Adhesives used in diagnostic devices must meet specific performance criteria to ensure safety, reliability, and functionality throughout the device’s lifecycle.  


Key properties include:  

• Biocompatibility: Compatible with biological samples and the assay (i.e., does not inhibit enzymes or interfere with signal) and able to adhere to required substrates. 
• Chemical resistance: Should withstand reagents and solvents used in assays.  
• Optical clarity: Important for optical detection methods.  
• Optical properties: Low auto‑fluorescence/background and minimal visual defects (e.g., haze, inclusions) for optical readouts. 
• Mechanical properties: Must maintain bond under stress and potentially conduct heat.  
• Material construction tolerances: Ability to hold tight thickness/flatness targets to maintain channel geometry and sealing. 
• Moisture and gas permeability: Critical for fluid control and sample integrity.  

Biocompatibility testing ensures that adhesives do not cause harm or interfere with biological samples. The requirements differ based on the device’s interaction with the body or sample. 

• Wearables: Focus on skin contact safety, irritation, and sensitization. 
• IVDs: Emphasize sample integrity, avoiding contamination or interference with biological assays. Testing may include cytotoxicity, hemocompatibility, and chemical leachables. 

• Diagnostic devices often consist of multiple layers and components, each requiring secure and compatible bonding for proper function. 
  
• Films (PET, polycarbonate, polypropylene) 
• Membranes for sample preparation and clean up 
• Glass or silicon substrates 
• Printed circuit boards (PCBs) 
• Reagent pads or reservoirs 
• Other molded formed components (i.e. injection molding, etc.) 

Surface energy is a measure of how well a surface can attract and bond with adhesives or liquids. High surface energy materials (like metals or glass) allow better adhesive wetting and bonding, while low surface energy materials (like polyethylene) are harder to bond. 

Surface energy drives how liquids interact with channel walls.  This in turn controls flow behavior in microfluidic devices. A high energy surface (i.e. a hydrophilic surface) allows fluid to spread more readily in a capillary flow driven device.  

Surface energy affects how well adhesives bond to different materials. Measuring it helps ensure strong and reliable adhesion. Measurement methods: 

• Contact angle: A droplet’s angle on the surface—lower angles indicate higher surface energy. 
• Dyne pens or solutions: Apply liquids of known surface tension to see which ones wet the surface. 

Hydrophilic films play a key role in fluid management within diagnostic devices, especially in microfluidic systems. 

Definition: Films that attract and distribute water, enabling fluid flow. 

Role: Used in microfluidic channels to guide sample movement. 

Benefits: 

• Enhance capillary action 
• Improve sample distribution 
• Support consistent assay performance 

Choosing the right adhesive involves evaluating the device’s materials, environment, and intended function to ensure optimal performance. 

Key factors include: 

• Bonding surfaces: Ensure compatibility with materials like plastics, films, glass, or membranes. 
• Environmental or Operational conditions: Consider exposure to heat, humidity, or solvents,  
• Device functionality: Choose adhesives that support optical requirements, fluid flow, mechanical strength, bio or assay compatibility—depending on the device’s purpose, stability/inertness. 

Selecting the right adhesive ensures reliable performance, durability, and assay accuracy. 

Several bonding characteristics determine how well an adhesive performs in diagnostic applications, especially under stress or over time. 

• Peel strength: Measures how well the adhesive resists separation from surfaces—important for maintaining bond integrity during handling or testing. 
• Tack: Indicates initial stickiness, which helps with fast and accurate placement during assembly. 
• Shear resistance: Ensures the adhesive can withstand lateral forces without shifting or failing. 
• Long-term stability: Critical for maintaining performance over time, especially in devices with extended shelf life or prolonged use. 
• Cohesive strength: Ability for the adhesive to not split and leave residue on bonding surfaces 
• Solvent resistance: Ability of the adhesive to avoid absorbing sample or assay fluids  

These properties help ensure reliable bonding under various conditions in diagnostic applications. 

Adhesive performance can vary based on environmental exposure and mechanical demands during device use or testing. 

• Heat or solvents: High temperatures or chemical exposure can weaken bonds or cause degradation. 
• Duration of use/testing: Long-term applications require adhesives with stable, lasting performance. 
• Mechanical stress: Flexing, bending, or pressure can lead to delamination or failure if the adhesive lacks flexibility or strength. 
• Rigidity under pressure: Devices with tight tolerances or rigid structures need adhesives that maintain shape and bond under compression. 
• Processing and device assembly conditions: Processing elements that can affect bonding performance (i.e. release agent contamination) 

Selecting adhesives that match the device’s operating environment ensures reliability and functionality. 

