Soft interface liquid crystal microfluidic device

Abstract

The invention relates to a microfluidic device capable of forming a stable interface between liquid crystal and water phases.

Description

[0001] SOFT INTERFACE LIQUID CRYSTAL MICROFLUIDIC DEVICE

[0002] Technical Field of the Invention

[0003] The invention relates to a microfluidic device capable of forming a stable interface between liquids and liquid crystals in microfluidic devices. With the help of this interface created with the invention, a single alternative for various analysis methods can be provided, and, thanks to the controlled flow of liquid crystals, advanced nanostructured materials synthesis can be realized.

[0004] State of the Art of the Invention

[0005] Microfluidic devices are systems that can process, separate and mix or transport liquids, which are liquids of about 1 to 10 nano-liter volume by manipulating said liquids using their microlevel properties in micro-meter-sized channels. Since these liquids move in nano-liter-sized volumes in micro-meter-sized channels, the properties of the liquids such as interfacial tension, microfluidic resistance, etc. dominate the characteristics of the systems.

[0006] Complex analytical methods are often used in current applications and currently there is a need for methods that are carried out in a simpler way. Instead of the expensive, complex and bulky devices found in chromatography methods, which are frequently used in chemical analysis methods, there is a need for a low-cost, small and simple-use platform that allows chemical identification based on the responses that can be determined by optical imaging. In particular, the platform needed should be able to be developed for any analyte (ranging from simple salts, surfactants, lipids, toxins, proteins, viruses, bacteria) and should allow for any engineering within the water phase rather than modification of the structure of the device.

[0007] In addition, there is no study on devices that can work in the logic of "a single device for whole analysis" rather than the logic of a separate device (or component, attachment, etc.) for each analysis.

[0008] Invention document no. CN114414568A discloses an invention capable of detecting organophosphates using devices as a result of the deposition of perchloride salts onto microfluidic channel surfaces. The invention mentioned in the document also does not allow multiple analyses to be performed at the same time.

[0009] In addition to this, Jinan Deng et. al in their study [1] also mention that although various analyses can be performed on microfluidic devices using droplet systems, this requires a lot of statistical data and cannot provide fast and comprehensive analysis due to the difficulty of providing the necessary droplet configuration.

[0010] As a result, all the above-mentioned problems have made it imperative to make an innovation in the relevant field.

[0011] Objects and Summary of the Invention

[0012] The main object of the invention is to introduce the structure of a microfluidic device that allows water and liquid crystal materials to flow in such a way as to form a stable and durable interface between each other, preserving the responsive properties of liquid crystals, enabling these properties to be examined by optical methods, and enabling the automation of liquid crystalbased sensors and allowing multiple analysis to be performed simultaneously.

[0013] Accordingly, the present invention proposes to coat the region inside the channel through which the liquid crystal is intended to flow with a hydrophobic chemical such as Dimethyloctadecyl 3 -(trimethoxy silyl) propyl ammonium chloride (DMOAP).

[0014] Descriptions of the Figures Describing the Invention

[0015] The figures and the related descriptions used in order to better describe the device designed with this invention are as follows.

[0016] Fig. 1. Representative image of the interface of the channel formed in the microfluidic device of the invention.

[0017] Fig. 2. Cross-sectional sketches showing the production steps of the channels formed in the microfluidic device of the invention. Fig. 2a. Isometric sketches showing the different geometries of the channels formed in the microfluidic device of the invention.

[0018] Fig. 3. Representative sketch of the formed channel.

[0019] Fig. 4a. Phase symmetry and molecular structure image of 5CB molecule, a nematic phase liquid crystal.

[0020] Fig. 4b. Images showing the wetting properties of the liquid crystal droplet on the DMOAP surface.

[0021] Fig. 4c. Drawings showing microfluidic channel surface modification processes and polarized light images showing liquid crystal filling stages.

[0022] Fig. 4d. Polarized optical microscopy images showing co-current flow and counter-current flow in dual inlet and outlet channels.

[0023] Fig. 4e Polarized optical images showing that liquid crystal and aqueous phase co-flow in nonfunctionalized channels is not possible.

[0024] Fig. 4f Polarized optical microscopy images showing co-current flow and counter-current flow in dual inlet and outlet channels.

[0025] Fig- 4g Polarized optical microscopy images showing co-current in three inlet and outlet channels.

[0026] Definitions of the Elements / Features / Parts of the Invention

[0027] In order to better describe the device developed with this invention, the features and parts in the figures are numbered and the equivalent of each number is given below.

