Patent Application
20060160206
The present invention relates to the miniaturization of analytical, synthetic, preparative etc procedures within chemical and biological sciences.
One aspect of the invention is a microfluidic instrument arrangement, which comprises a) one, two or more essentially equal microfluidic devices, and b) an instrument for processing the microfluidic devices. Additional aspects are: i) the instrument as such, ii) the use of the instrument for processing the microfluidic device (method of processing), iii) a microfluidic device as such, and (iv) a method for loading a predetermined liquid aliquot to each of the microchannel structure of a microfluidic device (“Dip-Chip technology”). The instrument may be used for processing different kinds of microfluidic devices. The microfluidic device may be processed in the innovative instrument but also by the use of other instruments and/or other means. The microfluidic device of item (iii) is adapted to the Dip-Chip technology.
A microfluidic device comprises a number of microchannel structures through which a liquid flow is used for transporting analytes, reactants etc. Devices used in the innovative arrangement/instrument utilize centrifugal force created by spinning the devices for the transport within at least a part of each microchannel structure. Devices of aspect (iii) above do not need to utilize centrifugal force for driving liquid flow.
Patents and patent applications cited in this specification are hereby incorporated by reference in their entirety.
Microfluidic Systems
The use of centrifugal force for moving liquids within microfluidic systems on circular platforms has been described among others by Abaxis Inc (U.S. Pat. No. 5,122,284, U.S. Pat. No. 5,591,643, U.S. Pat. No. 5,160,702, U.S. Pat. No. 5,472,603, WO 9533986, WO 9506870); Molecular Devices (U.S. Pat. No. 5,160,702); Gamera Biosciences/Tecan (WO 9721090, WO 9807019, WO 9853311), WO 01877486, WO 0187487; Gyros AB/Amersham Pharmacia Biotech (WO 9955827, WO 9958245, WO 0025921, WO 0040750, WO 0056808, WO 0062042, WO 0102737, WO 0146465, WO 0147637, WO 0147638, WO 0154810, WO 0241997, WO 0241998, WO 0275312, WO 274438, WO 0275775, WO 0275776, WO 03018198, WO 03024598 and WO 03093802 (SE0201310-0).
Centrifugal force has also been used for sector-shaped microfluidic discs. See WO 9607919 (Biometric Imaging).
WO 0173396 (Caliper) describes a microfluidic device in which there are inlet ports designed as capillary tips.
Non-Microfluidic Systems
Chromatographic columns have been placed in centrifugal rotors and spinning used for driving samples and other liquids through the columns.
Sedimentation in packed columns that are oriented parallel to each other in the same radial direction in a centrifugal field has been utilized for performing blood tests. See for instance U.S. Pat. No. 6,114,179 and U.S. Pat. No. 5,338,689 (Stiftung für diagnostische Forschung).
Other non-microfluidic systems based on circular discs that can be spun have been described in U.S. Pat. No. 4,469,973 (Guigan), U.S. Pat. No. 4,519,981 (Guigan), U.S. Pat. No. 4,390,499 (IBM), EP 392475 (Idemitsu) and many others.
Problems Associated with Prior Microfluidic Techniques Utilizing Centrifugal Force.
Procedures within chemical and biological sciences have been adapted to miniaturized formats in order to increase the productivity of performing analytical, synthetic, preparative etc. There is a general desire to increase a) the total number of successful tests per time unit, per test device and per instrument, and b) the number of successful tests/results from a given volume/amount of sample, reagent, etc.
Miniaturization often creates new problems and/or accentuates problems that are easy to handle in larger systems. Interfacing to a microfluidic device is more difficult the smaller and/or more dense-packed the microchannel structures are. The risk for inaccuracies in the transfer of liquid from the instrument to the individual microchannel structures increases dramatically when going down in the μl-range, in particular when entering into its lower part (sub-μl-range or nanolitre range, nl-range including picolitre range). The significance of losses caused by undesired evaporation and by irregular adherence to surfaces increases dramatically. Intermolecular forces become more important that may lead to a liquid behaviour that is different compared to larger scales. In total technical solutions that are applicable to the macroworld many times are not always applicable to the microworld. New technical solutions and modifications are required.
Objects of the invention are to provide an instrument for processing of identical or different microfluidic devices, which enables:
Item d. ii) typically means that the liquid flow is in the main direction in the upstream part of a microchannel structure and in the opposite direction in a subsequent downstream part, typically the last part of the structure. The definition of “main direction” is given under the heading “Microfluidic device”.
Item f) includes that the liquid flow velocity in corresponding parts of the microchannel structures in one device may differ in a predetermined manner from the liquid flow velocity in corresponding parts of another device that is processed in parallel.
