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Jong-uk Bu - One of the best experts on this subject based on the ideXlab platform.
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pzt cantilever array integrated with Piezoresistor sensor for high speed parallel operation of afm
International Conference on Micro Electro Mechanical Systems, 2003Co-Authors: J. W. Hong, Jong-uk BuAbstract:In this research, the self-actuating high quality PZT cantilever with a Piezoresistor was fabricated, and characterized for high speed AFM. The parasitic parameters inducing the electrical coupling between sensor and PZT actuator, was studied using simple equivalent circuit model of AFM cantilever. As a result of simulation, a new design was proposed to minimize the coupling capacitance between sensor and actuator by modifying the previous structure of cantilever described in [Appl. Phys. Lett. 72 (1998) 2340]. The fabricated PZT cantilever provided high tip displacement of 0.55 μm/V, has low leakage current, and enabled low voltage operation of AFM system. The optimized design at self-actuating PZT cantilever with a Piezoresistor shows five times lower coupling voltage than the current cantilever structure shown in [Appl. Phys. Lett. 72 (1998) 2340]. The measured resonant frequency was 73 kHz which was 100 times higher than that of conventional piezotube scanner. The piezotube scanner shows creep phenomena at scan speed of 180 μm/s scan speed, but the fabricated self-actuating PZT cantilever has a good scanned image even at I mm/s. Moreover, an array of 25 PZT cantilevers with Piezoresistor that are spaced by 100 μm for parallel operation, was fabricated successfully.
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Piezoelectric PZT Cantilever Array Integrated with Piezoresistor for High Speed Operation and Calibration of Atomic Force Microscopy
Journal of Semiconductor Technology and Science, 2002Co-Authors: Jong-uk Bu, J. W. HongAbstract:Two kinds of PZT cantilevers integrated with a Piezoresistor have been newly designed, fabricated, and characterized for high speed AFM. In first cantilever, a Piezoresistor is used to sense atomic force acting on tip, while in second cantilever, a Piezoresistor is integrated to calibrate hysteresis and creep phenomena of the PZT cantilever. The fabricated PZT cantilevers provide high tip displacement of 0.55µm/V and high resonant frequency of 73 kHz. A new cantilever structure has been designed to prevent electrical coupling between sensor and PZT actuator and the proposed cantilever shows 5 times lower coupling voltage than that of the previous cantilever. The fabricated PZT cantilever shows a crisp scanned image at 1mm/sec, while the conventional piezo-tube scanner shows blurred image even at 180µm/sec. The non-linear properties of the PZT actuator are also well calibrated using the piezoresistive sensor for calibration.
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a self actuating pzt cantilever integrated with Piezoresistor sensor for afm with high speed parallel operation
Proceedings IEEE micro electro mechanical systems, 2002Co-Authors: Jong-uk BuAbstract:In this research, we studied the parasitic parameters inducing the electrical coupling between sensor and PZT actuator using simple equivalent circuit model of cantilever with Piezoresistor sensor and PZT actuator. A fully integrated self-actuating PZT cantilever with a Piezoresistor has been newly designed, fabricated, and characterized for high speed AFM. The fabricated PZT cantilevers provide 0.55μm/V of high tip displacement and about 5 times lower crosstalk than the previous cantilever structure. The measured resonant frequency was 73 kHz that is 100 times higher than conventional piezotube scanner. The piezotube scanner shows creep phenomena at approximately 180μm/sec of scan speed, but the fabricated self-actuating PZT cantilever has a good scanned image at 1mmsec.
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A self-actuating PZT cantilever integrated with Piezoresistor sensor for AFM with high speed parallel operation
Technical Digest. MEMS 2002 IEEE International Conference. Fifteenth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.02CH37, 2002Co-Authors: Jong-uk BuAbstract:In this research, we studied the parasitic parameters inducing the electrical coupling between a sensor and PZT actuator using a simple equivalent circuit model of the cantilever with a Piezoresistor sensor and PZT actuator. A fully integrated self-actuating PZT cantilever with a Piezoresistor has been newly designed, fabricated, and characterized for high speed AFM. The fabricated PZT cantilevers provide 0.55 /spl mu/m/V of high tip displacement and about 5 times lower crosstalk than the previous cantilever structure. The measured resonant frequency was 73 kHz, which is 100 times higher than a conventional piezotube scanner. The piezotube scanner shows creep phenomena at approximately 180 /spl mu/m/sec of scan speed, but the fabricated self-actuating PZT cantilever has a good scanned image at 1 mm/sec.
Anja Boisen - One of the best experts on this subject based on the ideXlab platform.
