Electromechanical study of polyurethane films with carbon black nanoparticles for MEMS actuators

• Published in: Journal of micromechanics and microengineering Vol. 24; no. 5; pp. 55011 - 8
• Main Authors: Roussel, M, Malhaire, C, Deman, A-L, Chateaux, J-F, Petit, L, Seveyrat, L, Galineau, J, Guiffard, B, Seguineau, C, Desmarres, J-M, Martegoutte, J
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.05.2014; Institute of Physics
• Subjects: actuator; Actuators; Carbon black; Deflection; Electrodes; electrostriction; Engineering Sciences; Exact sciences and technology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical instruments, equipment and techniques; MEMS; Micromechanical devices and systems; Modulus of elasticity; Nanoparticles; Nanostructure; Physics; polyurethane; Polyurethane resins; Carbon black; Dielectric materials; Tensile tests; Nanoindentation; Microactuators; Dispersion reinforced material; Residual stresses; Adhesion; Polyurethanes; Thickness; Young modulus; Nanoparticles; Nanocomposites; Resonance frequency; Spin-on coating; Permittivity; Buckling; Microelectromechanical device
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/24/5/055011

Pure polyurethane and nanocomposite carbon black (CB) polyurethane solutions were deposited by spin-coating on a silicon substrate using gold as the adhesion layer and electrode. Different test structures were achieved for electrical and mechanical characterizations. The incorporation of CB nanoparticles in the polyurethane matrix has a significant influence on the dielectric permittivity of the material with an increase of about one third of its value. The Young's modulus of PU and nanocomposite PU films was determined by different characterization methods. Nanoindentation experiments have pointed out a Young's modulus gradient through the film thickness. By performing mechanical tests (tensile, bulge, point deflection) on freestanding films, an average Young's modulus value of about 30 MPa was found as well as a residual stress value of about 0.4 MPa. However, no influence of the presence of the nanoparticles was found. Finally, several MEMS actuators were realized and characterized. At their fundamental resonance frequency, the actuation of the nanocomposite membranes is more efficient than that of pure polyurethane. However, the time constant of the material seems to provide a major barrier for the development of high-frequency PU-based micro-actuators.