Another object is a microfluidic device that has an inlet arrangement, which simplifies a rapid, reproducible, reliable and accurate loading of well-defined minute liquid volumes to the individual microchannel structures of the device. This object in particular emphasizes volumes in the nl-range, i.e. ≦5,000 nl.
Terms, such as larger, enhanced, simplify etc, are relative to known technology.
Where appropriate these objects apply also to methods utilizing the innovative instrument, the innovative microfluidic device and/or the innovative arrangement.
These objects concern microfluidic systems in which electrokinetic and/or non-electro kinetic liquid flow is utilized. Centrifugal force or other inertia forces, or pressure differences created externally or internally within the individual microchannel structures may be used for creating non-electrokinetic liquid flow. Applying overpressure at the inlet and/or sub-pressure at the outlet of a microconduit/microchannel structure (relative to atmospheric pressure) may create useful pressure differences.
A liquid flow may be active or passive. In principle a liquid flow that is not driven solely by capillarity is active and typically created by external means. Active liquid flow includes flow driven by centrifugal force and other inertia forces, and any other force mentioned herein (except capillary force). Passive liquid flow and capillary liquid flow are in principle synonymous.
The first digit in each reference number refers to the figure while the subsequent two digits refer to the detail concerned.
a-d illustrate views of a variant of the innovative microfluidic arrangement which contains an annular arrangement of 10 microfluidic devices.
a-d illustrate views of a variant which contains an annular arrangement of 4 microfluidic devices. The arrangement is viewed in the same directions as in
a-d illustrates schematically a rectangular form of the innovative microfluidic device, which is constructed from several planar substrates and comprises five microchannel structures.
Microfluidic Instrument Arrangement (First Aspect)
This aspect is illustrated in
As illustrated in
The rotary member (103,203) typically has an axis of symmetry (Cn with n≧2, 3, 4 etc up to ∞) that coincides with a spin axis (104,204). n are in preferred variants ≧5 including in particular circular variants (n=∞). The rotary member (103,203) is spun around the spin axis in a spin plane that is perpendicular to the spin axis.
The first aspect comprises two main characteristic features in combination.
The first main characteristic feature is that the rotary member (103,203) comprises a group (group A) of one or more seats (105a,b . . . ,205a,b . . . ) for retaining at least one of the microfluidic devices (101a,b . . . ,201a,b . . . ) on the rotary member. Each of the seats can i) be positioned at the same radial distance as any of the other seat of the group, and ii) align layer I essentially radially at an angle a relative to the spin plane where 0°<α≦90°, with preference for 45°≦α≦90°, such as α being essentially equal to 90° (as illustrated in
Essentially equal to 90° includes α that is in the interval 85°-90°.
For variants where layer I has an essentially radial orientation and α is essentially equal to 90°, an extension of the device inwards the spin axis (104,204) will typically intersect this axis or, when αis 90°, fully encompass it. In preferred variants this applies also to layer I.
The arrangement may also comprise other kinds of microfluidic devices (not shown). In this case the rotary member may comprise separate groups of seats (group B, group C etc) for one or more of these other kinds of devices. Devices of different kinds may or may not fit into a specific group of seats.
In preferred variants, the microchannel structures of set I are essentially parallel. Each of the seats (105a,b . . . ,205a,b . . . ) of a group, in particular group A, can position corresponding parts of the internal microconduit portions (308a,b . . . ,
The second main characteristic feature is that the microconduit portion (308a,b . . . ,
The Instrument
The innovative instrument (100,200) illustrated in
Each microfluidic device shown in these figures has inlet ports in the form of protrusions (109,209). Each protrusion comprises an internal microconduit of capillary dimension and may be in the form of a tip separately attached to the surface of the microfluidic device. The protrusions in
The total number (x) of seats (105a,b . . . ,205a,b . . . ) that is possible on the rotary member (103,203) depends on the size of the rotary member, the size of the seats, the size of the microfluidic devices that are to be placed in the seats (thickness, extension in the radial direction etc), radial position of the seats, number of annular circles of seats/microfluidic devices, ability of the seats/devices to be rotated etc. Typical x may be found in the interval 2≦x≦1000, such as 2≦x≦100. This interval applies to many microfluidic devices that have a length to be oriented radially that is within the interval 2-30 cm.
Each seat (105,205) preferably is designed to secure that a microfluidic device placed in the seat can be retained while spinning the rotary member (103,203). This retaining function may, for instance, be a geometric configuration in the surface of the rotary member matching the part of a microfluidic device that is to be placed in the seat. Geometric configurations may be in the form of one or more grooves and/or one or more pins and/or other elevated and/or recessed structures. Sub-pressure and/or magnetic forces may also be used, typically in combination with geometric configurations and other retaining functions. There may be further functionalities for retaining the devices on the rotary member, for instance a top plate (110,210) that can be pressed to the upper parts of devices (101,201) that are placed in the seats (105,205) of the rotary member (103,203). This top plate (110,210) may comprise retaining functions on the side that is turned against the rotary member (typically the lower side of the top plate).
