Lead-Free LiNbO3 Thick Film MEMS Kinetic Cantilever Beam Sensor/Energy Harvester

In this paper, we present integrated lead-free energy converters based on a suitable MEMS fabrication process with an embedded layer of LiNbO3. The fabrication technology has been developed to realize micromachined self-generating transducers to convert kinetic energy into electrical energy. The process proposed presents several interesting features with the possibility of realizing smaller scale devices, integrated systems, miniaturized mechanical and electromechanical sensors, and transducers with an active layer used as the main conversion element. When the system is fabricated in the typical cantilever configuration, it can produce a peak-to-peak open-circuit output voltage of 0.208 V, due to flexural deformation, and a power density of 1.9 nW·mm−3·g−2 at resonance, with values of acceleration and frequency of 2.4 g and 4096 Hz, respectively. The electromechanical transduction capability is exploited for sensing and power generation/energy harvesting applications. Theoretical considerations, simulations, numerical analyses, and experiments are presented to show the proposed LiNbO3-based MEMS fabrication process suitability. This paper presents substantial contributions to the state-of-the-art, proposing an integral solution regarding the design, modelling, simulation, realization, and characterization of a novel transducer.

GRAPHICAL METHOD FOR DETERMINATION OF MQ-SERIES GAS SENSOR CIRCUIT PARAMETERS FOR A STAND-ALONE GAS ALARM SYSTEM

Background: MQ-series gas sensors belong to the metal oxide semiconductor (MOS) family of sensors that can sense the presence of many gases. These sensors find their application in gas alarm systems as key components. While necessary sensor circuit output voltage value for alarm point in a stand-alone gas alarm system is desirable, but what exact combination of the sensor circuit parameters is required? Hitherto, the determination of these circuit parameters has not been given much attention in the research community. Aim: the purpose of this work is to explore a structured graphical approach of determination of MQ series gas sensor circuit parameters for a stand-alone gas alarm system that yields desired sensor circuit output voltage value for the alarm point; the main objective of the study was to develop mathematical model equations that relate the: (i) sensor resistance (RS) with the gas concentration (x) and the sensor resistance at standard calibration concentration of the sensor base gas in the clean air (Ro) and (ii) sensor circuit output voltage (VRL), load resistance (RL) and sensor resistance (RS). It is expected from the model equations developed that graphical correlations of the sensor circuits parameters will be generated. Using these graphs for a particular case of an MQ-4 gas sensor under the influence of LPG, the parameters that yield desired sensor circuit output voltage of 2V for 1000 ppm of LPG alarm point will be determined. Methods: Model equations were developed for the sensor dynamics, and based on these model equations, graphs for the determination of required sensor parameters were plotted for a case of MQ-4 gas sensor response to LPG. Results and Discussion: The results yielded optimal values for R_O,R_S and R_L of 20 kΩ, 30 kΩ and 20 kΩ respectively, for alarm settings of 1000 ppm and a desired sensor circuit output voltage of 2 V. Based on determined parameters, the calibration equation for determination of best concentration value for a given value of emulated LPG concentration was developed. Using the method proposed in this study makes the process of determining the MQ-series gas sensor circuit parameters less cumbersome as their value can easily be obtained from the resulting graphs. Conclusions: a structured graphical approach for determination of MQ-series gas sensor circuit parameters for alarm points in a stand-alone gas alarm system showed that using MQ-4 gas sensor and LPG as the target gas, and for a sensor circuit output voltage of 2 V for alarm point at 1000 ppm of LPG, the corresponding value of R_O, R_S and R_L obtained were 20 kΩ, 30 kΩ, and 20 kΩ respectively. Hence, a structured graphical approach is suitable for determining MQ series gas sensor circuit parameters for a stand-alone gas alarm system under the influence of its associated gases.

The Improvement of Performance through Minimizing Scallop Size in MEMS Based Micro Wind Turbine

In this paper we report on the improvement of performance by minimizing scallop size through deep reactive-ion etching (DRIE) of rotors in micro-wind turbines based on micro-electro-mechanical systems (MEMS) technology. The surface profile of an MEMS rotor can be controlled by modifying the scallop size of the DRIE surface through changing the process recipe. The fabrication of a planar disk-type MEMS rotor through the MEMS fabrication process was carried out, and for the comparison of the improvements in the performance of each rotor, RPM testing and open circuit output voltage experiments of stators and permanent magnets were performed. We found that the smooth etching profile with a minimized scallop size formed using DRIE results in improved rotation properties in MEMS-based wind turbine rotors.

