Channels & points

Points and channels are what a fluid network is made of. A point is a terminal — a place a channel can end. A channel is the connection between two of them.

A channel always ends at a point. A junction is a point that several channels share, and a chamber is reached through a point riding its wall.

Points

A point is a position and a set of properties, and it fabricates nothing on its own, so it draws in the viewport as a marker — a small amber circle — and not as geometry.

A single point in an empty document, drawn as a small amber circle on the grid with no geometry under it

A point carries a width. Channel ends connected to it inherit that width, so a run through a point stays one width and editing the point moves every inherited end together. An end that sets its own width overrides the point’s, which is how you author a taper or a junction arm narrower than the run it leaves.

A point also records an offer — how many layers it can be connected from, counting up from its own layer row. A plain point offers 1 layer, its own; raise the count and channels on the slabs above may connect to it too, which is how a via is drawn. Tick all instead and it offers every layer of the stack, including ones you add later.

The offer says what is possible, not what is there. What a point actually joins comes from the channels and regions that connected to it, so a point offering three layers with one channel on it is an ordinary point. A point on a layer it does not offer is simply not a target there: the rubber band passes over it without snapping, and a release drops a fresh point instead. Narrowing an offer with a channel already attached is fine too — the channel stays exactly where it is, and the point stops advertising the layer.

A terminal inside a component you placed offers what its author drew, and you can override that from your own design without editing the component: select the pin in the Body tree and tick its offer row. Beside the layer count there is a floor, which the point’s own layer row plays for a point — set it to -1 to route a slab under the component. Both are relative to the terminal, so moving the component moves the whole range with it and nothing you typed changes.

A free point sits where you place it and accepts any number of channels. A wall-bound point rides one edge of a sibling region’s wall and accepts at most one, since it is a break-in through that wall. Binding is a property of the point, not of the channel: a channel adopts either kind the same way, and either can be exposed as a pin.

Channels

A channel is one connection, whatever shape it takes. A long run with five bends between two junctions is a single channel: one row in the Body tab, one thing to select, name and delete.

Its shape is a centerline polyline: the two ends, plus the interior vertices you place between them. The ends are anchored to the points they connect. The interior vertices are geometry, and deleting one straightens the channel through it. Selecting the channel puts a mint-green square handle on each of them, which is how a vertex reads apart from the amber circle of a point.

A selected channel between two points: an amber circle at each end and a mint-green square handle at each of its two interior vertices

Width is a value at each vertex, interpolated between them. Give the two ends different widths and the channel tapers along its length; give an interior vertex its own width and the taper turns there. An end with no width of its own inherits from its point.

A channel 200 µm wide at its inlet point, tapering to 100 µm where it meets the chamber wall

Channel ends

An end attaches to a pin or a point — either one you already have, or one the drawing gesture creates for you where you finish. Ending on the body of another channel splits that channel and puts a new point between the two halves. See Toolbar & tools for the four ways an end resolves and what each one creates.

Bends and junctions

Several channel ends may name one free point, and that point is the junction — a T, a cross, or the four-armed node inside a flow-focusing component. Two separate points never merge into one, so a junction exists only where channels share a point you placed.

An interior vertex is a bend rather than a junction, and nothing can attach to it. Promote to point on the right-click menu turns one into a junction, splitting the channel there into two channels meeting at a new point. Dissolve into channel is the reverse: a point where exactly two channels meet collapses back into a single channel through it, and the item is disabled with a reason where the point does not qualify.

One channel bent at a green interior vertex beside two channels meeting at an amber point, with Promote to point and Dissolve into channel moving between them

Neither changes the fabricated shape. A point where two channels meet straight through is mitered as the bend it replaced was, so you can promote a bend and dissolve it again without altering the geometry.

Region-wall landings

A channel reaches a chamber or a reservoir by ending at a wall-bound point, which rides one edge of that region’s wall. The channel breaks through the wall there, and the two shapes meet along an exact stretch of the edge with no material between them.

A channel ending at a wall-bound point on a rectangular region’s left wall, the two shapes meeting with no material between them

A landing has to fit the wall it sits on. It keeps at least half the channel’s width clear of each corner, sliding along the edge so the opening never runs off its end. A wall edge shorter than the channel is wide takes no landing at all.

A wall-bound point with no channel on it is a wall tap — a marked landing spot that opens nothing. Built-in components expose their taps as pins, so a chamber has inlet and outlet already placed on its wall, and the wall stays closed until you connect something.

Openings

An opening is the hole that gets the network out of its slab. It is one construction with three uses, differing only in what the two ends are:

A via joins a channel on one layer to a channel on another, through a point they share.
A world port joins a channel to the outside, through the face of the chip you chose.
A well opens a chamber or a reservoir to the outside, through a wall tap you marked as a world port and left unconnected.

There is no via tool and no well tool. You draw the network, mark what should reach the outside, and the openings follow from that.

An opening is derived, never drawn. A point forms one when what connects to it — its channels, plus the region a wall-bound point rides — sits on two or more slabs, or when you tick world port on it. A port you marked before drawing anything forms nothing: an opening joins two things, and one end would have nothing to join.

What it removes is decided per slab. Every layer between the two ends is cut through, except one whose feature already opens toward the hole, where there is nothing left to take. Two channels on neighbouring slabs facing each other are the case where that leaves nothing at all: they already meet across the bond, so the opening is real and no tool is needed for it.

Openings draw as shafts in the viewport (Viewport → Openings), and they are never geometry in a mask or a cut contour. They export as rows in a secondary-op table instead, because a hole is a call-out — where, which tool, what size — rather than a shape.

Sizing the hole

A terminal’s bore rows say how the opening it forms is cut: the punch size, the operation, whether it happens before or after the layers are bonded, and the pad. They are a conditional setting — they describe the opening this terminal would form, so they stay editable on one that forms none, and the detail says so above them. Unticked, each row falls through to the process the stack is built with. See Inspector for the rows and Fab processes window for the shop defaults under them.

Experiware Guide