CLOSE THE CHANNELS

Every channel needs a lid

A moulded or etched part has open grooves. Bonding a flat lid on top turns them into closed channels. The bond must survive the pressure inside and must not leak or contaminate what flows through.

A chip is only as good as its seal.

OXYGEN PLASMA

How PDMS bonds to glass

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Activate A short oxygen plasma creates reactive silanol (Si–OH) groups on both surfaces

Press together Within minutes, before the surfaces recover

Covalent bond Si–O–Si bridges form: the bond is permanent

Bake A short bake strengthens it further

Plasma bonding is fast and strong, but timing and cleanliness matter.

OTHER BONDS

Every material has its own glue

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Thermal

Plastics are pressed near their softening point and fuse

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Solvent

A solvent briefly softens plastic surfaces so they merge

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Anodic

Heat and high voltage bond glass to silicon

The bond must hold the pressure without changing the channel or its chemistry.

REVERSIBLE SEALS

Lids you can take off

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PDMS sticks to clean glass on its own, enough for low-pressure work. Clamps or magnets add more force. Reversible seals let you open a chip afterwards to stain or image the cells inside.

Sometimes being able to open the chip matters more than a permanent bond.

TROUBLESHOOTING

Why chips fail

Leaks at the bond, wide channels that sag shut, bubbles and dust clogs cause most chip failures. Support posts, clean handling and pressure tests catch them early.

Most chip failures are mundane: leaks, sags, bubbles and dirt.

UNIT 9 STUDY COMPLETE

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Ready for the Fab Challenge?

You've seen how chips are sealed, how bonds are tested, and how to diagnose the common ways chips fail.