Search

Vestibular otolithic organs are recognized as transducers of head acceleration and they function as such up to their corner frequency or undamped natural frequency. It is well recognized that these organs respond to frequencies above their corner frequency up to the 2–3 kHz range (Curthoys et al., 2016). A mechanics model for the transduction of these organs is developed that predicts the response below the undamped natural frequency as an accelerometer and above that frequency as a seismometer. The model is converted to a transfer function using hair cell bundle deflection. Measured threshold acceleration stimuli are used along with threshold deflections for threshold transfer function values. These are compared to model predicted values, both below and above their undamped natural frequency. Threshold deflection values are adjusted to match the model transfer function. The resulting threshold deflection values were well within in measure threshold bundle deflection ranges. Vestibular Evoked Myogenic Potentials (VEMPs) today routinely uses stimulus frequencies of 500 and 1000 Hz, and otoliths have been established incontrovertibly by clinical and neural evidence as the stimulus source. The mechanism for stimulus at these frequencies above the undamped natural frequency of otoliths is presented where otoliths are utilizing a seismometer mode of response for VEMP transduction. [ABSTRACT FROM AUTHOR]

An inertial microswitch with flexible contact-enhanced structure to prolong contact time has been designed and fabricated by surface micromachining technology. The flexible structure is an L-shaped compliant cantilever beam, which can realize elastic deformation during contact process when the movable electrode impacts to the stationary electrode. The influence of applied acceleration loads on contact time and threshold was analyzed, simulated and evaluated. The analysis results indicate that the stiffness of inertial system, amplitude and pulse width of acceleration loads are important influence factors for the contact time: the contact time will be increased along with the increase of acceleration amplitude and the decrease of inertial system stiffness. The broadening of pulse width of acceleration loads will result in a greater value of threshold acceleration and contact time. The simulated results demonstrate that the dynamic properties of designed inertial micro-switch are in agreement with the analytical ones. The fabricated microswitch has been tested by dropping hammer system, the test results indicate that the threshold acceleration is about 110g and the corresponding contact time is about 42 μs when the pulse width is about 1.7 ms. Meanwhile, the contact time increases with the broadening of pulse width. Finally, the fabricated inertial microswitch device has been also tested under applied half-sine wave acceleration with different amplitudes and pulse widths. It is indicated that the contact time does not increase after reaching to a maximum (75 μs under 259g applied acceleration load). From the analysis in the present work, the influence of applied shock loads on contact time and threshold level in an inertial microswitch with flexible contact-enhanced structure is revealed. The conclusions reached in this study provide guidance for future research into the design and fabrication of inertial microswitches. [ABSTRACT FROM AUTHOR]

Highlights: [•] We firstly propose a bi-directionally tunable MEMS acceleration switch. [•] Threshold decreased from 10.25g to 2.0g by applying tuning voltage. [•] Threshold increased from 10.25g to 17.25g by applying tuning voltage. [•] Additional functionality of safe/armed position convertibility is realized. [•] Additional functionality of mechanical latching is realized. [ABSTRACT FROM AUTHOR]

Abstract: Based on surface micromachining technology, a micro-electro-mechanical system (MEMS) inertia switch with single sensitive direction and reverse impact protection has been designed and fabricated on quartz substrate. The switch is laterally driven (i.e. its sensitive direction is parallel to the substrate plane), in which the conjoined snake springs are used to fix and suspend the movable electrode (i.e. proof mass), and blocks are used to protect the device against reverse impact. The relationship between the threshold acceleration a th and the intrinsic frequency has been investigated by theoretical analysis and finite element simulation, respectively, based on which the geometrical parameters of the switch can be decided to meet design objective. The proof mass thickness H was chosen as a variable, as the micro-fabrication of the device was carried out by low-cost and convenient multi-layer electroplating technology, where H can be easily adjusted while the plane geometry remains the same. The stress distribution of the switch in the contact process was also simulated. Packaged micro-switches were tested by dropping hammer experiments, which generated half-sine wave acceleration as in reality. The measured threshold acceleration generally met the design objective of 60g and the response time was in the order of 10−4 s, both agreed with the simulated results. [Copyright &y& Elsevier]

Separate and non-interfering photo-resist molded metal-electroplating processes have been applied to the fabrication of inertia micro-switches and their wafer-level packaging in sealed cavities. The height of a switch and that of its cavity are independently controlled. The low process temperature allows eventual modular integration of switches on active substrates containing pre-fabricated electronic signal-processing circuits. The scheme also provides leads for electrical access to the sealed devices. The switches were designed using a simple but accurate lumped spring-mass model. With the application of an anti-stiction hydrophobic coating, un-encapsulated switches making over 100 million contacts have been demonstrated in room ambient. [Copyright &y& Elsevier]

• Analytical solution for a non-linear SDOF governing equation of a latch accelerometer. • Energy constraints on the analytical model to define a threshold acceleration g-switch. • Automated SIMULINK model to solve for the design parameters for any arbitrary shock impulse profile. • Comparison between the experimentally obtained displacement response and the analytically obtained displacement response of the proof mass. We present an experimentally verified novel design framework for MEMS g-switch acceleration switches. These switches need to engage a physical latch upon sensing a specified threshold acceleration. It is this physical contact between two surfaces under dynamic conditions that introduces nonlinearity in the system response and makes the task of design optimization difficult. We first find analytical solutions for displacement and velocity of the proof mass by linearizing the friction term using a single degree of freedom model and representing the acceleration profile by a Fourier series. We then use these solutions, along with latching constraints on them, to study how the lumped design parameters – mass, suspension spring stiffness, and latching spring stiffness – vary with increasing threshold acceleration. The latching constraints ensure that latching does not occur for any magnitude of acceleration less than the specified threshold value. Subsequently, we build a g-switch model in SIMULINK that uses the variation in design parameters for a given acceleration profile to find an optimal set of values of design parameters for a specified threshold acceleration. We verify our model by fabricating a latch accelerometer using the parameters obtained from this model for a 60 g threshold acceleration. A shock input of 60 g magnitude and 1.2 ms pulse width is given to the fabricated acceleration switch and the experimental response is recorded using high-speed video images. The analytical response and the experimental response show good agreement. Hence, we believe that this novel design framework can be used to fabricate a latch accelerometer for any arbitrary input shock profile. [ABSTRACT FROM AUTHOR]