Digital microfluidic systems, cartridges, and methods involving integrated refractive index sensing - Patents.com

Abstract

A digital microfluidic (DMF) system, a DMF cartridge, and a method including integrated refractive index (RI) sensing are disclosed. The digital microfluidic DMF system and DMF cartridge may include, for example, an RI sensor (or sensor surface) directly in the droplet manipulation gap of the DMF cartridge. The digital microfluidic DMF system may include, for example, a DMF cartridge, one or more illumination sources, one or more optical measurement devices, and a controller. Additionally, methods of using the DMF system and DMF cartridge including integrated RI sensing are provided.

Description

Technical Field

[0001] This application claims priority to U.S. Patent Application No. 62 / 964,431, filed on January 22, 2020, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention generally relates to optical sensing technology, and more specifically, to digital microfluidic (DMF) systems, cartridges, and methods of using integrated refractive index (RI) sensing.

Background Art

[0003] In digital microfluidics, the use of optical sensing is well known. Optical sensing methods are integrated into continuous flow microfluidics. Conventional methods for measuring optical stimuli from DMF devices utilize free space optics to capture the stimuli. Free space optics suffers from the problem of stray light. Using lenses, filters, and / or other similar optical components to solve these problems can increase the cost of the system. A new approach is needed to implement optical sensing in DMF devices that process individual droplets.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a cartridge for use with an instrument, and a system including the cartridge functionally coupled to the instrument. Functional coupling can be, for example, electrical coupling, radioelectronic coupling, and / or optical coupling.

Means for Solving the Problems

[0005] The cartridge utilizes digital microfluidics. Digital microfluidics typically includes a plurality of electro-wetting electrodes that operate to perform droplet manipulation on droplets within a droplet manipulation gap of the cartridge.

[0006] The cartridge utilizes a refractive index sensor. The refractive index sensor can generally be exposed in a droplet manipulation gap proximate to one or more electro-wetting electrodes. In this configuration, a droplet present on one or more electro-wetting electrodes contacts the refractive index sensor. The arrangement of the one or more electro-wetting electrodes and the refractive index sensor defines a droplet interrogation site.

[0007] The refractive index sensor can be mounted on the top plate of the cartridge, for example, integrated within or mounted on a side surface of the top plate facing the gap. The refractive index sensor can be attached to the droplet manipulation gap. The droplet manipulation gap can be defined by a top plate and a bottom plate in a substantially parallel plane. In one example, the bottom plate includes the electro-wetting electrodes. The refractive index sensor can be attached to the droplet manipulation gap and can have a sensor surface that is perpendicular to a substantially parallel plane. The refractive index sensor can include a waveguide and / or be provided as a tip of a waveguide.

[0008] The cartridge can include a plurality of droplet interrogation sites. A subset of the interrogation sites can be operated in parallel or sequentially. A sub-subset of the interrogation sites can be operated in parallel or sequentially. Each interrogation site can interrogate a set of the same analyte or a set of different analytes. Each interrogation site can interrogate a single analyte or a plurality of analytes.

[0009] The present disclosure provides a system including a cartridge and an apparatus. The apparatus includes electronic devices and other components for controlling the cartridge and collecting data (such as optical data or temperature data) from the cartridge, and means for attaching the cartridge to effect electronic coupling, measurement, and control. The system can include one or more illumination sources configured to illuminate one or more droplet investigation sites. The one or more illumination sources can be present on the cartridge and / or the apparatus.

[0010] The system can include one or more optical measurement devices configured to sense light from one or more droplet investigation sites. The one or more optical measurement devices can be present on the cartridge and / or the apparatus. The arrangement of the illumination source and the optical measurement device with respect to the droplet investigation site can be selected for operation in transmission mode. The arrangement of the illumination source and the optical measurement device with respect to the droplet investigation site can be selected for operation in reflection mode. The system can include a scanning optical measurement device configured to scan (scan) a plurality of droplet investigation sites.

[0011] The present disclosure provides a method of performing an assay using the system of the present disclosure. The method can include, for example, loading a sample droplet into a droplet operation gap using droplet manipulation via electro-wetting. The method can include performing one or more sample processing steps on the sample droplet to generate an analysis-ready droplet. The method can include performing a refractive index analysis of the analysis-ready droplet at a droplet investigation site.

Brief Description of the Drawings

[0012] Having described the gist of the invention in general terms above, the following will be described with reference to the accompanying drawings, which are not necessarily drawn to scale.

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Best Mode for Carrying Out the Invention

[0013] The present disclosure provides a digital microfluidic (DMF) system, a DMF cartridge, and a method including integrated refractive index (RI) sensing. A digital microfluidic (DMF) system can include, for example, a DMF cartridge, one or more illumination sources, one or more optical measurement devices, and a controller. Further, one or more RI sensors can be provided directly within the droplet manipulation gap of the DMF cartridge.

