Howard Clyde Wikle

The design, fabrication and evaluation of a MEMS PZT cantilever with an integrated Si proof mass for vibration energy harvesting

A microelectromechanical system (MEMS) piezoelectric energy harvesting device, a unimorph PZT cantilever with an integrated Si proof mass, was designed for low vibration frequency and high vibration amplitude environment. Pt/PZT/Pt/Ti/SiO2 multilayered films were deposited on a Si substrate and then the cantilever was patterned and released by inductively coupled plasma reactive ion etching. The fabricated device, with a beam dimension of about 4.800 mm × 0.400 mm × 0.036 mm and an integrated Si mass dimension of about 1.360 mm × 0.940 mm × 0.456 mm produced 160 mVpk, 2.15 μW or 3272 μW cm−3 with an optimal resistive load of 6 kΩ from 2g (g = 9.81 m s−2) acceleration at its resonant frequency of 461.15 Hz. This device was compared with other demonstrated MEMS power generators.

Sequential detection of Salmonella typhimurium and Bacillus anthracis spores using magnetoelastic biosensors.

Multiple phage-based magnetoelastic (ME) biosensors were simultaneously monitored for the detection of different biological pathogens that were sequentially introduced to the measurement system. The biosensors were formed by immobilizing phage and 1mg/ml BSA (blocking agent) onto the magnetoelastic resonators surface. The detection system included a reference sensor as a control, an E2 phage-coated sensor specific to S. typhimurium, and a JRB7 phage-coated sensor specific to B. anthracis spores. The sensors were free standing during the test, being held in place by a magnetic field. Upon sequential exposure to single pathogenic solutions, only the biosensor coated with the corresponding specific phage responded. As the cells/spores were captured by the specific phage-coated sensor, the mass of the sensor increased, resulting in a decrease in the sensors resonance frequency. Additionally, non-specific binding was effectively eliminated by BSA blocking and was verified by the reference sensor, which showed no frequency shift. Scanning electron microscopy was used to visually verify the interaction of each biosensor with its target analyte. The results demonstrate that multiple magnetoelastic sensors may be simultaneously monitored to detect specifically targeted pathogenic species with good selectivity. This research is the first stage of an ongoing effort to simultaneously detect the presence of multiple pathogens in a complex analyte.

Infrared sensing techniques for penetration depth control of the submerged arc welding process

Abstract This paper presents an investigation into the development of a rugged, low cost, point infrared sensor to monitor and control the welding process in harsh fabrication environments. Perturbations occurring during the welding process create changes in the temperature distributions of the plates being welded. By monitoring the changes in these temperature distributions, action can be implemented to eliminate or mitigate defects that may form due to the process perturbations. Heat transfer analyses were performed to study the effects of disturbances to the welding process on the surface temperature of the plates being welded. A point sensor was used to monitor changes in the plate surface temperatures occurring during the welding process. The objective was to demonstrate that weld bead penetration depth could be monitored and controlled during both gas tungsten arc welding (GTAW) and submerged arc welding (SAW) processes to eliminate or reduce weld defects. The infrared energy exchange between a defined area on the topside plate surface and the sensor was monitored during the welding process and compared to predictions of the heat transfer analyses. Changes in the plate geometry (gap size, plate thickness, and cooling sinks representing stiffeners) were introduced during the experiments to perturb the welding process. Using the infrared sensor, constant depth of penetration was maintained in the presence of these perturbations by feedback control of the welding process parameters.

Infrared Sensing for On-Line Weld Geometry Monitoring and Control

This paper describes a method for on-line weld geometry monitoring and control using a single front-side infrared sensor. Variations in plate thickness, shielding gas composition and minor element content are known to cause weld geometry changes. These changes in the weld geometry can be distinctly detected from an analysis of temperature gradients computed from infrared data. Deviations in temperature gradients were used to control the bead width and depth of penetration during the welding process. The analytical techniques described in this paper have been used to control gas tungsten arc and gas metal arc welding processes.

