PUTTING LIFE IN

Coat, seed, attach, perfuse

Coat Line the channel with extracellular matrix proteins such as collagen or fibronectin

Seed Pipette a cell suspension in

Attach Pause the flow for hours so cells settle and grip

Perfuse Start a gentle flow to feed them for days to weeks

Cells need the right surface and a gentle start before the flow begins.

SHEAR STRESS

The drag of flowing liquid

Cells lining blood vessels feel shear from blood flow, from below 1 pascal in some veins to several pascals in arteries. Chips set shear with the flow rate and channel height.

Shear is a signal cells read, not just a force they survive.

CELLS RESPOND

Flow changes behaviour

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Line up

Vessel cells stretch out along the flow

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Tighten

Barriers between cells get tighter

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Switch genes

Flow turns on genes that a still dish never activates

Cells grown under flow behave more like cells in the body.

SET THE PUMP

From target shear to flow rate

Rearrange the shear formula to get the flow rate you need: Q = τ w h² ÷ (6 μ). Measure the real channel height, since a small error grows when it is squared.

Design starts from the force the cells should feel.

MORE THAN FLOW

Stretch, 3D and oxygen

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Stretch

Cyclic strain mimics breathing or gut movement

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3D gels

Cells embedded in hydrogels grow into tissue-like shapes

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Oxygen

Gas-permeable walls and flow keep cells from suffocating; some chips create low-oxygen zones on purpose

A chip is an environment: flow, force, matrix and gases all shape the tissue.

UNIT 16 STUDY COMPLETE

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Ready for the Fab Challenge?

You've seen how cells are seeded and fed, how shear stress is calculated, and how flow changes the way cells behave.