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A METHOD FOR PREVENTING CURING INHIBITION OF POLYDIMETHYLSILOXANE (PDMS) ON 3D-PRINTED RESIN MOLDS
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Abstract
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ORDINARY APPLICATION
Published
Filed on 15 November 2024
Abstract
The present invention provides a method for preventing curing inhibition of polydimethylsiloxane (PDMS) on 3D-printed resin molds. The process involves ultrasonication of the mold in water and isopropyl alcohol (IPA), followed by UV exposure and thermal treatment to cure the resin. A curing agent is then applied to the mold to form a protective layer, preventing chemical interaction between uncured resin residues and PDMS during the curing process. This method reduces post-treatment time and eliminates the need for toxic chemical coatings, enabling efficient and precise fabrication of PDMS microfluidic structures. The method is compatible with various types of resins and significantly improves the quality and reliability of PDMS molding.
Patent Information
Application ID | 202441088476 |
Invention Field | BIO-MEDICAL ENGINEERING |
Date of Application | 15/11/2024 |
Publication Number | 47/2024 |
Inventors
Name | Address | Country | Nationality |
---|---|---|---|
SAJAN DANIEL GEORGE | Professor and Head, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, 576104, Karnataka, India. | India | India |
B JYESHTA PRABHU | Research Scholar, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, 576104, Karnataka, India. | India | India |
PRATHEEKSHA RAO I K | Research Scholar, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, 576104, Karnataka, India. | India | India |
BHARATH B | Post - Doctoral Fellow, Department of Atomic and Molecular Physics, Manipal Academy of Higher Education, Manipal, 576104, Karnataka, India. | India | India |
Applicants
Name | Address | Country | Nationality |
---|---|---|---|
Manipal Academy of Higher Education | Madhav Nagar, Manipal, 576104, Karnataka, India. | India | India |
Specification
Description:FIELD OF THE INVENTION
[0001] The present invention relates to the field of microfluidic device fabrication, specifically methods for preventing curing inhibition of polydimethylsiloxane (PDMS) when molded on 3D-printed resin molds. The invention focuses on using a curing agent applied after UV and thermal treatment to eliminate the interaction between uncured resin residues and PDMS during the curing process.
BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] The Microfluidic technology is rapidly advancing due to its unique advantages over traditional experimental systems in fields such as tissue engineering, drug transport and screening, and cellular analysis. These advantages include reduced device size, increased sensitivity, and a lower consumption of reagents and samples. However, the success of these systems hinges on the fabrication of accurate, high-quality microfluidic devices. The biocompatible soft polymer polydimethylsiloxane (PDMS), which offers flexibility, transparency, and ease of manipulation, has become the material of choice for creating these devices. PDMS-based microfluidic structures are typically fabricated through soft lithography, a process in which PDMS is molded against a master structure fabricated using photolithography or electron beam lithography.
[0004] However, this standard lithography-based fabrication technique presents significant limitations. The use of clean rooms, specialized equipment, and the laborious, time-consuming nature of the iterative process make it difficult for widespread use, especially in settings without access to sophisticated infrastructure. As a result, the field of microfluidics has been seeking alternatives to simplify and accelerate the fabrication of PDMS-based devices.
[0005] The advent of 3D printing, often referred to as a hallmark of the Fourth Industrial Revolution, has revolutionized this process. 3D printing enables rapid and versatile fabrication of master structures or molds for PDMS replication without the need for clean rooms or complex processes. Resin-based 3D printing, in particular, offers higher resolution and is highly beneficial for creating intricate microfluidic channels. Using computer-aided designs, resin-based 3D printers can create molds layer by layer through the polymerization of photosensitive resins upon exposure to UV light. This method significantly improves the speed and accessibility of fabricating microfluidic devices.
[0006] However, despite its potential, resin-based 3D printing introduces a critical challenge in the form of PDMS curing inhibition. During the PDMS replication process, components such as uncured monomers, oligomers, photoinitiators, and other auxiliary chemicals present in the 3D-printed resin can leach into the PDMS, leading to incomplete curing at the interface between the mold and the PDMS. This curing inhibition results in sticky surfaces, improper mold replication, and the eventual failure of microfluidic device fabrication.
