MOVING LIQUID

What drives the flow?

Syringe pump Sets the flow rate directly; steady, but slow to settle

Pressure controller Sets the pressure; responds in milliseconds

Peristaltic pump Rollers squeeze tubing; good for recirculating loops

Passive Capillary action or gravity; no power needed

The pump decides how steady, how fast and how portable the chip can be.

VALVES

Switching flow with a membrane

In a two-layer PDMS chip, a control channel crosses over a flow channel. Pressurize the control channel and the thin membrane between them pinches the flow channel shut. Three in a row, fired in sequence, make a pump.

Valves turn a chip from a pipe into a programmable machine.

WORLD TO CHIP

The connector problem

🔌

🧵

Tubing

Long, soft tubing adds volume, delay and places for bubbles

🕳️

Dead volume

Liquid trapped in fittings wastes sample and slows changes

🧩

Standard ports

Luer fittings, manifolds and clamp-on interfaces make chips easier to use

A tiny chip often sits in a big tangle of tubes: "chip in a lab" instead of "lab on a chip".

BUBBLES

The chip's worst enemy

A bubble changes the resistance of a channel, can block it completely, and can tear cells off the walls as it passes. Degassing liquids, filling carefully and adding bubble traps keep them out.

Most chip failures are mundane: air, leaks and dirt.

OTHER WAYS TO MOVE LIQUID

Spin, charge and rock

💿

Centrifugal

Spin a disc and liquid moves outward through valves: a "lab on a CD"

⚡

Electro-osmosis

An electric field drags charged liquid along a glass channel

🎢

Gravity and rocking

Tilting a chip back and forth moves medium with no tubing at all

Not every chip needs a pump: some just need a spinner, a voltage or a rocker.

UNIT 11 STUDY COMPLETE

🚰

Ready for the Fab Challenge?

You've compared ways to drive flow, seen how membrane valves work, and learned why bubbles and connectors matter.