[0014] In some embodiments, the DMF system, the DMF cartridge, and the method can provide one or more RI sensors on the upper substrate of the DMF cartridge, on the lower substrate, on both the upper and lower substrates, and / or between the upper and lower substrates. In these embodiments, the lower substrate can include electrowetting electrodes. In some examples, only the lower substrate includes electrowetting electrodes.

[0015] In some embodiments, the DMF system, the DMF cartridge, and the method can provide optical elements for assisting in the coupling of light to the RI sensor. Examples of optical elements that can be used with the RI sensor can include, but are not limited to, one or more lenses, prisms, gratings, light sources, apertures, optical fibers, mirrors, or any arbitrary combination thereof.

[0016] In some embodiments, the present disclosure can provide one or more illumination sources for supplying excitation light to the RI sensor and one or more optical measurement devices for receiving and processing the emitted light from the RI sensor.

[0017] In some embodiments, the present disclosure can provide a plurality of RI sensors for supporting a plurality of channels of RI sensing.

[0018] In some embodiments, the present disclosure can provide a scanning optical measurement device for investigating multiple channels of integrated RI sensing.

[0019] In some embodiments, the present disclosure can provide backlighting (or back-illumination), frontlighting (or front-illumination), or both backlighting and frontlighting for integrated RI sensing.

[0020] Furthermore, the present disclosure provides a method of using a DMF system and provides a DMF cartridge that includes integrated RI sensing.

[0021] FIG. 1 is a block diagram of an example of a DMF system 100 that includes integrated RI sensing. The DMF system 100 can be, for example, a plasmon resonance (PR) system and / or a localized surface plasmon resonance (LSPR) system for the analysis of a sample. Analysis can mean, for example, the detection, identification, quantification, or measurement of a sample, and / or the interaction of the sample with other substances such as binding reaction rates and thermodynamics. Exemplary samples can include, but are not limited to, small molecules, proteins, peptides, atoms, and ions. For example, the DMF system 100 can be used to measure the binding reaction rate of a ligand to a macromolecule such as a receptor.

[0022] The DMF system 100 features the integration of an RI-based sensor and digital microfluidics. For example, the DMF system 100 may include a DMF cartridge 110. The DMF cartridge 110 can be a droplet actuator device with DMF capabilities for generally performing droplet operations such as droplet coalescence, splitting, dispensing, and dilution. One use of these DMF capabilities is sample preparation. However, the DMF capabilities can also be used for other processes such as waste removal or flushing between operations. The DMF cartridge 110 can include one or more detection spots 158, and an RI sensor 130 can be provided at each detection spot 158. Details of the DMF cartridge 110, the detection spots 158, and the RI sensor 130 will be shown and described below with reference to FIGS. 2 to 11.

[0023] The DMF system 100 can further include a controller 150, a DMF interface 152, an illumination source 154, and an optical measurement device 156. The controller 150 can be electrically coupled to various hardware components of the DMF system 100, such as the DMF cartridge 110, the illumination source 154, and the optical measurement device 156. For example, the controller 150 can be electrically coupled to the DMF cartridge 110 via the DMF interface 152, and the DMF interface 152 can be a pluggable interface for mechanically and electrically connecting to the DMF cartridge 110, for example. The DMF cartridge 110, the controller 150, the DMF interface 152, the illumination source 154, and the optical measurement device 156 together form the DMF apparatus 105.

[0024] The controller 150 can be, for example, a general-purpose computer, a dedicated computer, a personal computer, a microprocessor, or other programmable data processing device. The controller 150 serves to provide processing capabilities such as storage, interpretation, and / or execution of software instructions, and to control the overall operation of the DMF system 100. The controller 150 can be configured and programmed to control data and / or power aspects of these devices. For example, the controller 150 controls droplet operations within the DMF cartridge 110 by activating / deactivating electrodes. Generally, the controller 150 can be used for any function of the DMF system 100. For example, the controller 150 can be used to authenticate the DMF cartridge 110 in a manner similar to how a printer manufacturer checks its own brand of ink cartridges, the controller 150 can be used to verify that the DMF cartridge 110 has not expired, the controller 150 can be used to confirm the cleanliness of the DMF cartridge 110 by executing a protocol for that purpose, and so on. Authentication of the cartridge can be performed wirelessly using a protocol such as Bluetooth, NFC, or other RFID-based protocols.

[0025] The controller 150 can include one or more input interfaces that connect the processing unit to input devices. The input interfaces enable a user of the DMF system 100 to communicate commands to the processor. One such exemplary command is the execution of program code. The input devices can take the form of a keyboard, a mouse device, a voice activation system, a touch screen, and / or other suitable devices known to those skilled in the art.

[0026] In some embodiments, the controller 150 can include one or more output interfaces that connect a processing unit to an output device, such as a graphical user interface (GUI). Thereby, the DMF system 100 can communicate the results of various processing operations, such as experimental results, to the user. The software instructions can be stored in the memory unit of the controller 150, which can include a conventional semiconductor random access memory (RAM) or other forms of memory known in the art, and / or the software instructions can be stored in the form of program code on one or more computer-readable storage media, such as a hard drive, a USB drive, a read / write CD-ROM, a DVD, a tape drive, a flash drive, an optical drive, etc. These instructions can be executed in response to the interaction between the DMF system 100 and the user via an input device.

