Project Perses: Gas-selective membranes for helium and hydrogen sensors

As part of the Perses project, Fraunhofer IMM is developing highly selective thin-film membranes for separating helium and hydrogen for use in gas sensor technology. These technologies are well-established in industry and are used in modern leak detection systems.

Membrane processes are a well-established method for separating individual gases from a mixture. The goal of the Perses project is to separate low-molecular-weight gases such as helium (He) and hydrogen (H₂) in order to develop robust, miniaturized membranes with high selectivity and high mechanical stability for use in leak detection sensor systems.

The focus is on combining high permeability, pressure stability, and the ability to integrate into compact measurement systems.

The quartz and palladium thin-film membranes developed at IMM are based on a microstructured silicon substrate platform, which provides the necessary mechanical stability.

The membranes can be customized in terms of geometry and functional properties and integrated into sensor systems.

The membranes developed in the Perses project are specifically designed for use in gas sensing applications and have been industrially validated.

Applications:

• Industrial leak detection (leak testing)
• Helium sniffer method
  
• Hydrogen sensing
  
• Inline quality assurance in production processes
  

Technical Features:

• High selectivity for He and H₂
• High pressure stability due to a silicon support structure
  
• Integrated heating elements for stable operating conditions
  
• Miniaturized design for sensor systems
  

Manufacturing Technologies:

• Thermal oxidation
• Front- and back-side lithography
  
• Thin-film deposition (sputtering)
  

The helium-selective quartz membrane is the central component of modern helium leak detection systems. It combines maximum selectivity with high pressure stability, enabling reliable operation in industrial applications.

The sensor principle is based on a filter membrane. When a higher concentration of helium is drawn in via a sampling probe, it can diffuse through the membrane, causing a rise in pressure within the evacuated measurement cell, which is measured directly. This method eliminates the need for conventional mass spectrometers, including complex vacuum technology. Thanks to the robustness and precision of the devices, which are based on WISE^TM detection technology, new applications can be developed that are not accessible to mass spectrometer-based devices.

Specifications:

• Permeability (He): 1.0 × 10⁻⁶ mbar·l·s⁻¹
• Pressure stability: > 1 bar (up to 2 bar in system integration)
  
• Integrated platinum heating meander for operation at elevated temperatures
  
• Chip size: 23 × 50 mm²
  
• Active membrane area: 175 mm²
  
• Silicon substrate with 4895 micro-openings
  

The palladium-based membrane enables the selective detection or separation of hydrogen and can also be used in sensor systems.

Properties:

• Permeability (H₂): 1.0 × 10⁰ mbar·l·s⁻¹ (at 300 °C)
• Pressure stability: > 3 bar
  
• Alloyable with silver (Ag) and copper (Cu)
  
• Optional integrated heating meander
  
• Chip size: 23 × 50 mm²
  
• Active membrane area: 175 mm²
  
• Silicon substrate with 4895 micro-openings
  

Project partners:

• Inficon GmbH
• Technical University of Kaiserslautern