A Pendulum-Like Low Frequency Electromagnetic Vibration Energy Harvester Based on Polymer Spring and Coils

This paper presents a low-frequency electromagnetic vibrational energy harvester (EVEH) with two degrees of freedom and two resonant modes. The proposed EVEH is based on a disc magnet suspended in a pendulum fashion by a polymeric spring between two sets of polymer coil stacks. The fabricated EVEH is capable of harvesting vibration energy on two directions with an extended bandwidth. With a sinusoidal acceleration of ±1 g on Z direction, a peak-to-peak closed-circuit output voltage of 0.51 V (open-circuit voltage: 1 V), and an output power of 35.1 μW are achieved at the resonant frequency of 16 Hz. With a sinusoidal acceleration of ±1.5 g on X direction, a peak-to-peak output voltage of 0.14 V and power of 2.56 μW are achieved, at the resonant frequency of 20 Hz.

RECIPROCALLY INHIBITORY CIRCUITS OPERATING WITH DISTINCT MECHANISMS ARE DIFFERENTLY ROBUST TO PERTURBATION AND MODULATION

What features are important for circuit robustness? Reciprocal inhibition is a building block in many circuits. We used dynamic clamp to create reciprocally inhibitory circuits from GM neurons of the crab stomatogastric ganglion by injecting artificial synaptic and hyperpolarization-activated inward (H) currents. In "release", the active neuron controls the off/on transitions. In "escape", the inhibited neuron controls the transitions. We characterized the robustness of escape and release circuits to alterations in circuit parameters, temperature, and neuromodulation. Escape circuits rely on tight correlations between synaptic and H conductances to generate bursting but are resilient to temperature increase. Release circuits are robust to variations in synaptic and H conductances but fragile to temperature increase. The modulatory current (IMI) restores oscillations in release circuits but has little effect in escape. Thus, the same perturbation can have dramatically different effects depending on the circuits' mechanism of operation that may not be observable from circuit output.

Spice Modeling of LED Filament and its Simulation in Switch Drive Circuit

When designing the LED filament lamp device and driving circuit at the beginning, software simulation is an indispensable step. It is necessary to verify whether the circuit output results are consistent with the requirements through simulation. In this paper, first measure the volt-ampere characteristics of the actual 1W LED filament strip, and applied the six-segment linear approximation model method for Spice modeling. The simulated volt-ampere characteristics of the 1W model were consistent with the measured volt-ampere characteristics of the 1W LED filament strip. Then use the driver chip HV9910B to design the LED filament lamp switch constant current drive circuit. Combined with the piecewise linear equivalent method, 3W, 4W, 5W LED filament lamp loads are modeled, the detailed design process of the entire circuit is analyzed, and the output voltage, current, inductance output current, MOS output voltage and other parameters of the whole circuit are simulated and verified. The results show that the output voltages are 71V, 142V, 71V, and the output currents are 30.4mA, 20.7mA, 51.1mA respectively under the circuit topology of 3W, 4W, and 5W LED filament lamp. When the inductor current works in CCM mode, the duty cycle of MOS output voltage meets the requirements, and the circuit output results are consistent with the design requirements.