[0027] Furthermore, in some embodiments, the DMF cartridge 110 can include capacitive feedback sensing. That is, a signal from a capacitive sensor that can detect the position and volume of the droplets. Additionally, in other embodiments, the DMF cartridge 110 can include a camera that provides optical measurements of the position and volume of the droplets, and these measurements can trigger the controller 150 to re-route the droplets to the appropriate positions.

[0028] Furthermore, in some embodiments, the DMF cartridge 110 can include a heating zone (not shown) that can be individually controlled via the controller 150. For example, in order to provide a heating zone, a heating device, such as a heating bar and / or a resistive heating element, can be positioned in relation to the DMF cartridge 110.

[0029] Furthermore, the DMF device 105 can be connected to a network. For example, the controller 150 can communicate with a networked computer 160 via the network 162. The networked computer 160 can be, for example, any centralized server or cloud server. The network 162 can be, for example, a local area network (LAN) or a wide area network (WAN) for connecting to the Internet.

[0030] In the DMF system 100, the illumination source 154 and the optical measurement device 156 can be arranged in relation to the detection spot 158 of the DMF cartridge 110 and / or the RI sensor 130 such that the illumination source 154 can illuminate the detection spot 158 and the optical measurement device 156 can detect the light from the detection spot 158. The illumination source 154 can be a light source in the visible range (wavelength 400 - 800 nm), such as, but not limited to, a white light emitting diode (LED), a halogen lamp, an arc lamp, an incandescent light source, a fluorescent light source, a laser, etc. The illumination source 154 is not limited to a white light source. The illumination source 154 can be light of any color useful in the DMF system 100. The illumination source 154 can be monochromatic or multi - colored. The illumination source 154 can be coherent or incoherent. The illumination source 154 can be modulated so as to be able to adjust its intensity very quickly. The illumination source 154 can also include one or more sensors, such as a photodetector, to adjust the luminance. The illumination source 154 can also include additional filters to guarantee the quality of the incident light. Furthermore, the illumination source 154 can be a combination of a plurality of individual light - emitting elements. These elements can be active at the same wavelength or different wavelengths. The illumination source 154 supplies the excitation light 132 to the detection spot 158 of the DMF cartridge 110.

[0031] The optical measurement device 156 can be, for example, any optical transducer device used to obtain a reading of light intensity. The optical measurement device 156 receives and processes the emitted light 134 from the RI sensor 130 at each detection spot 158 of the DMF cartridge 110. The optical measurement device 156 can be, for example, a charge-coupled device, a photodetector, a photomultiplier tube, a spectrometer, a photodiode array, a camera, a hyperspectral imager, or any combination thereof. Further, the optical measurement device 156 can include an optical filter for assisting and enhancing the detection of RI changes. The optical measurement device 156 can include additional components that enable control of the illumination source 154 using closed-loop control such as a correlator.

[0032] Furthermore, the DMF system 100 is not limited to only one illumination source 154 and one optical measurement device 156. The DMF system 100 can include multiple illumination sources 154 and / or multiple optical measurement devices 156 to support any detection operations required in the DMF system 100 and / or the DMF cartridge 110. The illumination source 154 can be multiple identical sources or multiple different sources. The optical measurement system 156 can be multiple identical sources or multiple different sources.

[0033] The components of the DMF system 100 and / or the DMF instrument 105 (e.g., the illumination source 154 and the optical measurement device 156) can be optically coupled to and also decoupled from the detection spots 158 and / or the RI sensor 130 of the DMF cartridge 110. This optical coupling / decoupling can be, for example, an optical fiber connector, an optical fiber coupler, and / or a free-space optical coupler.

[0034] In the DMF system 100, the DMF device 105, and / or the DMF cartridge 110, the RI sensor (or sensor surface) 130 means any method for investigating the RI of a droplet. The RI sensor 130 can be in the form of a surface, for example, or in the form of colloidal particles dissolved in a solution. Examples of RI sensing surfaces include, but are not limited to, surface plasmon resonance, localized surface plasmon resonance, photonic crystals, thin film interference filters, diffraction gratings, and the like.

[0035] In some embodiments, the RI sensor 130 can include an additional surface (not shown) on top of the RI sensing surface to enhance the selectivity of the surface. The selective surface serves the purpose of directly concentrating the stimulus from the droplet onto the sensor surface. Examples of selective surfaces can include, but are not limited to, antibodies, aptamers, polymers, or chemical groups.

