Wireless Sensor Nodes are basic building blocks for future ubiquitous networks. These nodes have to be able to gather and transmit information to their neighbors in complete autonomy. This means that with no battery, they rely on scavenging the energy necessary to operate directly from their environment, like conversion of solar or vibration based energy. This stringent requirement drastically limits the power budget of those devices to a level below 100μW. From the architecture prospective, work on reducing the complexity of the transceiver is mandatory, in order to reduce both size and power consumption. The simplest approach relies on the on/off modulation of a GHz range carrier frequency signal in a transmit channel, which is then directly selected and demodulated in the receiving path. For these particular functionalities, i.e. frequency generation and filtering, nano-mechanical resonators present a strong advantage of scalability that helps to integrate them into dense arrays directly on top of CMOS. This avoids package parasitic, allows for MEMS/circuitry co-design, and eventually leads to size shrinkage and power saving.
The reliability study of advanced 3D self-assembled micro- machined polysilicon structures is investigated here with the aim of preventing the dynamic snap-through from occurring; snap-through is a vibratory phenomenon, which can lead to the destruction of a whole structure. 3D polysilicon micro-parts are self-assembled by beam buckling induced by the compressive force produced by Scratch Drive Actuator; this work considers the reliability of these micro-parts, and particularly the response of homogeneous, clamped- clamped polysilicon microfabricated buckled beams.
This work demonstrates a novel technique for the realization and the actuation of continuous-membrane for adaptive optic applications. This original device exhibits, for the first time, both positive and negative membrane deflection with individual pixel displacement of +/- 10 micrometers , which is one order of magnitude larger than usual approaches, without diffractive interference.
This work considers the reliability of an elementary 3D structure, and particularly the response of a homogeneous, clamped-clamped polysilicon microfabricated beam, buckling under the compressive force produced by Scratch-Drive Actuators (SDA). First, using Galerkin's method, the governing partial differential equation reduced to a modified Duffing equation and was solved by the harmonic balance method. Besides the solution of simple harmonic motion (SHM) and superharmonic motion (SPHM) were found numerically using a Newton iteration method. Then, the study of continuity -- of these solutions -- allowed to analyze the stability boundaries. Finally, Runge-Kutta numerical integration method was used to investigate the snap-through problem. Intermittent, as well as continuous, snap-through behavior was obtained. The theoretical results agreed well with the experiments.
The novelty of our study lies in the first controlled use of the phenomenon of stiction to lock three-dimensional self- assembled polysilicon microstructures. The stiction refers to the permanent adhesion of the microstructures to adjacent surfaces. It can occur either during the final stage of the micromachining process, that is to say the releasing of the microstructural material, or after the packaging of the device, due to overrange input signals or electromechanical instability. As a result, we often regard stiction as a major failure issue in the MEMS field of research. This paper reports both the theory of our stiction-controlled locking system operation mode and the validation of our original concept through the stiction-locking of a 3-D self-assembled device.