WO2004040319A1

WO2004040319A1 - A microfluidic system and a microdevice for velocity measurement, a method of performing measurements and use hereof

Info

Publication number: WO2004040319A1
Application number: PCT/DK2003/000745
Authority: WO
Inventors: Klaus Bo Mogensen; Jörg Peter KUTTER
Original assignee: Technical University Of Denmark
Priority date: 2002-11-01
Filing date: 2003-10-31
Publication date: 2004-05-13
Also published as: AU2003275942A1

Abstract

A microfluidic system for velocity measurement of an object moving along a microfluidic channel, wherein, illumination of said channel is performed at a plurality of locations along the microfluidic channel, wherein a plurality of optical waveguides are arranged adjacent said microfluidic channel, and wherein at least two of said plurality of optical waveguides form part of an optical beamsplitter arrangement. The system according to the invention allows multi-point optical addressing and detection along a microfluidic channel wherein an object is driven. By proper processing of detected optical signals, e.g. by performing a Fourier transformation, information regarding velocity of the object can be achieved.

Description

A MICROFLUIDIC SYSTEM AND A MICRODEVICE FOR VELOCITY MEASUREMENT, A METHOD OF PERFORMING MEASUREMENTS AND USE HEREOF

Field of the invention

The invention relates to, as specified in the preamble of claim 1, a microfluidic system for velocity measurement of an object moving along a microfluidic channel. The invention further relates to microdevices for velocity measurements as specified in the preamble of claim 22 and claim 23, respectively. The invention also relates to a microdevice for performing measurements relating to a moving object as specified in the preamble of claim 28 and a method of performing measurements as specified in claim 34. Finally, the invention pertains to use hereof as specified in the preamble of claim 36.

Background of the invention

Velocity measurement of small particles, e.g. particles of micro- or nano-size, is important in many technical fields and applications. For example, velocity measurements are very important in the field of biochemistry since the velocity of a cell under the influence of an electrical field can provide information regarding the state of the cell.

Velocity data of particles may be obtained with two-point measurements. However, the disadvantage of this approach is that only a single particle/cell is allowed in a detection zone at a given time, which makes this approach inappropriate for complex sample mixtures.

Experiments regarding measurements of particles in a microfluidic chip have been described in Kwok, Y.C., Jeffery, N.T. and Manz, A. "Velocity Measurement of Particles Flowing in a Microfluidic Chip Using Shah Convolution Fourier Transformation Detection", Analytical Chemistry, Vol. 73, No. 8, April 15, 2001, pp. 1748 to 1753. Further, US 6,233,048 Bl describes a similar technology for determining velocity of species bands moved through a channel in a microfluidic system by electrophoretic forces. Light from periodically spaced regions along the channel are received by a photodetector. The intensity of the light received by the photodetector is modulated by the movement of the species bands through the channel, and by Fourier analysis, the velocity of each species band may be determined. The identification of the species is made based on the electrophoretic mobility in the channel.

The technology described in the above article and the abovementioned US patent specification relies on free-space optical elements, such as lenses, mirrors and beam expanders. This makes these systems very sensitive to correct optical alignment and hence also to shock and vibrations. Such a system is furthermore difficult to miniaturize and expensive due to e.g. high packaging costs.

A further example of related prior art is described in WO 01/38844 A2 that describes a capillary electrophoresis device with a plurality of electrophoresis channels formed in a substrate layer. An optical waveguide system transmits excitation radiation into each of these channels with the purpose of detecting the migration rate of chemical components. Fluorescence radiation from the channels is detected by a detector system. Detection of fluorescence is, however, only monitored at one point or possibly two points along the channel, and velocity measurements are not involved in this prior art technique.

It is an objective of the present invention to provide a system for performing measurements related to objects such as particles, cells etc. moving along a microfluidic channel that provides improvements in relation to the prior art systems.

Further, it is an objective to provide such a system by means of which measurements may be performed in a miniaturized domain. Another objective is to provide such a system for performing measurements involving complex sample mixtures.

A further objective is to provide such a system by means of which reliable measurements may be performed.

A still further objective is to provide such a system by means of which reliable measurements may be performed at reduced costs and/or with reduced efforts.

Another objective is to provide such a system for performing measurements in the field of life science, e.g. for measurements performed on cells and/or particles for analyses, assays etc.

These and other objectives are achieved by the invention as explained in the following.

Summary of the invention

The invention relates to, as stated in claim 1, a microfluidic system for velocity measurement of an object moving along a microfluidic channel, wherein illumination of said channel is performed at a plurality of locations along the microfluidic channel, wherein a plurality of optical waveguides are arranged adjacent said microfluidic channel, and wherein at least two of said plurality of optical waveguides form part of an optical beamsplitter arrangement.

