaces. Usually, those are soft, rubber-like materials. [0016] Advantageous is the fact that mechanical clamping is usually cheap, fast and secure, if properly adjusted to fulfil all requirements of the task. On the other hand, the external pressing forces have to be applied somehow. This might be achieved using additional screws, clips or even frames that hold and press the contact partners against one another. All these solutions require space and possibly other materials than the one of the fluidic system, in turn resulting in higher end prices and possibly bulkier devices. But still, mechanical fastening has the advantages over other joining methods due to its speed and simplicity. A main disadvantage of entirely flat shaped contact surfaces is the fact that distributions of contact pressures are highly dependent on the places where the external compression forces are coupled into the contact partners from the outside. For example, if a flat, square-shaped device is held together by screws located in its four corners, the contact pressure will be very high close to the corners, and will significantly lesson towards the centers of the surfaces. Uneven pressure distribution can even go so far that a gap is formed in the center, since the lid might be strongly deformed through excessive compression forces in way that they lead to unwanted outward bulging of the lid (and/or the base). [0017] Uneven pressure distribution, however, usually leads to leakage of the fluidic system, if not even the lowest contact pressure is high enough to seal the system (i.e. higher than the highest fluidic pressure plus a safety factor). In order to ensure proper sealing, the compression forces need to be rather high and the lateral dimensions of the devices may not, in comparison to its thickness, exceed a certain value (approx. 5:1 to 10:1). Otherwise, bulging may occur. Such practice is not considered to be efficient since high compression forces result in higher loads on places where otherwise being unnecessary, in enhanced creep (if using polymeric materials), the need for stiffer constructions, and the like. SUMMARY OF THE INVENTION [0018] The present invention discloses a significant improvement regarding the problem of uniformly sealing a fluidic device with a protective lid or cover, respectively. Starting from the fact the pure mechanical sealing could be suitable for many applications if the contact pressure between base and lid would be more uniform, a way of overcoming this disadvantage is presented hereinafter. [0019] Basically, the invention proposes to change the shape of at least one or both joined components or partners, preferably the lid, in a way that when pressed against its counterpart, uniform contact pressure occurs. This is achieved by exactly calculating a curvature of the contact partner(s) resulting in said uniform or an intentionally non-uniform pressure distribution. It has to be understood that the shape calculated is valid only for this special case of geometry, thickness, material stiffness, desired pressure-tightness and clamping forces. [0020] Nevertheless, the basic principle can be used for virtually all shapes, materials, etc., although the resulting shapes can look rather different if compared with one another. This is the reason why only some preferred embodiments of the invention can be described hereinafter more in detail. [0021] The above-mentioned external forces either can be coupled into a lid/fluidic structure either by application of the external forces along the outward edges, the corners or other points of the lid-shaped element's outer surface or alternatively can be created after application of said lid-shaped element on the sealing surface of the fluidic structure or by creation of connecting points by means of laser welding or the like. In the latter case the connecting points are established by the laser welding points themselves between the lower surface of the lid-shaped element and the sealing surface of the fluidic structure to be sealed. In the case the preformed lid element is subject to external forces applied thereon, after flattening of the preformed lid element and performing of the laser welding operation, said external forces are removed. Continue reading about Method of transforming a pre-determined force or pressure pattern... Full patent description for Method of transforming a pre-determined force or pressure pattern Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method of transforming a pre-determined force or pressure pattern patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Method of transforming a pre-determined force or pressure pattern or other areas of interest. ### Previous Patent Application: Apparatus and method for controlling the speed of a pump in a well Next Patent Application: Pump and pump control circuit apparatus and method Industry Class: Pumps ### FreshPatents.com Support Thank you for viewing the Method of transforming a pre-determined force or pressure pattern patent info. IP-related news and info Results in 0.22883 seconds Other interesting Feshpatents.com categories: Qualcomm , Schering-Plough , Schlumberger , Seagate , Siemens , Texas Instruments , 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
