Design and fabrication of a continuously tuned capacitor by microfluidic actuation

Abstract

This paper presents the design and the fabrication of a continuously tunable RF MEMS capacitor using micro fluidics as a tuning parameter. The impedance variation principle is based on the modification of the capacitor gap permittivity produced by the presence of deionized water and its displacements in a channel inserted between electrodes. In addition, the electric field distribution changes in equiponderant way according to the DI water positions in the channel. This change modifies the capacitive coupling, the stored energy and consequently the self-resonant frequency. The fabrication process is based on two parts: metallic paths having a spiral form, and obtained by electroplating a 7 µm thick gold layer to constitute electrodes; and fluidic channels, realized by super imposing two SU-8 films. The measurements show a non-linear variation of the capacitor value according to the water positions. The tuning range is very large, reaching up to 4650% for the capacitance, and 335% for the resonant frequency. However, the quality factor reaches Qmax = 79 at 550 MHz if the capacitor is empty and decreases with the fluid displacements to Qmin = 3.13.

Design and optimization of a microfluidic-based inductor used as a multifunction-sensor

“…The cross-section of the device (Fig. 1(b)) shows different elements constituting the inductor: spiral-shaped channels designed by using the photosensitive polymer SU8 [14,15], with gold electrodes; these elements are disposed on a dielectric glass substrate Borofloat 33 [14,15]. This insolating support is used instead of common substrate for its good RF characteristics such as a low relative permittivity ε = 4.6 and an almost zero dielectric loss (tanδ = 0.0037); the choice of Au for metallic lines is based on its resistance to corrosion and its high electrical conductivity (σ = 41.106 S/m).…”

“…Used as a sensor, this passive electrical component will be necessary in physical contact with liquid samples [15][16][17][18]. In order to predict its electrical behavior or its performances for a particular use, it is necessary to study some parameters like the magnetic field distribution and current density in the channel for a particular liquid, Galinstan (σ = 3.46 10 6 S/m) [21][22][23].…”

RF MEMS electrostatically actuated tunable capacitors and their applications: a review

“…Similarly, another work is presented in [90] based on changing the dielectric medium using deionized (DI) water between the plates. DI water is injected into the SU 8 channel for changing the dielectric between capacitor plates.…”

Microfluidics-Based Four Fundamental Electronic Circuit Elements Resistor, Inductor, Capacitor and Memristor

“…In this way, the authors succeeded in increasing capacitance from 0.52 pF to 18.5 pF when the channel was empty or filled, respectively, in the frequency range from 0.1 GHz to 4 GHz. The same group of authors described a similar principle in [14], for a continuously tuned capacitor. An interdigitated capacitor with a PDMS microreservoir of fluid on top of the structure was presented in [15].…”