DIRECT WRITING

No mask, no cleanroom

file → nozzle → device

Printing methods deposit electrode inks exactly where they're needed. A design file replaces the photomask, so changing the pattern is as quick as changing the file. That suits prototypes, small runs, and unusual substrates like paper, plastic, and fabric.

The design lives in software, not in a mask.

THE PRINTING FAMILY

Four ways to lay down ink

Screen printing A squeegee pushes thick ink through a patterned mesh. Fast and simple, with features of roughly 100 µm

Inkjet printing Tiny droplets from a nozzle. Fine detail and thin layers, but the ink must be runny

Direct ink writing A paste is extruded layer by layer, building thick or even tall electrodes

Roll-to-roll A long flexible sheet runs past printing and drying stations, for high volume

Pick the method by feature size, layer thickness, and volume.

INK DESIGN

The ink is half the device

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Viscosity

Inkjet needs a runny ink; screen printing and extrusion need thicker pastes

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Particle size

Particles must be far smaller than the nozzle or mesh opening, or they clog it

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Post-treatment

Printed layers are dried, cured, or sintered, at a temperature the substrate can survive

Great printing depends on an ink tuned to the method.

LASER SCRIBING

Burning a pattern into carbon

laser + polyimide

A focused infrared laser scans a polymer film such as polyimide, and the heat converts the surface into porous graphene, called laser-induced graphene, in a single step. Scan the laser in a comb pattern and you have interleaved electrodes in minutes, with no mask or furnace.

Draw a design, and the laser writes conductive carbon.

LASER WRITING TRADE-OFFS

Fast, but not the finest

Speed A pattern goes from drawing to device in minutes

Substrate Works on plastic films, so devices can be flexible

Resolution Limited by the laser spot and heat spread, so features are wider than lithography's

Reproducibility Rough, porous surfaces need tight control of laser power and speed

Ideal for fast prototyping, less so for micron-scale precision.

UNIT 34 STUDY COMPLETE

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Ready for the Fab Challenge?

You've covered mask-free inks, laser-written graphene, and roll-to-roll production.