THREE FAMILIES

Ways to build a barrier

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Sandwich

Two stacked channels with a thin porous membrane between them

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Hydrogel lanes

Side-by-side lanes where a gel holds cells and no plastic membrane is needed

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3D tube

A hollow vessel formed in a gel or grown into a network, perfused through

Each layout answers the same question differently.

LAYOUT ONE

The sandwich

Blood flows through the top channel over endothelial cells on a membrane. Support cells, such as astrocytes, sit on the other side. It mirrors a Transwell, but with flow.

Familiar structure, plus the missing ingredient: flow.

LAYOUT TWO

Hydrogel lanes

Small pillars hold liquid gel in a middle lane while it sets. Endothelial cells line the gel's edge, and astrocytes can live inside the gel, in direct 3D contact.

No artificial membrane, and cells can organize more freely.

TRADE-OFFS

Every layout gives something up

Sandwich Easy imaging and electrical readings, but the membrane is artificial

Hydrogel lanes More natural 3D contact, but electrodes are harder to place across the layer

3D tube The most vessel-like shape, but hardest to build and to measure

There is no best layout, only one that fits the question.

CHOOSING

Match the layout to the question

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Need standard readouts?

Choose the sandwich, since TEER and imaging are easier

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Need cells to self-organize?

Choose hydrogel lanes or a tube

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Need many chips?

Pick a layout that can be manufactured in plastic

Design begins with what you want to measure.

UNIT 13 STUDY COMPLETE

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Ready for the Fab Challenge?

You've compared the main chip layouts and seen why choosing one means choosing trade-offs.