Virial and Energy Dissipation in Measurement of Dynamic Acoustic Forces Using Bimodal-frequency Excitation of Micro-cantilever Array

Virial and energy dissipation, related to oscillation observable responses, possess complementary information regarding acoustic force measurements. In this paper, we introduce a mathematical framework describing the analytic relationship between oscillation observables and energy quantities at the second eigenmode in the measurement of dynamic acoustic forces. We utilize a bimodal-frequency excitation scheme for actuation of the micro-cantilever array to obtain high-sensitivity frequency bands. Herein, we analyze the virials of acoustic force interaction and the energy dissipation levels on the domain of acoustic force frequency. For our case, we obtain the high-frequency bands of around 200-270 kHz and 440-570 kHz for the force strengths in the range of 4.0-36.0 pN. In addition, results of virials and dissipated power with respect to acoustic force strengths are introduced for low- and high-sensitivity frequency regions. Therefore, the energy quantities can be robustly utilized to determine high-sensitivity frequency windows in the measurement of dynamic acoustic forces.

Design of Microfabricated Mechanically Interlocking Metamaterials for Reworkable Heterogeneous Integration

Next–generation interconnects utilizing mechanically interlocking structures enable permanent and reworkable joints between microelectronic devices. Mechanical metamaterials, specifically dry adhesives, are an active area of research which allows for the joining of objects without traditional fasteners or adhesives, and in the case of chip integration, without solder. This paper focuses on reworkable joints that enable chips to be removed from their substrates to support reusable device prototyping and packaging, creating the possibility for eventual pick-and-place mechanical bonding of chips with no additional bonding steps required. Analytical models are presented and are verified through Finite Element Analysis (FEA) assuming pure elastic behavior. Sliding contact conditions in FEA simplify consideration of several design variations but contribute ~10% uncertainty relative to experiment, analysis, and point-loaded FEA. Two designs are presented; arrays of flat cantilevers have a bond strength of 6.3 kPa, and non-flat cantilevers have a strength of 29 kPa. Interlocking designs present self-aligning in-plane forces that emerge from translational perturbation from perfect alignment. Stresses exceeding the material yield stress during adhesion operations present a greater concern for repeatable operation of compliant interlocking joints and will require further study quantifying and accommodating plastic deformation. Designs joining a rigid array with a complementary compliant cantilever array preserve the condition of reworkability for the surface presenting the rigid array. Eventual realization of interconnect technology based on this study will provide a great improvement of functionality and adaptability in heterogeneous integration and microdevice packaging.

Recent Progress in Self-sensing Probe Technology in Atomic Force Microscope

: The imaging speed of atomic force microscope (AFM) is limited by the cantilever mechanical bandwidth, which can be increased by reducing the size of the cantilever. However, the ordinary laser reflection method cannot measure the deflection of a small cantilever. And some samples are sensitive to light detection and not suitable for the laser reflection method. Therefore, the self-induction probe technology was developed to solve this problem. This article reviews the latest AFM self-induction probe technology and introduces three types of self-induction probes. Firstly, it is introduced that the current self-sensing probes can be divided into piezoresistive type, piezoelectric type and tuning fork type according to the working mechanisms and preparation materials. Then, the latest materials and structures of various self-sensing probe technologies are introduced to improve imaging performance and their applications in various fields. And, compared with traditional laser reflection methods, the self-sensing probe technologies have a simpler structure, take up less space and can be integrated in a large cantilever array and adopted for imaging of photosensitive products. Finally, some prospects of the novel imaging and sample characterization techniques and new applications of atomic force microscopy are also discussed.

Analytical Model for Enhanced Eigen-Mode Sensitivities in a Coupled Micro-Resonator Array for Ultra-Sensitive Mass Measurement

Resonant sensors using coupled micro-cantilever array have applications in a wide range of areas including ultrasensitive mass detection of bio-molecules and chemical analytes. A target mass deposited on one of the cantilevers can be detected by measuring shift in eigen-spectrum. Experimental observations indicate that eigenmodes are more sensitive to mass perturbation than resonant frequencies or eigenvalues. However, analytical works, available in literatures, are limited to only two and three cantilever array for eigenvalue sensitivity and only two cantilever array for eigenmode sensitivity. In the present work, an analytical foundation for estimation of eigenmode sensitivities for a general n-array micro-resonator sensor is developed using matrix perturbation theory. The formulation characterizes the modal spectrum and eigenmode sensitivities as a function of elastic interconnection stiffness parameter and unperturbed eigenmodes. Measurement of added mass is demonstrated for different analyte locations using numerically constructed frequency response function (FRF) curves. Error in measurement is also investigated as a function of interconnection stiffness ratio, position of analyte mass, and selection of particular eigenmode to be measured.

Low-Frequency Piezoelectric Accelerometer Array for Fully Implantable Cochlear Implants

We demonstrate a low-volume, stress-free, piezoelectric micro-electromechanical system (MEMS) cantilever array for fully implantable hearing aids. The 12-element spiral-matrix is sensitive to the lower part of audible frequency range (300–700 Hz) through the proper resonant frequency of the individual spirals tuned by dimensions of the cantilevers. The obtained high Q-factors (117–254) provide high frequency selectivity. The generated open circuit voltage signals could be sufficient for the direct analog conversion of the signals for cochlear multielectrode implants. By comparing different geometries we have also demonstrated that the initial stress, which is derived from silicon-dioxide (SiO2) and aluminum-nitride (AlN) layers, could be drastically reduced simply by the spiral geometry. The results of vibration measurements have shown a good agreement with the calculated resonant frequencies.