Retaining functions that are based on sub-pressure require introduction of sub-pressure on the rotary member (103,203). This is typically done from a non-rotary part of the innovative instrument, possibly involving also rotary parts other than the rotary member (103,203). Examples of other rotary parts are the spindle (106,206) and/or the shaft (107,207). The sub-pressure connection between a rotary part and a non-rotary part preferably a) provides low or no friction between these parts when spinning the rotary member and/or b) permits leakage of air between the rotary part and the non-rotary part concerned. A preferred variant is illustrated in WO 03024596 (Gyros AB). Also other kinds of connections may be used.
Retaining functions that are based on magnetic forces requires that either one or both of the microfluidic device (101a,b . . . ,201a,b . . . ) or the rotary member (103,203) with its seats (105,205) comprise magnetic or magnetizable material.
One or more of the seats may be designed to permit rotation of a microfluidic device (201) about an axis that is parallel to but remote from the spin axis (204) of the rotary member (203). This axis typically is unique for each seat and passes through the seat and/or a device placed in the seat. The rotation may be a full turn or a part of a turn. The rotation of the devices is in a plane that is parallel to the plane of the rotary member (spin plane). In a subvariant, one or more, preferably all, of the seats of a group may have two or more alternative retaining structures (e.g. geometric) that enables orientation of a microfluidic device at fixed angles relative to the radius passing from the centre of the rotary member through the seat concerned. Typically angles are 0°, 90° and/or 180°. A change in orientation of the device is typically accomplished manually. In another subvariant, each of the seats of a group is present on a separate turntable (211a,b . . . ) that is present on the rotary member (203) and can rotate independent of the spinning of the rotary member (203). The plane of rotation of a turntable is parallel to the spin plane of the rotary member. The turntables (211a,b . . . ) may be driven by an electric motor or manually. A change of orientation may be accomplished automatically according to a predetermined time schedule defined by the process protocol programmed into a controller of the instrument (not shown). The use of seats permitting separate rotation of microfluidic devices is in particular of importance for variants in which α is 90° or essentially equal to 90°.
The ability of rotating a device 180° as described in the preceding paragraph permits reversal of the flow direction. It thus becomes possible to transport a liquid (including dissolved reagents and dispensed particles) back and forth in a part of a microchannel structure.
One can also envisage that the possibility of reversing the liquid flow will make it possible with extended microchannel structures comprising extremely large number of functional units permitting more complex procedures without increasing the size of a device. A microchannel structure may thus start at one edge side, reach the opposite edge side where a reversing unit permits the microchannel structure to go back towards the starting edge side. Once the reagents/products etc that are under processing end up in the reversing unit the device is rotated 180° and the process continued.
In other variants the seats can be moved laterally, for instance in a radial direction. In these variants it may be possible to regulate the flow velocity in the internal microconduit portions (308) by moving the seats (105,205) in the radial direction. Presuming constant spin velocity, the flow velocity will increase when increasing the radial distance by moving a seat outwards (and the microfluidic device), and decrease when moving a seat inwards. By placing a number of essentially equal microfuidic devices at different radial distances a spectrum of flow velocities can be effectuated simultaneously.
The capability of radial movement of individual seats (105,205) will simplify individual process treatments of the devices (101,201). A device may thus from time to time be separately placed at a more outward position than the other devices on the rotary member (103,203). This will facilitate measurements, irradiations etc of part areas of individual microfluidic devices (101,201) that are present simultaneously on the rotary member (103,203).
The capability of radial movement also provide a simple way for the transfer of microfluidic devices between two properly aligned innovative instruments, for instance in order to reverse the flow without rotating a device 180°.
In still another subvariant, the seats may permit that microfluidic devices (101,201) placed in the seats (105,205) can be moved upwards and/or downwards in relation to the plane of the rotary member (103,203) (axial movement). The movement for a device/seat may be dependent or independent from the movement of the other devices/seats. This variant will also facilitate individual process treatments of the devices, e.g. measurement, irradiation etc.