Hereby a system is achieved that allows multi-point detection along a microfluidic channel and whereby correct optical alignment will be assured, e.g. since the locations of the optical addressing will remain fixed and stable in all circumstances. Further, such a system may be provided using fewer free-space elements than the prior art systems, and thus a less complicated system may be provided. Thereby measurements may be performed with a higher degree of dependability and credibility. Further, such a system may provide a high degree of user-friendliness and measurements may be performed in an efficient manner. Further, since the free-space optical elements are avoided a small and rugged analysis system may be provided according to the invention. Finally, since an optical beamsplitter arrangement, e.g. a planar waveguide beamsplitter, is an inherent part of the system, light intensity in the waveguides leading light to the detection channel may be arranged, particularly to achieve equivalent light intensity at all optical addressing locations at the detection channel. The optical power in each branch of the beamsplitter may furthermore be controlled by a suitable design of the waveguide design.

Furthermore a miniaturization is achievable according to the invention. A detector arrangement may furthermore be positioned in close proximity to the microchannel, which significantly improves the light collection efficiency compared to the conventional approach where the detector is placed several centimeters from the detection channel.

According to a preferred embodiment, as stated in claim 2, said plurality of optical waveguides may be arranged essentially transversely to said microfluidic channel in the vicinity of the microfluidic channel. Hereby, a system according to the invention may be designed in an advantageous manner, whereby a plurality of waveguides may be arranged with very small mutual spacing. Though, it will be understood that other forms may be possible.

According to a further preferred embodiment, as stated in claim 3, said optical beamsplitter arrangement may involve a 1 X k waveguide beamsplitter, and k waveguides may be arranged adjacent said channel.

Preferably, as stated in claim 4, k > 4, in a more preferred form k > 16 and in an even more preferred form k> 32. Hereby a sufficient number of addressing points is provided to facilitate measurement of velocity of objects with a tolerance that may be satisfactory for certain applications and purposes. In a further preferable form, k > 64, in a more preferred form k > 128 and in an even more preferred form k> 256. Hereby a sufficient number of addressing points is provided to facilitate measurement of velocity of objects with a relatively high degree of accuracy. It will be understood though, that a higher number of addressing points, e.g. 512, 1024 etc. may be chosen, if needed. Further, it will be understood that other numbers than those mentioned may be used instead.

Advantageously, as stated in claim 6, said beamsplitter arrangement may comprise a rejection structure for stray light. Hereby problems with detection of stray light that might otherwise hamper the performance of the system, e.g. light propagating in a waveguiding layer and stemming from e.g. a branching point, maybe circumvented.

Preferably, as stated in claim 7, said rejection structure may comprise a channel arranged transversely between two corresponding branching waveguides of said beamsplitter arrangement. Hereby such a blocking structure may be arranged in an advantageous manner in the same layer as the waveguides of the beamsplitter arrangement.

According to a further preferred embodiment, as stated in claim 8, said rejection structure may comprise at least two of said channels arranged transversely between two corresponding branching waveguides of said beamsplitter arrangement, said at least two channels being arranged essentially parallel. Hereby an enhanced efficiency can be achieved. It will be understood that any number of such parallel channels may be provided, e.g. two, three, four or more.

According to an embodiment, as stated in claim 9, said rejection structure may comprise means for transferring stray light away from the waveguide plane. Such means may comprise means for dispersing light beams, e.g. caused by different refractive indices for different material. The stray light may be transferred to other layers, e.g. a lid layer, a substrate etc. According to another embodiment, as stated in claim 10, said rejection structure may comprise means for reflecting stray light. Such means may be mirror surfaces etc.

Further, as stated in claim 11, said rejection structure may comprise means for absorbing stray light.

In a still further preferred embodiment, as stated in claim 12, said waveguides arranged adjacent said microfluidic channel may comprise means for shaping, e.g. condensing or spreading light beams guided towards said microfluidic channel. Hereby, the light entering the detection channel and particularly the profile of the light beam may be shaped in order to achieve an enhanced performance of the system.

Advantageously, as stated in claim 13, said means for shaping light beams may involve shaping of said waveguides locally in the vicinity of said microfluidic channel, e.g. at the end portion of said waveguides.

Preferably, as stated in claim 14, said shaping of said waveguides may involve a gradually enlarged dimension of said waveguides. Hereby a focusing of the light beam may be achieved at the addressing point.

Alternatively, as stated in claim 15, said shaping of said waveguides may involve a gradually reduced dimension of said waveguides. Hereby a spreading of the light beam may be achieved at the addressing point.

Advantageously, as stated in claim 16, said means for shaping light beams may involve shaping of said microfluidic channel locally in the vicinity of said waveguides, e.g. at the end portion of said waveguides. Hereby the wall of the microfluidic channel may serve as an optical element locally, e.g. as a micro-lense.

Preferably, as stated in claim 17, said shaping of said microfluidic channel may involve a spreading lens. Alternatively, as stated in claim 18, said shaping of said microfluidic channel may involve a focusing lens.

Advantageously, as stated in claim 19, said system may comprise means for producing and/or guiding light into said optical beamsplitter arrangement. Such means may advantageously be coupling means for coupling and aligning a light source with the beamsplitter arrangement, whereby reliability and ruggedness is enhanced. Optionally, light producing means, e.g. laser light sources, may also form part of an integrated system.

Further, as stated in claim 20, said system may comprise means for detecting and or recording light emanated from said microfluidic channel caused by passing objects. Such means may be a photo multiplier tube, CCD devices etc. or means for facilitating coupling to such means, whereby user-friendliness, reliability and ruggedness is enhanced.

