Parylene-bonded micro-fluidic channels for cryogenic experiments at superfluid He-4 temperatures

Area of Science:

• Cryogenics
• Microfluidics
• Quantum Fluids

Background:

• Superfluid helium-4 (4He) research requires specialized microfluidic devices.
• Traditional chip bonding methods can be complex and unsuitable for cryogenic applications.

Purpose of the Study:

• To present a novel chip-to-chip bonding technique for microfluidic flow channels.
• To demonstrate the suitability of Parylene-C bonding for superfluid 4He experiments at cryogenic temperatures.
• To evaluate the impact of integrated heaters on superfluid flow.

Main Methods:

• Fabrication of a microfluidic channel (24.5 × 100 μm2) in monocrystalline silicon with an integrated platinum heater.
• Chip-to-chip bonding using a thin Parylene-C layer between silicon and Pyrex glass.
• Testing leak tightness at approximately 1.6 K with superfluid 4He.
• Conducting flow experiments with and without activating the on-chip heater.

Main Results:

• The Parylene-C bonding method proved leak-tight for superfluid 4He at 1.6 K.
• The bonding process is a simpler alternative to techniques like anodic bonding.
• Activating the on-chip platinum heater locally overheated the channel, affecting the superfluid flow rate.

Conclusions:

• Parylene-C chip-to-chip bonding is a viable and simpler technique for fabricating cryogenic microfluidic devices for superfluid 4He.
• The integrated heater allows for localized temperature control, influencing superfluid dynamics within the microchannel.