This thesis deals in the theoretical part with the non-contact vibration measurement by single point Laser Doppler vibrometer and it concretes constructions used in practice. It deals also with the possibilities of the laser beam scanning to measure the vibrations in the plane and there are also listed suitable-commercial systems for this solution. Mentioned sweep is immediately necessary for 2D scanning vibrometer construction. In the practical part, the single-point laser vibrometer OFV-5000 was expanded by scanning galvo system, supplemented by a measuring cards for signal acquisition from the vibrometer and suitable control hardware was chosen for mentioned laser. For the resulting hardware assembly was designed and implemented in LabVIEW measurement software, to control the 2D scanning system, to set the position of the laser beam and to process and to visualize of measured vibration signals in the plane. The functionality of the developed measuring system was checked by performed measurement and visualization of the velocity vibration of restraint girder, excited by shaker.

Many research studies have analyzed the effect that whole-body vibration (WBV) has on sleep, and some have sought to use vibration to treat sleep disorders such as insomnia. It has been shown that low frequencies (f < 2Hz) are generally sleep inducing, but oscillations of this frequency are typically difficult to achieve using electromagnetic vibration drives. In the research that has been performed, optimal vibration parameters have not been determined, and the effects of multiple vibration sources vibrating at different frequencies to induce a low frequency traveling wave have not been explored. Insomnia affects millions of people worldwide, and non-pharmacological treatment options are limited. A bed excited with multiple vibration sources was used to explore beat frequency vibration as a non-pharmacological treatment for insomnia. A repeated measures design pilot study of 14 participants with mild-moderate insomnia symptom severity was conducted to determine the effects of beat frequency vibration, and traditional standing wave vibration on sleep latency and quality. Participants were monitored using high-density electroencephalography (HD-EEG). Sleep latency was compared between treatment conditions. Trends of a decrease in sleep latency due to beat frequency vibration were found (p ≤ 0.181 for AASM latency, and p ≤ 0.068 for unequivocal sleep latency). Neural complexity during wake, N1, and N2 stages were compared using Multi-Scale Sample Entropy (MSE), which demonstrated significantly lower MSE between wake and N2 stages (p ≤ 0.002). Lower MSE was found in the transition from wake to N1 stage sleep but did not reach significance (p ≤ 0.300). During N2 sleep, beat frequency vibration shows lower MSE than the control session in the left frontoparietal region. This indicates that beat frequency vibration may lead to a decrease of conscious awareness during deeper stages of sleep. Standing wave vibration caused reduced Alpha activity and increased Delta activity during wake. Beat frequency vibration caused increased Delta activity during N2 sleep. These preliminary results suggest that beat frequency vibration may help individuals with insomnia symptoms by decreasing sleep latency, by reducing their conscious awareness, and by increasing sleep drive expression during deeper stages of sleep. Standing wave vibration may be beneficial for decreasing expression of arousal and increasing expression of sleep drive during wake, implying that a dynamic vibration treatment may be beneficial. The application of vibration treatment as part of a heuristic sleep model is discussed.

Experimental vibration analysis of mechanical structures is a well established field.Plenty of literature exists on macro scale structures in the fields of civil, mechanical and aerospace engineering, but the study of vibrations of micro scale structures such as MEMS, liquid droplets, and biological cells is relatively new. For such structures, the amplitudes of vibration are typically in nanometeror sub-nanometer range and the frequencies are in KHz to MHz range depending upon the dimensions of the structure. In our study, we use a scanningLaser Doppler Vibrometer (LDV) to measure the vibrations of micro-scale objects such as MEMS structures, micro droplets and cells. The vibrometercan capture frequency response up to 24 MHz withpicometer displacement resolution. First, we present the study of dynamics of a 2-D micromechanical structure—a MEMSelectrothermal actuator. The structure is realized using SOI MUMPs process from MEMSCAP. The fabricated device is tested for its dynamic performance characteristics using the LDV. In our experiments, we could capture up to 50 out-of-plane modes of vibration—an unprecedented capture—with a single excitation. Subsequent FEM based numerical simulations confirmed that the captured modes were indeed what the experiments indicated, and the measured frequencies werefound to be within 5% of theoretically predicted. Next, we study the dynamics of a 3-D micro droplet and show how the substrate adhesion modulates the natural frequency of the droplet. Adhesion properties of droplets are decided by the degree of wettability that is generally measured by the contact angle between the substrate and the droplet. In this work, we were able to capture 14 modes of vibration of a mercury droplet on different substrates and measure the correspondingfrequencies experimentally. We verify these frequencies with analytical calculations and find that all the measured frequencies are within 6% of theoretically predicted values. We also show that considering any two pairs of natural frequencies, we can calculate the surface tension and the contact angle, thus providing a new method for measuring adhesion of a droplet on an unknown surface. Lastly, we present a study of vibrations of biological cells.Our first study is that of single muscle fibers taken from drosophila.Muscle fibers with different pathological conditions were held in two structural configurations—asa fixed-fixed beam and a cantilever beam—and their vibration signatures analysed.We found that there was significant reduction in natural frequency of diseased fibers. Among the diseased fibers, we could confidently classify the myopathies into nemaline and cardiac types based on the natural frequency of single fibers. We have noticed that the elastic modulus of the muscle which decides the natural frequency is dictated by the myosin expression levels. Our last example isa study of the vibration signatures of cancer cells. Here we measure the natural frequencies of normal and certain cancerous cells, and show that we can distinguish the two based on their natural frequencies. We find that the natural frequency of cancerous cells is approximately half of that of normal cells. Within the cancerous cells, we are able to distinguished epithelial cancer cells and mesenchymal cancer cells based on their natural frequency values. For Epithelial cells,we activate the signaling pathways to induce EMT and notice the reduction in the natural frequency. This mechanical assay based on vibration response corroborates results from the biochemical assays such as Western blots and PCR, thus opening a new technique of mechano-diagnostics.

This diploma thesis deals with the theoretical description of interference methods used to measure vibrations, examines main parasitic effects and analyses its contribution to achievable the resolution. In the practical part, it uses several measurements to verify the effects of the level of reflected beam, stand-off distance and speckle noise. It also proposes a practical experiment for measuring dynamic parameters and signal-noise ratio. Results show that, the noise is exponentially dependent on the level of the reflected beam. The visible maximum of the vibrometer proved to be critical in terms of time stability of the measured signal level in two of the three measurements. Results of the dynamic measurement show that, the measured deviations were not degraded or significantly disturbed by the noise signal. From the measurement of the speckle noise, it emerged that the lowest level of noise is achieved with smooth and highly reflective materials.