The spinner motor (102,202) should be able to create the necessary centrifugal force for driving a liquid between an upstream position and a downstream position in the internal microconduit portions (308) of devices that are placed on the rotary member (103,203). Centrifugal force may be utilized in combination with a second liquid volume to create a sufficient local hydrostatic pressure within a structure to drive a first liquid volume through an outward (downward) and/or an inward (upward) bent of a microchannel structure. See for instance WO 0146465. The spinner motor (102,202) should be able to provide spin velocities that typically are within the interval 50-30000 rpm, such as 50-25000 rpm, or part(s) of these intervals. Spinner motors providing even higher spin velocities may be used. The spinner motor is preferably regulatable in the sense that the spin velocity can be set to different values and different accelerations and/or decelerations. Centrifugal force may also be combined with other forces and/or means to drive liquid flow in a microfluidic device.
The Microfluidic Device
The microfluidic device (300) is illustrated in
The device (300) is preferably a disc or is disc-shaped. The disc may be planar in which is included variants in which planar substrates of different lengths and/or widths have been used in the manufacture as illustrated in
The number of microchannel structures (304a,b . . . ) per device (300) depends on the size of the device and/or the individual microchannel structures. Typically the microfluidic device comprises in total ≧2, such as ≧3 or ≧5 or ≧10 or ≧25 or ≧50 microchannel structures. A typical upper limit is between 100 and 1000, such as between 100 and 500 microchannel structures per device. The microchannel structures may be divided into sets (sets I, II, III etc) depending on design, direction in the device, layer in which they extend in the device etc. The number of microchannel structures in a set is typically within the interval of 1-50, such as 2-25 or 2-20. Microchannel structures of the same set may have a common inlet port, possibly associated with a common distribution manifold (see below). Many times there is only one set in each device. The microchannel structures of a set are typically essentially parallel. The layer (layer I) in which the microchannel structures of a set extend is typically parallel to the top side or to the bottom side of the device.
The prefix “micro” contemplates that each individual microchannel structure (304) comprises one or more microcavities and/or microconduits that have a depth and/or a width that is ≦103 μm, such as ≦5×102 μm or ≦102 μm. Dimensions within this interval are preferably at hand in any location in a microchannel structure. The volume of a microcavity and thus also of liquid aliquots to be transported and processed are typically in the nl-range, i.e. <5,000 nl, such as ≦1,000 nl, or ≦500 nl or ≦100 nl or ≦50 nl or smaller. There may also be larger microcavities extending above the nl-interval, e.g. with volumes 1-10 μl, 1-100 μl, and 1-1,000 μl (μl-range). These larger microcavities are typically associated with inlet ports for liquid and used for the introduction of samples or washing liquids and the like.
Microcavities or microchambers may have the same or a different cross-sectional geometry compared to surrounding microconduits.
The microchannel structures are typically enclosed, e.g. covered, but have openings for inlet/outlet of liquid and/or air (ports/vents).
Different Parts of a Microchannel Structure
A microchannel structures (304) comprises the functional units that are necessary to carry out a predetermined process within the structure and therefore has at least:
An inlet arrangement typically comprises also a volume-metering unit for liquids (309a,b . . . and 310a,b . . . ;
An inlet arrangement may also comprise other functional units, e.g. a separation unit for removing particulate material upstream a volume-metering unit. Separation units for removing particulate material may be based on sedimentation, filtering etc.
An outlet arrangement may or may not be directly linked to a downstream end of an internal microconduit portion (308a,b . . . ).
An outlet arrangement may or may not comprise a waste treatment function. Outlet ports are typicallya also used as air vents or outlets of air
The internal microconduit portion (308a,b . . . ) typically comprises one or more functional units in which a liquid, such as a sample, is processed. In this portion an active liquid flow is typically used for transport of liquid, reactants and the like in at least a part of the portion.
An inlet port, such as IP I1 (305) or IP I2 (306), is primarily used as an inlet for liquid and/or particles (e.g. in suspensed form). An outlet port, such as OP I1 (307), is primarily used as an outlet vent for air and liquid. Ports may also have other functions or combinations of functions, for instance selected from inlet for air (vent), outlet for air (vent), inlet for liquid, and outlet for liquid.
A functional unit (microconduit or system of microconduits) that is common to several microchannel structures is a part of each of the microchannel structures it is common to. Inlet port 305 and also the distribution manifold 315 in
A volume-metering unit is used to meter a part of a liquid volume that has been dispensed into the inlet port associated with the unit. The metered volume is then further transported downstream into the microchannel structure concerned from the inlet arrangement. The precision in the metering should be high, typically within the interval ±10%, such as within ±5%, around a predetermined volume.