[0007] Researchers have attempted various solutions to mitigate PDMS curing inhibition. These include prolonged UV exposure, thermal treatments, and chemical treatments such as silanization. However, these methods often require extensive processing times-UV treatments lasting several hours, thermal treatments up to 24-48 hours, and silanization with toxic chemicals like trichloro(1H,1H,2H,2H)-perfluoro-octyl)silane. Additionally, the efficacy of these treatments varies depending on the type of resin used. Despite these efforts, the replication of PDMS from 3D-printed molds can be delayed by one or two days, limiting the potential for rapid prototyping and iterative testing.
[0008] At the molecular level, PDMS cross-linking occurs through a hydrolyzation reaction, where silicon-hydrogen bonds react with carbon-carbon double bonds in the presence of a platinum-based catalyst. However, uncured resin constituents, such as organophosphates, vinyl compounds, photo initiators, and polyethylene glycols, can inhibit this reaction by interacting with the catalyst, leading to incomplete PDMS curing.
[0009] To address these limitations, there is a dire need to introduce a novel approach that simplifies and accelerates the post-treatment process for 3D-printed molds used in PDMS microfabrication by applying a curing agent after a simplified UV and thermal treatment, in order to significantly reduce the curing inhibition problem along with cutting down the time required for mold preparation and eliminating the need for toxic chemicals.
OBJECTIVE OF THE INVENTION
[0010] An objective of the present invention is to provide a method that prevents curing inhibition of PDMS on 3D-printed resin molds
[0011] Another objective of the present invention is to provide a method which employs a curing agent after pre-treating the mold with water, isopropyl alcohol (IPA), ultraviolet (UV) light, and thermal exposure.
[0012] Another objective of the present invention is to provide a method which reduces post-treatment time and simplifies the process, making it more efficient for fabricating PDMS microfluidic structures without using toxic chemical coatings.
[0013] Another objective of the present invention is to significantly reduce the post-treatment time for 3D-printed molds.
[0014] Another objective of the present invention is to be applicable to various types of resins.
[0015] Another objective of the present invention is to avoid the use of toxic chemical coatings.
[0016] Another objective of the present invention is to ensure proper curing and replication of PDMS structures.
SUMMARY OF THE INVENTION
[0017] In an aspect of the present invention, the disclosure provides a combination of ultrasonication in water and isopropyl alcohol (IPA), followed by short-duration UV exposure and thermal treatment, prepares the mold. Afterward, a curing agent is applied, which prevents the uncured resin components from interacting with the PDMS during curing. This innovative approach reduces the total processing time from days to just a few hours, making it a time-efficient and practical solution for rapid microfluidic device fabrication using 3D-printed molds.
[0018] In an aspect of the present invention, it discloses a method for preventing curing inhibition of polydimethylsiloxane (PDMS) on 3D-printed resin molds, the method comprising:
i. ultrasonication of the mold in water and isopropyl alcohol (IPA) to remove uncured resin;
ii. exposure of the mold to ultraviolet (UV) light for a specific duration;
iii. thermal treatment of the mold at a set temperature for a reduced period of time;
iv. application of a curing agent onto the treated mold to prevent curing inhibition of PDMS.
[0019] In another aspect, present invention discloses a method for improving the replication of PDMS structures from 3D-printed molds, the method comprising applying a curing agent after UV and thermal treatment to prevent inhibition at the interface between the mold and PDMS.
[0020] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.
BRIEF DESCRIPTION OF FIGURES
[0021] The accompanying drawings are included to provide a clear understanding of the present invention and a detailed description, and they constitute a part of this complete specification.
[0022] FIG. 1 illustrates: (a) CAD Design of Mold (b) Fabrication of Mold (c) post-curing treatments to the mold (d) PDMS casting on printed mold
[0023] FIG. 2 shows the molds printed using a) water washable clear resin, b) water washable grey resin, c) ABS-like resin and d) standard resin
[0024] FIG. 3 displays PDMS casted using (a) water washable clear resin, (b) water washable grey resin, (c)ABS-like resin and (d) standard resin.
[0025] FIG. 4 shows the dimension analysis of the mold and replicated structure
DETAILED DESCRIPTION OF THE INVENTION
[0026] The following is a full description of the disclosure's embodiments. The embodiments are described in such a way that the disclosure is clearly communicated. The level of detail provided, on the other hand, is not meant to limit the expected variations of embodiments; rather, it is designed to include all modifications, equivalents, and alternatives that come within the spirit and scope of the current disclosure as defined by the attached claims. Unless the context indicates otherwise, the term "comprise" and variants such as "comprises" and "comprising" throughout the specification are to be read in an open, inclusive meaning, that is, as "including, but not limited to."