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Temperature effects in Au Piezoresistors integrated in SU-8 cantilever chips
Journal of Micromechanics and Microengineering, 2006Co-Authors: Alicia Johansson, Ole Hansen, Jan Harry Hales, Anja BoisenAbstract:We present a cantilever-based biosensor chip made for the detection of biochemical molecules. The device is fabricated entirely in the photosensitive polymer SU-8 except for integrated Piezoresistors made of Au. The integrated Piezoresistors are used to monitor the surface stress changes due to binding of biomolecules on the surface of the cantilever. Here we present the characterization of the chip with respect to temperature changes in the surrounding environment. Furthermore, self-heating of the Piezoresistors due to the applied voltage over the resistors is investigated including the temperature increase of the cantilever surfaces. The obtained results indicate that although low voltages of about 0.5–1 V are required to avoid self-heating of the cantilevers, surface stress changes below 1 mN m−1 can still be detected. The results are compared to previously presented results for Si-based cantilevers.
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Noise in piezoresistive atomic force microscopy
Nanotechnology, 1999Co-Authors: Ole Hansen, Anja BoisenAbstract:The noise performance of piezoresistive atomic force microscopy (AFM)\ndevices is investigated. The total deflection noise of a piezoresistive\nAFM device comprises vibrational noise from the cantilever, and Johnson\nand flicker noise from the Piezoresistor. The vibrational deflection\nnoise is found to have a minimum when the length of the Piezoresistor\nis IMG of the cantilever length. The minimum vibrational deflection\nnoise is IMGfor a free cantilever, whereas a supported cantilever\nhas a minimum vibrational noise of IMG, where K is the spring constant\nof the device. Taking self-heating of the device into account, it\nis shown that an optimum power level exists at which the total equivalent\ndisplacement noise of a device is minimized. This minimum deflection\nnoise is, for a fixed value of the spring constant, approximately\nproportional to the cantilever thickness, whereas it varies rather\nslowly with the length of the Piezoresistor.
Ravi A Sankar - One of the best experts on this subject based on the ideXlab platform.
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A Finite Element Method Based Approach of Modeling of a Piezoresistive Accelerometer by Incorporating Doping Profile of a Diffused Resistor
2018 IEEE SENSORS, 2018Co-Authors: K V Meena, Ribu Mathew, Ravi A SankarAbstract:Finite element analysis (FEA) is an efficient method to observe the behavior of a sensor and to optimize the design to achieve high performance. In the modeling of piezoresistive sensors, typical FEA techniques simplify the doping concentration as a constant profile throughout the junction depth of a Piezoresistor. This approximation overestimates or underestimates the performance of the modeled device from the actual fabricated device. In this paper, a two-step modeling of piezoresistive sensors by incorporating nonuniformly doped Piezoresistor is presented using TCAD TSUPREM4® and IntelliSuite® tools to achieve lower deviation between simulation and experimental results. The two-step modeling technique illustrates the method of choosing the number of slices and the slicing strategy to effectively model the uniform doping profile of a Piezoresistor. A quad-beam proof-mass aligned piezoresistive accelerometer is considered for the validation of the modeling method by comparing the simulated results with the fabrication results. From the results, it is observed that the proposed adaptive slicing method with more slices at the surface of the Piezoresistor provides the least deviation error of 5.43 %.
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performance comparison of a single element Piezoresistor with a half active wheatstone bridge for miniaturized pressure sensors
Measurement, 2017Co-Authors: K V Meena, Ribu Mathew, Jyothi Leelavathi, Ravi A SankarAbstract:Abstract In recent years, miniaturized piezoresistive pressure sensors have been extensively explored, especially for biomedical applications. Typically, the electromechanical transduction of a measurand into an equivalent electrical signal is accomplished by a fully active Wheatstone bridge (WSB). Even though, a fully active WSB has advantages in terms of improved sensitivity and noise cancellation, still it suffers from a major limitation in terms of area, especially for applications like cardiac catheters that demand ultra-miniaturized pressure sensors. Hence for miniaturized sensor design, half-active WSB or single element Piezoresistor is deployed by various researchers. In this paper, performance of a single element Piezoresistor (3TP-1) is compared with a half-active WSB configuration and other single element Piezoresistors such as four terminal Piezoresistor (4TP), multi-terminal Piezoresistor (MTP) and another three terminal Piezoresistor (3TP-2) for area constrained applications. Investigation of the 3TP-1 is carried out by using a finite element method (FEM) based numerical simulation tool IntelliSuite® (version 8.7). Simulation results show that compared to a half-active WSB, the 3TP-1 has 35% better performance in terms of output voltage. Furthermore, it is found that compared to other single element Piezoresistors, the 3TP-1 is more suited for realizing ultra-miniaturized pressure sensors both in terms of area and performance.
