Electrostatically driven drumhead resonators based on freestanding membranes of cross-linked gold nanoparticles

Abstract

Freestanding, nanometer-thin membranes of alkanedithiol cross-linked gold nanoparticles represent elastic, mechanically robust and electrically conductive materials, which are interesting for the fabrication of novel nano- and microelectromechanical devices. In this work we present the first electrostatically driven drumhead resonators based on such nanoparticle membranes. These circular membranes have a thickness of 33 to 52 nm, a diameter of either 50 μm or 100 μm, and are equally spaced from their back electrode by ∼10 μm. Using an interferometric nanovibration analyzer various vibrational modes with resonance amplitudes of up to several 100 nm could be detected when the membranes are excited by applying AC voltages (<30 V) with drive frequencies of up to 2 MHz. Further, spatial amplitude distributions of different vibrational modes could be imaged. The devices showed fundamental resonance frequencies in the high kHz range and quality factors Q up to ∼2000. Finally, vibrational spectra and observed mode patterns could be well interpreted using the theory for a clamped circular membrane with negligible bending stiffness. Our findings mark an important step towards the integration of freestanding gold nanoparticle composite membranes into electromechanical devices with various applications, such as novel types of pressure or mass sensors.

Gold nanoparticle superlattices: structure and cavities studied by GISAXS and PALS

“…This provides the opportunity to tailor materials with desired properties for various specic applications like resistive [5][6][7] or optical 8,9 strain and vapor sensing, catalysis, 10 nanoelectromechanical systems, 11,12 and surface enhanced Raman scattering.…”

Electrostatically Actuated Membranes of Cross-Linked Gold Nanoparticles: Novel Concepts for Electromechanical Gas Sensors

“…For the fabrication of the sensor devices these films were detached from their original substrates and transferred onto 3D-structured substrates, which were equipped with gold electrodes. These substrates were structured using standard photolithography, either to prepare square cavities within a ~10 µm thick SU-8 layer deposited onto a thermally oxidized silicon wafer (device A), or to etch trenches into a thermally oxidized silicon wafer (device B) [6,7]. In case of device A the back electrode was deposited onto the oxidized silicon wafer before depositing and structuring the SU-8 layer.…”

“…For transferring the crosslinked GNP-films onto these 3D-structured substrates two different methods were used. The first approach is based on detaching the cross-linked GNP-film from the original substrate by flotation on water [5,6]. The detached film remained floating at the water surface and could be transferred onto the sensor substrate using the Langmuir-Schaefer technique.…”

“…Recently, freestanding GNP-membranes gained considerable attention and current research activities explore their fundamental electromechanical properties as well as their application as actuators and highly sensitive sensors [2][3][4]. In previous works we studied the application of α,ω-alkanedithiol crosslinked GNP-membranes as electrostatically driven actuators [5] and resonators [6]. When exposing such resonators to solvent vapors at reduced total pressure we observed a significant decrease of their resonance frequency, suggesting that such devices may find applications as novel types of highly sensitive electromechanical chemical sensors [7].…”

Hydrogel Microelectromechanical System (MEMS) Resonators: Beyond Cost‐Effective Sensing Platform

“…[47] However, the dependency of the frequency on the out-of-plane deflection has not been reported thoroughly, except a few studies such as silicon-based membrane sensors driven by magnetic force. When the closed circular hydrogel membrane is pressurized negatively or positively from the side of the through-hole, the membrane bulges inward or outward.…”