Low-cost infrared sensing system for monitoring the welding process in the presence of plate inclination angle

Abstract A point infrared sensing system was developed for weld penetration control in the presence of plate inclination angle change for the tractor-based submerged arc welding process. Changes in the temperature distribution surrounding the weld pool were measured using a thermopile infrared detector and used to control weld penetration through changes of wire feed speed (welding current). Plate inclination angle on weld bead parameters was investigated. IR sensor signal variation was examined in the presence of plate inclination angles. Process control in the presence of plate inclination angle can be applied by using a point infrared sensor monitor the temperature distribution at a point adjacent to the weld pool and adjusting welding current.

A surface-scanning coil detector for real-time, in-situ detection of bacteria on fresh food surfaces

Proof-in-principle of a new surface-scanning coil detector has been demonstrated. This new coil detector excites and measures the resonant frequency of free-standing magnetoelastic (ME) biosensors that may now be placed outside the coil boundaries. With this coil design, the biosensors are no longer required to be placed inside the coil before frequency measurement. Hence, this new coil enables bacterial pathogens to be detected on fresh food surfaces in real-time and in-situ. The new coil measurement technique was demonstrated using an E2 phage-coated ME biosensor to detect Salmonella typhimurium on tomato surfaces. Real-time, in-situ detection was achieved with a limit of detection (LOD) statistically determined to be lower than 1.5×10(3) CFU/mm(2) with a confidence level of difference higher than 95% (p<0.05).

A sensing system for weld process control

Abstract The development of a point infrared sensor was undertaken in an effort to reduce the size and cost of an infrared sensing system for welding process monitoring and control. Numerical modeling, sensor development and welding process control were integral phases in the course of this effort. A numerical model of the heat transfer during autogenous arc welding was used to estimate the net heat exchange between a weldment surface and a point infrared detector as a function of sensor position about the welding arc. The gas tungsten arc welding process was monitored with a point infrared sensor. Feedback control of the infrared exchange between the weldment and the point infrared sensor was accomplished by adjusting the welding current. Welding process control was demonstrated on both constant thickness plates and plates with a step change in thickness.

Design of a surface-scanning coil detector for direct bacteria detection on food surfaces using a magnetoelastic biosensor

The real-time, in-situ bacteria detection on food surfaces was achieved by using a magnetoelastic biosensor combined with a surface-scanning coil detector. This paper focuses on the coil design for signal optimization. The coil was used to excite the sensors vibration and detect its resonant frequency signal. The vibrating sensor creates a magnetic flux change around the coil, which then produces a mutual inductance. In order to enhance the signal amplitude, a theory of the sensors mutual inductance with the measurement coil is proposed. Both theoretical calculations and experimental data showed that the working length of the coil has a significant effect on the signal amplitude. For a 1 mm-long sensor, a coil with a working length of 1.3 mm showed the best signal amplitude. The real-time detection of Salmonella bacteria on a fresh food surface was demonstrated using this new technology.

Surface-scanning coil detectors for magnetoelastic biosensors: A comparison of planar-spiral and solenoid coils

This research introduces a planar spiral coil as a surface-scanning detector for magnetoelastic biosensors, which have been used to detect bacteria directly on food surfaces. The planar coil was compared with the previously investigated solenoid coil, in terms of the magnetic flux change, signal amplitude, and detection distance. Both theoretical calculations and experimental results demonstrated that the planar coil detector yields a dramatically improved signal amplitude and greater detection distance. In addition, simultaneous measurement of multiple biosensors on surfaces was demonstrated. This planar coil is therefore anticipated to facilitate the detection of bacteria on surfaces using magnetoelastic biosensors.

Real-time welding process control using infrared sensing

The thermal distribution changes associated with gas tungsten are welding process were studied to identify and correct for weld joint offsets for butt joints. These changes were experimentally measured using infrared thermography. In the weld offset conditions the slope of the temperature distributions were found to be altered dramatically. Not only did offset produce asymmetric temperature distributions but a steep increase in gradients was also observed. These changes were then used to detect and correct initial errors in the position of the torch during the welding of straight and curved contours of perfectly fitted butt joints and joints with gap.