Furthermore a miniaturization is achievable according to this embodiment of the invention. A detector arrangement may be positioned in close proximity to the microchannel, which significantly improves the light collection efficiency compared to the conventional approach where the detector is placed several centimeters from the detection channel.

In a further advantageous form, as stated in claim 21, said system may comprise means for processing signals stemming from objects passing said microfluidic channel. Such mean may be e.g. computerbased processing means for providing resulting measured values of e.g. velocity, display means for displaying these etc.

The invention also relates to, as stated in claim 22, a microdevice for velocity measurement of an object moving along a microfluidic channel of said microdevice, comprising means for illumination of said channel at a plurality of locations along the microfluidic channel, a plurality of optical waveguides arranged adjacent said microfluidic channel, and an optical beamsplitter arrangement involving at least two of said plurality of optical waveguides.

Hereby a microdevice, e.g. a biochemical microdevice, is provided that allows multipoint detection along a microfluidic channel and whereby measurements may be performed in an uncomplicated manner. Further measurements may be performed with a higher degree of dependability and credibility and such a system may provide a high degree of user-friendliness and efficiency. Since free-space optical elements are avoided by such a microdevice a small and rugged analysis system may be provided according to the invention. Finally, since an optical beamsplitter arrangement is an inherent part of the system, light intensity in the waveguides leading light to the detection channel may be arranged, particularly to achieve equivalent light intensity at all optical addressing locations at the detection channel. The optical power in each branch of the beamsplitter may be controlled by a suitable design of the waveguide layout.

Furthermore a miniaturization is achievable according to the invention. A detector arrangement may furthermore be positioned in close proximity to the microchannel, which significantly improves the light collection efficiency compared to the conventional approach where the detector is placed several centimeters form the detection channel.

Further, the invention relates to, as stated in claim 23, a microdevice for velocity measurement of an object moving along a microfluidic channel of said microdevice, comprising a microfluidic system according to one or more of claims 1 to 21.

Advantageously, as stated in claim 24, said microdevice may comprise a substrate layer, a layer of waveguding medium, a plurality of waveguides arranged in an optical waveguide beamsplitter arrangement, and a microfluidic system comprising at least a detection channel for multiple-point light detection, wherein said plurality of waveguides are formed in said layer of waveguiding medium, and said at least one microfluidic detection channel is formed at least partially in said layer of waveguiding medium.

Preferably, as stated in claim 25, said microdevice may comprise a lid placed above said layer of waveguiding medium.

In a further advantageous form, as stated in claim 26, said microdevice may comprise a layer placed on one or both sides of said layer of waveguiding medium, e.g. for restricting propagation of optical waves to said layer of waveguiding medium.

In a still further advantageous embodiment, as stated in claim 27, said microdevice may comprise two or more layers of waveguiding medium, each layer comprising waveguides formed in said layer. Hereby, waveguides leading light to the detection channel may be arranged in two or more levels in the microdevice, whereby a number of advantages may be achieved. For example, it will hereby be possible to detect objects in different levels, i.e. vertical locations in the detection channel, and it will be possible to measure velocities in different levels and/or detect/measure a velocity profile.

Further, the invention relates to, as stated in claim 28, a microdevice for performing measurements related to an object moving along a microfluidic channel of said microdevice, comprising means for illumination of said channel at a plurality of locations along the microfluidic channel, a plurality of optical waveguides arranged adjacent said microfluidic channel, and an optical beamsplitter arrangement involving at least two of said plurality of optical waveguides.

The invention also relates to, as stated in claim 29, a microdevice for performing measurements related to an object moving along a microfluidic channel of said microdevice, comprising a microfluidic system according to one or more of claims 1 to 21.

Preferably, as stated in claim 30, said microdevice may comprise a substrate layer, a layer of waveguding medium, a plurality of waveguides arranged in an optical waveguide beamsplitter arrangement, and a microfluidic system comprising at least a detection channel for multiple-point light detection, wherein said plurality of waveguides are formed in said layer of waveguiding medium, and said at least one microfluidic detection channel is formed at least partially in said layer of waveguiding medium.

Advantageously, as stated in claim 31, said microdevice may comprise a lid placed above said layer of waveguiding medium.

Preferably, as stated in claim 32, said microdevice may comprise a layer placed on one or both sides of said layer of waveguiding medium, e.g. for restricting propagation of optical waves to said layer of waveguiding medium.

In a further preferred form, as characterized in claim 33, said microdevice may comprise two or more layers of waveguiding medium, each layer comprising waveguides formed in said layer. Hereby, waveguides leading light to the detection channel may be arranged in two or more levels in the microdevice, e.g. located adjacent to the detection channel, whereby a number of advantages may be achieved. For example, it will hereby be possible to detect objects in different levels, i.e. vertical locations in the detection channel, and it will be possible to measure velocities in different levels and/or detect/measure a velocity profile.

