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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]

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]