Orientation and supports

How you lay the chip on the plate changes what prints well, how it drains, and whether the ports fit anything.

Print it flat

For almost every microfluidic chip, flat on the plate, channel side up is right.

Why	Detail
Channels stay in-plane	A channel running along X or Y is defined by pixels, which are the finest thing the machine has. Tilt it and the width becomes a staircase across layers.
Ports stay round	A luer taper printed vertically is a surface of revolution around the Z axis. Tilt it and it is an ellipse with layer steps.
Threads stay sane	A luer-lock helix has an unsupported underside at every turn. Flat is the only orientation where that is bearable.
Nothing needs supports	A flat-bottomed block on the plate is its own support.

The usual counter-argument — that tilting reduces peel force — matters for tall parts. A chip is a few millimetres thick and its cross-sectional area is constant, so peel force is uniform and modest throughout.

Two-piece chips

Print the channel plate channel-side up and the lid flat.

Channel-side up means the grooves are open to the air and drain by gravity while the part is still on the plate. Channel-side down means every groove is a pocket facing the plate.

Both pieces are separate STL files, so you can lay them out however you like — but lay the lid bonding-face up as well, so the face you will glue is the one that did not touch the plate.

When to tilt

Two genuine cases:

A large flat area suctioning to the FEP. A chip much larger than about 100 × 100 mm can generate enough suction force during peel to distort. A 10–15° tilt breaks the seal. You will need supports, and you will need to accept staircased channel edges.

Deliberately draining a monolithic chip. Tilting so that every channel runs downhill towards a port helps resin leave while the part is still on the plate. See Draining uncured resin.

In both cases, tilt about the axis that keeps the ports vertical if you can. A staircased channel wall costs you surface finish; a staircased luer taper costs you the fitting.

Supports

Flat on the plate, a chip needs none. That is most of why flat is the answer.

If you do tilt:

Support the underside of the block, never a port face and never inside a channel.
Use the smallest contact points your slicer offers. Every contact leaves a mark that needs sanding, and sanding near a port ruins the seal face.
Keep supports off the bonding face of a two-piece chip entirely. A support scar there is a leak path.

Most slicers will happily generate supports inside a channel void on a monolithic chip if you let them auto-support. Check before printing; internal supports are unremovable and turn a chip into a paperweight.

Overhangs OpenChip warns about

port-overhang fires when a port socket’s wall flares more than 45° from vertical — the roof of the socket is then unsupported and sags into the cavity as it cures.

The fix is geometric, not orientational: deepen the socket or reduce the diameter change. Tilting does not help, because the socket is a revolution about Z.

thread-support is an info on every luer-lock port and the advice is simply: print flat.

Layer height

30–50 µm is the range. Lower is smoother and slower.

For a chip whose critical dimension is channel width, layer height barely matters — go for speed. For a droplet generator whose throat surface finish affects the size distribution, go finer.

A checklist before you slice

Chip flat on the plate, channel side up.
Lid flat, bonding face up.
Parts separated by a few millimetres.
Supports off, or manual and only under the block.
No supports inside any channel.
Nothing touching a port face or a bonding face.