A volume-metering unit (309a,b . . . ,310a,b . . . ) typically comprises a volume-defining microcavity (311a,b . . . (
When two or more microchannel structures are associated with the same inlet port (305) for liquid, the volume-metering units (309a,b . . . ) may define a distribution manifold (315) that is common for the microchannel structures connected to the inlet port (IP I1, 305). The distribution manifold (315) illustrated in
When only one microchannel structure is associated with an inlet port (306), the volume-metering unit (310a,b . . . ) typically comprises a volume-defining microcavity (312a,b . . . ) which at its outlet end has a valve function (314a,b . . . ) and at its inlet end is connected to the inlet port (306a,b . . . ) via an inlet microconduit and to an overflow microconduit (319a,b . . . ) through which excess liquid can leave the main flow path. The cross-sectional area of the volume-defining microcavity (312a,b . . . ) is typically increasing at its inlet end where the over-flow microconduit (319a,b . . . ) is attached and decreasing at its outlet end. The overflow microconduit (319a,b . . . ) in the variant shown in
Microconduits (overlow microconduits) (321 and 319a,b . . . ) typically have valve functions (331 and 332a,b . . . , respectively).
In the preferred variants the volume-metering units are directed downwards with their connections (valves 313 and 314) to downstream portions of the microchannel structures (304a,b . . . ) at the lowest level of each unit. The outlet ends (316 and 320a,b) of the excess microconduits (321 and 319) are typically at a level that is lower than the inlet(s) vents (317a,b . . . ), e.g. lower than the connection between the corresponding volume-metering unit (309,310) and the corresponding downstream parts of the microchannel structure, i.e. between a volume-metering unit (309,310) and an internal microconduit portion (308).
The level at which the inlet ports for liquid is located is not critical as long as self-suction (capillarity) is relied upon for filling the volume-metering units.
A volume-metering unit is capable of metering a liquid volume within the interval/subinterval for volumes discussed elsewhere in this specification.
In order to prevent losses of metered liquids due to wicking, anti-wicking structures may be located between an inlet port for liquid and a volume-metering unit located downstream.
Further information on the design of distribution manifolds, volume-metering units, anti-wicking structures, valves, separation units for removing particulate material etc can be found in for instance WO 9853311 (Gamera Biosciences), WO 02074438 (Gyros AB), WO 0318198 (Gyros AB) and many others. See in particular units 3, 7, 10-12 (
Inlet ports that have the same function are typically present on the same side, for instance on an edge side (303) or on the top side or bottom side (301,302). Inlet ports having different functions are typically present on different sides, for instance on different edge sides (303a,b,c or d), or on an edge side and on one of the parallel opposite sides (301,302), or on the top side and the bottom side (301,302). An inlet port, such as OP I1 (305) in
The opening of a port may be on a tip (323 and 324 in
The protrusion design of the inlet ports is particularly well adapted to our innovative methodology herein called “Dip-Chip technique” which comprises that the loading of liquid is accomplished by simultaneously dipping ports of the same kind into a liquid to be introduced. If there are more than one inlet port of the same kind, the individual ports may be dipped simultaneously into separate liquids, for instance into wells of a microtitre plate. If the interior surface of the corresponding inlet arrangement(s) has/have a sufficient wettability as discussed elsewhere in this specification capillarity will cause the liquid to fill each of the microchannel structures (304) to the first valve function(s) (313 and 331 for inlet port 305, and 314 and 332 for inlet ports 306). Upon spinning the microfluidic device in the innovative instrument and opening the valve functions. (332 and 331) in the overflow micrconduits (319 and 332, respectively), excess liquid will leave the microchannel structures via the overflow microconduits (321 for inlet port 305, and 319 for inlet ports 306) leaving a well-defined volume of liquid in each of the volume-defining microcavities (311a,b . . . for inlet port 305, and 312a,b . . . for inlet ports 306). When increasing the spin velocity the liquid in the volume-defining microcavities will be transported further downstream to the reaction microcavities (327a,b . . . ). If each of the reaction microcavities ends with a valve function it will be possible to carry out a reaction at non-flow conditions. If the there is no valve function present the reaction is typically performed under flow conditions. Se further the publications cited as background publications, in particular WO 0275312 (Gyros AB) and WO 03093802 (SE 0201310-0) (Gyros AB).
Loading of ports that are plain openings in the flat surface of the device may be performed in 30 a conventional manner, typically by the use of pipettes and/or more or less automated dispensers. If the same liquid is to be introduced to all ports of a side, the side concerned may simply be dipped into the liquid.