[0027] When "one embodiment" or "an embodiment" is used in this specification, it signifies that a particular feature, structure, or characteristic described in conjunction with the embodiment is present in at least one embodiment. As a result, the expressions "in one embodiment" and "in an embodiment" that appear throughout this specification do not necessarily refer to the same embodiment. Furthermore, in one or more embodiments, the specific features, structures, or qualities may be combined in any way that is appropriate.
[0028] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0029] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference.
[0030] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations.
[0031] It should also be appreciated that the present invention can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0032] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
Definitions
[0033] For the purpose of the present invention, PDMS (Polydimethylsiloxane) may be defined as a silicone-based elastomer commonly used in microfluidics due to its excellent molding and mechanical properties.
[0034] For the purpose of the present invention, curing Agent may be defined as chemical compound or mixture applied to the mold to prevent PDMS curing inhibition by forming a protective layer on the mold surface.
[0035] For the purpose of the present invention, ultrasonication may be defined as the process using high-frequency sound waves to agitate a solution, often used to clean surfaces by removing contaminants.
[0036] For the purpose of the present invention, curing inhibition may be defined as the phenomenon where chemical residues from the mold prevent the complete curing of PDMS, leading to incomplete structure replication or sticky surfaces.
[0037] In a general embodiment, the present invention relates to a novel method for preventing curing inhibition of PDMS when using 3D-printed resin molds in microfluidic device fabrication. The method involves a series of post-processing steps comprising ultrasonication of the mold in water and isopropyl alcohol (IPA) to remove uncured resin residues followed by exposure to ultraviolet (UV) light for a brief period, thermal treatment of the mold for 3 hours and application of a thin layer of a curing agent to the mold before casting PDMS.
[0038] In an embodiment, the present invention discloses a method for preventing curing inhibition of polydimethylsiloxane (PDMS) on 3D-printed resin molds, the method comprising:
i. ultrasonication of the mold in water and isopropyl alcohol (IPA) to remove uncured resin;
ii. exposure of the mold to ultraviolet (UV) light for a specific duration;
iii. thermal treatment of the mold at a set temperature for a reduced period of time;
iv. application of a curing agent onto the treated mold to prevent curing inhibition of PDMS.
[0039] In another embodiment, the ultrasonication in water is carried out for three cycles of 5 minutes each and in IPA for 15 minutes.
[0040] In another embodiment, the mold is UV treated at wavelengths of 365 nm or 405 nm for 10 minutes at a distance of 5 cm from the UV light source.
[0041] In another embodiment, the mold is thermally treated at a temperature of 120°C for 3 hours.
[0042] In another embodiment, the curing agent is applied by the techniques selected from, but not limited to, brush coating, dip coating, spray coating, and spin coating.
[0043] In another embodiment, the process is applied on resins, selected from, but not limited to, water-washable clear resin, water-washable grey resin, ABS-like resin, and standard resin.
[0044] In another embodiment, the UV treatment duration and intensity are adjustable based on the thickness or type of 3D-printed resin mold used.
[0045] In another embodiment, the thermal treatment duration is reduced further 3 hours by using an accelerated curing process with a combination of UV and thermal treatment.
[0046] In another embodiment, the present invention provides a method for improving the replication of PDMS structures from 3D-printed molds, the method comprising applying a curing agent after UV and thermal treatment to prevent inhibition at the interface between the mold and PDMS.
[0047] In another embodiment, the process is effective on both photopolymer and thermoplastic resins used in additive manufacturing of 3D-printed molds.
[0048] In a preferable embodiment, the mold is ultrasonicated in water for three 5-minute cycles to remove uncured resin, followed by ultrasonication in IPA for 15 minutes. This step ensures thorough cleaning of the mold surface.
[0049] In a preferable embodiment, after cleaning, the mold is exposed to UV light (at 365 nm or 405 nm) for 10 minutes, with the UV source positioned 5 cm away from the mold. This promotes resin curing at the surface and reduces curing inhibition.