The invention further relates to a method as stated in claim 34 of performing measurements related to an object moving along a microfluidic channel, comprising the steps of driving said object along said microfluidic channel located in a microdevice, guiding light into an optical waveguide placed on said microdevice, performing beamsplitting of said light guided into said optical waveguide, guiding a multiplicity of light beams resulting from said beamsplitting to locations in the vicinity of said microfluidic channel, said locations being distributed in the longitudinal direction of said channel, and detecting and or recording of light caused by optical addressing of the passing of said object in said microfluidic channel.

Hereby a method is provided that allows multi-point detection along a microfluidic channel and whereby measurements may be performed in an uncomplicated manner. Further measurements may be performed with a higher degree of dependability and credibility and such a method may provide a high degree of user-friendliness and efficiency. Free-space optical elements are avoided by such a method.

Advantageously, as stated in claim 35, said multiplicity of light beams resulting from said beamsplitting may be guided to locations in the vicinity of said microfluidic channel, said locations being distributed in the longitudinal direction of said channel as well as in the vertical direction. Hereby, it will be possible to detect objects in different levels, i.e. vertical locations in the detection channel, and it will also be possible to measure velocities in different levels and/or detect/measure a velocity profile for the medium in the detection channel. Further advantages may be achieved as explained in the detailed description. Finally, the invention relates to use of a microfluidic system according to one or more of claims 1 to 21, a microdevice according to claim 22, a microdevice according to one or more of claims 23 to 27, a microdevice according to claim 28, a microdevice according to one or more of claims 29 to 33 and/or a method according to claim 34 or 35 for measuring velocity of objects such as particles, cells, beads etc., in particular chemical or biochemical objects.

Further, a system, a microdevice and/or method according to the invention may be combined with other micro-machined chemical and/or medical devices, e.g. particle counters for blood or food analysis.

The figures

The invention will be explained in further detail below with reference to the figures of which

fig. 1 shows in a general view a measurement system, e.g. a velocity measurement system according to an embodiment of the invention, fig. 2 shows a picture of a planar waveguide beamsplitter arrangement without any stray light rejection measures, fig. 3 shows a velocity measurement system as illustrated in fig. 1, but provided with stray light rejection measures, fig. 4 shows in a detailed view from above a chip according to an embodiment of the invention in a region with optical waveguides, stray light rejection structures and a microfluidic channel, fig. 5a and b illustrate a sectional view of two embodiments of stray light rejection structures, fig. 6 shows in a view from above a microdevice according to an embodiment of the invention comprising a planar waveguide beamsplitter, stray light rejection structures and a microfluidic channel network, fig. 7 shows a microscope picture of a detection channel being illuminatd through an integrated 1x128 waveguide beamsplitter, fig. 8 shows a microscope picture of embodiments of stray light rejection structures between two waveguides, fig. 9 shows a diagram showing 128 peaks generated from an object passing a detection region of a microfluidic channel according to an embodiment of the invention, fig. 10 shows data resulting from a processing of the data shown in fig. 9 involving a Fourier transformation, fig 11 shows examples of different designs of the waveguides in the vicinity of the detection channel in order to achieve a shaping of the optical beam profile, fig. 12 shows sectional sideview of a part of a microchip according to a still further embodiment, and fig. 13 illustrates such a chip in a form essentially corresponding to the embodiment shown in fig. 1.

Detailed description

A device generally designated 1 according to an embodiment of the invention is shown in fig. 1. This device 1 comprises a microfluidic chip 2 comprising microfluidic channels 3 to 7 and reservoirs 10 to 14, e.g. sample and/or buffer reservoirs and/or sample and/or buffer waste reservoirs.

Objects, e.g. particles, cells, etc. may be driven in the channels, e.g. by means of electrokinetics. In order to determine the velocity of such objects being moved along the microfluidic channel 3, a number of waveguides 20 are arranged in or on the chip 2 in such a manner that light propagating by means of these waveguides will illuminate the microfluidic channel 3 at locations, which are preferably evenly distributed along the channel.

The waveguides 20 are arranged in a beamsplitter arrangement, e.g. a planar waveguide beamsplitter, as illustrated, e.g. the eight waveguides 20 being branches connected to waveguides 21, that on their part are connected to waveguides 22 etc. As indicated, the waveguides are connected at branching-out locations 26. In the illustrated example, three consecutive branchings are involved, resulting in eight (i.e. 2³) waveguides 20 leading light to the illumination locations at the detection channel 3. In general, if n branchings are involved, 2ⁿ illumination locations are provided.

Light propagating via the beamsplitter arrangement is fed into a waveguide 23 from a light source 30, for example a laser light source, and transmitted through the beamsplitter arrangement to the channel 3.

The objects, e.g. objects of micro- or nano-size, being driven along the channel 3, that may also be referred to as the detection channel, may be treated to be fluorescent, whereby the movement of a given object will be indicated by light radiating from the locations at the ends of the waveguides when the object passes each of these. When a particle or cell moves along the microfluidic channel a signal is generated at distinct time intervals corresponding to when the particle or cell is in one of the detection zones. This generates a signal with a peak for each detection window.

The light emanated from the channel 3 caused by the passing of an object may be detected and/or recorded in order to determine the velocity of the object being driven along the channel 3.

