Name: Improved Polydimethylsiloxane (PDMS) Double Casting via Silicone Oil Treatment for Densely Packed Microstructure Replication (Video) | JoVE Journal
Uploaded: 2025-07-18T16:10:00.000+00:00
Duration: 7 min 1 s
Description: Learn an improved PDMS double casting technique using silicone oil treatment to replicate dense microstructures reliably. This cost-effective method eliminates expensive equipment needs and enables precise demolding for biomaterials research.

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5 minutes

This research was supported by the Challengeable Future Defense Technology Research and Development Program through the Agency for Defense Development (ADD), funded by the Defense Acquisition Program Administration (DAPA) in 2023 (No.915067201)

1. Fabrication of the PDMS mold (M2) from a silicon mold (M1) (Figure 1)
NOTE: All hexane procedures should be conducted in a fume hood or glove box to prevent inhalation of volatile organic compounds and ensure operator safety.
<ol>
	<li>Silicon mold coating (M1)
	<ol>
		<li>Mix a solution of hexane and octadecyltrichlorosilane (OTS) in a 40:1 volume ratio in a clean glass beaker with a stirring rod.</li>
		<li>Cover the glass beaker with aluminum foil to minimize evaporation.</li>
		<li>Place the sealed glass beaker into a room-temperature ultrasonic bath filled with water. Sonicate at 40 kHz and 135 W for 5 min to ensure complete mixing.</li>
		<li>Immerse the silicon mold (previously fabricated via deep reactive ion etching to feature a hole array) into the prepared hexane-OTS mixture for 30 min at room temperature (RT) (Figure 1A). 
		NOTE: In this study, a silicon mold with dimensions of 5&#8239;cm &#215; 0.5&#8239;cm &#215; 725&#8239;&#181;m was used.</li>
		<li>Using clean tweezers, gently lift the entire silicon mold vertically out of the hexane-OTS solution. Immediately transfer the mold into a beaker containing neat hexane. Rinse the mold by gently agitating it back and forth 5-10 times in hexane.</li>
		<li>Gently dry the mold using an N2&#160;blower from a distance of ~3 cm for 6-10 s. Ensure that no visible moisture remains on the surface.</li>
	</ol>
	</li>
	<li>PDMS mold fabrication (M2)
	<ol>
		<li>Mix the PDMS base and curing agent at a 10:1 ratio (w/w) in a clean plastic Petri dish for 15 min.</li>
		<li>Place the mixed PDMS in a chamber and degas at 160 torr for approximately 30 min, or longer if needed, until no visible air bubbles remain on the surface.</li>
		<li>Lightly coat a clean plastic Petri dish (e.g., 90&#8239;mm in diameter) with SO-100cSt (silicone oil with a viscosity of 100 cSt) using a lint-free wiper pre-soaked in&#160;SO-100cSt.</li>
		<li>Place the OTS-coated silicon mold face-up in the center of the coated Petri dish. Slowly pour the degassed PDMS mixture over the mold until it is fully covered (Figure 1B).</li>
		<li>Degas the mold again in the vacuum bubble remover until no visible bubbles remain.</li>
		<li>Place the Petri dish on a preheated hot plate set to 90&#8239;&#176;C and cure the PDMS for 50 min. After curing, allow the mold to cool to RT before demolding (Figure 1C).</li>
		<li>Once cured, gently peel the PDMS mold from the silicon mold, taking care to preserve the microstructure (Figure 1D).</li>
	</ol>
	</li>
</ol>
2. Fabrication of the final PDMS product using the PDMS mold (M2) (Figure 2)
<ol>
	<li>PDMS mold (M2) surface treatment
	<ol>
		<li>Place the fabricated PDMS mold on a hot plate set to 150&#8239;&#176;C and thermally age it for 3 days in ambient air (Figure 2A).</li>
		<li>After the thermal aging, immerse the mold in SO-100cSt.</li>
		<li>Degas the mold under vacuum 160 torr for 10-15 min, or until no visible bubbles remain.</li>
		<li>Remove the mold using tweezers and gently wipe the surface 3-5 times with a clean lint-free wiper to remove excess oil while leaving a uniform thin film (Figure 2B).</li>
	</ol>
	</li>
	<li>Minimizing the thickness of the oil layer between PDMS pillars 
	NOTE: This step is crucial, as an excessively thick oil layer can lead to inaccurate replication. The diameter of the thread should be determined depending on the geometry of the microstructure.
	<ol>
		<li>Prepare a PDMS mixture (10:1 w/w base to curing agent), following the same mixing and degassing steps described in step 1.2.</li>
		<li>Gently pour the degassed PDMS mixture onto the PDMS mold treated with SO-100cSt, allowing it to spread across the surface (Figure&#8239;2C). Apply a sufficient volume so that the poured PDMS reaches at least halfway up the height of the micropillars.</li>
		<li>Secure a 0.5&#8239;&#181;m nylon thread under gentle tension. Swipe it once or twice across the PDMS surface in a single direction to thin out excess oil between micropillars and ensure uniform coating (Figure 2D).</li>
		<li>Degas the PDMS mold with the thin PDMS layer in a vacuum chamber until no visible air bubbles remain.</li>
	</ol>
	</li>
	<li>Hole-array pattern PDMS fabrication
	<ol>
		<li>Lightly coat a clean plastic Petri dish with SO-100cSt, as described in step 1.2.3.</li>
		<li>Place the PDMS mold into the coated plastic Petri dish, then pour the degassed PDMS mixture over the mold until the PDMS reaches the desired height (Figure 2E). 
		NOTE: In this study, the mixture was filled to a level 0.5 cm above the micropillar tips.</li>
		<li>Degas the assembled mold again to remove any air bubbles that may have formed during the pouring step.</li>
		<li>Cure the PDMS on a preheated hot plate at 110&#8239;&#176;C for 10 min, or longer if needed, until fully solidified. 
		NOTE: The curing temperature must be sufficiently high to avoid prolonged curing times. Extended curing at lower temperatures could lead to silicone oil diffusion into the PDMS, thereby increasing adhesion between the mold and the replicated structure. In this study, the curing temperature was set to 110&#8239;&#176;C, allowing complete curing within 10 min.</li>
		<li>After curing, gently insert clean tweezers between the mold and the replica and carefully demold the final product from the mold (Figure 2F).</li>
		<li>Gently wipe the final PDMS product using a wiper soaked in isopropyl alcohol to remove any residual SO-100cSt or dust.</li>
		<li>Dry the surface using a N2 blower.</li>
	</ol>
	</li>
</ol>

