KR-102964501-B1 - APPARATUS AND METHOD OF SURFACE ACOUSTIC WAVE-BASED ACOUSTO-MICROFLUIDIC DEVICE FOR RESIDUE-FREE MANIPULATION OF MICROSCALE OBJECTS, AND SEPARATION/DISCHARGE METHOD OF MICROSCALE OBJECTS

KR102964501B1KR 102964501 B1KR102964501 B1KR 102964501B1KR-102964501-B1

Abstract

The present invention relates to a surface acoustic wave-based acoustic microfluidic device for residue-free manipulation of micro-objects, a method for manufacturing the same, and a method for separating and discharging micro-objects. More specifically, the invention relates to a device and a method for manufacturing the same that prevents the formation of an acoustic anechoic region by utilizing a hemispherical microchannel manufactured using the thermal reflow of a positive photosensitive liquid as a microchannel within the acoustic microfluidic device, thereby controlling the position and separating all micro-objects floating within the microchannel without residue using surface acoustic wave-induced acoustic radiation force. Compared to a conventional surface acoustic wave-based acoustic microfluidic device utilizing a microchannel with a rectangular cross-section, where an acoustic anechoic region is formed when a wave propagates along the surface of a piezoelectric substrate and then encounters the microchannel, propagating within the microchannel in the form of a longitudinal wave with a specific angle of refraction, and micro-objects located in this region cannot be manipulated by the acoustic field, the invention has the advantage of being able to precisely control all micro-objects within the microchannel without separate sheathing flow. Therefore, when controlling micro-objects such as microplastics and cells using the acoustic microfluidic device produced by the present invention, no residue is left, which increases the yield, and it has the advantages of a simpler configuration compared to conventional devices and reduced costs for operation and maintenance.

Inventors

박진수
무함마드 소반 칸

Assignees

전남대학교산학협력단

Dates

Publication Date: 20260513
Application Date: 20221017

Claims (15)

In a surface acoustic wave-based acoustic microfluidic device, A piezoelectric substrate having electrodes formed thereon for generating MHz ultrasonic band surface acoustic waves; and a microfluidic chip having microchannels patterned with a hemispherical cross section that are interlocked on the piezoelectric substrate patterned with the electrodes, wherein traveling surface acoustic waves generated from the electrodes are converted into longitudinal waves and propagated therefrom; wherein surface acoustic waves are applied to a fluid passing through the microchannels to control the flow position of micro-objects, thereby separating and discharging micro-objects. A surface acoustic wave-based acoustic microfluidic device characterized in that the microchannel having the above-mentioned hemispherical cross-section is formed such that the contact angles at both ends of the hemispherical cross-section are formed to have an angle equal to the difference between the right angle and the angle of refraction, taking into account the angle of refraction of the surface acoustic wave.
In paragraph 1, A surface acoustic microfluidic device characterized by the above electrode being a straight interdigital transducer composed of a pair of intersecting electrodes, a slanted-finger interdigital transducer formed with a change in interspan distance such that the intersecting electrodes gradually widen or narrow from one side to the other, or a focused interdigital transducer formed with intersecting electrodes in a fan shape.
In paragraph 2, A surface acoustic wave-based acoustic microfluidic device characterized in that the above-mentioned comb-shaped electrodes have the same thickness (t1) and spacing (t2) as each other at the same point where a surface acoustic wave of a specific frequency is generated.
In paragraph 1, A surface acoustic microfluidic device based on acoustic waves, characterized in that the piezoelectric substrate is made of any one of lithium lineobate (LiNbO3), quartz, lithium tantalate (LiTaO3), lithium borate (Li2B4O7), or langasite (La3Ga5SiO14).
In paragraph 2, A surface acoustic microfluidic device characterized in that the above-mentioned comb-shaped electrode is fabricated with a chromium (Cr)/gold (Au) layered structure or a titanium (Ti)/aluminum (Al) layered structure.
In paragraph 1, A surface acoustic wave-based acoustic microfluidic device characterized in that the microfluidic chip patterned with the above-mentioned microchannels is fabricated from PDMS, PC, or polymethyl methacrylate (PMMA).
In any one of paragraphs 1 through 6, A surface acoustic wave-based acoustic microfluidic device characterized by the above-mentioned microchannel having at least one fluid inlet through which a fluid containing a micro-object is introduced, and at least two outlets for discharging the fluid containing the micro-object separated while flowing through the microchannel, the fluid from which the micro-objects have been separated, or the two types of micro-objects, respectively.
delete
In the method for fabricating a microchannel with a hemispherical cross section according to claim 1 above, (a) a step of applying a positive photosensitive solution to a wafer (34) in the form of a thin film liquid film through a spin coating process; (b) a step of irradiating ultraviolet rays to an area outside the microchannel shape using a photomask; (c) a step of forming a microchannel mold by removing the ultraviolet-irradiated area through the development of the photosensitive solution; (d) a step of forming a mold by applying a high temperature above the glass transition temperature of the photoresist to induce thermal re-flow of the photoresist so that the rectangular cross-section changes into a hemispherical cross-section; (e) a step of pouring material into the mold obtained in step (d) above and performing a soft lithography process; and (f) a step of finally completing the fabrication of a microchannel having a hemispherical cross section; thereby comprising a method for fabricating a microchannel having a hemispherical cross section, characterized in that an acoustic anechoic region is not formed within the microchannel.
(1) A hemispherical microchannel is manufactured using thermal reflow of a positive photosensitive material to eliminate the formation of an acoustic anechoic region, and is utilized as a microchannel in an acoustic microfluidic device. (2) Surface acoustic waves are irradiated toward the hemispherical microchannel to induce acoustic radiation, and the flow position of all micro-objects floating in the hemispherical microchannel is controlled using the acoustic radiation. (3) A mixed fluid of liquid and solid particles containing micro-objects that flow through the hemispherical microchannel and have their flow positions controlled to one side; and a pure fluid that maintains flow only in the liquid phase while the micro-objects are deflected to one side by acoustic radiation force; each separated and discharged separately through two discharge ports branched from the rear end of the microchannel to recover the micro-objects.
In Paragraph 10, A method for separating and discharging micro-objects in a surface acoustic wave-based acoustic microfluidic device, characterized in that the fluid flowing into the inlet of the microchannel contains at least two types of micro-objects of different sizes, and the surface acoustic wave is set to a frequency capable of controlling the positional movement of only one of the two types of micro-objects.
In Article 10 or Article 11, A method for separating and discharging micro-objects in a surface acoustic wave-based acoustic microfluidic device, characterized in that the microchannel comprises at least one inlet or two inlets, each comprising a first and a second inlet for introducing different fluids.
In Paragraph 12, A method for separating and discharging micro-objects of a surface acoustic wave-based acoustic microfluidic device, characterized in that a fluid containing one type of micro-object of one size or two types of micro-objects of different sizes is introduced into the first inlet, and a coating liquid of a predetermined color is introduced into the second inlet, so that the outer surface of a micro-object among the micro-objects that undergoes positional displacement due to deflection is coated by the coating liquid and separated and discharged with a changed color.
In Paragraph 13, A method for separating and discharging micro-objects in a surface acoustic wave-based acoustic microfluidic device, characterized in that the above-mentioned inlet includes a third inlet, and the sheath fluid introduced into the above-mentioned third inlet flows laminarly to push the coating liquid toward the electrode side that irradiates surface acoustic waves.
In Paragraph 14, A method for separating and discharging micro-objects of a surface acoustic wave-based acoustic microfluidic device, characterized in that a micro-object of a size that causes deflection by the surface acoustic wave passes through the coating liquid and moves into a sheath fluid, and is discharged together with the sheath fluid.