[0036] Figures 2, 3, and 4 show side views of some examples in the DMF cartridge 110 of the DMF system 100 shown in Figure 1, in which at least one RI sensor 130 is integrated in the upper substrate therein. In this example, the DMF cartridge 110 can include a lower substrate 112 and an upper substrate 114 separated by a droplet operation gap 116. Further, the arrangement of the droplet operation electrodes 120 (e.g., electro-wetting electrodes) can be made on the lower substrate 112. The DMF cartridge 110 can include any lines or paths in the droplet operation electrodes 120. The sample droplet 140 can be present within the droplet operation gap 116 and on a specific droplet operation electrode 120.

[0037] In one example, the lower substrate 112 can be made of a material that is substantially transparent to white light (or any colored light). For example, the lower substrate 112 can be formed of glass, plastic, or polymers known as thermoplastic elastomers (TPE). In another example, the lower substrate 112 can be a printed circuit board (PCB) that is substantially transparent, or a PCB that includes holes or openings that allow light transmission. Similar to the lower substrate 112, the upper substrate 114 can be formed of a material that is substantially transparent to white light (or any colored light). For example, the upper substrate 114 can be formed of glass, plastic, or TPE. Further, the inner surface of the upper substrate 114 can be coated with a conductive layer 118 such as a transparent conductive layer (e.g., indium tin oxide (ITO), poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS)), or other similar transparent or non-transparent (e.g., opaque) conductive coatings. In other embodiments, not all regions of the DMF cartridge 110 need to include a substantially transparent substrate and / or coating or layer. For example, the substrate and / or coating or layer may not be transparent, translucent, and / or opaque except in the detection region.

[0038] The terms "top", "bottom", "over", "under", "in", and "on" are used throughout the specification to refer to the relative positions of the components of the DMF cartridge, such as the relative positions of the upper and lower substrates of the DMF cartridge. It will be understood that the DMF cartridge functions regardless of its orientation in space. Thus, without departing from the scope of the present disclosure, "top", "bottom", etc. can be replaced with "first", "second", etc.

[0039] In the DMF cartridge 110, the droplet operation gap 116 can be a space for processing any liquid of interest via droplet operations, such as, but not limited to, liquid reagents, buffers, sample fluids, etc. The height of the gap (e.g., the distance between the upper substrate 114 and the lower substrate 112) can be, for example, several hundred microns. The droplet operation electrodes 120 can be used to perform droplet operations via electro-wetting. "Droplet operations" means any droplet operations on the DMF device or cartridge. Examples of droplet operations include, but are not limited to, droplet loading into a digital microfluidic device, dispensing of one or more droplets from a source droplet, dividing, separating or splitting one droplet into two or more droplets, transporting a droplet in any direction from one location to another, fusing or combining two or more droplets into one droplet, droplet dilution, droplet mixing, droplet stirring, droplet deformation, holding a droplet at a predetermined position, droplet incubation, droplet heating, droplet evaporation, droplet cooling, droplet discard, transporting a droplet from a droplet actuator, other droplet operations described herein; and / or any combination of the above-described operations. Further, in order to control the temperature of the process occurring in the droplet operation gap 116, a temperature control element (not shown), such as a Peltier heat pump, can be used in combination with the DMF cartridge 110.

[0040] Referring now to FIG. 2, the DMF cartridge 110 of the DMF system 100 is shown, wherein in the figure, the RI sensor 130 is provided on the surface of the upper substrate 114 facing the droplet operation gap 116. Thus, the RI sensor 130 can directly interact within / with the sample droplet 140, thereby forming a detection spot 158. The RI sensor 130 can be a RI layer deposited on the upper substrate 114 to form a RI sensing surface on the upper substrate 114. The RI sensor 130 can be designed to be small enough so as not to interfere with the hydrophobic surface of the substrate. Further, a hydrophobic layer (not shown) can be provided on the RI sensor 130 as part of the sensing film. The investigation of the RI sensor 130 (sensing surface) can be performed using the illumination source 154 and the optical measurement device 156 shown in FIG. 1. Similarly, the RI sensor 130 can be a RI layer deposited on the lower substrate 112 to form a RI sensing surface on the lower substrate 112. The RI sensor 130 can likewise be designed to be small enough so as not to interfere with the hydrophobic surface of the substrate. Further, the RI sensing surface can be designed to fit between electrowetting electrodes (regardless of whether provided on either the upper substrate 114 and / or the lower substrate 112) so that it can be more easily optically investigated.

[0041] The DMF cartridge 110 can be used to move droplets to and from the detection spot 158 via droplet manipulation. The direct integration within the droplet operation gap 116 of the RI sensor 130 and within the path of the sample droplet 140 enables the localization of optical investigation techniques. FIG. 2 shows the excitation light 132 being delivered to the RI sensor 130 and the sample droplet 140. The investigation of the RI sensor 130 (sensing surface) can be carried out in transmission, reflection and / or evanescent mode.

[0042] To reiterate, RI sensor 130 refers to any method for investigating the RI of droplets such as sample droplet 140. The RI sensor 130 can be in the form of, for example, the surface morphology or in the form of colloidal particles dissolved in a solution. Examples of RI sensing surfaces include, but are not limited to, surface plasmon resonance, localized surface plasmon resonance, photonic crystals, thin film interference filters, diffraction gratings, and so on. Further, the RI sensor 130 can include an additional surface on top of the RI sensing surface to enhance the selectivity of the surface. The selective surface serves the purpose of directly concentrating the stimulus from the droplet onto the sensor surface. Examples of selective surfaces include, but are not limited to, antibodies, aptamers, polymers, or chemical groups.

