Frequently Asked Questions

General FAQs
How are Redbud Posts made?

At our headquarters in RTP, NC, we manufacture and package thousands of chips per month using a proprietary molding process. We deposit magnetic material into a mold, backfill with our silicone elastomer, then remove the mold. The result is a sheet of silicone film with millions of Redbud Posts on the surface. Finally, we laminate this film against other layers and dice the sheet to form individual packaged chips.

How do I assemble Redbud Lab's microfluidic chips into my cartridge?

Our chips can be clamped, welded, or bonded into cartridges using a wide range of methods common to both prototyping and high-volume manufacturing.

Has Redbud Labs compared MXR to other mixing techniques?

Absolutely. We’ve found that passive mixing techniques (herringbone structures, serpentine channels, diffusion, etc.) are limited in their ability to effectively mix volumes of unequal size and are prohibitively slow. We have compared MXR to application driven active mixing techniques (e.g. bubble mixing for microarrays).

Does Redbud Labs design or build microfluidic cartridges?

No, but we work closely with a lot of smart people who do. We often work side-by-side with contract engineers (CEs) and contract manufacturers (CMs) vendors to help you develop the best possible product. If you’re looking for a CE or CM, feel free to contact us. We’re happy to give you a recommendation based on your specific technology and stage of development.

My assay requires optical detection. Will Redbud Posts interfere with the imaging?

Redbud Post arrays are optically clear. They have been used for fluorescence, transmission brightfield, reflectance, and more.

How much does a microfluidic chip cost?

Our microfluidic chips are targeted at applications where managing consumable cost structure is essential. We work to ensure that MXR is highly manufacturable, so that cost never has to be a barrier to including our chips in your cartridge. MXR chip sizes vary and so does the cost per chip. However, expect to pay more for low volume feasibility studies and far less per chip when designs are set for chip incorporation into high-volume consumables (e.g. point-of-care diagnostics).

How can I try Redbud’s microfluidic chips?

The first step is usually to get a starter kit and try it out. If you’re too busy, we may be able to do your early feasibilty testing in-house. Either way, just contact us to get started.

What kind of chips should I use?

It depends on your assay. We can help you determine if your testing can be performed with a standard, off-the-shelf chip, or whether you should consider a made-to-order, custom chip. You’ll also want to decide between our Black (standard) or Blue formulations of MXR. MXR Black is a hydrophobic silicone. MXR Blue is hydrophillic, and usually preferable for genomic applications, or in assays where there is little or no surfactant.

Which magnet driver should I use?

The Redbud mini-Stage driver is our most popular magnet driver: it’s compact, cost-effective, and easy to use. If you need temperature control, you’ll want to use the Redbud Stage driver. If you need to position the driver on a breadboard system, the mounted or basic drivers are convenient alternatives. We always assist in helping you select the right choice among the four options available.

Mixing FAQs

How does MXR work?

Redbud Posts are flexible, magnetic micro-pillars that are fixed to the surface of the MXR microfluidic chip. When the posts are subjected to a changing magnetic field, the posts flex and rotate generating turbulent mixing. Redbud Posts are like artificial cilia which move in response to a changing magnetic fields, enabling fluid processing at the microscale.

How far can the magnet be without affecting mixing efficiency?

Our magnetic driver typically needs to be within 5 mm of the Redbud Post film.

What volumes can MXR mix effectively?

MXR can be used to mix over a wide range of volumes, from greater than 100 µL to less than 1 µL.

Can MXR be used to reconstitute dried reagents?

Yes, mixing with MXR improves reagent uniformity, enabling the highest possible reaction yield. Dried or lyophilized reagents can even be pre-loaded into MXR, streamlining cartridge assembly.

My assay uses magnetic beads. Can I still use MXR?

Perhaps. We have worked with customers using magnetic beads and may be able to accommodate your application.

Should I worry about magnetic materials leaching into my sample/assay with MXR?

No. Redbud Posts are loaded with a magnetic material that makes them responsive to our magnetic driver. This magnetic material is encased in silicone and not exposed to the sample.

What geometry limitations are there with using MXR?

Our microfluidic chips can be rapidly customized for any application, from microchips to microscope slides to microplates. Our microfludic chips can be as small as 1 mm square and as large as 11.5 cm x 9 cm. Chamber heights can vary from less than 100 µm to more than 1 mm.

What temperatures can MXR tolerate?

MXR is compatible in assays up to at least 100ºC.

Who else uses MXR?

We can’t wait to tell you more, but we must respect confidentiality agreements exercised with our clients. For now, suffice it to say that we’re working with leading firms and the hottest startups in molecular diagnostics, sequencing, cell analysis, liquid biopsy, biomanufacturing, and more. We also have active partnerships with collaborators and consortia.

Sorting & Sample Prep FAQs

What is STR?

STR (“sorter”) is a solid-phase affinity sorter chip ideally suited to use in microfluidic cartridges. STR is Cartridge-ready™. STR streamlines sample prep in cartridge-based assays and employs Redbud Post™ technology on both the ceiling and floor of the microfluidic chip’s active chamber. In the STR chip, Redbud Posts are functionalized with NeutrAvidin for use with an antibody probe of choice. STR enables immuno-capture of analytes from complex samples such as whole blood and supports sample volumes from microliters to milliliters and target sizes from nanometers to microns. STR ideal for a wide range of applications, including molecular testing, immunoassays, sequencing, and cell analysis. STR is the first component designed ideally to enable rapid and efficient sample prep for point-of-care diagnostic tests.

How does STR perform sorting of targets?

STR allows you to customize your assay by selecting an antibody probe to capture your target of interest, then purify and concentrate the analyte for downstream analysis. It is designed with an easy-to-customize avidin surface chemistry bound to Redbud Post (which rotate in response to  a rotating magnetic driver placed nearby the chip) and plugs in simply with an assay protocol- flow in the probe, wash, flow in sample, wash, lyse and recover.

How do I work with STR?

Unlike existing sample prep methods, STR is easy to use at any stage of assay development, from biomarker discovery, through product development, and into volume manufacturing. STR can be used in either batch or perfusion mode depending upon your assay development needs.


Can STR be used for nucleic acid isolation?

Yes, STR is currently being evaluated by customers for nucleic acid sample prep, including isolation, concentration, and ligation.

Can STR be used for liquid biopsy sample prep?

Yes, as long as there is a probe such as an antibody, aptamer, or other binding moiety that you can use to capture your target. Thanks to Redbud Posts, STR is capable of capturing targets of widely varying size, from CTCs to molecules. Your target can also be concentrated by 100x or more.

Can STR be used for analyte capture from blood, urine, and other biofluids?

Yes, provided that you have a probe, such as an antibody or aptamer, that adequately binds to your target in the fluid of interest, STR can process raw biospecimens. Redbud Posts generate a gentle agitation that prevents cells and other debris from settling in the chamber, minimizing non-specific contamination.

Offices, Production, and Labs
400 Park Offices Dr. #301
RTP NC 27709

PO Box 13195
RTP NC 27709

We support inquiries via Science Exchange
View Storefront
About Us

Redbud Labs, headquartered in Research Triangle Park, North Carolina, manufactures breakthrough components for life science industry, intended to solve the industry’s ubiquitous microscale fluidic challenges.

Connect With Us

12 + 15 =

Connect With Us

11 + 14 =