Description

Surface Acoustic Wave-Based Acoustic Microfluidic Device for Residue-Free Manipulation of Microscale Objects, Method for Manufacturing the Same, and Method for Separating and Discharging Microscale Objects The present invention relates to a surface acoustic wave-based acoustic microfluidic device for manipulating micro-objects, such as microplastics and cells, in a label-free, non-contact, and continuous manner without leaving residue, a method for manufacturing the same, and a method for separating, discharging, and recovering micro-objects. Specifically, the invention relates to a device and method for separating and purifying micro-objects by controlling their position using a microscale acoustic radiation phenomenon that occurs when a propagating surface acoustic wave in the ultrasonic band generated from a comb electrode is applied to a micro-object within a microchannel. Unlike conventional technology, the invention is characterized by using a microchannel having a hemispherical cross-section that matches the refraction angle of the sound waves within the microchannel, thereby ensuring that no residue remains. Microfluidics technology is utilized in various fields, including microchemical and bioreactors, microplastic separation, and cell and bacteria separation, for controlling fluid flow within microfluidic chips featuring microchannels with micrometer-level characteristic lengths and microscale or nanoscale objects dispersed within fluids. It is recognized as one of the core source technologies of the bio-healthcare industry, which is one of the nation's key growth engines. In particular, the separation of microplastics, cells, and other substances with characteristic lengths smaller than the microscale presents several limitations for existing macroscale technologies, making this the field where the application of microfluidics is most prominent. Various technologies based on microfluidics have been developed for the separation of such micro-objects. Filter methods, which separate micro-objects by installing structures within microchannels, and passive methods, which utilize hydrodynamic forces derived from fluid flow, have limitations: they make precise separation difficult, do not allow for on-demand operation, and their separation performance is highly sensitive to the physical properties of the fluid and objects as well as flow conditions. On the other hand, active methods utilizing magnetic forces from magnets, electric forces induced by electrodes, and dielectric forces enable precise separation of micro-objects, but they are applicable only to labeled micro-objects, such as those with magnetic properties or polarity. Additionally, while laser-based optical force methods allow for precise positioning of micro-objects in an unlabeled manner, they have limitations: the force is very small at the pN level, severely restricting the movement distance of the objects; complex optical devices are required; and in the case of biomaterials such as cells, the laser is absorbed, causing heat generation and inducing thermal damage. Recently, acoustic microfluidics technology, which utilizes bulk acoustic waves or surface acoustic waves to control micro-objects within microchannels in a label-free, contactless, and continuous manner, is gaining attention as an alternative to conventional technology. Waves are classified as bulk acoustic waves when they propagate through the entire substrate within the sound generation unit, and as surface acoustic waves when they propagate along the surface of the substrate. These waves propagating through the substrate encounter fluid flow within the microchannels of a microfluidic chip and propagate in the form of longitudinal waves. While bulk acoustic wave-based methods suffer significant energy loss because they propagate through the entire substrate before encountering fluid flow, surface acoustic wave-based methods have the advantage of enabling energy-efficient and precise position control of micro-objects because almost no sound wave attenuation occurs before meeting fluid flow. Surface acoustic waves are generated by the inverse piezoelectric effect when an alternating current signal having the electrode's resonant frequency is applied to an interdigital transducer (IDT) deposited on a substrate with piezoelectric properties. The surface acoustic waves generated in this way encounter fluid flow within a microchannel, are converted into longitudinal waves, and apply an acoustic field to a micro-object. At this time, anisotropic sound wave scattering occurs due to the micro-object, and as a result, the micro-object is subjected to an acoustic radiation force in the direction of sound wave propagation and moves. In this process, a single interdigital transducer generates a bidirectional traveling surface acoustic wave. By positioning a microchannel in the propagation path of a traveling surface acoustic wave that propagates in one direction, the position of the mic