[0043] To assist in coupling light to the RI sensor 130, other optical elements can be provided in the DMF cartridge 110. Examples of optical elements that can be used with the RI sensor include, but are not limited to, one or more lenses, prisms, gratings, light sources, apertures, optical fibers, mirrors, or any combination thereof.

[0044] In one example, FIG. 3 shows a lens 142 installed in combination with the RI sensor 130. The lens 142 is attached to the path of the excitation light 132. For example, the lens 142 is attached to the side surface of the upper substrate 114 opposite to the RI sensor 130 side such that the excitation light 132 first passes through the lens 142, then through the upper substrate 114, and then to / through the RI sensor 130.

[0045] In another example, FIG. 4 shows a prism 144 installed in combination with the RI sensor 130. The prism 144 is attached to the path of the excitation light 132. For example, the prism 144 is attached to the side surface of the upper substrate 114 opposite to the RI sensor 130 side such that the excitation light 132 first passes through the prism 144, then through the upper substrate 114, and then to / through the RI sensor 130.

[0046] Figures 2, 3, and 4 show the RI sensor 130 on the upper substrate 114. However, in other embodiments, the RI sensor 130 may be on the lower substrate 112. For example, the RI sensor 130 can be deposited on the surface of the lower substrate 112 facing the droplet manipulation gap 116. In the DMF cartridge 110, the lower substrate 112 can be a substrate including the active droplet manipulation electrodes 120 for performing droplet manipulation. Although the lower substrate 112 is arranged to avoid droplet pinning during droplet manipulation, it can also include the sensing surface.

[0047] For example, FIG. 5 is a plan view of an embodiment of the RI sensor 130 integrated on the lower substrate 112. In this embodiment, the RI sensor 130a and the RI sensor 130b are provided. The RI sensor 130a is sized small enough to fit into the space between the droplet manipulation electrodes 120 without any modification to the surrounding droplet manipulation electrodes 120. In contrast, the RI sensor 130b is not sized large enough to fit into the space between the droplet manipulation electrodes 120 without modifying the droplet manipulation electrodes 120. Therefore, each of the four surrounding droplet manipulation electrodes 120 requires a corner notch to provide clearance for fitting the RI sensor 130b.

[0048] In yet another example, FIG. 6 shows a waveguide layer 146 provided in a droplet operation gap 116 between a lower substrate 112 and an upper substrate 114 and substantially parallel to the plane of the DMF cartridge 110. In this example, the RI sensor 130 is provided at the tip of the waveguide layer 146 within the droplet operation gap 116. In one example, the waveguide layer 146 can be an optical fiber. This configuration can be referred to as a side-entry RI sensor. The excitation light 132 travels through the waveguide layer 146 towards the RI sensor 130. The emitted light 134 is then returned through the same waveguide layer 146. In this embodiment, the investigation of the RI sensor 130 (sensing surface) can be carried out in reflection mode. The measurement can also be performed in evanescent mode. One or more evanescent-wave-based refractive index sensors (e.g., Fiber Bragg gratings, Mach-Zehnder interferometers, Fabry Perot etalons) can be arranged along the waveguide. These sensors can be read independently, and thus simultaneous capture by multiple sensors is possible.

[0049] Furthermore, FIGS. 2 - 6 illustrate the DMF cartridge 110 as handling droplets via an electro-wetting method (e.g., using droplet operation electrodes 120), which is merely exemplary. In other embodiments, the droplets can be handled within the DMF cartridge 110 via other methods such as, but not limited to, optical methods, magnetic methods, thermo-capillary methods, surface acoustic wave methods, other electrical methods such as dielectrophoresis, etc., and any combination of such methods.

[0050] During operation, the excitation light 132 from the illumination source 154 travels towards the RI sensor 130. The RI sensor 130 directs the incident light onto the droplet being investigated (e.g., sample droplet 140). The emitted light 134 is then returned to the optical measurement device 156 for processing. Again, the investigation of the RI sensor 130 (sensing surface) can be carried out in transmission, reflection, and / or evanescent mode.

[0051] In the DMF system 100, the DMF device 105, and / or the DMF cartridge 110, multiple different basic architectures for reading one or more RI sensors 130 are possible. Examples thereof are shown below with reference to FIGS. 7A to 11.

[0052] Referring now to FIGS. 7A, 7B, and 7C, these are respectively a top view and first and second cross-sectional views of an embodiment of the DMF cartridge 110 of the DMF system 100 including multiple channels of integrated RI sensing. For example, the DMF system 100 can include X or more channels of integrated RI sensing (e.g., X = 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 20, 30, 40, or 50). In this embodiment, the DMF cartridge 110 includes multiple RI sensors 130, and each RI sensor 130 correlates with an RI sensing channel.

