Modeling and simulation of organic MEM relay for estimating the coefficient of thermal expansion of PEDOT:PSS

N.Z. Khan
Rutgers University,
United States

Keywords: PEDOT:PSS, conducting polymer, MEMS simulation, CoventorWare, relay


PEDOT:PSS is becoming a popular transparent electrode material for organic electronic and optoelectronic devices, replacing the more commonly used Indium Tin Oxide (ITO). PEDOT: PSS has good conductivity, transparency, superior electrical and thermal stability and high flexibility. Thermomechanical properties of PEDOT:PSS such as Coefficient of Thermal Expansion have not been reported which would be of interest to researchers in the fields of material science and electronics. In a recent paper, our group presented the development of two polymer based (purely and partially polymeric) electrostatically actuated relays, which use PEDOT:PSS as a conductive layer in the three polymer layer movable gate. The top layer has SU-8 as structural polymer and bottom layer has Cytop as dielectric polymer. The influence of temperature on the switching characteristics of these relays was examined and reported in the earlier work. Experimental results showed that threshold Voltage, VNPI decreases with increasing temperature, due to the thermal strain gradient produced in the composite polymer structure, as a result of different rate of thermal expansion in the three layers. The decrease in VNPI is also due to the temperature dependence of young’s modulus, E of polymers, VNPI being directly proportional to the equivalent elastic modulus, √Eeq of the materials composing the movable structure. This paper presents the modeling and simulation of these prototype micro electro mechanical relays on finite element analysis software CoventorWare. Thermo mechanical analysis was applied to find a set of VNPI values at different temperatures which best fit the experimental (measured) data. A number of simulations were run on compound field solver (CoSolveEM) using different values of Coefficient of Thermal Expansion of PEDOT:PSS aiming at each of ten available data points. From the simulated results an upper estimate of thermal expansion coefficient of PEDOT:PSS was extrapolated, which came out to be 49.92 ppm/°C.