In certain variants there may be a need for inlet portions of different microchannel structures to cross or intersect each other while keeping them physically apart in order to avoid unwanted mixing of liquids. This is the case for variants in which
Placing crossing microconduit parts of different microchannel structures in different sublayers can avoid the risk of undesired mixing. This is illustrated in
The internal microconduit portion (308) may comprise one or more of the following functional units: microconduit for liquid transport, valve unit, branching unit, vent to ambient atmosphere (outlet port), unit for mixing liquids, unit for performing chemical reactions or bioreactions, unit for separating soluble or particulate material from a liquid phase, waste liquid unit including waste cavities and overflow channels, detection unit, unit for collecting an aliquot processed in the structure, possibly for further transfer to another device e.g. for analysis, branching unit for merging or dividing a liquid flow, etc. Units may be combined, for instance detecting/measuring may take place in a reaction microcavity, for instance via a transparent wall (detection window) of this microcavity. The presence of functional units in the internal microconduit portion is illustrated in
Further details about useful functional units can be found in the publications cited above, primarily with Gamera Biosciences/Tecan or Gyros AB/Amersham Biosciences as assignees.
A microchannel structures typically has a main direction of liquid flow (D1) which is defined as the direction from the start to the end of the internal microconduit portion (308a,b . . . ) regardless of turns, branches, parts where the liquid is taken back and forth etc. In the case there are no microchannel structures having other main directions of flow, D1 for a microchannel structure will also be the main direction of flow for the device concerned. In a typical case D1 is directed from one edge side (first edge side (303a)) to another edge side of the device, e.g. an opposite edge side (second edge side (303c)). In variants of the microfluidic device (300) that allow for reversal of liquid flow relative to D1, the main direction D1 is the main flow direction in the initial part of the internal liquid microconduit (308), typically up to the stage where reversal occurs.
If not otherwise is apparent from the context, terms such as “higher”, “upper” and “inner” level/position of a microchannel structure (304) are relative and means that the level/position concerned is located in a direction that is opposite to the main direction D1 compared to a level/position that is at a “lower” level/position. The terms “up”, “upward”, “inwards” etc and “down”, “downwards”, “outwards” will mean “against” and “along”, respectively, the main direction D1 of a microchannel structure.
The device (300) may be placed in a seat (105,205) on the rotary member (103,203). It is always possible to orient the disc plane outwards with the upstream part of the internal microconduit portion (308a,b . . . ) at a shorter radial distance than the downstream part. This orientation means that the first edge side (303a) becomes closest to the centre (axis of symmetry, spin axis) (104,204) of the rotary member (103,203). The main direction D1 of the device will be from the first edge side (303a) (the centre) to the opposite edge side (303c) (outwards), possibly at a certain angle (β) relative to the spin plane (−90°<β<90° with preference for −45°<β<45°, such as 0°).
Wettabillty/Non-Wettability of Inner Surfaces
The microchannel structures have in preferred variants inner surfaces that are hydrophilic. Hydrophilicity may be introduced, for instance as described in WO 0056808, WO 0147637, or U.S. Pat. No. 5,773,488 (Gyros AB). The hydrophilicity should be as given in these publications, i.e. the wettability of the interior of a structural unit should be sufficient for capillary forces to fill the unit with liquid once the liquid front has passed the inlet of the unit. Where appropriate hydrophobic surface breaks (e.g. as anti-wicking means and/or valves) are introduced as outlined in WO 9958245 and WO 0274438. See also WO 0185602 (Åmic AB & Gyros AB).
The exact demand on hydrophilicity (liquid contact angles) of inner surfaces of the microchannel structure may vary between different functional units. Except for local hydrophobic surface breaks the liquid contact angel for at least two or three inner walls of a microconduit in a particular unit should be wettable (=hydrophilic=liquid contact angle≦90°) for the liquid to be transported, with preference for liquid contact angels that are ≦60°, such as ≦50° or ≦40° or ≦30° or ≦20°. In the case one or more walls have a higher liquid contact angle, for instance is non-wettable (hydrophobic), this can be compensated by a lowered liquid contact angle on the remaining walls. This may be particularly important if non-wettable lids are used to cover open hydrophilic microchannel structures. The values above apply to the temperature of use. The liquid referred to is typically water including also other aqueous liquids.
The liquid contact angles given above refer to equilibrium contact angles and measured at the temperature of use, for instance room temperature such as +25° C.±5° C.
What has been said above about hydrophilicity/hydrophobicity applies in particular to the inlet arrangement of the microchannel structures (304) in the preferred microfluidic devices (300), including also the tip part of the microchannel structures, if present.
Microconduits that are used solely for venting purposes (inlet and/or outlet venting) typically have hydrophobic inner surfaces at least at their connection to a microconduit intended for liquid.
Valve Functions
Valve functions can typically be selected from three main categories:
Type 1 valves typically require physically closing of a microconduit and are therefore called “closing valves”. They often have movable mechanical parts.
Type 2 valves function without closing and are therefore “non-closing”. A typical example is directing an electrokinetic flow at the intersection of two channels by switching the electrodes. See for instance U.S. Pat. No. 5,716,825 (Hewlett Packard) and U.S. Pat. No. 5,705,813 (Hewlett Packard).