[0053] For example, multiple RI sensors 130 (e.g., RI sensors 130A, 130B, 130C, 130D, 130E) are arranged along a line within the DMF cartridge 110. As shown in FIG. 7A, the aperture 170 extends across the line of the multiple RI sensors 130. The aperture 170 is provided in the lower substrate 112 of the DMF cartridge 110, for example, as shown in FIGS. 7B and 7C. Thus, illumination can be directed through the aperture 170 and across the line of the multiple RI sensors 130. The aperture 170 may be required in embodiments where the lower substrate 112 is not optically transparent.

[0054] Figures 7B and 7C are cross-sectional views taken along line A-A of Figure 7A. Figure 7B shows a configuration in which the illumination source 154 is disposed on the upper substrate 114 side of the DMF cartridge 110 and the optical measurement device 156 is disposed on the lower substrate 112 side. In this embodiment, the aperture 170 provides an opening for the emitted light 134 to pass through the lower substrate 112 and reach the optical measurement device 156. In contrast, Figure 7C shows a configuration in which the optical measurement device 156 is disposed on the upper substrate 114 side of the DMF cartridge 110 and the illumination source 154 is disposed on the lower substrate 112 side. In this embodiment, the aperture 170 provides an opening for the excitation light 132 to pass through the lower substrate 112 and reach the illumination source 154.

[0055] In any of the configurations shown in Figures 7B and 7C, the optical measurement device 156 can sample the RI sensors 130A, 13B, 130C, 130D, 130E through the opening provided by the aperture 170. The optical measurement device 156 can be, for example, a line-scan hyperspectral imager (e.g., a hyperspectral imaging (HSI) camera), and thus can independently and simultaneously capture the spectra from each of the individual sensor spots. In another example, the optical measurement device 156 can include an element (e.g., a scanning mirror or a spatial light modulator) that can change its field of view, and thus can enable a temporal separation of the capture for each channel.

[0056] Referring now to Figures 8A, 8B, and 8C, these are respectively a top view and first and second cross-sectional views of another embodiment of the DMF cartridge 110 of the DMF system 100 including a plurality of channels of integrated RI sensing. This configuration is substantially the same as that shown in Figures 7A, 7B, and 7C, except that the aperture 170 is replaced by individual optical fibers 172. For example, the optical fibers 172A, 172B, 172C, 172D, 172E respectively correlate with the RI sensors 130A, 13B, 130C, 130D, 130E.

[0057] In this example, the optical fiber 172 can be a lower entry fiber introduced through the lower substrate 112 as shown in FIGS. 8B and 8C. Each RI sensor 130 forms a layer at the tip of the optical fiber 172. Each optical fiber 172 can be associated with any one or more optical measurement devices 156 (FIG. 8B) or illumination sources 154 (FIG. 8C). The plurality of optical fibers 172 may be arranged in an arbitrary pattern (not necessarily arranged in a row).

[0058] Although FIGS. 8B and 8C show operation in transmission mode, in another embodiment, the plurality of optical fibers 172 can be investigated in reflection mode (the excitation light 132 and the emission light 134 are coupled and read in the same direction). Further, although FIGS. 8A, 8B, and 8C show a plurality of optical fibers 172 installed on the lower substrate 112, in another embodiment, the plurality of optical fibers 172 can be installed on the upper substrate 114.

[0059] Referring now to FIG. 9, this is a perspective view of an embodiment of a DMF system 100 including a scanning optical measurement device and backlighting illumination for investigating a plurality of channels of integrated RI sensing. For example, the DMF system 100 can include a scanning optical measurement device 156' and a backlight illumination source 154'. In one embodiment, the scanning optical measurement device 156' can be a line scan hyperspectral imager (e.g., a hyperspectral imaging (HSI) camera) that acquires data from one or more RI sensors 130 arranged in a row. The RI sensors 130 are arranged between the backlight illumination source 154' and the scanning optical measurement device 156' (and thus arranged in a backlighting configuration). In this configuration, the lines of the RI sensors 130 can be "remotely" scanned using a slit arranged in the scanning optical measurement device 156'.

[0060] In one example, the backlight illumination source 154’ can be in the form of LEDs integrated within the DMF cartridge 110 or in the form of a remote illumination source. For example, FIG. 10 shows an LED light source 174 installed on the lower substrate 112 of the DMF cartridge 110.

[0061] Referring now to FIG. 11, this is a side view of an embodiment of a DMF system 100 that includes frontlight illumination and integrated RI sensing. For example, in this configuration of the DMF system 100, the measurement is performed using coaxial illumination (i.e., illumination of the RI sensor 130 on the same side as the optical measurement device side). In one example, the optical measurement device 156 can be a scanning optical measurement device 156’. In one embodiment, the illumination source 154 can be in the form of a light source disposed around the collection optics of the optical measurement device 156. In another embodiment, the illumination source 154 can be in the form of a beam splitter 176 that enables fully coaxial illumination. To maximize the performance of the system, other illumination techniques such as brightfield imaging and diffuse imaging can be used.