[0050] In a preferable embodiment, the mold is thermally treated at 100-130°C for 2-4 hours to enhance the curing of the 3D-printed resin and remove remaining uncured resin components.
[0051] In a preferable embodiment, the mold is coated with a curing agent to prevent inhibition at the PDMS interface. The curing agent can be applied using techniques such as brush coating, dip coating, spray coating, or spin coating. The thin, uniform layer formed ensures that PDMS curing proceeds without interference.
[0052] In a preferable embodiment, the PDMS mixture, prepared in a 10:1 ratio, is poured into the treated mold and cured at 100°C for 1 hour. The PDMS structure is then peeled from the mold, resulting in a precise replication of the mold features.
[0053] It will be appreciated by a skilled artisan that the present disclosure invention offers an effective solution for preventing PDMS curing inhibition on 3D-printed resin molds, improving the efficiency and precision of microfluidic device fabrication. By reducing post-treatment times and avoiding toxic chemicals, the method enhances the practicality of using 3D-printed molds for PDMS applications. The use of a curing agent after UV and thermal treatment ensures complete curing of PDMS, resulting in high-quality replications of microstructures without inhibition. This technique is versatile, environmentally friendly, and compatible with a wide range of 3D-printed resins, making it a valuable advancement in PDMS microfabrication.
[0054] Accordingly, the method disclosed herein significantly reduces the post-treatment time compared to traditional approaches, enabling the mold to be used within hours of 3D printing. Furthermore, it avoids the use of toxic chemicals typically used to prevent PDMS curing inhibition. The method is demonstrated to work across various resin types, making it versatile and widely applicable
[0055] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions, or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
EXAMPLES
[0056] The present invention is further explained in the form of the following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.
[0057] All the raw materials used in this invention are commercially available in the open markets and can be procured easily.
Example 1: Method for Fabricating PDMS Structures Using 3D-Printed Molds with Optimized Post-Treatment
[0058] The mold to be 3D-printed is designed using computer-aided software. Then the file is converted to the required format and loaded to the 3D printer and allowed for printing. Once the printing process is completed, the mold which is adhered to the stage will be removed out. Then the mold is ultrasonicated in water for 5 minutes and the process is repeated thrice so that the uncured resin is washed away.
[0059] After this, the mold is ultrasonicated in IPA for 15 minutes. This mold is placed under a UV lamp (365/405 nm, 5 W) at 5 cm from the lamp for 10 minutes and then placed on a hot plate set to 120℃ for 3 hours. Following it, the mold is allowed to cool for 5 minutes. Once it is cooled, the mold is uniformly coated with the curing agent. Any coating technique can be followed such as brush coating, dip coating, spray coating, spin coating etc. Afterward, the prepared 10:1 ratio PDMS is poured and allowed for curing at 100℃ for one hour. The PDMS structure is slowly peeled from the mold. FIG. 1(a) is the design of the mold, FIG 1(b), FIG. 1(c) and FIG.1 (d) shows the schematic of the process followed.
Example 2: Post-Treatment Process for 3D-Printed Molds to Eliminate PDMS Curing Inhibition
[0060] The 3D-printed molds are first ultrasonicated in water thrice for 5 minutes and then in IPA for 15 minutes. Then the molds are UV treated for 10 minutes and thermal treated for 3 hours. Then curing agent is applied to the mold. Then prepared PDMS is poured into the mold and allowed for curing. This usage of curing agent cuts down the long UV treatment as well as thermal treatment. The mold can be used within a few hours of printing.
Example 3: Prevention of PDMS Curing Inhibition in 3D-Printed Molds Using Post-Treatment with a Curing Agent
[0061] It is observed that there is no stickiness at the interface of the PDMS structure and mold (which occurs if there is curing inhibition), and the structure replication to the PDMS happens without any peeling off residues. This process is investigated for anycubic water washable clear and grey resins, ABS-like resin and Standard resin. It is observed that only UV-treated, only thermal, and only UV+thermal treated mold couldn't replicate the structure properly due to PDMS curing inhibition. However, the usage of curing agent after UV+thermal treatment hinders the curing inhibition of PDMS at the interface demonstrating successful curing. FIGs. 2(a-d) shows the image of the printed molds. FIGs. 3(a-d) are the images of the PDMS structures after peeling from the molds
Example 4: Dimension analysis of the mold and replicated structure
[0062] Quantification of the curing inhibition of PDMS was performed by comparing the feature dimensions of the replica with those of the mold. If curing inhibition occurs, the dimensions of the replica was not matched with those of the mold. Conversely, if curing is successful, the dimensions should align closely. It was examined that the dimensions of the molds alongside the replicated PDMS, as shown in FIG. 4. It was observed that the replicated dimensions closely matched the mold dimensions, demonstrating the successful curing of PDMS (FIG. 4).