Thus, the emanated light may be detected by e.g. a photomultiplier tube placed for example above the channel 3. Other means of detecting and/or recording the light may be utilized, e.g. CCD-devices etc.

The determination of the velocity of a passing object may be performed as described in for example Kwok, Y.C., Jeffery, N.T. and Manz, A. "Velocity Measurement of Particles Flowing in a Microfluidic Chip Using Shah Convolution Fourier Transformation Detection", Analytical Chemistry, Vol. 73, No. 8, April 15, 2001, pp. 1748 to 1753. This method may be referred to as the SCOFT-method (Shah Convolution Fourier Transformation). Other data analysis schemes besides Fourier transformations can also be used, e.g. Wavelet transformations. This is especially advantageous when measuring on a single bead. Such a method is described in "Wavelet transform for Shah convolution velocity measurements of single particles and solutes in a microfluidic chip" by Jan C. T. Eijkel, Yien C. Kwok, Andreas Manz, Lab on a Chip, 2001, pp. 122 to 126.

Other data processing methods and schemes may be used as well, which will be obvious to a skilled person.

Fig. 2 shows a picture of a planar waveguide beamsplitter arrangement having 16 waveguides 20, corresponding to four branching points, but apart from this designed as generally shown in fig. 1. It will be understood that the picture shows incoming light that may arrive at a detection channel 3 and that the light beams from the ^" waveguides 20 are indicated by the references 20' (only four of these are indicated for clarity reasons). However, evidently stray light is also present at this location, primarily stemming from the first branching as indicated at 28. But also between the other illumination locations stray light is - more or less - present, as indicated by 29. It will be understood that if stray light is present in a certain amount, this may influence on the measurements performed by means of the invention, e.g. the measurements may provide results with reduced creditability and/or more complicated signal processing, processing circuitry and/or processing software may be needed.

An embodiment of the invention, whereby unwanted influence from stray light may be avoided, is exemplified in fig. 3. In fig. 3, a microfluidic chip 2' corresponding essentially to the chip shown in fig 1, is illustrated. This chip 2' has been provided with a number of stray light rejection measures, e.g. for transferring, reflecting, absorbing etc. stray light. Primarily, stray light rejection measures 31 have been provided between the waveguides 22 in order to reject stray light stemming from the branching 26. However, similar measures may also be provided between the following branches of the optical waveguide beamsplitter arrangement, e.g. measures 32 between the waveguides 21, measures 33 between the waveguides 20 etc. as illustrated.

An example of such stray light rejection measures according to an embodiment of the invention is illustrated in detail in fig. 4, showing from above in an enlarged view part of a chip according to an embodiment of the invention. It will be understood that dark areas on fig. 4 illustrates a layer of optical waveguiding medium, e.g. arranged on a substrate layer (not shown in fig. 4) and that light areas indicate channels in this layer. The detection channel 3 is designed as a microfluidic channel in this layer, and the optical waveguides 20 may be shaped by means of grooves 27 formed in the waveguiding layer. In this case the grooves 27 will of course not extend into the microfluidic channel 3, but will be separated from this channel by a small distance. Other means of providing the waveguides, e.g. 20 may be utilized. The stray light rejection measures 23 comprise in this example a number of parallel grooves, channels, slots etc. 35 in the layer of waveguiding medium, arranged from one waveguide 20 to the next. It will be understood that these grooves 35 need not extend into grooves 27 defining the waveguides 20. However, preferably, the ends of these stray light rejection grooves 35 are situated in the vicinity of the waveguides 20, whereby an optimal stray light rejection may be achieved. In the example four of these grooves have been arranged in a single stray light rejection arrangement, but it will be understood that any number of grooves may be used, e.g. one, two, three, four or even more if found practical and/or necessary.

Embodiments of these stray light rejection grooves are illustrated in fig. 5a and 5b. These figures show in a enlarged sideview a section of a part of a microfluidic chip through a groove or channel 35 of a stray light rejection groove. The chip is based on a substrate 40, upon which a layer of waveguiding medium 41 is arranged. This layer 41 is utilized for providing the waveguides of the optical waveguide beamsplitter according to the invention, e.g. by forming grooves 27 as shown in fig. 4. Between the layer 41 and the substrate 40 a further layer 42 may be arranged. Similarly, above the layer 41 a further layer 43 may be placed. These layers may serve a number of purposes, e.g. for guiding the light in the layer 41 by total internal reflection. Above the layer 43 a lid 45 is placed, e.g. for closing the microfluidic structures, e.g. channels, reservoirs etc., in the vertical direction, for providing electric connections and electrodes for the microfluidic operation etc.

In fig. 5a stray light is shown propagating from the left towards the rejection channel 35. As illustrated, when the stray light reaches the channel 35 through the side wall 46, the light will be dispersed, caused by the different refraction indices of the waveguide medium and the medium, e.g. air, in the channel 35. An amount of the light will enter the lid 45 or the substrate 40 and will thus not propagate further via the waveguide 41 on the right side of the channel in fig. 5a. Thus, the stray light propagating via the layer 41 has been reduced significantly, and if one or more further rejection grooves are arranged in parallel with the illustrated groove or channel 35, an enhanced reduction will be achieved.

