Your first chip

Twenty minutes, ending in an STL file. You will build a Y-junction mixer: two inlets meeting into one mixing leg — the simplest device that does something useful, and the one whose failure modes teach the most.

You need nothing but a browser. Print it afterwards or don’t; the file is the same either way.

1 · Set up your printer (2 minutes)

On first run the wizard asks which printer you have. Pick the closest preset — if you are not sure, Standard 4K resin printer is a safe default — and give the project a name.

You can change every one of those numbers later from Settings → Printer. What matters right now is that the checks have something to check against.

Note

The printer profile is saved in the project file, so a chip you send someone carries the assumptions it was designed under. See Printer profile fields.

2 · Draw the network (6 minutes)

You are in the Draw tab. The rectangle is your chip — 40 × 60 mm by default.

Press P for the draw tool, then click to lay down points:

1. Click near the top left, inside the dashed clearance line.
2. Click at the middle, about two-thirds of the way up — this is the junction.
3. Press Escape to end the run.

That is one arm. Now the second:

4. Press P again, click near the top right.
5. Click exactly on the junction node you made in step 2. It will highlight as you approach — that is endpoint snapping, and it means the two arms share one node rather than merely touching.
6. Press Escape.

And the mixing leg:

7. Press P, click the junction node again, then click near the bottom middle.
8. Press Escape.

You now have a Y. If a click landed somewhere unhelpful, ⌘Z undoes it.

Tip

Snapping is doing real work here. Getting the two arms to share a junction node is the difference between a chip that mixes and two channels that print close together and never meet. See Drawing channels.

3 · Make the ends into ports (3 minutes)

Right now all three ends are plain waypoints. Fluid needs a way in and out.

Press V for the select tool, click the top-left end node, and in the inspector on the right set Node type to Port.

The default is a luer slip — the friction-fit taper that fits a standard syringe. Under Catalogue fitting you can pick a real part instead; the dimensions fill in from the catalogue.

Repeat for the top-right end and the bottom end.

Watch the Design checks panel at the bottom as you do this. Before you place any ports it says “The chip has no ports”. It stops once all three are in.

4 · Set the channel width (2 minutes)

Every segment is currently the chip default — 0.8 × 0.5 mm. That is a sensible size and you could leave it.

Try one thing instead. Press D for the dimension tool and click about a third of the way along the mixing leg. A marker appears; set its width to 1.2 mm. Click again near the end of the leg and set that one to 0.6 mm.

Look at the canvas: the channel now tapers smoothly between the two. That is lofting, and it is how you build a flow-focusing throat or a gradual expansion without drawing either. See Dimension markers and lofting.

5 · Look at the solid (2 minutes)

Click CAD Preview.

The block appears with your channels as voids inside it. Drag to orbit, scroll to zoom, Fit to re-frame.

Switch the display mode to X-ray to see the channels through the block. This is the view where a mistake becomes obvious — a channel that does not reach a port, a junction that did not connect.

The right-hand panel has the chip parameters. Change Width to 50 and watch the block rebuild. Change it back.

Leave Split type on Two-piece. It means the chip prints as a channel plate and a flat lid you bond afterwards, which is far easier to drain than a sealed block. See Monolithic vs. two-piece.

6 · Read the checks (2 minutes)

Expand the Design checks panel.

On a chip like this you will probably see nothing, or a caution or two. If you do see something, click it — the app selects the offending elements and centres the view on them, and each row has a Learn more link into the catalogue.

Nothing here blocks you. The panel is advisory by design; the export buttons have no relationship to it at all. If you understand a warning and want to print anyway, print anyway.

7 · Estimate the flow (2 minutes)

Click Fluid Dynamics.

Assign the two top ports as inlets and the bottom one as an outlet. Set both inlets to 10 µL/min of water.

The table fills in: per-segment Reynolds number, velocity, pressure drop, residence time. The heatmap colours the network by whichever metric you pick.

Look at the Reynolds column. It will be well under 1. That is the central fact about microfluidics: there is no turbulence, so nothing stirs on its own, and mixing is diffusion across the interface between the two streams. See Laminar flow and the Reynolds number.

The line at the bottom says these are estimates, not a full CFD simulation. Believe it.

8 · Export (1 minute)

Back in CAD Preview, in the export block on the right:

• STL — both pieces gives you the channel plate and the lid.
• Save (⌘S) writes the .openchip project so you can come back to it.

Do both. The STL is what you slice; the .openchip is the design.

What next

Before you print, two pages are worth ten minutes:

• Draining uncured resin from channels — the failure that ruins most first chips.
• Orientation and supports — how to lay the pieces on the plate.

And if you would rather start from something more capable than a Y: Templates has seven, including a serpentine mixer, a gradient generator and a droplet generator.