Stretchable Encapsulation for Implantable Strain Sensors.

Area of Science:

• Biomedical Engineering
• Materials Science
• Sensor Technology

Background:

• Implantable strain sensors monitor organ function but face challenges with stretchability, biocompatibility, and stability in physiological fluids.
• High water permeability of common stretchable materials degrades sensor performance.

Purpose of the Study:

• To develop a highly stretchable, biocompatible, and stable encapsulation for implantable capacitive strain sensors.
• To enhance the performance and longevity of organ-monitoring sensors.

Main Methods:

• Conformal parylene deposition followed by mechanical buckling and thermal annealing to create microscale wrinkles.
• Utilizing wrinkled parylene to enhance stretchability and barrier properties.
• Testing sensor stability and performance on phantoms and ex vivo organs.

Main Results:

• Achieved over 60% mechanical stretchability and excellent barrier properties (0.07 g mm/m² /day WVTR) with wrinkled parylene encapsulation.
• Enhanced gauge factor for capacitive strain sensing by over two times.
• Demonstrated long-term stability and successful real-time organ deformation sensing on bladder models.

Conclusions:

• The wrinkled parylene encapsulation offers a superior combination of stretchability, barrier function, and biocompatibility for implantable sensors.
• This method significantly improves capacitive strain sensor performance and durability.
• The versatile encapsulation technique holds promise for various implantable devices for continuous organ monitoring and targeted therapies.