Fig. 5b corresponds to fig. 5a, apart from the fact that the side walls, one or both, of the channel 35, are provided with reflecting surfaces 47, e.g. designed with mirror surfaces. Thus, stray light propagating via the waveguiding medium 41 from the left will be reflected and will propagate in the opposite direction as indicated. Further, stray light can not enter the waveguiding medium from the channel 35, e.g. to the left in fig. 5b, as this will be prohibited by the reflecting surface 47. Also in this example, more than one rejection channel 35 may be provided.

Fig. 6 shows in a view from above a microdevice 1" according to a further embodiment of the invention comprising a planar waveguide beamsplitter, stray light rejection structures e.g. 31, 32 and a microfluidic channel network 10, 11, 12, 13, 14, 3 arranged on a microfluidic chip 2". This embodiment is generally laid out in the same manner as the embodiment shown in fig. 3. However, in fig. 6 a 1x64 waveguide beamsplitter has been utilized.

Fig. 7 shows a microscope picture of a part of a detection channel 3 being illuminated through an integrated 1x128 waveguide beamsplitter, showing light emanating, e.g. at 50 from the waveguides, e.g. 20, at the detection channel 3. Further, in fig 7 the location of stray light rejection structures 33 are indicated between the waveguides 20.

Fig. 8 shows a microscope picture of embodiments of stray light rejection structures, e.g. two different structures 34a and 34b, arranged between two waveguides 21, and each comprising rejection grooves. Unguided light is scattered out of the plane in the rejection structure and does hence not reach the detection channel. As indicated, these rejection of blocking structures may each comprise a number of parallel grooves. Further, these grooves may extend essentially from one waveguide 21 to the next or a distance may be provided between the end of these grooves and the waveguide 21.

Fig. 9 shows a diagram with measurements of the light intensity versus time along a detection channel, e.g. showing 128 peaks, e.g. one for every window, generated from an object, e.g. a single 6 μm fluorescing bead passing a detection region of a microfluidic channel according to an embodiment of the invention,

By making a Fourier transformation, e.g. by using the SCOFT measurement scheme, of the signal information of the frequency between adjacent detection zones (and hence the object velocities) can be obtained. An example of this is shown in fig. 10, showing that the signal 51 at 3.5 Hz is the fundamental peak, while the second peak 52 is the first overtone.

The detection scheme can furthermore be used for analysis of a sample mixture by capillary electrophoresis or liquid chromatography, c.f. e.g. the above mentioned article by Kwok, Y.C., Jeffery, N.T. and Manz, A., wherein the SCOFT method is described.

As mentioned above, other data analysis schemes besides Fourier transformations can also be used, e.g. for example Wavelet transformations, which may be especially advantageous when measuring on a single bead. Such a method is described in "the above mentioned article by Jan C. T. Eijkel, Yien C. Kwok and Andreas Manz. The advantage of Wavelet transformation compared to Fourier transformation is that the frequency is obtained as a function of the time. The time is related to a specific position of the bead in the channel. This means that a change in the frequency of a single object such as a bead can be obtained, so the velocity of the bead at different positions in the channel can be calculated. This information is not available with Fourier transformations, because only an overall value for the frequency of the bead is given.

Other data processing and/or measuring methods and schemes may be used as well, which will be obvious to a skilled person.

Obviously, it is important that the light beams illuminating the detection channel provide well defined, distinct and/or precise illumination location or illumination points, e.g. in order to achieve reliable detection of passing objects such as beads, cells, particles etc. This is of particular importance when a large number of waveguides are utilized on a microfluidic chip and/or when a large degree of miniaturization is applied.

Special means may be utilized for achieving this. In particular, different designs of the waveguides in the vicinity of the detection channel may be utilized in order to achieve a shaping of the optical beam profile. Shaping of the beam profile may result in a better performance of the devices, e.g. increasing the signal-to-noise of the detection.

Shaping of the optical beam profile in the fluidic channel can, e.g., be done in a number of ways as illustrated in fig. 11 (or by any combination hereof).

Fig. 11 shows in a view from above part of a microfluidic chip according to an embodiment of the invention. A microfluidic channel 3 serving as a detection channel and a number of waveguides 20 leading light to the detection channel are illustrated. The shown waveguides are shaped by means of grooves 27 as explained above, but obviously other means of providing the waveguides may be utilized. These four waveguides have each been provided by special means to achieve beam shaping.

Either a lens may be created by shaping the fluidic channel, e.g. as shown at 61 and 62, or the waveguides may be tapered by narrowing or increasing the width as shown at 63 and 64. By these procedures both spreading lenses, e.g. 62 and focusing lenses e.g. 61 can be made.