[0063] The foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.
ADVANTAGES OF THE PRESENT INVENTION
[0064] By applying a curing agent after UV and thermal treatment, the method effectively prevents the interaction between the mold surface and PDMS, ensuring successful curing.
[0065] The process reduces post-treatment time by minimizing the duration of thermal treatment and eliminating the need for toxic chemical coatings.
[0066] The method works across a range of 3D-printed resins, including water-washable, ABS-like, and standard resins, offering flexibility and versatility.
[0067] The uniform coating of the curing agent ensures that fine microfluidic structures are accurately transferred from the mold to PDMS without dimensional errors.
[0068] The method avoids the use of hazardous chemicals, making it safer and more environmentally sustainable.
, Claims:1. A method for preventing curing inhibition of polydimethylsiloxane (PDMS) on 3D-printed resin molds, the method comprising:
i. ultrasonication of the mold in water and isopropyl alcohol (IPA) to remove uncured resin;
ii. exposure of the mold to ultraviolet (UV) light for a specific duration;
iii. thermal treatment of the mold at a set temperature for a reduced period of time;
iv. application of a curing agent onto the treated mold to prevent curing inhibition of PDMS.
2. The method as claimed in claim 1, wherein the ultrasonication in water is carried out for three cycles of 5 minutes each and in IPA for 15 minutes.
3. The method as claimed in claim 1, wherein the mold is UV treated at wavelengths of 365 nm or 405 nm for 10 minutes at a distance of 5 cm from the UV light source.
4. The method as claimed in claim 1, wherein the mold is thermally treated at a temperature of 120°C for 3 hours.
5. The method as claimed in claim 1, wherein the curing agent is applied by the techniques selected from, but not limited to, brush coating, dip coating, spray coating, and spin coating.
6. The method as claimed in claim 1, wherein the process is applied on resins, selected from, but not limited to, water-washable clear resin, water-washable grey resin, ABS-like resin, and standard resin.
7. The method as claimed in claim 1, wherein the UV treatment duration and intensity are adjustable based on the thickness or type of 3D-printed resin mold used.
8. The method as claimed in claim 1, wherein the thermal treatment duration is 3 hours by using an accelerated curing process with a combination of UV and thermal treatment.
9. A method for improving the replication of PDMS structures from 3D-printed molds, the method comprising applying a curing agent after UV and thermal treatment to prevent inhibition at the interface between the mold and PDMS.
10. The method of claim 13, wherein the process is effective on both photopolymer and thermoplastic resins used in additive manufacturing of 3D-printed molds.
Documents
Name | Date |
---|---|
202441088476-COMPLETE SPECIFICATION [15-11-2024(online)].pdf | 15/11/2024 |
202441088476-DECLARATION OF INVENTORSHIP (FORM 5) [15-11-2024(online)].pdf | 15/11/2024 |
202441088476-DRAWINGS [15-11-2024(online)].pdf | 15/11/2024 |
202441088476-EDUCATIONAL INSTITUTION(S) [15-11-2024(online)].pdf | 15/11/2024 |
202441088476-EVIDENCE FOR REGISTRATION UNDER SSI [15-11-2024(online)].pdf | 15/11/2024 |
202441088476-EVIDENCE FOR REGISTRATION UNDER SSI(FORM-28) [15-11-2024(online)].pdf | 15/11/2024 |
202441088476-FORM 1 [15-11-2024(online)].pdf | 15/11/2024 |
202441088476-FORM FOR SMALL ENTITY(FORM-28) [15-11-2024(online)].pdf | 15/11/2024 |
202441088476-FORM-9 [15-11-2024(online)].pdf | 15/11/2024 |
202441088476-POWER OF AUTHORITY [15-11-2024(online)].pdf | 15/11/2024 |
202441088476-REQUEST FOR EARLY PUBLICATION(FORM-9) [15-11-2024(online)].pdf | 15/11/2024 |
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