Research Papers

Nanomanufacturing Methods for the Reduction of Noise in Carbon Nanotube-Based Piezoresistive Sensor Systems

[+] Author and Article Information
Michael A. Cullinan

Massachusetts Institute of Technology,
Department of Mechanical Engineering,
Cambridge, MA 021391;
National Institute of Standards and Technology,
Intelligent Systems Division,
Gaithersburg, MD 20899

Martin L. Culpepper

Massachusetts Institute of Technology,
Department of Mechanical Engineering,
Cambridge, MA 021391
e-mail: culpepper@mit.edu

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF Micro AND Nano-Manufacturing. Manuscript received January 8, 2012; final manuscript received August 22, 2012; published online March 22, 2013. Assoc. Editor: Liwei Lin.

J. Micro Nano-Manuf 1(1), 011011 (Mar 22, 2013) (6 pages) Paper No: JMNM-12-1003; doi: 10.1115/1.4023159 History: Received January 08, 2012; Revised August 22, 2012

Carbon nanotube (CNT)-based piezoresistive strain sensors have the potential to outperform traditional silicon-based piezoresistors in MEMS devices due to their high strain sensitivity. However, the resolution of CNT-based piezoresistive sensors is currently limited by excessive 1/f or flicker noise. In this paper, we will demonstrate several nanomanufacturing methods that can be used to decrease noise in the CNT-based sensor system without reducing the sensor's strain sensitivity. First, the CNTs were placed in a parallel resistor network to increase the total number of charge carriers in the sensor system. By carefully selecting the types of CNTs used in the sensor system and by correctly designing the system, it is possible to reduce the noise in the sensor system without reducing sensitivity. The CNTs were also coated with aluminum oxide to help protect the CNTs from environmental effects. Finally, the CNTs were annealed to improve contact resistance and to remove adsorbates from the CNT sidewall. The optimal annealing conditions were determined using a design-of-experiments (DOE). Overall, using these noise mitigation techniques it is possible to reduce the total noise in the sensor system by almost 3 orders of magnitude and increase the dynamic range of the sensors by 48 dB.

Copyright © 2013 by ASME
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Fig. 1

(a) Schematic of experimental setup where Vs is the voltage source, Vb is the voltage bias and Rstc are the span temperature compensation resistors. (b) Experimental setup consisting of (1) a Wheatstone bridge, (2) a precision bridge circuit with a precision voltage reference and instrumentation amplifier, (3) a dc power supply, and (4) an analog-to-digital converter [41,42].

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Fig. 2

Test Structure with CNTs connected between the two central electrodes. Reprinted from Ref. [43] with permission from the American Physical Society.

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Fig. 3

I-V curve for CNT-based sensor showing ohmic contact

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Fig. 4

Power spectral densities of CNT-based piezoresistive sensors with dielectrophoresis deposition times of 5 and 10 min

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Fig. 5

Schematic of noise reduction fabrication process

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Fig. 6

Power spectral densities of as deposited, Al2O3 and annealed CNT-based piezoresistive sensors

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Fig. 7

Power spectral densities of CNR-based sensor annealed at 525 °C

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Fig. 8

Performance of various piezoresistive materials on microscale flexure beams




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