<ol><li>Morbioli, G. G., Speller, N. C., Stockton, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+practical+guide+to+rapid-prototyping+of+PDMS-based+microfluidic+devices%3A+A+tutorial%5BTitle%5D)+AND+%22Anal+Chim+Acta%22%5BJournal%5D)">A practical guide to rapid-prototyping of PDMS-based microfluidic devices: A tutorial.</a> Anal Chim Acta. 1135, 150-174 (2020).</li>
<li>Olmos, C. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cost-effective+fabrication+of+photopolymer+molds+with+multi-level+microstructures+for+PDMS+microfluidic+device+manufacture%5BTitle%5D)+AND+%22RSC+Adv%22%5BJournal%5D)">Cost-effective fabrication of photopolymer molds with multi-level microstructures for PDMS microfluidic device manufacture.</a> RSC Adv. 10 (7), 4071-4079 (2020).</li>
<li>Wang, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+highly+sensitive+tapered+fiber+biosensor+modified+by+PDMS+combustion+product+and+graphene+oxide+for+MUC1+detection%5BTitle%5D)+AND+%22Sens+Actuators+Rep%22%5BJournal%5D)">A highly sensitive tapered fiber biosensor modified by PDMS combustion product and graphene oxide for MUC1 detection.</a> Sens Actuators Rep. 9, 100287(2025).</li>
<li>Staicu, C. E., Jipa, F., Axente, E., Radu, M., Radu, B. M., Sima, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Lab-on-a-chip+platforms+as+tools+for+drug+screening+in+neuropathologies+associated+with+blood-brain+barrier+alterations%5BTitle%5D)+AND+%22Biomolecules%22%5BJournal%5D)">Lab-on-a-chip platforms as tools for drug screening in neuropathologies associated with blood-brain barrier alterations.</a> Biomolecules. 11 (6), 916(2021).</li>
<li>Chudy, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Miniaturized+tools+and+devices+for+bioanalytical+applications%3A+an+overview%5BTitle%5D)+AND+%22Anal+Bioanal+Chem%22%5BJournal%5D)">Miniaturized tools and devices for bioanalytical applications: an overview.</a> Anal Bioanal Chem. 395 (3), 647-668 (2009).</li>
<li>Aghvami, S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Rapid+prototyping+of+cyclic+olefin+copolymer+%28COC%29+microfluidic+devices%5BTitle%5D)+AND+%22Sens+Actuators+B+Chem%22%5BJournal%5D)">Rapid prototyping of cyclic olefin copolymer (COC) microfluidic devices.</a> Sens Actuators B Chem. 247, 940-949 (2017).</li>
<li>Amadeo, F., Mukherjee, P., Gao, H., Zhou, J., Papautsky, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Polycarbonate+masters+for+soft+lithography%5BTitle%5D)+AND+%22Micromachines%22%5BJournal%5D)">Polycarbonate masters for soft lithography.</a> Micromachines. 12 (11), 1392(2021).</li>
<li>Lim, W. -B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+novel+UV-curable+acryl-polyurethane+for+flexural+3D+printing+architectures%5BTitle%5D)+AND+%22Addit+Manuf%22%5BJournal%5D)">A novel UV-curable acryl-polyurethane for flexural 3D printing architectures.</a> Addit Manuf. 51, 102625(2022).</li>
<li>Asad, A., Sadrzadeh, M., Sameoto, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Direct+micropatterning+of+phase+separation+membranes+using+hydrogel+soft+lithography%5BTitle%5D)+AND+%22Adv+Mater+Technol%22%5BJournal%5D)">Direct micropatterning of phase separation membranes using hydrogel soft lithography.</a> Adv Mater Technol. 4 (7), 1800384(2019).</li>
