Person:

Brand, Oliver

Permanent Link

https://hdl.handle.net/1853/71115

Associated Organization(s)

Organizational Unit

School of Electrical and Computer Engineering

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Publication Search Results

Now showing 1 - 10 of 10

Effect of Stress Due to Plastic Package Moisture Absorption in Hall Sensors

(Georgia Institute of Technology, 2009-06) Cesaretti, Juan Manuel ; Taylor, W. P. ; Monreal, G. ; Brand, Oliver

Commercial magnetic sensors based on the Hall effect are usually encapsulated in non-hermetic plastic packages. These plastic packages are known to swell in high humidity conditions due to moisture absorption. This swelling will modify the stress seen by the Hall sensor, causing the Hall sensitivity to be altered due to the piezo-Hall effect. The sensitivity drift, which is random in nature, may become the long-term stability limiting factor in high-end sensors. The objective of this work is to characterize in depth the sensitivity change due to moisture absorption and to review and implement two Hall sensitivity compensation methods.
Cancellation of environmental effects in resonant mass sensors based on resonance mode and effective mass

(Georgia Institute of Technology, 2009-06) Naeli, Kianoush ; Brand, Oliver

novel technique is developed to cancel the effect of environmental parameters, e.g., temperature and humidity, in resonant mass sensing. Utilizing a single resonator, the environmental cancellation is achieved by monitoring a pair of resonant overtones and the effective sensed mass in those overtones. As an eminent advantage, especially compared to dual-mode temperature compensation techniques, the presented technique eliminates any need for previously measured look-up tables or fitting the measurement data. We show that a resonant cantilever beam is an appropriate platform for applying this technique, and derive an analytical expression to relate the actual and effective sensed masses on a cantilever beam. Thereby, it is shown that in applying the presented technique successfully, the effective sensed masses must not be the same in the investigated pair of resonance overtones. To prove the feasibility of the proposed technique, flexural resonance frequencies of a silicon cantilever are measured before and after loading with a strip of photoresist. Applying the presented technique shows significant reductions in influence of environmental parameters, with the temperature and humidity coefficients of frequency being improved from −19.5 to 0.2 ppm °C⁻¹ and from 0.7 to −0.03 ppm %RH⁻¹, respectively.
Chemical microsystem based on vertical integration of sensor array and CMOS circuit

(Georgia Institute of Technology, 2009-04-30) Brand, Oliver ; Mizaikoff, Boris
Dimensional considerations in achieving large quality factors for resonant silicon cantilevers in air

(Georgia Institute of Technology, 2009-01) Naeli, Kianoush ; Brand, Oliver

This work aims to provide guidelines for designing rectangular silicon cantilever beams to achieve maximum quality factors for the fundamental flexural resonance at atmospheric pressure. The methodology of this work is based on experimental data acquisition of resonance characteristics of silicon cantilevers, combined with modification of analytical damping models to match the captured data. For this purpose, rectangular silicon cantilever beams with thicknesses of 5, 7, 8, 11, and 17 µ m and lengths and widths ranging from 70 to 1050 µ m and 80 to 230 µ m, respectively, have been fabricated and tested. Combining the three dominant damping mechanisms, i.e., the air damping, support loss, and thermoelastic damping, the variation in the measured Q-factors with the cantilever geometrical dimensions is predicted. Also to better describe the experimental data, modified models for air damping have been developed. These modified models can predict the optimum length and thickness of a resonant cantilever to achieve the maximum quality factor at the fundamental flexural resonance mode in air.
Nanojets – Formation, characterization and applications

(Georgia Institute of Technology, 2008-12-21) Landman, Uzi ; Glezer, Ari ; Allen, Mark G. ; King, William ; Brand, Oliver ; Luedtke, William ; Gao, Jianping
Silicon-Based Resonant Microsensors

(Georgia Institute of Technology, 2008-10-21) Brand, Oliver

The presentation gives an introduction to resonant microsensors providing a frequency output signal. These sensors generally benefit from an excellent frequency resolution, which is ideally limited only by the length of the counting period and the short-term frequency stability of the microstructure's resonance frequency. Device-level and system-level approaches to generate a measurand-dependent frequency signal are discussed and concepts to improve Q-factor, short-term frequency stability and ultimately sensor resolution are highlighted. Furthermore, the presentation discusses frequency drift challenges and introduces methods for drift compensation. The above concepts and approaches are illustrated using two resonant microsensor examples: (i) a mass-sensitive microsensor platform for gas- and liquid-phase chemical sensing based on disktype silicon microstructures and (ii) a cantilever-based resonant magnetic microsensor with a resolution suitable for Earth field applications.
Mass-Sensitive Biochemical Microsensors