[0028] 1. Top coating

[0029] 2. Water phase

[0030] 3. Interface 4. Liquid crystal phase

[0031] 5. Channel

[0032] 6. Hydrophobic coating

[0033] 7. Channel inlet

[0034] Detailed Description of the Invention

[0035] The subject matter of the invention is a microfluidic device that allows water and liquid crystal phases to flow in such a way as to form a stable and durable interface (3) therebetween. To create the microfluidic device set forth in the invention, firstly, a channel (5) was embedded into the glass surface by chemical etching method within glass surfaces in order to utilize their chemical resistance and optical transparency. The channel (5) placed within the glass surfaces was coated with a top coating (1) such as polydimethylsiloxane (PDMS) elastomer and the liquid flow was ensured by drilling inlet and outlet holes on this top coating (1). In Fig. 1, in order to form channel (5) within the glass surface, the following steps are applied to the glass surface is respectively preferably as in Fig. 2: i. Coating the glass surface using the chemical hexamethyldisilazane or dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMO AP)) ii. Coating the prepared glass surface with photoresist iii. Etching the coated surface with the help of UV or electron beams with photolithography technique iv. Developing the channel in the glass surface exposed in the previous stage with the help of chemicals v. Stripping the photoresist coating vi. Covering with top coating (1).

[0036] In addition, "deep reactive ion etching" or etching with concentrated acid-base solutions can be used to create channels (5) and useful channels (5) can be prepared by physical "laser ablation" or "micromachining" in addition to chemical etching. The reason for photoresist coating on the glass surface is to be able to determine the geometry of the channel to be etched in the glass. With the help of chemical etching in the geometry determined by the etched photoresist, channels are developed within the glass and then the photoresist coating is stripped. In addition, physical methods such as laser ablation or micromachining can be used to create channels. Again, the glass surface is used because it allows optical observations thanks to its optical transparency. Preferably said top coating (1) is PDMS coating or glass.

[0037] The surfaces of the channels where liquid crystal phase (4) is passing through is formed by one of the different liquid phases being introduced to the channel, referred to as the central flow, while the central flow is surrounded by other liquids called the sheath flow, in such a way that the liquids flow through the channels forming a wall from the interfaces. This method is also called hydrodynamic flow focusing. Using this method, the region in the channel (5) where the liquid crystal phase (4) is planned to pass was coated with a hydrophobic coating (6). The flow of the water phase (2) and the liquid crystal phase (4) in the channel was achieved by pressure. As a result of these stages, the liquid crystal phase (4) flows stably from surfaces coated with hydrophobic coating (6) and the water phase (2) flows stably from uncoated surfaces.

[0038] The invention can also enable 2 or 3 different phases to flow in the same or opposite directions. Configuration changes in the bulk of the liquid crystal phase (4) or at its interfaces (3) with water resulting from these different flow configurations can be easily determined by optical imaging methods. Thanks to these configuration changes, analyte materials present in the water phase (2) can also be detected. In addition, the invention may enable the automation of liquid crystal sensors, as it can easily detect whether changes in the optical appearance changes at the interface (3) between the liquid crystal phase (4) and the water phase (2) are caused by analytes or flow direction. Since the invention can also provide a controlled flow between the liquid crystal phase (4) and the water phase (2), since the stable and durable interfaces (3) formed will be a liquid crystal-water interface, the properties such as size, shape, nanostructure of the nanomaterials to be formed by the reactions to be carried out on these interfaces (3) can be controlled by changing the liquid crystal phase (4) and orientation properties.

[0039] Fig. 1 shows the stable interface between the liquid crystal and water phases and the crosssection of the channel used in the invention. In this cross-section, the liquid crystals (4) and the water phase (2) flow without mixing in the channel (5) coated with the top coating (1), which is designed in a perforated way for filling with liquids, and form a stable interface (5). In addition, the part where the liquid crystal phase (4) is planned to flow is coated with hydrophobic coating (6) by hydrodynamic flow focusing method. This creates hydrophobicity on the surface of the microfluidic channels, creating a stable and durable interface between the liquid crystal phase and the water phase. In the invention, DMO AP coating is preferably used as hydrophobic coating (6).

[0040] In another preferred embodiment of the invention, different channel geometries can also be used within the microfluidic device to perform multiple analyses simultaneously. Fig. 2a also shows different channel structures with more than two channel inlets (7) to allow the flow of more than two phases at the same time, designed to be used for multiple quantitative analyses at the same time. These channel structures can be made by providing multiple inlets into the channel within the microfluidic device.

[0041] Said microdevice is also used in sensing and diagnostic device applications. For example, it is possible to apply this microdevice for tests for blood glucose measurement, covid, influenza, pregnancy, swab, or body fluid sampling. In addition, the invention can detect microplastics and micro-pollutants in groundwater and surface water.

