MEMS and Microfluidics Applications for Micro 3D Printing: Answering Your Questions from Our Latest Webinar

Did you miss our latest webinar, Micro 3D Printing Applications of MEMS & Microfluidics? During the webinar Blaise Will, Senior Product Manager at BMF, and Norman Wen, Associate Director of Chip Development at Emulate, discussed how micro 3D printing is becoming a game changer in MEMS and microfluidics applications. We had a great group of attendees that asked our speakers many topical questions. Here are the answers to your questions!

If you missed the webinar, you can watch the full recording for free here.

Q: Can you tell us a little bit about the difference between PµSL and other SLA or DLP technologies?

A: PµSL is similar to some of the other processes out there, but there are a few key differences. We are using a top-down approach, introducing a high precision lens in between the light source and the resin vat. We also highly control the XYZ movement by using high precision stages. These are components similarly used in coordinate measuring machines. This combination allows us to achieve resolutions of 2-10 µm depending on the machine and tight tolerances in the +/- 25 µm range.

Q: What is the standard deviation in geometries between printers in the x, y, and z dimensions?

A: The microArchTM system can achieve part tolerances of +/- 25 μm. This means each feature size will be within 25 μm of the nominal value. For smaller parts and features the tolerance is much tighter than that. The pixel size has a tolerance of about +/-50 nm and the DLP light intensity varies by 5%, so dimensional deviation caused by hardware is minimal.

Q: For microfluidics applications, what is the smallest channel width currently achievable by BMF technology?

A: Our 2 µm series design guidelines recommend channel aspect ratios of less than or equal to 500:1 if the channel diameter is greater than 20 µm. We recommend vertical hole diameters of no smaller than 10 µm and horizontal hole diameters of no smaller than 50 µm. These limits are mainly for allowing proper channel cleaning but are also helpful for maintaining feature resolution.

Q: Is the process of emptying channels once printed easy?

A: There are various methods to clean parts with narrow channels. Methods we currently use include IPA, vacuum chamber, and ultrasonic bath. Our design guidelines recommend channel aspect ratios of no greater than 500:1 (for ≥ ⌀ 0.02 mm channel) for proper channel cleaning.

Q: Can you print onto a silicon wafer?

A: We often print directly onto a silicon wafer. This is especially helpful when printing parts with delicate features, since we can leave the part on the wafer without removing it for shipping.

Q: Can prefabrication parts be inserted into the bath and a 3D layer grow on top?

A:  This is not an official feature of the microArch platform; however, we have had users experiment successfully with printing onto prefabricated parts.

Q: Are the feature resolutions consistent among all type of printing materials? What is the resolution in the z direction?

A: BMF currently offers 6 materials with diverse material characteristics including high strength, tough, flexible, high temp, and biocompatible to meet the needs of different customer applications. Our users do find that different materials can achieve slightly different levels of feature resolution, but as a general rule our 2 µm series can achieve 2 µm resolution and our 10 µm series can achieve 10 µm resolution.

Regarding surface roughness, parts produced on microArch printers can typically achieve a surface roughness of 0.4-0.8 µm Ra on the top surface and 1.5-2.5 µm Ra on side surfaces.

Q: Does your materials list include any hydrophilic or hydrophobic materials?

A: The microArch family of printers is an open material platform which means users are welcome to print using compatible resins from any source. All the resins currently in our portfolio are slightly hydrophilic, with contact angles between 45-60 degrees. Coating can be applied to a finished part to alter the contact angle making it more hydrophilic or hydrophobic.

Q: Is metal 3D printing possible with this technology?

A: We use a UV resin curing technology which works best with photocurable polymer-like resins and composites. We have not validated any metal materials on our printer.

Q: When working with a transparent resin, is the printed part intrinsically transparent or is some post processing needed?

A: Transparent parts are intrinsically transparent. Our process typically requires that printed parts are UV and/or thermally cured, but this doesn’t impact transparency or optical clarity.

Q: Is shrinking controllable so not only resolution but also final dimensions are guaranteed?

A:  Yes, shrinkage is compensated for in both CAD file scaling during build set up and within the print software itself.

Q: Is it possible to print with electrically conductive materials? Can that be integrated with non-conductive polymer layers?

A: While microArch is an open material platform, printing electrically conductive materials is inherently challenging due to the fact that the conductive particles need to touch to carry current, which is nearly impossible when they are suspended in a resin matrix and then polymerized. We are currently exploring a few ways that it might be achieved.

Q: How flat are the parts?

A: Generally speaking, the microArch system can achieve part tolerances of +/- 25 μm. This means each feature size will be within 25 μm of the nominal value, although for smaller parts and features the tolerance will be much tighter than that.

Flatness of a specific part or feature depends on geometry, material, wall thickness, and aspect ratios. Surfaces that are printed flat against the platform or substrate, including microfluidic chips, come out of the printer quite flat and if needed can also be clamped flat during post-processing (UV + thermal curing) to maintain dimensional accuracy.

Q: How can I evaluate the technology? Can I get a benchmark?

Absolutely! Benchmarks are a great way to evaluate any 3D printing technology. We are always happy to talk about your potential applications and print a benchmark for you. If you have a specific application in mind and are interested in a benchmark, please fill out the form on this page to request a benchmark part.