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Dipartimento di Fisica - Politecnico di Milano

Wet etching in hydrofluoric acid for microfluidic circuits

The HF etching lab is specifically intended to support wet HF etching processing of any material under optimum temperature, reagent and fume control. This etching is an essential step of the Femtosecond Laser Irradiation followed by Chemical Etching technique (FLICE), to fabricate microfluidic circuits.
In particular when fused silica is irradiated with the femtosecond laser, at a moderate fluence, sub-wavelength nanocracks are produced, yielding a high etching selectivity of the irradiated volume with respect to the pristine one (up to two orders of magnitude). Subsequent HF etching, of the irradiated samples, gives long (≈5mm) and smooth (250 nm rms surface roughness) microfluidic channels.
The main facilities of the laboratory are:
A GLORIA ARTEC fume cupboard, designed with particular care for all safety criteria, for the quick removal of toxic fumes as well as for protecting operators. It is totally made of fireproof materials and all internal acid-proof linings can be easily decontaminated.
A  Branson Ultrasonic cleaner (model B-3510) with a 5,5 l capacity ultrasonic bath with heat and timer digital control. It is equipped with a homemade cooling system to better control bath temperature during ultrasonic working.
A BRAND Dispensette® HF bottletop dispenser to dispense metered amounts of hydrofluoric acid safely, reliably, and accurately. Its integral safety discharge system reduces the risk of inadvertent dispensing.