Polydimethylsiloxane (PDMS) is one of the most widely used chip materials in the field of microfluidics for its excellent biocompatibility, chemical inertness and biocompatibility. PDMS is inexpensive, easy to process, and can be easily molded into a preset pattern. Creative Biolabs provides our clients all over the world with high-precision, high-surface smoothness reprographic molds for rapid reproducible processing of PDMS microfluidic chips in the laboratory.
Reprographic Molds for PDMS
The mold's precision and physical properties directly determine the PDMS pattern replication quality. In theory, any material whose stiffness exceeds PDMS can be used to reprint PDMS structure. However, considering the processing technology, cost, precision and usage, we recommend the following PDMS molds for our clients.
Fig 1. Workflow of PDMS molding. (Creative Biolabs)
Metal
Our optimized micro-electroforming molds will be one of the most cost-effective choices for your polymer microfluidic chip injection molding processing and medium/low-scale experimental needs. Metal molds are capable of reprinting PDMS chips hundreds of times with a well-patterned structure. It is worth noting that the critical size of the metal mold is 30μm.
SU-8
As a highly photosensitive resist, Epoxy SU-8 is used as a negative photoresist protective layer for substrate etching or deposited tens of millimeters thick to form structures with high aspect ratios for PDMS structure reproduction. This revolutionary patterned epoxy material is our most recommended and most economical PDMS reprint mold. SU-8 can meet the aspect ratio patterning of 1:1 to 10:1 after curing. Creative Biolabs provides standard silicon substrate size SU-8-PDMS molds with micron-level accuracy through standardized photolithography technology. The recommended processing depth of this type of mold is between 50-300μm due to the physical properties of SU-8 after curing.
Fig 2. PDMS reprography. (Sweet, et al., 2020)
Pure Silicon
Dry etching is used to fabricate pure silicon molds with a higher aspect ratio and processing precision. Silicon mold has the best mechanical strength and processability with a size error within 1μm and the maximum aspect ratio is 20:1. The repeated etching technology allows us to process multi-layer silicon boards with different heights. The pure silicon mold can be processed with 2 μm minimum width and a depth between 1 μm and 400 μm.
PDMS molding enables simple, low-cost fabrication of chip structures in the laboratory. Noted when using:
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Handle with care at all times to avoid chipping;
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Note the cleanliness of the surface, especially the chip structure pattern;
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Avoid cleaning with organic solvents (especially pure silicon molds);
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The PDMS-reprint mold we provide is defaulted to be hydrophobic, but it is still recommended to pay attention to the hydrophobicity of the mold before use. If it is hydrophilic, the PDMS cannot peel off from the substrate smoothly and ultimately cause mold damage.
Creative Biolabs provides our clients with high-precision PDMS reprint mold fabrication and prototyping services. You may provide designed drawings or sketches to entrust us to graph and design. You may select the most suitable product for your project from various molds with different cost-effectiveness, processing precision and structural size, or entrust us with small-scale chip production, characterization, testing and large-scale injection molding. In addition, Creative Biolabs is also capable of performing any biological downstream experiments you need. Please don’t hesitate to contact us for more information.
Published Data
The following are results highlighted in articles related to the molding for microfluidic chips:
1. Replication of a printed volatile mold: an innovative microfabrication technique for microfluidic systems
Fig. 3 Process of fabrication of a microfluidic chip.2,3
A new and straightforward method for fabricating microchannels using inkjet printing of volatile solid molds has been developed. This technique involves printing with sacrificial materials that can be removed in the gas phase. In this work, the authors focus on hexanediol, a material that can be printed in its liquid form at 60 °C. This material is deposited onto a cold substrate, where it solidifies. Following this, polydimethylsiloxane (PDMS) is poured over the system and allowed to solidify. The hexanediol can then be easily and quickly removed through evaporation, leaving behind open channels. This process significantly improves over other methods that use sacrificial molds, where material removal typically takes a long time. Using this technique, microchannels can be created on various natural surfaces, including glass, paper, uncrosslinked PDMS layers, and non-planar substrates. Additionally, microfluidic systems with a height of millimeters, as well as three-dimensional structures like bridges, can be generated with ease.
References
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Sweet, A.; et al. 3D microfluidic gradient generator for combination antimicrobial susceptibility testing. Microsystems & Nanoengineering. 2020, 6: 92.
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Brossard, Rémy, Thomas Brouchet, and Florent Malloggi. "Replication of a printed volatile mold: a novel microfabrication method for advanced microfluidic systems." Scientific Reports 9.1 (2019): 17473.
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Distributed under Open Access license CC BY 4.0, without modification
For Research Use Only. Not For Clinical Use.