A still further embodiment of the invention is illustrated in figs. 12 and 13. According to this embodiment, a microfluidic chip may comprise two or more layers of waveguides for transmitting light to the microfluidic channel 3. Fig. 12 shows a sectional sideview of a part of such a chip, i.e. a sectional view through the microfluidic channel 3 and the structure of the chip in the vicinity of the channel 3. As explained above, the chip comprises a substrate 40 and a waveguiding layer 41. Between the layer 41 and the substrate 40 a further layer 42 may be arranged as well as a further layer 43 above the layer 41. According to this embodiment, a further layer of waveguiding medium 48 may be arranged for guiding light towards the channel 3, e.g. above the intermediate layer 43, and a still further layer 49, e.g. for guiding the light in the waveguiding layer 48 by total internal reflection may be placed on top of the layer 48 and immediately beneath the lid 45 that closes the microfluidic structure.

Thus, two light beams 20' and 20" will be led into the detection channel 3, e.g. for detecting objects moving in the channel 3 as explained above.

In fig. 13 a chip 2'" essentially corresponding to the embodiment shown in fig. 1 is illustrated. However, this chip 2'" may be configured with two (or more) layers of waveguiding medium, at least in the vicinity of the detection channel 3. It will be understood that fig. 13 illustrates a first planar system of waveguides 23, 22, 21 and 20 leading from a light source to the detection channel 3 as previously described, but it will further be understood that a second layer of waveguiding medium may be present beneath the illustrated and configured with beamsplitters corresponding to the first system. Thus, the second layer may be identical to the first layer and may be placed directly beneath this. Further, it will be understood that one light source may feed both systems or one light source may be utilized for each. It will also be possible to configure a second (or further) layer differently from the first layer, e.g. with fever or more beamsplitters, branches and/or waveguides leading to the detection channel. Further, the waveguides in the second (or third etc.) layer may be placed askew in relation to the first layer, e.g. not immediately beneath the waveguides of the first layer. This is illustrated in fig. 13, where - for the sake of clarity- only four waveguides 50 leading to the channel 3 are illustrated with dotted lines, and only for the parts in the immediate vicinity of the channel. It will also be possible to configure a beamsplitting in the vertical direction, e.g. between two layers of waveguiding medium.

By such an embodiment it will be possible to detect objects in the channel in different positions in the vertical direction, e.g. for detecting or measuring a velocity profile etc. Further, it will be possible to configure different waveguide structures in the different layers, e.g. 64 waveguides leading to the channel in the first layer and 128 waveguides leading to the channel in the second layer, etc. More detailed, extensive and/or precise measurements may thus be achieved.

In connection with the described examples it has been explained that light has been coupled from a light source, e.g. 30 in fig. 3, to the beamsplitter arrangement. According to the invention, a microdevice, e.g. 2' or 2", may be provided with special coupling means for such a light source, e.g. for providing alignment between the light source and the beamsplitter arrangement or between an optical waveguide and the beamsplitter arrangement.

It will be understood that the system according to the invention may be manufactured in a number of ways, e.g. using generally available techniques utilized for manufacturing microfluidic devices and optical waveguide systems. It will thus be understood that the microstructures may be fabricated using a number of technologies, e.g. by etching, moulding etc. Further, it will be understood that materials used in these connections may be used in connection with the present invention, e.g. normally used waveguiding materials, polymers etc.

The invention has been described above in general, but it will be understood that the measurement system according to the invention may be used in connection with a wide variety of applications.

It will also be understood that the invention is not limited to the particular examples described above, but may be designed in a multitude of varieties within the scope of the invention as specified in the claims.

Claims

Patent Claims

1. A microfluidic system for velocity measurement of an object moving along a microfluidic channel, wherein illumination of said channel is performed at a plurality of locations along the microfluidic channel, wherein a plurality of optical waveguides are arranged adjacent said microfluidic channel, and wherein at least two of said plurality of optical waveguides form part of an optical beamsplitter arrangement.

2. Microfluidic system according to claim 1, wherein said plurality of optical waveguides are arranged essentially transversely to said microfluidic channel in the vicinity of the microfluidic channel.

3. Microfluidic system according to claim 1 or 2, wherein said optical beamsplitter arrangement involves a 1 X k waveguide beamsplitter, and wherein k waveguides are arranged adjacent said channel.

4. Microfluidic system according to claim 3, wherein k > 4, in a more preferred form k > 16 and in an even more preferred form k> 32.

5. Microfluidic system according to claim 3 or 4, wherein k > 64, in a more preferred form k > 128 and in an even more preferred form k> 256.

6. Microfluidic system according to one or more of claims 1 to 5, wherein said beamsplitter arrangement comprises a rejection structure for stray light.

7. Microfluidic system according to claim 6, wherein said rejection structure comprises a channel arranged transversely between two corresponding branching waveguides of said beamsplitter arrangement.

8. Microfluidic system according to claim 7, wherein said rejection structure comprises at least two of said channels arranged transversely between two corresponding branching waveguides of said beamsplitter arrangement, said at least two channels being arranged essentially parallel.

9. Microfluidic system according to claim 6, 7 or 8, wherein said rejection structure comprises means for transferring stray light away from the waveguide plane.

10. Microfluidic system according to one or more of claims 6 to 9, wherein said rejection structure comprises means for reflecting stray light.

11. Microfluidic system according to one or more of claims 6 to 10, wherein said rejection structure comprises means for absorbing stray light.

