Time Domain Multiplexing for Efficiency Enhanced Piezoelectric Energy Harvesting in MEMS

The conversion efficiency of piezoelectric energy harvesters (EH) have been improved by several approaches including frequency up-conversion (FUC) techniques that trigger the high-frequency (HF) piezoelectric resonators using low-frequency (LF) mechanical inputs. This work proposes a new time-domain multiplexing technique to further improve the harvesting efficiency for random mechanical impacts using commercially available microfabrication processes. The FUC is implemented by a slowly moving shuttle beam, which represents the LF mechanical inputs, that triggers the free ends of piezoelectric cantilever beams. Mechanical impacts by the LF shuttle lead to the cantilever beams vibrating at their higher natural resonance frequencies. In the proposed approach, resonators are exposed to the LF mechanical input at unequal distances, which results in sequential HF vibrations. As a result, the HF electrical outputs fit sequentially within the long period of the LF input. Analytical and experimental comparisons support the increased electrical output using time domain multiplexing.</p

An integrated magnetic programming technique for mechanical microresonators

Mechanical memory devices are needed for harsh environments where electronic components fail to operate. An integrated electro-Thermal technique for local magnetic annealing, which enables post-production programming capabilities for mechanical micro-resonators is presented. It is verified by a prototype with ferromagnetic resonating elements suspended on top of a polysilicon resistive heater. The magnetization (M-H) loop, with and without post-fabrication annealing are measured to prove the validity of technique.</p

An integrated magnetic programming technique for mechanical microresonators

Mechanical memory devices are needed for harsh environments where electronic components fail to operate. An integrated electro-Thermal technique for local magnetic annealing, which enables post-production programming capabilities for mechanical micro-resonators is presented. It is verified by a prototype with ferromagnetic resonating elements suspended on top of a polysilicon resistive heater. The magnetization (M-H) loop, with and without post-fabrication annealing are measured to prove the validity of technique.</p

Enhancing heuristic bubble algorithm with simulated annealing

In this study, a new way to improve the Heuristic Bubble Algorithm (HBA) is presented. HBA is a nature-inspired algorithm, which is a new approach to and initially implemented for, vehicle routing problems of pickup and delivery (VRPPD). Later, it was reinforced to solve other routing problems, such as vehicle routing problem with time windows (VRPTW), and vehicle routing problem with stochastic demands (VRPSD). HBA is a greedy algorithm. It will mostly find local optimal solutions. The proposed method is an improvement over HBA enabling it to reach the global minimum. It uses specialized simulated annealing methods in its operators. A well-known data-set is used to benchmark the proposed method. Better results over HBA and some best results in literature are recorded

A comparison of two excitation modes for MEMS electrothermal displacement sensors

MEMS electrothermal displacement sensors can be operated in constant current (CC) or constant voltage (CV) excitation modes. The CV mode is more commonly used. However, there have been reports that the CC excitation mode may lead to a larger measured signal, and thus, it may be a better choice than the CV mode. In this letter, we present an analytic comparison of the two methods, and show that from a signal-to-noise-ratio point of view, benefits of operating a sensor in CC mode are only marginal. The analytical investigation is supported by experiments performed on sensors integrated in a SOI-MEMS nanopositioner with low noise read out circuits, which leads to 0.04-nm/√Hz displacement resolution for both excitation modes

Frequency modulation technique for MEMS resistive sensing

Frequency modulation technique can be applied to microelectromechanical systems (MEMS) transducers that require some form of resistive sensing. For example, electrothermal sensing is being investigated as a viable means of measuring displacement in micromachined transducers. This paper proposes a highly sensitive readout circuit, which can convert 10 Ω change of resistance in a 400 Ω electrothermal sensor to more than 200 kHz frequency variation (350-550 KHz). The frequency variations are then converted to voltage values by means of a frequency demodulation. In addition, the proposed technique achieves high linearity from the voltage applied to the actuator to the voltage measured at the sensor's output, which can potentially eliminate the need for an additional linearization if the sensor is used in a feedback loop. The proposed approach leads to high sensitivity in the MEMS electrothermal sensing since the method is not affected by amplitude variations that could arise from the readout circuit

The effect of colchicine on alveolar bone loss in ligature-induced periodontitis

Abstract Colchicine is widely used in the treatment of several inflammatory diseases due to its anti-inflammatory effect, but effects on bone metabolism are unclear. The aim of this study was to evaluate the effects of systemically-administered colchicine on healthy periodontium and experimentally-induced periodontitis. In total, 42 male Wistar rats were included in this study. A non-ligated group constituting the negative control group (Control, C, n = 6) and a ligature-only group forming the positive control group (LO, n = 12) were created separately. Twelve rats were treated with 0.4 mg/kg colchicine and another 12 with 1 mg/kg colchicine. In the colchicine-administered groups, right mandibles constituted the ligated groups (1 mgC-L or 0.4 mgC-L) and left mandibles formed the corresponding non-ligated controls (1mgC or 0.4mgC). Silk ligatures were placed at the gingival margin of the lower first molars. The animals were euthanized at different time-points of healing (11 or 30 days). Alveolar bone loss was clinically measured and TRAP+ osteoclasts, osteoblastic activity, and MMP-1 expression were examined histologically. There was no increase in alveolar bone loss with either colchicine dose in healthy periodontium (p > 0.05) and the highest level of alveolar bone loss, TRAP+ osteoclast number, and MMP-1 expression were measured in the LO group (p < 0.05). The 0.4 mgC-L group showed less alveolar bone loss at 11 days (p < 0.05), but greater loss at 30 days. The 1 mgC-L group showed higher osteoblast number than the other ligated groups (p < 0.05) at both time-points. In summary, colchicine did not increase alveolar bone loss in healthy periodontium and also may tend to reduce periodontitis progression. However, further extensive study is necessary to understand the mechanism of colchicine action on alveolar bone loss in periodontitis