[0042] The present invention, due to the structure described above, is of a nature that allows quantitative analysis of the interactions occurring at liquid crystal water interfaces through the orientation of liquid crystals. Literature examples have shown that liquid crystal materials can show response to molecules at picomolar levels in aqueous media. The present invention enables the identification of marker molecules in micromolar to nanomolar concentrations for critical diseases. It provides the opportunity for periodic control and early diagnosis of these diseases with fast and low-cost analyzes.

[0043] The present invention, with its disclosed structure, provides a microfluidic platform that can be completely tailorable according to the use, location, condition, and even the individual. In this context, the present invention is of a structure that is capable of performing complex and comprehensive analyses in short periods of time and at low costs. It also demonstrates properties of high-precision identification of liquid crystals.

[0044] Fig. 4a shows the orientation symmetry of the nematic liquid crystal phase. In addition to the nematic phase, cholesteric and blue phase liquid crystals can also be used in applications to exploit the advantages of liquid crystal phase symmetry in sensor and material synthesis applications. Fig. 4b shows that 5CB liquid crystal wets the DMO AP surface under water but does not wet the uncoated glass surfaces. This result shows that the stabilization of the liquid crystal-water interface obtained in this study is due to the wetting properties of the liquids in contact with the solid surfaces.

[0045] Fig. 4c schematically shows the hydrophobic and hydrophilic interfacial regions formed by surface functionalization and the formation of the liquid crystal-water interface during flow.

[0046] Fig. 4d shows a liquid crystal during filling in a coated channel. It is seen that the liquid crystal flows by forming the liquid crystal-water interface during filling and that this interface is stably maintained after filling.

[0047] Fig. 4e shows that a stable liquid crystal-water interface is not achieved in channels obtained without DMOAP coating or with DMOAP coating of the entire channel. Fig. 4f comprises microscope images and schematic drawings showing that liquid crystal and water phases flowing in the co-current direction and in counter-current direction forming a stable liquid crystal-water interface in these flow geometries. With the weak and strong flows shown in these examples, liquid crystal elastic straining can be easily implemented and sensor and synthesis conditions can be easily changed in applications. At the same time, flows in the co-current direction and in counter-current direction will provide engineering opportunities in sensor platform designs.

[0048] The three-phase flow configurations shown in Fig. 4g make it possible to achieve multiple liquid crystal-water interfaces on the same chip. This feature allows two different analytes to be simultaneously identified and used as reference interfaces in analytical methods, and two different interfaces to be used independently but simultaneously in synthetic methods.

[0049] References

[0050] [1] Jinan Deng, Dandan Han, and Jun Yang Applications of Microfluidics in Liquid Crystal- Based Biosensors 2021 / 10 / 11

Claims

CLAIMS1. A microfluidic device, characterized in that, in order to form a stable interface (3) between the coated liquid crystal (4) and water phases (2), it comprises: a channel (5) arranged according to the hydrodynamic flow focusing method and coated with a hydrophobic coating (6), a top coating (1), which covers the upper part of said channel in such a way that it leaves at least one inlet.

2. A microfluidic device according to claim 1, characterized in that it comprises multiple channel inlets (7) to enable multiple simultaneous analyses.

3. A microfluidic device according to claim 1, characterized in that said top coating (1) is a PDMS elastomer or glass.

4. A microfluidic device according to claim 1, characterized in that said hydrophobic coating (6) is DM0 AP.

5. A method for forming channels in a microfluidic device according to claim 1, characterized in that the following processes are applied respectively to the glass surface intended for the formation of the channel (5): i. Coating the glass surface using the chemical hexamethyldisilazane or DM0 AP ii. Coating the prepared glass surface with photoresist iii. Etching the coated surface with the help of UV or electron beams with photolithography technique iv. Developing the channel in the glass surface exposed in the previous stage with the help of chemicals v. Stripping the photoresist coating vi. Covering with top coating (1) in order to create channels within the glass surface to act as microfluidic devices.

6. A method according to claim 5, characterized in that said top coating (1) is a PDMS elastomer or glass.

7. A method according to claim 5, characterized in that said hydrophobic coating (6) is DMOAP.

8. An analyte analysis method, characterized in that: as a result of feeding an analyte solution and liquid crystals into a device according to claim1, the configuration changes caused by the analytes dissolved in the liquid phase (2) at the interface are examined using optical methods.

9. A diagnostic apparatus comprising a microfluidic device according to claim 1.

10. A sensor comprising a microfluidic device according to claim 1.

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