Adhesion and cohesion in structures containing suspended microscopic polymeric films

Area of Science:

• Materials Science
• Mechanical Engineering
• Polymer Science

Background:

• Characterizing adhesion and cohesion in micro-scale polymeric films is crucial for advanced material applications.
• Existing techniques often lack precision or are not suitable for suspended micro-films.

Purpose of the Study:

• To present a novel push-out testing technique for quantifying adhesion and cohesion in suspended micro-scale polymeric films.
• To validate the technique using a standard material and apply it to a drug-eluting stent model.

Main Methods:

• Utilized focused ion beam (FIB) fabrication for precise probe tip geometries.
• Employed push-out testing to measure critical forces for film-substrate interface failure (adhesion) and film penetration (cohesion).
• Used finite element analysis (FEA) to compute underlying stresses for various probe tip sizes.

Main Results:

• Validated the technique by measuring polycarbonate shear strength at approximately 70 MPa, aligning with literature values.
• Successfully applied the method to assess adhesion and cohesion in polymeric films within drug-eluting stent reservoirs.
• Determined the cohesive strength of the stent's polymeric formulation to be comparable to common plastics like HDPE.

Conclusions:

• The novel FIB-based push-out testing technique provides a reliable method for characterizing adhesion and cohesion in micro-scale polymeric films.
• This technique offers valuable insights into the mechanical integrity of materials used in biomedical devices like drug-eluting stents.
• The findings demonstrate the technique's versatility and accuracy for both standard materials and complex device components.