<li>Soffe, R., Bernach, M., Remus-Emsermann, M. N. P., Nock, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Replicating+Arabidopsis+model+leaf+surfaces+for+phyllosphere+microbiology%5BTitle%5D)+AND+%22Sci+Rep%22%5BJournal%5D)">Replicating Arabidopsis model leaf surfaces for phyllosphere microbiology.</a> Sci Rep. 9 (1), 14420(2019).</li>
<li>Li, S., Van Nguyen, S., Lee, B. -K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Role+of+heat+treatment+in+improving+replication+quality+of+PDMS+double-casting%5BTitle%5D)+AND+%22Soft+Matter%22%5BJournal%5D)">Role of heat treatment in improving replication quality of PDMS double-casting.</a> Soft Matter. 18 (18), 3473-3478 (2022).</li>
<li>Gitlin, L., Schulze, P., Belder, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Rapid+replication+of+master+structures+by+double+casting+with+PDMS%5BTitle%5D)+AND+%22Lab+Chip%22%5BJournal%5D)">Rapid replication of master structures by double casting with PDMS.</a> Lab Chip. 9 (20), 3000-3002 (2009).</li>
<li>Zhuang, G., Kutter, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Anti-stiction+coating+of+PDMS+moulds+for+rapid+microchannel+fabrication+by+double+replica+moulding%5BTitle%5D)+AND+%22J+Micromech+Microeng%22%5BJournal%5D)">Anti-stiction coating of PDMS moulds for rapid microchannel fabrication by double replica moulding.</a> J Micromech Microeng. 21 (10), 105020(2011).</li>
<li>Sung, J., So, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Facile+and+cost-effective+PDMS+double-casting+method+based+on+curing+temperature+and+ratio+for+solvent+detecting+applications%5BTitle%5D)+AND+%22Sens+Actuators+B+Chem%22%5BJournal%5D)">Facile and cost-effective PDMS double-casting method based on curing temperature and ratio for solvent detecting applications.</a> Sens Actuators B Chem. 387, 133834(2023).</li>
<li>Shao, G., Wu, J., Cai, Z., Wang, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Fabrication+of+elastomeric+high-aspect-ratio+microstructures+using+polydimethylsiloxane+%28PDMS%29+double+casting+technique%5BTitle%5D)+AND+%22Sens+Actuators+A+Phys%22%5BJournal%5D)">Fabrication of elastomeric high-aspect-ratio microstructures using polydimethylsiloxane (PDMS) double casting technique.</a> Sens Actuators A Phys. 178, 230-236 (2012).</li>
<li>Kim, S. -H., Lee, S., Ahn, D., Park, J. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((PDMS+double+casting+method+enabled+by+plasma+treatment+and+alcohol+passivation%5BTitle%5D)+AND+%22Sens+Actuators+B+Chem%22%5BJournal%5D)">PDMS double casting method enabled by plasma treatment and alcohol passivation.</a> Sens Actuators B Chem. 293, 115-121 (2019).</li>
<li>Kwapiszewska, K., Żukowski, K., Kwapiszewski, R., Brzózka, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Double+casting+prototyping+with+a+thermal+aging+step+for+fabrication+of+3D+microstructures+in+poly%28dimethylsiloxane%29%5BTitle%5D)+AND+%22AIMS+Biophys%22%5BJournal%5D)">Double casting prototyping with a thermal aging step for fabrication of 3D microstructures in poly(dimethylsiloxane).</a> AIMS Biophys. 3 (4), 553-562 (2016).</li>
</ol>