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design and optimization of a doubly clamped piezoresistive acceleration sensor with an integrated silicon nanowire Piezoresistor
Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems, 2017Co-Authors: S. Vetrivel, Ribu Mathew, Ravi A SankarAbstract:Piezoresistive acceleration sensors have found a wide range of applications for the last four decades. However, in recent times, high performance piezoresistive acceleration sensors with lower footprint are in demand, especially in the fields of consumer electronics and biomedical engineering. The design of such sensors remains a challenging task due to the competing requirements of high electrical sensitivity (∆R/R) and resonant frequency (f0) along with low device footprint. In this paper, we elaborate the design and optimization of a highly miniaturized doubly clamped acceleration sensor with an integrated silicon nanowire as a Piezoresistor. The diminutive size of the silicon nanowire helps in reducing the device foot print. The design is performed using two methods: (1) electrical approach and (2) mechanical approach. In the electrical approach, the conventional bulk silicon diffused Piezoresistors are replaced with a silicon nanowire without changing the dimensions of the original structure. It is shown that compared to the conventional design, a silicon nanowire based sensor exhibits 2.51 times better performance in terms of electrical sensitivity. One of the major constraints with miniaturized high performance acceleration sensors is reduced resonant frequency. Therefore, in the mechanical approach we have devised a geometrical optimization technique to miniaturize the sensor geometry by keeping its resonant frequency constant. Numerical simulations are performed to validate the proposed miniaturized sensor with an integrated silicon nanowire as the Piezoresistor. The sensor performance is evaluated with a new performance factor given as \({{\left( {{{\Delta R} \mathord{\left/ {\vphantom {{\Delta R} R}} \right. \kern-0pt} R}} \right)f_{0}^{2} } \mathord{\left/ {\vphantom {{\left( {{{\Delta R} \mathord{\left/ {\vphantom {{\Delta R} R}} \right. \kern-0pt} R}} \right)f_{0}^{2} } {Diesize}}} \right. \kern-0pt} {Diesize}}\), which takes into account the electrical sensitivity, the resonant frequency and the die size of the sensor. Results show that the proposed sensor design with an integrated silicon nanowire has 48.2 times better performance factor than a bulk Piezoresistor based conventional acceleration sensor.
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Design and simulation of a doubly clamped accelerometer with integrated silicon nanowires
2016 3rd International Conference on Emerging Electronics (ICEE), 2016Co-Authors: S. Vetrivel, Ribu Mathew, Ravi A SankarAbstract:Inertial MEMS piezoresistive acceleration sensors have found a wide range of applications in last four decades. This paper presents design and simulation of a doubly clamped acceleration sensor with integrated Piezoresistors. Prime objective of this work is to enhance the electrical sensitivity of the sensor. In this regard, silicon nanowire (SiNW) based Piezoresistors are deposited at the fixed end of the beams where maximum stress is experienced when the beam undergoes deformation. The complete device with integrated Piezoresistors is virtually fabricated using a finite element method (FEM) based computer aided design (CAD) tool IntelliSuite®. For analysis, SiNW Piezoresistors with two diiferent widths of 35 nm and 140 nm with a length and thickness of 2 μm and 40 nm respectively are considered. Results show that the device integrated with a 35 nm width Piezoresistor depicts 1.36 times and 2.51 times more sensitivity than the devices with 140 nm width SiNW and bulk Piezoresistors respectively.
Ole Hansen - One of the best experts on this subject based on the ideXlab platform.
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Temperature effects in Au Piezoresistors integrated in SU-8 cantilever chips
Journal of Micromechanics and Microengineering, 2006Co-Authors: Alicia Johansson, Ole Hansen, Jan Harry Hales, Anja BoisenAbstract:We present a cantilever-based biosensor chip made for the detection of biochemical molecules. The device is fabricated entirely in the photosensitive polymer SU-8 except for integrated Piezoresistors made of Au. The integrated Piezoresistors are used to monitor the surface stress changes due to binding of biomolecules on the surface of the cantilever. Here we present the characterization of the chip with respect to temperature changes in the surrounding environment. Furthermore, self-heating of the Piezoresistors due to the applied voltage over the resistors is investigated including the temperature increase of the cantilever surfaces. The obtained results indicate that although low voltages of about 0.5–1 V are required to avoid self-heating of the cantilevers, surface stress changes below 1 mN m−1 can still be detected. The results are compared to previously presented results for Si-based cantilevers.
