Characterization of water vapor permeation through thin film Parylene C

2011

Micromachines

Abstract:We report the design, fabrication and characterization of micromachined Parylene structures for self-sealing liquid encapsulation applications. Automatic sealing is enabled through the use of an integrated annular-plate stiction valve which greatly reduces device footprint over in-plane configurations. We achieve automatic wafer-level liquid entrapment without using adhesives or processing at elevated pressures or temperatures. The ability to track changes to the internal liquid volume through the use of electrochemical impedance measurements is also presented.

Section: Liquid Loss Mechanismsupporting

confidence: 92%

Liquid Encapsulation in Parylene Microstructures Using Integrated Annular-Plate Stiction Valves

2011

Micromachines

“…This value agrees closely with the previously reported WVTR value of 5.78 × 10 -12 g·μm/μm 2 ·hr (20ºC, 30% RH) for Parylene C films [6]. This result confirms that the liquid loss mechanism is indeed water vapor transmission directly through the Parylene membrane and not the stiction valve seal.…”

Section: Liquid Loss Mechanismsupporting

confidence: 92%

“…Increasing membrane thickness improves encapsulation lifetime proportionally while WVTR and exposed surface area are inversely proportional. The WVTR of as-deposited Parylene-C films can be reduced by nearly 50% with additional high temperature annealing steps [4,6]. Furthermore, deposition of thin films such as gold or aluminum can also be used to reduce the SA available for transmission and provide a nearly impermeable protective coating [5].…”

Section: Discussion and Applicationsmentioning

confidence: 99%

Improved self-sealing liquid encapsulation in Parylene structures by integrated stackable annular-plate stiction valve

2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS)

2010

We report on an improved self-sealing structure for Parylene-based liquid encapsulation. The specific improvements are an integrated stiction valve which reduces overall device footprint by nearly 50% over inplane designs and the use of an annular-plate design in a stackable multi-layered configuration for successful longterm liquid encapsulation. We achieve automatic waferlevel liquid entrapment without using adhesives or processing at elevated pressures or temperatures. We also demonstrate the use of electrochemical impedance measurements as a means for tracking internal liquid volume.

“…The WVTR (5.6 × 10 −12 g · μm/μm 2 · h) of Parylene films was previously reported in literature [35]. Although DI water was utilized as the electrolyte here, alternative solutions, such as ethylene glycol-based conductive fluids, may be used for increased resistance to evaporation.…”

Section: A Liquid Encapsulationmentioning

confidence: 88%

“…• C) was shown to reduce the WVTR by nearly 50% in addition to improving Parylene-Parylene adhesion [14], [35]. Additional coatings such as thin film metals have also improved barrier performance [23].…”

Section: A Liquid Encapsulationmentioning

confidence: 99%

Parylene-Based Electrochemical-MEMS Transducers

J. Microelectromech. Syst.

2010

Abstract-We report the design, fabrication, and characterization of electrochemical microelectromechanical systems (EC-MEMS) devices featuring encapsulated fluid as the basis for transduction. Parylene microstructures, including discrete chambers (square or circular geometry), are utilized as physical transducers for electrochemically mediated liquid impedance transduction of physical phenomenon such as contact and force. Parylene-based EC-MEMS technologies uniquely leverage advantages in size (< 500 μm diameter), packaging (no hermetic packaging necessary), power (nanowatts to microwatts), and flexibility to address the physical sensing requirements of in vivo applications. Robust EC impedance (EI) sensor responses (up to 20% from base-line) and discrimination of 200-nm chamber deflections were possible using the EI transduction technique. Additional transducer configurations enabling electrolysis-based out-of-plane actuation and biomimetic mechanotransduction in microfluidic channels are also presented.[2010-0157]