In type 3 valves, the non-passage or passage of a liquid may be based on:
Type 3a valves are illustrated in WO 0102737 (Gyros AB) in which stimulus-responsive polymers (intelligent polymers) are suggested to create a valve function, and in WO 9721090 (Gamera Biosciences) in which relaxation of non-equilibrium polymeric structures and meltable wax plugs are suggested as valves.
Type 3b valves typically are based on local changes in chemical and/or geometric surface characteristics. Through-flow is achieved by increasing the force driving the liquid. The use of hydrophobic surface breaks (changes in chemical surface characteristics) as valves has been described in WO 9958245, (Gyros AB) WO 0146465 (Gyros AB), WO 0185602 (Åmic AB & Gyros AB), WO 0187486 (Gyros AB) and WO 0274438 (Gyros AB) and WO 031898 (Gyros AB). The use of changes in geometric surface characteristics as valves has been described in WO 9615576 (David Sarnoff Res. Inst.), EP 305210 (Biotrack), and WO 9807019 (Gamera Biosciences). Other alternatives are a porous membrane having pores or clusters of small holes that require a sufficient driving force for the liquid to pass through. The pores/holes are typically hydrophobic and have sizes corresponding to circular areas with a diameter ≦5 μm such as ≦1 μm.
Type 3b valves often comprise an anti-wicking function if they utilize changes in chemical and/or geometrical surface characteristics in edges as described for anti-wicking structures.
Type 3c valves for centrifugal based systems may be achieved by linking the downstream end of a downwardly bent microconduit (U- or Y-shaped) to an upwardly bent microconduit. This is illustrated in WO 0146465 (Gyros AB) with two or more Y/U-shaped structures in sequence in the downstream direction.
If a closing valve is used in a microfluidic device, there is typically an outlet vent associated with the upstream end of the valve function.
Anti-Wicking Structures
Anti-wicking structures are typically local surface modifications that counteract wicking, i.e. undesired liquid transport in the inner edges of microconduits. In microfluidic devices anti-wicking structures are particularly important when retaining liquid volumes that are in the nl-range within predetermined microcavities.
An anti-wicking structure typically comprises a change in surface characteristics in an inner length-going edge of a microconduit. The edge typically starts in a microcavity and stretches into a microconduit connected to the microcavity. The change may relate to a change in geometric and/or chemical surface characteristics. Anti-wicking structures may be present upstream or downstream a microcavity intended to contain a liquid. An anti-wicking functionality may inherently also be present in inner valves that are based on the presence of a hydrophobic surface break in an inner edge.
A change in geometric surface characteristics is typically local and may be selected from deformations, such as indentations and protrusions (projections). In most cases the deformation will also stretch into and across an inner wall of the microconduit concerned. See further WO 0274438 (Gyros AB) and WO 031898 (Gyros AB).
Deformations in the form of indentations, for instance in the form of “ear-like” or triangular, trapezoidal etc grooves as illustrated in
A change in chemical surface characteristics (surface break) for anti-wicking purposes means in a typical case that the inner surface of a wettable microconduit comprises regions that are non-wettable. These regions are primarily present in inner edges of the microconduit but will in the preferred cases extend fully between edges.
A change in geometric and a change in chemical surface characteristics may fully or partially coincide in the inner surface of microconduit.
Further information about various kinds of anti-wicking structures possibly combined with an inner valve function is given in WO 0274438 (Gyros AB) and in WO 031898 (Gyros AB).
Manufacture of the Microfluidic Device.
The microfluidic device may be manufactured from inorganic or organic material. Typical inorganic materials are silicon, quartz, glass etc. Typical organic materials are plastics including elastomers, such as rubber silicone polymers (for instance poly dimethyl siloxane) etc. In a preferred variant, open microstructures are formed in the surface of a planar substrate by various techniques such as etching, laser ablation, lithography, replication etc. From the manufacturing point of view, plastic material are preferred and the microstructures, typically in the form of open microchannels are formed by replication, such as embossing, moulding, casting etc. The microstructures are then covered by a top substrate that if required also is microstructured. See for instance WO 9116966 (Pharmacia Biotech AB). The microstructures in the substrates are designed such that when the surfaces of two planar substrates are apposed the desired enclosed microchannel structure is formed between the two substrates.