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Noise in piezoresistive atomic force microscopy
Nanotechnology, 1999Co-Authors: Ole Hansen, Anja BoisenAbstract:The noise performance of piezoresistive atomic force microscopy (AFM)\ndevices is investigated. The total deflection noise of a piezoresistive\nAFM device comprises vibrational noise from the cantilever, and Johnson\nand flicker noise from the Piezoresistor. The vibrational deflection\nnoise is found to have a minimum when the length of the Piezoresistor\nis IMG of the cantilever length. The minimum vibrational deflection\nnoise is IMGfor a free cantilever, whereas a supported cantilever\nhas a minimum vibrational noise of IMG, where K is the spring constant\nof the device. Taking self-heating of the device into account, it\nis shown that an optimum power level exists at which the total equivalent\ndisplacement noise of a device is minimized. This minimum deflection\nnoise is, for a fixed value of the spring constant, approximately\nproportional to the cantilever thickness, whereas it varies rather\nslowly with the length of the Piezoresistor.
Ching-hsiang Cheng - One of the best experts on this subject based on the ideXlab platform.
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NEMS - Artificial hair cell sensors using liquid metal alloy as Piezoresistors
The 8th Annual IEEE International Conference on Nano Micro Engineered and Molecular Systems, 2013Co-Authors: Ching-hsiang ChengAbstract:In this paper, we present the design, fabrication process, and testing results of an artificial hair cell sensor made by liquid metal encapsulated in a polydimethylsiloxane (PDMS) substrate. Previously, a flexible force sensor was reported from our group, which can detect both normal and shear forces by using liquid metal alloy (Ga-In-Sn) as piezoresistive gauge material encapsulated in a PDMS substrate. Based on this method, we propose an artificial hair cell sensor which can detect two-axis tactile force with a standing artificial hair shaft. Since the liquid-metal Piezoresistors deform with the elastomeric substrate, normal and shear force can be detected with resistance changes of the Piezoresistors. Each force sensor comprises a pair of symmetric Piezoresistors, which is screen-printed on a suspended PDMS membrane with opposite direction to be sensitive to shear forces. The testing results demonstrate the sensitivity of the force sensor in two-axis directions.
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Artificial hair cell sensors using liquid metal alloy as Piezoresistors
Nano Micro Engineered and Molecular Systems (NEMS) 2013 8th IEEE International Conference on, 2013Co-Authors: Xiaomei Shi, Ching-hsiang ChengAbstract:—In this paper, we present the design, fabrication process, and testing results of an artificial hair cell sensor made by liquid metal encapsulated in a polydimethylsiloxane (PDMS) substrate. Previously, a flexible force sensor was reported from our group, which can detect both normal and shear forces by using liquid metal alloy (Ga-In-Sn) as piezoresistive gauge material encapsulated in a PDMS substrate. Based on this method, we propose an artificial hair cell sensor which can detect two-axis tactile force with a standing artificial hair shaft. Since the liquid-metal Piezoresistors deform with the elastomeric substrate, normal and shear force can be detected with resistance changes of the Piezoresistors. Each force sensor comprises a pair of symmetric Piezoresistors, which is screen-printed on a suspended PDMS membrane with opposite direction to be sensitive to shear forces. The testing results demonstrate the sensitivity of the force sensor in two-axis directions.
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A piezoresistive normal and shear force sensor using liquid metal alloy as gauge material
2012 7th IEEE International Conference on Nano Micro Engineered and Molecular Systems (NEMS), 2012Co-Authors: Xiaomei Shi, Ching-hsiang Cheng, Like Wang, Chen Chao, Yongping ZhengAbstract:We present a novel normal and shear force sensor by using liquid metal alloy (Ga-In-Sn) as piezoresistive gauge material encapsulated in a polydimethylsiloxane (PDMS) substrate. By using liquid metal alloy as gauge material, it can detect large forces without breaking the sensor wires. Since the liquid-metal Piezoresistors deform with the elastomeric substrate, shear and normal forces can be detected with resistance changes of the Piezoresistors. Each force sensor comprises a pair of symmetric Piezoresistors, which is screen-printed on the cavity of PDMS substrate with tilt angle around 30° to be sensitive to both normal and shear forces. Normal force will compress both Piezoresistors as common mode while shear force will shorten one Piezoresistor but elongate the other as differential mode. The testing results demonstrate the sensitivity of the force sensor in both normal and shear directions. The hysteresis of the force sensor was also measured.