The authors have nothing to disclose.

This protocol presents&#160;a cost-effective and reproducible approach for PDMS double casting that combines thermal aging with silicone oil surface treatment to overcome demolding challenges in microfabrication. Conventional techniques such as chemical surface treatments or thermal aging alone often require specialized equipment or provide inconsistent results, especially when replicating dense, high-aspect-ratio features. By integrating thermal aging with a non-adhesive barrier, our method simplifies implementation whi...

Soft-lithographic casting underpins microfluidics1,2, biosensing3,4, and analytical diagnostics5 by enabling rapid, high-fidelity pattern transfer. Various polymeric materials have been explored for this purpose, including thermoplastics6,7, UV-curable polymers8,and hydrogels9. However, these materials often involve trade-offs: thermoplastic materials are generally rigid and require high-temperature processing, which limits their ability to conform to soft or flexible features; UV-curable polymers require specialized equipment and may suffer from limited flexibility; and hydrogels are mechanically fragile and unstable under dry conditions. Among these, polydimethylsiloxane (PDMS) has become the most widely adopted casting material due to its mechanical flexibility, ease of molding, biocompatibility, and gas permeability. In particular, PDMS double casting is frequently used to replicate delicate or expensive silicon and SU-8 molds, or to duplicate non-inverted geometries such as biomimetic topographies10. Nevertheless, a persistent challenge in this method is the strong adhesion between the cured and uncured PDMS layers during the secondary casting step, driven by interfacial chain entanglement. This often results in incomplete demolding or structural failure, thereby limiting its broader applicability11.
To address this issue, various surface treatment strategies have been developed to reduce adhesion between PDMS layers. These include surface coatings12,13, varying curing conditions14, and plasma treatment15,16. However, these approaches typically require expensive equipment and involve delicate surface modification processes. As a simpler alternative, thermal aging has been proposed11,17. This technique involves heat-treating the PDMS mold to reduce the presence of uncrosslinked or low-molecular-weight chains on the surface. Studies by Kwapiszewska et al.17 and Li et al.11 have shown that thermally aged PDMS molds significantly improve replication fidelity without requiring additional chemical modification. However, even with thermal aging, problems such as adhesion-induced tearing and feature distortion persist, particularly in structures with high density and complex geometries.
This study presents an improved PDMS double casting method that combines thermal aging with an additional surface treatment using silicone oil. After the PDMS mold undergoes thermal aging, a thin layer of silicone oil is coated on the mold surface, forming a non-adhesive barrier that reduces interfacial adhesion. This simple modification significantly improves mold release performance, even for densely packed and high-aspect-ratio microfeatures, and eliminates the need for plasma treatment or specialized equipment. The protocol is designed to be reproducible and easily adoptable by users with limited access to surface modification infrastructure. Figure 1 and Figure 2 provide a detailed, step-by-step description of the fabrication and surface treatment procedure. In contrast, Figure 6&#160;demonstrates the successful replication of high-density hole-array structures, confirming the method&#39;s effectiveness under challenging geometric conditions.