Robust and Attack Resilient Logic Locking with a High Application-Level Impact

Logic locking is a hardware security technique aimed at protecting intellectual property against security threats in the IC supply chain, especially those posed by untrusted fabrication facilities. Such techniques incorporate additional locking circuitry within an integrated circuit (IC) that induces incorrect digital functionality when an incorrect verification key is provided by a user. The amount of error induced by an incorrect key is known as the effectiveness of the locking technique. A family of attacks known as “SAT attacks” provide a strong mathematical formulation to find the correct key of locked circuits. To achieve high SAT resilience (i.e., complexity of SAT attacks), many conventional logic locking schemes fail to inject sufficient error into the circuit when the key is incorrect. For example, in the case of SARLock and Anti-SAT, there are usually very few (or only one) input minterms that cause any error at the circuit output. The state-of-the-art s tripped functionality logic locking (SFLL) technique provides a wide spectrum of configurations that introduced a tradeoff between SAT resilience and effectiveness. In this work, we prove that such a tradeoff is universal among all logic locking techniques. To attain high effectiveness of locking without compromising SAT resilience, we propose a novel logic locking scheme, called Strong Anti-SAT (SAS). In addition to SAT attacks, removal-based attacks are another popular kind of attack formulation against logic locking where the attacker tries to identify and remove the locking structure. Based on SAS, we also propose Robust SAS (RSAS) that is resilient to removal attacks and maintains the same SAT resilience and effectiveness as SAS. SAS and RSAS have the following significant improvements over existing techniques. (1) We prove that the SAT resilience of SAS and RSAS against SAT attack is not compromised by increase in effectiveness . (2) In contrast to prior work that focused solely on the circuit-level locking impact, we integrate SAS-locked modules into an 80386 processor and show that SAS has a high application-level impact. (3) Our experiments show that SAS and RSAS exhibit better SAT resilience than SFLL and their effectiveness is similar to SFLL.

Role of neuronal positioning in jaw motor circuit function in zebrafish

Development of the vertebrate nervous system involves substantial cell migration, where immature neurons move to specific locations to generate functional circuits. Precise neuronal migration and positioning are essential for proper brain architecture and function. Abnormal neuronal migration can contribute to neurological disorders such as lissencephaly, autism and schizophrenia. However, the consequences of abnormal neuronal migration for circuit organization and functional output are poorly understood. To provide some insight, I used the facial branchiomotor (FBM) neurons in zebrafish as a model system to analyze the effects of aberrant neuronal migration on circuit function. The FBM neurons are a subset of the branchiomotor neurons, which are generated in the vertebrate hindbrain and innervate facial and jaw muscles. During development in zebrafish and mice, FBM neurons migrate caudally from rhombomere 4 (r4) to r6 to form the facial motor nucleus and innervate jaw and gill muscles (in fish). In order to examine the consequences of aberrant neuronal migration, one must first characterize the normal functional output of the FBM circuit that drives jaw movements. In collaboration with colleagues in the MU Department of Computer Science, we developed an automated image analysis system to extract motion features from video recordings of jaw movement, enabling rapid and accurate high-throughput analysis. We used this software to examine the emergence of jaw movement in zebrafish larvae between 3-9 days post fertilization (dpf). While gape, the displacement of the lower jaw to form the mouth opening, was minimal at 3 dpf, gape frequency increased sharply by 5 dpf, and stabilized by 7 dpf. A detailed analysis of branchiomotor axons and neuromuscular junctions (NMJs) on jaw muscles suggest that this "maturation" of branchiomotor circuit output may be driven by changes in presynaptic structures at the jaw NMJs. To evaluate the consequences of defective neuronal migration on circuit output, I examined whether jaw movement was affected in the zebrafish off-limits (olt) mutant in which FBM neurons fail to migrate out of r4. In olt mutants, the increase in gape frequency occurred normally between 3-5 dpf. However, the average gape frequency was [approximately] 50 [percent] lower than wildtype siblings from 5-9 dpf while gape amplitude was unaffected. Given the jaw movement defect in olt mutants, I evaluated food intake, an independent measure of jaw movement and another functional output of the branchiomotor circuit. Olt mutants ate poorly compared to their wildtype siblings, consistent with their reduced jaw movement. I then tested several potential mechanisms that could generate the functional deficits in olt mutants. While fzd3a, the gene inactivated in olt mutants, is ubiquitously expressed in neural and non-neural tissues, jaw cartilage and muscle developed normally in olt mutants, and muscle function also appeared to be unaffected. Although FBM neurons were mispositioned in olt mutants, axon pathfinding to jaw muscles were unaffected. Moreover, neuromuscular junctions established by FBM neurons on jaw muscles were similar between wildtype siblings and olt mutants. Interestingly, FBM axons innervating the interhyoideus jaw muscle were frequently defasciculated in olt mutants. Furthermore, GCaMP imaging revealed that mutant FBM neurons were less active than their wildtype counterparts. These data suggest that aberrant positioning of FBM neurons in olt mutants results in subtle defects in fasciculation and neuronal activity, potentially generating defective functional outputs. In the future, we will examine modulatory inputs from other brain regions to the branchiomotor neurons and examine their roles in impacting circuit output in olt mutants.