Microfluidic Manifold — PEEK for Point-of-Care Diagnostic Device

Why Microfluidic Channels in PEEK Are Difficult

PEEK is the right material for this application — it’s biocompatible per ISO 10993, resistant to the reagent chemicals used in blood diagnostics, and can survive repeated autoclave sterilization cycles. But machining micro-scale features in PEEK introduces problems that don’t show up in metals.

PEEK is a semi-crystalline thermoplastic. Under cutting forces, thin sections deflect rather than fracture. A 0.020″ endmill running at standard feeds will push the channel floor downward instead of cutting cleanly, leaving inconsistent depths and a rough surface that traps biological fluid. Conventional clamping on the manifold body compresses the part and distorts the channel geometry — you release the clamps and the channels spring back to a different depth than what the CMM read under load.

The floor radius specification of 0.012″ added another constraint. In a 0.020″-wide channel, the floor radius is determined entirely by the endmill’s corner geometry. There’s no room for a separate finishing pass with a ball-nose tool. The channel width, depth, floor radius, and surface finish all have to come from the same tool in the same operation.

How We Solved It

Our programmer reviewed the CAD and identified three risks during the free DFM review — before we quoted the job:

• Custom fixturing on registration bosses. Instead of clamping the manifold body, we machined a Delrin fixture that located the part on its registration bosses — features the customer had already designed into the part for device assembly. This eliminated clamp-induced deflection entirely. The manifold sat in the fixture with zero clamping force on the channel region.
• High-RPM micro-endmill strategy. We ran 0.020″-diameter endmills at 24,000 RPM with extremely light axial depths of cut (0.002″ per pass). At these parameters, the cutting forces on the PEEK were low enough to avoid floor deflection. We took 5 finishing passes per channel rather than the typical 1–2, trading cycle time for depth consistency.
• Precision deburring under magnification. PEEK generates fine, flexible burrs that fold over rather than break off. We deburred every channel under 10x magnification using hand tools specifically ground for the channel geometry. Each manifold took 45 minutes of deburring alone — but clean channels were non-negotiable for a diagnostic device.

Vapor Polishing for Improved Flow

After machining and deburring, we vapor polished the channel surfaces. Vapor polishing exposes the PEEK to a controlled solvent atmosphere that softens the outermost surface layer, allowing micro-roughness peaks to flow together. The result is a smoother channel surface that reduces sample fluid adhesion and dead volume — critical in a diagnostic manifold where every microliter of sample matters.

The customer’s bench testing confirmed that the vapor-polished channels showed measurably lower carryover contamination between test runs compared to their 3D-printed prototypes.

Startup Speed: 3 Iterations in 2 Weeks

This is where working with a startup-focused shop makes a difference. The customer’s engineering team was iterating on channel geometry based on flow simulation data — they didn’t have the luxury of locking down the design before cutting parts. They needed a shop that could turn revised STEP files into functional hardware in days, not weeks.

We ran V1 (5 pieces) in 4 days. Their bench testing revealed a dead zone in channel 6 — a geometry issue in the original design, not a machining defect. They sent a revised STEP file on a Thursday evening. We had V2 parts on their bench by Tuesday. V3 followed the next week with a minor channel depth change.

No setup fees between iterations. No re-quoting. Same fixture, same programs (modified for the geometry changes), same operator. That kind of continuity matters when you’re racing toward a board meeting.

Documentation for FDA-Track Medical Devices

Even at the prototype stage, the customer needed documentation that would hold up in their Design History File. We provided dimensional reports for each iteration, material certification confirming FDA-grade PEEK (Victrex 450G), and high-resolution photographs of channel quality under magnification. When they eventually file their 510(k), the machining documentation is already in order.