12. Microfluidic system according to one or more of claims 1 to 11, wherein said waveguides arranged adjacent said microfluidic channel comprise means for shaping, e.g. condensing or spreading light beams guided towards said microfluidic channel.

13. Microfluidic system according to claim 12, wherein said means for shaping light beams involve shaping of said waveguides locally in the vicinity of said microfluidic channel, e.g. at the end portion of said waveguides.

14. Microfluidic system according to claim 13, wherein said shaping of said waveguides involves a gradually enlarged dimension of said waveguides.

15. Microfluidic system according to claim 13, wherein said shaping of said waveguides involves a gradually reduced dimension of said waveguides.

16. Microfluidic system according to claim 12, wherein said means for shaping light beams involve shaping of said microfluidic channel locally in the vicinity of said waveguides, e.g. at the end portion of said waveguides.

17. Microfluidic system according to claim 16, wherein said shaping of said microfluidic channel involves a spreading lens.

18. Microfluidic system according to claim 16, wherein said shaping of said microfluidic channel involves a focusing lens.

19. Microfluidic system according to one or more of claims 1 to 18, wherein said system comprises means for producing and/or guiding light into said optical beamsplitter arrangement.

20. Microfluidic system according to one or more of claims 1 to 19, wherein said system comprises means for detecting and or recording light emanated from said microfluidic channel caused by passing objects.

21. Microfluidic system according to one or more of claims 1 to 19, wherein said system comprises means for processing signals stemming from objects passing said microfluidic channel.

22. A microdevice for velocity measurement of an object moving along a microfluidic channel of said microdevice, comprising means for illumination of said channel at a plurality of locations along the microfluidic channel, a plurality of optical waveguides arranged adjacent said microfluidic channel, and an optical beamsplitter arrangement involving at least two of said plurality of optical waveguides.

23. A microdevice for velocity measurement of an object moving along a microfluidic channel of said microdevice, comprising a microfluidic system according to one or more of claims 1 to 21.

24. Microdevice according to claim 23 comprising a substrate layer, a layer of waveguding medium, a plurality of waveguides arranged in an optical waveguide beamsplitter arrangement, and a microfluidic system comprising at least a detection channel for multiple-point light detection, wherein said plurality of waveguides are formed in said layer of waveguiding medium, and said at least one microfluidic detection channel is formed at least partially in said layer of waveguiding medium.

25. Microdevice according to claim 24 comprising a lid placed above said layer of waveguiding medium.

26. Microdevice according to claim 24 or 25 comprising a layer placed on one or both sides of said layer of waveguiding medium, e.g. for restricting propagation of optical waves to said layer of waveguiding medium.

27. Microdevice according to claim 24, 25 or 26 comprising two or more layers of waveguiding medium, each layer comprising waveguides formed in said layer.

28. A microdevice for performing measurements related to an object moving along a microfluidic channel of said microdevice, comprising means for illumination of said channel at a plurality of locations along the microfluidic channel, a plurality of optical waveguides arranged adjacent said microfluidic channel, and an optical beamsplitter arrangement involving at least two of said plurality of optical waveguides.

29. A microdevice for performing measurements related to an object moving along a microfluidic channel of said microdevice, comprising a microfluidic system according to one or more of claims 1 to 21.

30. Microdevice according to claim 29 comprising a substrate layer, a layer of waveguding medium, a plurality of waveguides arranged in an optical waveguide beamsplitter arrangement, and a microfluidic system comprising at least a detection channel for multiple-point light detection, wherein said plurality of waveguides are formed in said layer of waveguiding medium, and said at least one microfluidic detection channel is formed at least partially in said layer of waveguiding medium.

31. Microdevice according to claim 30 comprising a lid placed above said layer of waveguiding medium.

32. Microdevice according to claim 30 or 31 comprising a layer placed on one or both sides of said layer of waveguiding medium, e.g. for restricting propagation of optical waves to said layer of waveguiding medium.

33. Microdevice according to claim 30, 31 or 32 comprising two or more layers of waveguiding medium, each layer comprising waveguides formed in said layer.

34. A method of performing measurements related to an object moving along a microfluidic channel, comprising the steps of driving said object along said microfluidic channel located in a microdevice, guiding light into an optical waveguide placed on said microdevice, performing beamsplitting of said light guided into said optical waveguide, guiding a multiplicity of light beams resulting from said beamsplitting to locations in the vicinity of said microfluidic channel, said locations being distributed in the longitudinal direction of said channel, and detecting and/or recording of light caused by optical addressing of the passing of said object in said microfluidic channel.

35. Method according to claim 34 whereby said multiplicity of light beams resulting from said beamsplitting are guided to locations in the vicinity of said microfluidic channel, said locations being distributed in the longitudinal direction of said channel as well as in the vertical direction.

36. Use of a microfluidic system according to one or more of claims 1 to 21, a microdevice according to claim 22, a microdevice according to one or more of claims 23 to 27, a microdevice according to claim 28, a microdevice according to one or more of claims 29 to 33 and/or a method according to claim 34 or 35 for measuring velocity of objects such as particles, cells, beads etc., in particular chemical or biochemical objects.