In the past decade, the use of Parylene as a structural material in microelectromechanical systems (MEMS) devices has attracted significant attention.  Parylene C, known for its biocompatibility, is widely used in implantable medical devices.  Parylene C is also compatible with MEMS microfabrication processes.

WHAT ARE MEMS?

Microelectromechanical systems (MEMS) is the technology of very small devices; it merges at the nano-scale into nanoelectromechanical systems (NEMS) and nanotechnology.  MEMS are made up of components between 1 to 100 micrometres in size (i.e. 0.001 to 0.1 mm), and MEMS devices generally range in size from 20 micrometres (20 millionths of a metre) to a millimetre (i.e. 0.02 to 1.0 mm). They usually consist of a central unit that processes data (the microprocessor) and several components that interact with the outside such as microsensors.

WHAT IS PARYLENE?

Parylene is a polymer applied through a deposition process.  Parylene coatings are completely conformal, have a uniform thickness and are pinhole free.  Parylene is chemically and biologically inert and stable and make excellent barrier material.  Parylene has excellent electrical properties: low dielectric constant and loss with good high-frequency properties; good dielectric strength; and high bulk and surface resistance.

PARYLENE AND MEMS TECHNOLOGY

Parylene has an easy coating process, controllable conformal coating thickness, and is highly compatible with the plasma etching process.  As a result of this, parylene has been easily integrated with the fast growing MEMs technology.  An example of current usage would be neuron cages, which are manufactured using a multiple parylene layer etching process.  Another current use is parylene enabled retinal ocular implants.

Sources:

Parylene Technology for Neural Probes Applications.  Changlin Pang.  California Institute of Technology.  Pasadena, California.  2008.

A Parylene MEMS Electrothermal Valve.  Po-Ying Li et al.  J Microelectromech Syst. 2009 December; 18(6): 1184–1197.  doi:  10.1109/JMEMS.2009.2031689.