(Georgia Institute of Technology, 2008-10-10) Brand, Oliver

A resonant microsensor platform based on disk-type microstructures vibrating in an in-plane resonance mode for chemical and biochemical sensing applications in gas and liquid environments is presented. Based on measured short-term frequency stabilities of 1.1 10^-8 in air and 2.3 10^-6 in water, mass detection limits in the low femtogram and sub-picogram, respectively, are achieved. In a biosensing application, biomolecules are immobilized on the resonator surface. Upon selective binding of analyte molecules (e.g. via antibody-antigen binding), the mass of the resonator is increased, resulting in a measurable decrease of its resonance frequency. The feasibility of liquid-phase biosensing using the disk resonators is demonstrated experimentally by detecting anti-beta-galactosidase antibody using covalently immobilized beta-galactosidase enzyme.
Temperature compensation method for resonant microsensors based on a controlled stiffness modulation

(Georgia Institute of Technology, 2008-07-01) Seo, Jae Hyeong ; Demirci, Kemal Safak ; Byun, Albert ; Truax, Stuart ; Brand, Oliver

A strategy to compensate for frequency drifts caused by temperature changes in resonant microstructures is presented. The proposed compensation method is based on a controlled stiffness modulation of the resonator by an additional feedback loop to extract the frequency changes caused by temperature changes. The feasibility of the suggested method is verified experimentally by compensating for temperature-induced frequency fluctuations of a micromachined resonator. The developed compensation scheme requires only one additional feedback loop and is applicable to any resonant microstructure featuring excitation and detection elements.
Microsensor integration into systems-on-chip

(Georgia Institute of Technology, 2006-06) Brand, Oliver

Sensing systems-on-chip (SSoCs), combining micromachined sensing structures and microelectronic building blocks on a single chip, are reviewed. While single-chip pressure and inertial sensing systems have been commercially available for more than a decade, the recent expansion of SsoC into new application areas, ranging from chemical and biochemical sensing to atomic force microscopy, demonstrates the full potential of this microsensor integration approach. Available fabrication processes for integrated sensing systems are summarized, categorizing them into pre-, intra-, and post-CMOS approaches depending on the way the micromachining module is merged with the integrated circuit (IC) technology. Examples of SSoCs are presented to highlight the different integration options, ranging from cointegration of micromachined sensors with purely analog signal chains to microsystems with cointegrated digital signal processors and digital interfaces.
Microjet cooling devices for thermal management of electronics

(Georgia Institute of Technology, 2003-06) Kercher, Dan S. ; Lee, Jeong-Bong ; Brand, Oliver ; Allen, Mark G. ; Glezer, Ari

This research is an effort to demonstrate the applicability of miniaturized synthetic jet (microjet) technology to the area of thermal management of microelectronic devices. Synthetic jets are jets which are formed from entrainment and expulsion of the fluid in which they are embedded. Design issues of microjet cooling devices are discussed along with characterization of excitation elements and the turbulent synthetic jets produced thereby. Geometrical parameters of the microjet cooling devices were empirically optimized with regards to cooling performance. The cooling performance of the optimized microjets was compared with previous theoretical and empirical studies of conventional jet impingement. The cooling performance of the microjet devices has been investigated in an open environment as well as in a vented and closed case environment. In such experiments, the synthetic jet impinges normal to the surface of a packaged thermal test die, comprising a heater and a diode-based temperature sensor. This test assembly allows simultaneous heat generation and temperature sensing of the package, thereby enabling assessment of the performance of the synthetic jet. Using microjet cooling devices, a thermal resistance of 30.1 °C/W has been achieved (when unforced cooling is used, thermal resistance is 59.6 °C/W) when the test chip is located at 15 mm spacing from the jet exit plane. In order to more directly compare and scale the cooling results, a preliminary study on heat transfer correlations of the microjet cooling device has been performed. Finally, a comparison of the performance of the microjet cooler with standard cooling fans is given.