Liquid crystal polymer and cyclic olefin copolymer are rarely searched for and constantly specified by people designing micro parts. They solve opposite problems: LCP fills walls nothing else will, and COC gives a clear, dry, clean part for fluid paths and optics. Each has one behaviour that decides whether a design works.
LCP’s molecules are already ordered in the melt, and they slide past each other under shear, so its viscosity drops sharply in a thin, fast-moving channel. That is what lets it fill very thin walls over a long flow length, and why connectors and thin-walled micro parts are made from it. It also freezes fast, so it fills quickly or it does not fill at all.
The same ordering that makes LCP flow makes its weld lines weak. Where two flow fronts meet, the ordered structures butt against each other instead of entangling, so a weld line in LCP is far weaker than the bulk material. Any hole, pin or insert creates one behind it. Gate position decides where those seams land, and on an LCP part that decision decides whether it survives assembly.
Along the flow, LCP barely shrinks at all. Across it, it shrinks noticeably more. That is excellent for a long, slender dimension that runs with the flow, and a trap for one that runs across it. On an LCP part, the question is not “what is the shrink” but “which way does this dimension run relative to the gate.”
COC is amorphous and absorbs almost no water, so it holds its dimensions and its optical properties in wet service. It is used for microfluidic chips, diagnostic cartridges and drug-delivery parts because it combines glass-like clarity with low extractables and low autofluorescence. Its sensitivities are the ones a clear part always has: flow lines and molded-in stress show as birefringence, and a scratch on the cavity is a scratch on every part.
A microfluidic channel is a raised rib on the cavity steel, and its width, depth and wall angle are set there. Whether the plastic replicates it faithfully depends on the melt reaching the bottom of the feature before it freezes, which is a mold-temperature and injection-speed question more than a pressure one. The cavity is where channel dimensions are won, which is why the steel is cut and measured to a tighter figure than the part.
The shop’s molded-part figure is ±10 µm. On a 2 mm feature, this is how much of that band each grade’s own shrink range takes before the machine, the tool or the gauge have done anything — the same arithmetic the shrinkage calculator runs, on the Lab’s starting-point table for the family.
| Grade | Direction | Shrink range | Tolerance taken | Reading |
|---|---|---|---|---|
| LCP | Along flow | 0.0–0.3% | 30% | Room to work |
| LCP | Across flow | 0.4–0.8% | 40% | Room to work |
A family range is wider than a stable process window on one grade, so these are the worst-case budget, not a prediction. Replace the range with your grade’s datasheet figure in the calculator and the answer tightens.
Run your own dimension in the shrinkage calculator.
Thin-wall · micro-flow
Liquid Crystal Polymer offers the lowest melt viscosity of any structural thermoplastic, enabling sub-0.1 mm wall sections in micro injection molding. Dimensional stability after molding is exceptional — linear shrink is near zero in the flow direction.
Optical · low extractables
Cyclic olefin copolymer combines glass-like optical clarity with extremely low extractables and leachables, making it the preferred substrate for microfluidic diagnostics, drug-delivery cartridges, and lab-on-chip devices.
These are standards the material grade is tested or supplied to by its manufacturer. They describe the resin or the bar stock, not a finished part — qualifying a part for patient contact is the device owner’s decision, made under their own quality system.
Have a part in LCP and COC? Send the drawing with the grade and the dimensions that matter, or talk it through with Marve first.