In devices that rely on optical detection, adhesive transparency and compatibility are critical to maintaining assay accuracy. 

• Transparency: Clear adhesives are essential for optical detection methods (e.g., fluorescence, colorimetric assays) to ensure accurate signal transmission. 
• Low fluorescence: Prevents background interference that could distort assay results, especially in sensitive imaging or light-based detection systems. 
• Assay compatibility: Similar to transparency, adhesives must not block detection wavelengths, ensuring reliable performance across different assay types. 

Precise alignment and material compatibility are essential when assembling multi-layer diagnostic devices to ensure consistent performance. 

• When assembling devices with multiple layers (e.g., films, adhesives, membranes), precise registration and alignment are critical to ensure functionality and performance. 
• Heat shrinkage during processing or after processing such as during use (e.g., lamination or sterilization) can cause misalignment, curl and other deformations, so materials must be matched for thermal stability. 
• layer matching is essential - especially for optical paths, fluid channels, or sensor placement - to avoid assay errors or mechanical failure. 

Thermal management: Tape may help manage heat during reactions. Use thermally conductive tapes to spread heat evenly during thermally sensitive reactions.  

Vapor transmission management: aluminum is a better barrier compared to plastic backings for long term storage to avoid assay dry out.  

Adhesive degradation can compromise device performance. Understanding the causes and implementing proper storage and material selection helps maintain stability. 

• Causes of degradation: 
• Aging: Natural breakdown over time reduces bond strength. 
• Chemical exposure: Solvents, reagents, or environmental contaminants can weaken adhesives. 
• Storage conditions: Heat, humidity, and UV light accelerate degradation. 
• Ensuring stability: 
• Choose adhesives with proven long-term performance. 
• Store in controlled environments (cool, dry, away from light). 
• Use chemical-resistant formulations when exposure is expected. 

Proper selection and handling help maintain adhesive integrity throughout a diagnostic device’s lifecycle. 

Adhesive testing ensures that materials meet performance standards under various conditions and use cases.  

Types of testing we perform: 

•  Adhesion testing: Peel, shear, and tack tests. 
• Liner release testing: Measures force to remove protective liner. 
• Optical testing for transmission, haze, fluorescence, clarity 
• Peel speed evaluations: Assess performance under different application speeds. 
• Controlled environment stability testing: Temperature, humidity, and chemical exposure. 
• Conditioning methods: Simulate environmental exposure.* 

*on occasion, not in all instances 
Note: Different adhesive suppliers may perform different testing. 

Diagnostic devices often consist of multiple layers and components, each requiring secure and compatible bonding for proper function.  

• Films (PET, polycarbonate, polypropylene)  
• Membranes for sample preparation and clean up  
• Glass or silicon substrates  
• Printed circuit boards (PCBs)  
• Reagent pads or reservoirs  
• Other molded formed components (i.e. injection molding, etc.)  

Choosing the right adhesive involves evaluating the device’s materials, environment, and intended function to ensure optimal performance.  
Key factors include:  

• Bonding surfaces: Ensure compatibility with materials like plastics, films, glass, or membranes.  
• Environmental or Operational conditions: Consider exposure to heat, humidity, or solvents,   
• Device functionality: Choose adhesives that support optical requirements, fluid flow, mechanical strength, bio or assay compatibility—depending on the device’s purpose, stability/inertness.  

Selecting the right adhesive ensures reliable performance, durability, and assay accuracy.  

Adhesive performance can vary based on environmental exposure and mechanical demands during device use or testing.  

• Heat or solvents: High temperatures or chemical exposure can weaken bonds or cause degradation.  
• Duration of use/testing: Long-term applications require adhesives with stable, lasting performance.  
• Mechanical stress: Flexing, bending, or pressure can lead to delamination or failure if the adhesive lacks flexibility or strength.  
• Rigidity under pressure: Devices with tight tolerances or rigid structures need adhesives that maintain shape and bond under compression.  
• Processing and device assembly conditions: Processing elements that can affect bonding performance (i.e. release agent contamination)  

Selecting adhesives that match the device’s operating environment ensures reliability and functionality.  

Adhesive testing ensures that materials meet performance standards under various conditions and use cases.   
Types of testing we perform:  

•  Adhesion testing: Peel, shear, and tack tests.  
• Liner release testing: Measures force to remove protective liner.  
• Optical testing for transmission, haze, fluorescence, clarity  
• Peel speed evaluations: Assess performance under different application speeds.  
• Controlled environment stability testing: Temperature, humidity, and chemical exposure.  
• Conditioning methods: Simulate environmental exposure (on occasion, not in all instances). 

Note: Different adhesive suppliers may perform different testing.