Microelectrical Mechanical Systems in Surgery and Medicine

Salzberg, Arnold D.; Bloom, Matthew B.; Mourlas, Nicolas J; Krummel, Thomas M.

doi:10.1016/s1072-7515(01)01179-6

Cited by 11 publications

(2 citation statements)

References 19 publications

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“…Microelectricalmechanical systems (MEMS) have generated increasing interest in the past decade with the number of devices employed growing exponentially [1]. Micro-mechanical resonators constitute a large portion of MEMS devices and are making significant contributions to the fields of physical, chemical, and biological sensing [2,3].…”

Section: Introductionmentioning

confidence: 99%

Piezoresistive geometry for maximizing microcantilever array sensitivity

Fletcher

Gopinath

et al. 2008

2008 IEEE Sensors

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Our group has focused on the development of piezoresistive cantilevers for gas detection using a nonreactionbased method -viscous damping. This work represents a continuation of this effort by reporting on the development, fabrication and testing of a second generation device consisting of asymmetric piezoresistive cantilevers to maximize device sensitivity. The first mode of resonance, static & dynamic sensitivities, and Q-factors ranged from 40 kHz -63 kHz, 1-6 Ω/µm & 3-17 Ω/µm, and 1700 -4200, respectively, depending on piezoresistor geometry and beam length. The redesigned piezoresistive microcantilevers were 15 -200 times more sensitive than the best symmetric design previously reported by our group.

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Section: Introductionmentioning

confidence: 99%

Piezoresistive geometry for maximizing microcantilever array sensitivity

Fletcher

Gopinath

et al. 2008

2008 IEEE Sensors

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“…Micro-electrical-mechanical systems (MEMS) have been generating increasing research interest in the past two decades, which has resulted in an exponential growth of commercially-available MEMS devices (Salzberg, 2002). MEMS and Nano-electricalmechanical systems (NEMS) have found widespread applications in the fields of sensors, actuators, and other microsystems Blencowe, 2005;Craighead, 2000;Roukes, 2001).…”

Section: Introductionmentioning

confidence: 99%

Alternative piezoresistor designs for maximizing cantilever sensitivity.

Fletcher¹

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APPROVAL PAGEiii Over the last 15 years, researchers have explored the use of piezoresistive microcantilevers/resonators as gas sensors because of their relative ease in fabrication, low production cost, and their ability to detect changes in mass or surface stress with fairly good sensitivity. However, existing microcantilever designs rely on irreversible chemical reactions for detection and researchers have been unable to optimize symmetric geometries for increased sensitivity. Previous work by our group showed the capability of T-shaped piezoresistive cantilevers to detect gas composition using a nonreaction-based method -viscous damping. However, this geometry yielded only small changes in resistance. Recently, computational studies performed by our group indicated that optimizing the geometry of the base piezoresistor increases device sensitivity up to 700 times. Thus, the focus of this work is to improve the sensitivity of nonreaction-based piezoresistive microcantilevers by incorporating asymmetric piezoresistive sensing elements in a new array design.A three-mask fabrication process was performed using a 4" silicon-on-insulator wafer. Gold bond pads and leads were patterned using two optical lithography masks, gold sputtering, and acetone lift-off techniques. The cantilevers were patterned with v electron-beam lithography and a dry etch masking layer was then deposited via electronbeam evaporation of iron. Subsequently, the silicon device layer was deep reactive ion etched (DRIE) to create the vertical sidewalls and the sacrificial silicon dioxide layer was removed with a buffered oxide etch, completely releasing the cantilever structures.Finally, the device was cleaned and dried with critical point drying to prevent stiction of the devices to the substrate. For the resonance experiments, the cantilevers were driven electrostatically by applying an AC bias, 10 V pp , to the gate electrode. A DC bias of 10 V was placed across the piezoresistor in series with a 14 kΩ resistor. The drive frequency (0 -80 kHz) was swept until the cantilever resonated at its natural frequency, which occurred when the output of the lock-in amplifier reached its maximum. These devices have been actuated to resonance under vacuum and their resonant frequencies and Qfactors measured.The first mode of resonance for the asymmetric cantilevers was found to range between 40 kHz and 63 kHz, depending on the piezoresistor geometry and length of the cantilever beam. The redesigned piezoresistive microcantilevers tested yielded static and dynamic sensitivities ranging from 1-6 Ω/µm and 2-17 Ω/µm displacement, respectively, which are 40 -730 times more sensitive than the best symmetric design previously reported by our group. Furthermore, the Q-factors ranged between 1700 and 4200, typical values for MEMS microcantilevers.vi = maximum resistance at deflection Δx R 1 = resistance at resonance RF = radio frequency Rpm = rotations per minute sccm = standard cubic centimeters per minute SEM = scanning electron microscope SOI = silicon-on-ins...

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Comprehensive Nanorobotic Control of Human Morbidity and Aging

Freitas

2010

The Future of Aging

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Microelectrical Mechanical Systems in Surgery and Medicine

Cited by 11 publications

References 19 publications

Piezoresistive geometry for maximizing microcantilever array sensitivity

Piezoresistive geometry for maximizing microcantilever array sensitivity

Alternative piezoresistor designs for maximizing cantilever sensitivity.

Comprehensive Nanorobotic Control of Human Morbidity and Aging

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