[0062] In another embodiment of the DMF system 100 that includes integrated RI sensing, the DMF system 100 includes a linear optical transducer (e.g., a linear optical measurement device 156). In this example, either the field of view of the RI sensor 130 or the linear optical transducer is moved in a direction perpendicular to the line being scanned (thus enabling the acquisition of pushroom data). Thereby, the DMF system 100 can acquire a two-dimensional image using a line scanning system. This example can be combined with the previous embodiment, thereby enabling the distribution of the sensor surface in any 2D pattern.

[0063] In yet another embodiment of the DMF system 100 including integrated RI sensing, the DMF system 100 includes a spatial spectral optical converter (e.g., spatial spectral optical measurement device 156) that can simultaneously acquire a 2D image and a spectral decomposition image of the RI sensor 130. This enables any real-time data acquisition from the 2D sensor surface. This can be combined with backlighting illumination or frontlighting illumination.

[0064] Referring now to FIG. 12, this is a flow diagram of an example of a method 200 of using a DMF system 100 and / or a DMF cartridge 110 including integrated RI sensing. The method 200 can include, but is not limited to, the following steps.

[0065] In step 210, a DMF system and / or a DMF cartridge including integrated RI sensing is prepared. For example, a DMF system 100 and / or a DMF cartridge 110 including an integrated RI sensor 130 is prepared in the droplet operation gap 116 of the DMF cartridge 110, for example, as shown in FIGS. 2 to 11.

[0066] In step 215, the droplet to be processed is transported to the sensing region of the DMF cartridge. For example, referring now to FIGS. 2 to 11, the sample droplet 140 to be processed can be transported to the detection spot 158 of the DMF cartridge 110 using droplet operation, where the detection spot 158 is located on the RI sensor 130.

[0067] In step 220, the optical sensing operation is performed within the DMF cartridge using integrated RI sensing. For example, referring now to FIGS. 2 - 11, the optical sensing operation is performed in the DMF cartridge 110 using an integrated RI sensor 130 in the droplet operation gap 116, illumination source 154, and optical measurement device 156 of the DMF cartridge 110. During the operation, the excitation light 132 from the illumination source 154 is directed towards the RI sensor 130. The RI sensor 130 guides the incident light to the droplet under investigation (e.g., sample droplet 140). The emitted light 134 is then returned to the optical measurement device 156 for processing. The investigation of the RI sensor 130 (sensing surface) can be performed in transmission, reflection, and / or evanescent mode.

[0068] As a summary, and referring again now to FIGS. 1 - 11, the DMF system 100, DMF cartridge 110, and / or method 200 use an RI sensor 130 directly integrated into a disposable cartridge (e.g., DMF cartridge 110) to enable local optical investigation techniques. Compared to conventional methods, the integration of digital microfluidics and RI sensing in the DMF system 100, DMF cartridge 110, and / or method 200 enables local optical investigation techniques.

[0069] In accordance with long - standing patent law convention, the terms "a", "an", and "the", as used in this application, including in the claims, refer to "one or more". Thus, for example, a reference to "a subject" includes a plurality of subjects, unless the context clearly dictates otherwise (e.g., multiple subjects), etc.

[0070] Throughout this specification and the claims, the term “comprise”, “comprises” and “comprising” is used in a non-exclusive sense, unless the context requires otherwise. Similarly, the term “include” and its grammatical variations are intended to be non-limiting, such that a recitation of items in a list does not exclude other like items that may be substituted for or added to the listed items.

[0071] For the purposes of this specification and the appended claims, unless otherwise specified, all numbers expressing quantities, sizes, dimensions, ratios, shapes, formulations, parameters, percentages, amounts, properties, and other numerical values used in the specification and claims are to be understood as being modified in all instances by the term “about”, even if the term “about” is not explicitly stated with respect to the value, amount or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are not and need not be exact, but may, as appropriate, be approximations and / or larger or smaller, reflecting, among other things, tolerances, conversion factors, rounding, measurement error, and other factors known to those of skill in the art, in accordance with the desired properties sought to be obtained from the subject matter. For example, the term “about” when referring to a value can mean, in some embodiments, a variation of ±100%, in some embodiments ±50%, in some embodiments ±20%, in some embodiments ±10%, in some embodiments ±5%, in some embodiments ±1%, in some embodiments ±0.5%, and in some embodiments ±0.1% from the specified amount, such variations being appropriate for practicing the disclosed methods or using the disclosed compositions.

[0072] The present disclosure can be implemented using hardware, software, or a combination thereof, and can be implemented in one or more computer systems or other processing systems. In one aspect, the present disclosure contemplates one or more computer systems capable of performing the functions described herein.