Microfluidic devices that require that different parts of a microchannel structure are in different sublayers of layer I (=the layer in which the microchannel structures of set I extend) may be formed by including several substrate layers in the manufacturing method. See FIG. 3 and the text above. A common inlet arrangement (305+309) as an uncovered microstructure ay thus be defined in the surface of a first substrate (III, as indicated in the bottom side of the substrate) and the parts of the microchannel structures (304) that are not defined in the first substrate (III) may be defined in the surface of one or more additional planar substrates (I, as indicated in the top side of the substrate). The microstructures in the substrates match each other such that when the substrates are apposed and joined together the microfluidic device with its microchannel structures will be formed. If needed there may be an intermediary planar substrate (II) placed between two juxta-positioned substrates. An intermediary planar substrate (II) that provides for liquid communication (330a,b . . . ) between parts of the microchannel structures that are defined in different substrates (III and I). A hole, or a cluster of smaller holes or a porous membrane are typically present at the locations where liquid communication is to take place.
At the priority date of this invention the preferred plastic material was a) polycarbonates and plastic material comprising polyolefines. Polyolefins in this context are polymers comprising repeating hydrocarbon monomeric units which preferably consist of one or more polymerisable carbon-carbon doubles or triple bonds and saturated branched straight or cyclic alkyl and/or alkylene groups. Typical examples are Zeonex™ and Zeonor™ from Nippon Zeon, Japan, with preference for the latter. See for instance WO 0056808 (Gyros AB).
The Second Main Aspect—The Instrument.
The instrument may be used in the innovative arrangement. The main characteristic feature is that the instrument comprises the kind of seats (105a,b . . . ,205a,b . . . ) discussed for the first aspect of the invention. In other words the rotary member comprises seats, each of which is capable of orienting layer I of a microfluidic device (300) in the same manner as for the first aspect of the invention. Different variants are apparent from the description above and concern both the instrument as such and features of the instrument that are related to the microfluidic device to be used.
The Third Main Aspect—The Method/Use of the Instrument for Processing Two or more Microfluidic Devices in Parallel.
This method/use comprises the steps of:
Step iii) may be carried out before and/or after step iv). Reactants and other necessary chemicals may also be predispensed to the microchannel structures (304), i.e. be included in the devices provided in step ii). If the microfluidic devices allow for it they may be loaded as outlined by the innovative “Dip-Chip” technique. See the fifth aspect of the invention. The innovative method may be part of a protocol comprising several additional process steps within or external to the instrument. Such external process steps may take place prior to or after steps i)-v) or as a step inserted into this sequence of steps.
The Fourth Main Aspect—a Microfluidic Device.
This aspect is a variant of the microfluidic devices generally described above as a part of the innovative arrangement. The main characteristic feature of the fourth aspect is a) that there is one, two or more inlet ports (305,306) in an edge side of the device (300), and b) that the hydrophilicity in the most upstream part of each of the microchannel structure(s) (304a,b . . . ) that is connected to this/these inlet port/ports is/are such that at least a predetermined volume of liquid is capable of penetrating this part in each microchannel structure by self-suction (capillarity). Each inlet port (305,306) may be in the form of a protrusion (324,333a,b . . . ) comprising a microconduit as described elsewhere herein. This volume may differ between the inlet ports of a set, for instance set I. It typically is at least the sum of the volume-defining cavities (311,312) in the volume-metering unit/units (309,310) which is/are associated with the inlet port concerned (305,306). See under the heading “Microfluidic devices” above.
In preferred variants the characteristic feature is that the corresponding parts of the internal microconduit portion (308a,b . . . ) of each of the microchannel structures are at essentially the same distance from said first edge side (303a) or at the same level.
Further characteristic features of the innovative microfluidic device has been described above in the context of the first aspect of the invention.
The Fifth Main Aspect—Loading by Dip-Chip Technique.
This aspect relates to a method for loading a microfluidic disc with liquid. The characteristic feature comprises the steps of:
Step (iv) may be performed by utilizing centrifugal force for driving the liquid flow, for instance in an instrument of the present invention. Other driving forces may also be utilized by appropriately adapting the microfluidic device to the instrument and driving force utilized.
In the case the kind of port utilizes comprises two or more ports and different liquids are to be introduced through each of the ports, these liquid are preferably provided in separate vessels, for instance in wells of a microtitre plate. In this case the distances between the ports and/or between the wells are adapted to fit each other. Other ports may be used in the similar manner if they are adapted to the Dip-Chip technique. Alternatively there may be ports that are adapted to conventional dispensation techniques, such as by drop dispensers, pipettes etc.
Subsequent to step (iv) the metered volumes are transported further downstream in parallel in the microchannel structures associated with the kind of inlet port(s) used.
At the priority date the best mode embodiment corresponds to the variant shown in the drawings.
The invention is further defined in the appending claims that are part of the specification.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0203595-4 | Dec 2002 | SE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/SE03/01850 | 12/1/2003 | WO | 12/6/2005 |
| Number | Date | Country | |
|---|---|---|---|
| 60430978 | Dec 2002 | US |