<table><tbody><tr><td>Contact Angle measurement equipment</td><td>Surface Elecrto Optics(SEO)</td><td>Phoenix 300</td><td></td></tr><tr><td>Curing agent</td><td>Dow</td><td>Sylgard 184b</td><td></td></tr><tr><td>Digital camera</td><td>SONY</td><td>E3ISPM06300KPB</td><td></td></tr><tr><td>Hexane</td><td>Sigma-Aldrich</td><td>32293</td><td>&amp;ge;99% (GC), ACS reagent</td></tr><tr><td>Hot plate</td><td>MTOPS</td><td>HSD180</td><td></td></tr><tr><td>Isopropyl alcohol (IPA)</td><td>Raontech</td><td>PS2032-001</td><td></td></tr><tr><td>MR-100 (vacuum pump oil)</td><td>Moresco</td><td>1802-00005-02</td><td>44.6 cSt</td></tr><tr><td>Optical microscope</td><td>OLYMPUS</td><td>BX51</td><td></td></tr><tr><td>PDMS base</td><td>Dow&amp;nbsp;</td><td>Sylgard 184a</td><td></td></tr><tr><td>SEM</td><td>Thermo Fisher Scientific</td><td>Verios 5 UC</td><td></td></tr><tr><td>Silicone oil</td><td>ShinEtsu&amp;nbsp;</td><td>KF-96-100CS</td><td>100 cSt</td></tr><tr><td>Silicone oil</td><td>ShinEtsu&amp;nbsp;</td><td>KF-96-1000CS</td><td>1000 cSt</td></tr><tr><td>Spin coater</td><td>DONG AH TRADE CORP</td><td>ACE-200</td><td></td></tr><tr><td>Trichloro(octadecyl)silane (OTS)</td><td>Sigma-Aldrich</td><td>104817</td><td></td></tr><tr><td>Ultrasonic cleaner</td><td>Branson</td><td>5510E-DTH</td><td></td></tr><tr><td>Vacuum pump</td><td>GAST</td><td>DOL-701-AA</td><td></td></tr></tbody></table>

improved polydimethylsiloxane (pdms) double casting via silicone oil treatment for densely packed microstructure replication

Improved Polydimethylsiloxane (PDMS) Double Casting via Silicone Oil Treatment for Densely Packed Microstructure Replication

Polydimethylsiloxane (PDMS) double casting is widely used for replicating microscale structures, including microfluidic channels and biomedical microdevices such as Bio-MEMS. Despite its versatility, strong interfacial adhesion between PDMS layers often results in incomplete replication or structural damage, particularly in densely packed microfeatures. Conventional approaches to reduce adhesion, such as plasma or chemical surface modification, require specialized equipment and can be time-consuming and costly. To address these limitations, we present an improved demolding strategy that combines thermal aging with the application of a thin silicone oil layer as a non-adhesive release barrier. A critical step in the protocol involves sweeping a tensioned thread across the surface to distribute the oil and promote even PDMS penetration between micropillars. This enhances mold release and preserves structural integrity without compromising delicate microstructures. The method is demonstrated using densely packed hole-array patterns, achieving clean replication with minimal dimensional deviation. This simple, reproducible, and cost-effective approach is well-suited for fabricating PDMS-based microsystems, including multilayer devices and geometrically complex features in soft lithography applications.

A silicon mold (M1) featuring a densely packed array of circular holes was used to evaluate the improved double casting method. Figure 3A illustrates the SEM image of the top surface demonstrating a uniform pattern of hole array with a diameter of 143 µm and a period of 150 µm. The side-view image reveals a hole depth of 284 µm in Figure 3B, corresponding to an aspect ratio of approximately 2:1 and confirming a tightly packed mic...

This protocol presents an improved demolding procedure for the Polydimethylsiloxane (PDMS) double casting technique by introducing silicone oil as a non-adhesive barrier between PDMS layers. Unlike plasma or chemical surface modification methods, this approach requires no specialized or costly equipment, making it a more accessible and cost-effective alternative.

Polydimethylsiloxane (PDMS) double casting is widely used for replicating microscale structures, including microfluidic channels and biomedical ...