[0073] Furthermore, the term "about", when used in connection with one or more numerical values or numerical ranges, is understood to refer to all such numerical values that include all values within the range, and also to modify that range by extending the boundaries above and below the recited numerical values. The recitation of a numerical range by endpoints includes all numbers within that range (e.g., the recitation of 1-5 includes 1, 2, 3, 4, and 5, as well as fractional values thereof, such as 1.5, 2.25, 3.75, 4.1, etc.) and all numbers within any range within that range, e.g., integers including their fractional parts.

[0074] Terms such as "preferably", "commonly", and "typically" are not used herein to limit the scope of the claimed embodiments or to imply that a particular feature is important or essential to the structure or function of the claimed embodiments. These terms are intended to emphasize alternative or additional features that may or may not be utilized in particular embodiments of the present disclosure.

[0075] The term "substantially" is used herein to represent the degree of inherent uncertainty that may be attributable to any quantitative comparison, value, measurement, or other representation, and also to represent the degree to which a quantitative representation may vary from a reference described without causing a change in the basic function of the subject matter in question.

[0076] The terms "a", "an", and "the", as used in this application, including in the claims, refer to "one or more". Thus, for example, a reference to "a subject" includes a plurality of subjects, unless the context clearly dictates otherwise (e.g., multiple subjects), etc.

[0077] The terms "comprise", "comprises", and "comprising", and "include", "includes", and "including" are intended to be non - limiting, and the recitation of items in a list is not intended to exclude other similar items that may be substituted for or added to the listed items.

[0078] Various modifications and variations of the disclosed methods, compositions, and uses of the present disclosure will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. While the present disclosure has been disclosed in connection with specific preferred embodiments or implementations, it should be understood that the claimed present disclosure should not be unduly limited to such specific embodiments or implementations.

Claims

1. 1. A cartridge for use with an instrument, comprising: a plurality of electrowetting electrodes operative to perform droplet operations on droplets within a droplet operations gap of the cartridge; a refractive index sensor configured in the form of a thin film interference filter, the refractive index sensor exposed in the droplet operations gap proximate to one or more electrowetting electrodes such that a droplet present on the one or more electrowetting electrodes can contact the refractive index sensor, the arrangement of the one or more electrowetting electrodes and the refractive index sensor defining a droplet interrogation site; A cartridge comprising:

2. 10. The cartridge of claim 1, wherein the cartridge includes a top plate and the refractive index sensor is attached to the top plate.

3. The cartridge of claim 1 , wherein the refractive index sensor is mounted in the droplet operations gap.

4. 2. The cartridge of claim 1, wherein the droplet operations gap is defined by a top plate and a bottom plate in substantially parallel planes, and the refractive index sensor is mounted in the droplet operations gap and has a sensor face perpendicular to the substantially parallel plane.

5. 5. A cartridge according to claim 1, wherein the refractive index sensor is provided as the tip of a waveguide.

6. The cartridge according to any one of claims 1 to 5, further comprising X or more (X > 2) refractive index sensing channels.

7. The cartridge according to any one of claims 1 to 6, further comprising X or more (X≧2) optical fibers.

8. The cartridge according to any one of claims 1 to 5, further comprising X or more (X > 10) refractive index sensing channels.

9. The cartridge of any one of claims 1 to 5 or 8, further comprising X or more (X≧50) refractive index sensing channels.

10. The cartridge according to any one of claims 1 to 9, further comprising a lens attached to the side opposite the refractive index sensor and the droplet operations gap side.

11. 1. A system comprising: A cartridge according to any one of claims 1 to 10, and an apparatus including electronics for controlling said cartridge and a means for mounting said cartridge to provide electronic coupling and control; A system comprising:

12. 12. The system of claim 11, further comprising one or more illumination sources configured to illuminate the one or more droplet interrogation sites.

13. 13. A system according to claim 11 or 12, further comprising one or more optical measurement devices arranged to detect light from one or more droplet interrogation sites.

14. A system according to any one of claims 11 to 13, further comprising an illumination source and an optical measurement device arranged with respect to the droplet interrogation site to operate in a transmission mode.

15. A system according to any one of claims 11 to 14, further comprising an illumination source and an optical measurement device arranged with respect to the droplet interrogation site to operate in reflection mode.

16. A system according to any one of claims 11 to 15, further comprising a scanning optical measurement device configured to scan the plurality of droplet interrogation sites.

17. 16. The system of claim 12, 14 or 15, wherein the illumination source is integrated into the cartridge.

18. 18. The system of claim 12, 14, 15 or 17, wherein the illumination source comprises a light emitting diode integrated into the cartridge.

19. 20. The system of claim 12, 14, 15, 17 or 18, wherein the illumination source comprises a coaxial illumination source.

20. Providing a system according to any one of claims 11 to 19; loading a sample droplet into the droplet operations gap; performing one or more sample processing steps on the sample droplets to produce analysis-ready droplets; performing a refractive index analysis of said analysis-ready droplet at a droplet interrogation site; A method comprising:

21. 21. The method of claim 20, wherein one or more of the loading steps or one or more of the sample processing steps are performed using droplet manipulation via electrowetting.

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