To address demolding challenges in dense and high aspect ratio microstructures, we modified the PDMS double casting process by adding a silicone oil treatment that applied with a tension thread. Our protocol offers a simple cost-effective solution that avoids the need for expensive equipment or specialized materials, enabling reliable replication of advanced microstructures without damage.Our laboratory will focus on automating the oil application process and developing custom silicone oils to identify optimal conditions for improved reproducibility and precision.[Narrator] To begin, mix a solution of hexane and OTS in a 40:1 volume ratio using a clean glass beaker and a stirring rod. Cover the beaker with aluminum foil to minimize evaporation. Sonicate the sealed glass beaker into a room temperature ultrasonic bath filled with water. Then immerse the pre-etched silicon mold with a hole array into the prepared hexane OTS solution. Now, use clean tweezers to gently lift the entire silicon mold vertically out of the solution. Immediately transfer it to a fresh beaker containing neat hexane, then rinse by gently agitating it back and forth five to 10 times. Gently dry the mold using a nitrogen blower held approximately three centimeters away for six to 10 seconds until no visible moisture remains. Next, mix the PDMS base and curing agent in a 10:1 weight ratio in a clean plastic Petri dish for 15 minutes. Place the mixture into a chamber and degas at 160 torr until no visible air bubbles remain. Lightly coat a clean plastic Petri dish with silicone oil of 100 centistokes viscosity using a lint-free wiper pre-soaked in the oil. Then place the OTS-coated silicon mold face up in the center of the coated Petri dish. Slowly pour the degassed PDMS mixture over the mold until it is fully covered. Degas the filled mold again in the vacuum bubble remover until no visible bubbles remain. Now, place the Petri dish on a preheated hot plate set to 90 degrees Celsius to cure the PDMS. Once cured, gently peel the PDMS mold from the silicon mold, ensuring the microstructure remains intact. Place the fabricated PDMS mold on a hot plate set to 150 degrees Celsius. After three days of thermal aging, immerse the mold in silicone oil of 100 centistokes viscosity. Degas the oil-immersed mold under vacuum at 160 torr for 10 to 15 minutes. Then remove the mold using tweezers and gently wipe the surface three to five times with a clean lint-free wiper to leave a uniform thin film of oil. Next, prepare a PDMS mixture at a 10:1 base to curing agent weight ratio using the same mixing and degassing method as before. Gently pour the degassed mixture onto the treated mold, allowing it to spread and reach at least halfway up the micropillars. Secure a 0.5 micrometer nylon thread under gentle tension. Swipe the thread once or twice across the PDMS surface in one direction to reduce excess oil between micropillars. Then degas the mold with the thin PDMS layer in a vacuum chamber until no air bubbles remain. To fabricate a hole array pattern PDMS product, lightly coat a clean plastic Petri dish with silicone oil. Place the PDMS mold into the coated Petri dish and pour the degassed PDMS mixture over it until the desired height is reached. Degas the mold assembly once more to eliminate any trapped air bubbles. Then place the Petri dish on a preheated hot plate set to 110 degrees Celsius and cure until fully solidified. After curing, gently insert clean tweezers between the mold and the replica, and carefully demold the final product from the mold. The silicon mold featured a dense array of circular holes measuring 143 micrometers in diameter with 150 micrometer spacing and a depth of 284 micrometers, yielding a 2:1 aspect ratio. The PDMS mold replicated from the silicon template produced micropillars measuring 142 micrometers in diameter and 283 micrometers in height, closely matching the original dimensions. The PDMS replica thermal aged one day and subsequently treated with 100 centistokes silicone oil showed severe tearing and disintegration of wall structures during demolding. After two days of thermal aging followed by 100 centistoke silicone oil treatment, distinct pillar outlines became visible, but the walls remained heavily damaged due to insufficient release. With three days of thermal aging and no oil layer, cross-linking between cured and uncured PDMS resulted in recombined structures. Using low viscosity MR-100 oil after three days of thermal aging led to poor coverage and tearing as the oil drained off vertical sidewalls. High viscosity oil formed a thick coating, preventing mold filling and causing the final product to appear wavy and malformed. Under optimized conditions of three days thermal aging and 100 centistoke silicone oil coating, the final replica preserved hole patterned microstructures with 148 micrometers diameter and 280 micrometers height, showing minor dimensional variation, but intact structure.

improved-polydimethylsiloxane-pdms-double-casting-via-silicone-oil

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Learn an improved PDMS double casting technique using silicone oil treatment to replicate dense microstructures reliably. This cost-effective method eliminates expensive equipment needs and enables precise demolding for biomaterials research.

Improved Polydimethylsiloxane (PDMS) Double Casting via Silicone Oil Treatment for Densely Packed Microstructure Replication

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