scholarly journals Granular metal–carbon nanocomposites as piezoresistive sensor films – Part 2: Modeling longitudinal and transverse strain sensitivity

2018 ◽  
Vol 7 (1) ◽  
pp. 69-78 ◽  
Author(s):  
Silvan Schwebke ◽  
Ulf Werner ◽  
Günter Schultes
Keyword(s):  
Electron Transport ◽  
Large Strain ◽  
Local Strain ◽  
Carbon Matrix ◽  
Morphological Characterization ◽  
Transverse Strain ◽  
Strain Sensitivity ◽  
Sensor Material ◽  
Piezoresistive Sensor ◽  
Disordered Films

Abstract. Granular and columnar nickel–carbon composites may exhibit large strain sensitivity, which makes them an interesting sensor material. Based on experimental results and morphological characterization of the material, we develop a model of the electron transport in the film and use it to explain its piezoresistive effect. First we describe a model for the electron transport from particle to particle. The model is then applied in Monte Carlo simulations of the resistance and strain properties of the disordered films that give a first explanation of film properties. The simulations give insights into the origin of the transverse sensitivity and show the influence of various parameters such as particle separation and geometric disorder. An important influence towards larger strain sensitivity is local strain enhancement due to different elastic moduli of metal particles and carbon matrix.

Noise Mitigation Techniques for Carbon Nanotube-Based Piezoresistive Sensor Systems

2011 ◽  
Vol 1303 ◽  
Author(s):  
Michael A. Cullinan ◽  
Martin L. Culpepper
Keyword(s):  
Carbon Nanotube ◽  
Dynamic Range ◽  
Flicker Noise ◽  
Sensor System ◽  
Strain Sensitivity ◽  
Mems Devices ◽  
Noise Mitigation ◽  
Piezoresistive Sensors ◽  
Piezoresistive Sensor ◽  
Mitigation Techniques

ABSTRACTCarbon 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 noise mitigation techniques 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 variations. Finally, the CNTs were annealed to improve contact resistance and to remove adsorbates from the CNT sidewall. Overall, using these noise mitigation techniques it is possible to reduce the total noise in the sensor system by almost two orders of magnitude and increase the dynamic range of the sensors by 29 dB.

DESIGN OF A LOAD CELL WITH LARGE OVERLOAD CAPACITY

2010 ◽  
Vol 34 (3-4) ◽  
pp. 449-461 ◽  
Author(s):  
Farhad Aghili
Keyword(s):  
Large Strain ◽  
Load Cell ◽  
Load Force ◽  
Strength Analysis ◽  
Special Design ◽  
Sensor Material ◽  
Overload Protection ◽  
Sensor Structure ◽  
Margin Of Safety ◽  
Overload Capacity

To increase the signal-to-noise (S/N) ratio and sensitivity of a load cell, it is desirable to design a structure that generates large strain close to maximum allowable strain of the sensor material for a given rating load force. However, accommodating the margin of safety with respect to overloading, compromises the sensitivity. This paper presents the design, analysis, and prototype testing of a load cell which can provide large overload protection capacity without compromising the sensitivity of the sensor. This is achieved by a special design of sensor structure that becomes virtually rigid after its flexures reach their maximum deflection, thereby the sensor can be protected against a large over load. The sensor dimensions, which maximizes the sensor’s sensitivity, for given values of rating load and overload are obtained through mechanical strength analysis. A load cell prototype is fabricated and then tested to measure its linearity and overload characteristics. The experimental results show an accuracy of 0.2% of full scale and overload protection of the sensor flexures.

scholarly journals Granular metal–carbon nanocomposites as piezoresistive sensor films – Part 1: Experimental results and morphology

2018 ◽  
Vol 7 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Günter Schultes ◽  
Hanna Schmid-Engel ◽  
Silvan Schwebke ◽  
Ulf Werner
Keyword(s):  
Metal Concentration ◽  
Plasma Deposition ◽  
Thermal Coefficient ◽  
Strain Sensitivity ◽  
Carbon Phase ◽  
Piezoresistive Sensor ◽  
Transmission Electron ◽  
Deposition Processes ◽  
Two Phases ◽  
Thermal Coefficient Of Resistance

Abstract. We have produced granular films based on carbon and different transition metals by means of plasma deposition processes. Some of the films possess an increased strain sensitivity compared to metallic films. They respond to strain almost linearly with gauge factors of up to 30 if strained longitudinally, while in the transverse direction about half of the effect is still measured. In addition, the film's thermal coefficient of resistance is adjustable by the metal concentration. The influence of metal concentration was investigated for the elements Ni, Pd, Fe, Pt, W, and Cr, while the elements Co, Au, Ag, Al, Ti, and Cu were studied briefly. Only Ni and Pd have a pronounced strain sensitivity at 55 ± 5 at. % (atomic percent) of metal, among which Ni–C is far more stable. Two phases are identified by transmission electron microscopy and X-ray diffraction: metal-containing nanocolumns densely packed in a surrounding carbon phase. We differentiate three groups of metals, due to their respective affinity to carbon. It turns out that only nickel has the capability to bond and form a stable and closed encapsulation of GLC around each nanoparticle. In this structure, the electron transport is in part accomplished by tunneling processes across the basal planes of the graphitic encapsulation. Hence, we hold these tunneling processes responsible for the increased gauge factors of Ni–C composites. The other elements are unable to form graphitic encapsulations and thus do not exhibit elevated gauge factors.

Morphological characterization of ion-sputtered C–Ag, C/C–Ag and Ag/C films by GISAXS

1999 ◽  
Vol 32 (2) ◽  
pp. 226-233 ◽  
Author(s):  
D. Babonneau ◽  
A. Naudon ◽  
D. Thiaudière ◽  
S. Lequien
Keyword(s):  
Thin Film ◽  
Surface Diffusion ◽  
Carbon Matrix ◽  
Grazing Incidence ◽  
Deposition Process ◽  
Morphological Characterization ◽  
Carbon Surface ◽  
Silver Clusters ◽  
X Ray ◽  
Silver Thin Film

A carbon–silver thin film (33 at.% Ag and thickness of 2100 Å) has been synthesized by co-sputtering of a C–Ag target and characterized by grazing-incidence small-angle X-ray scattering (GISAXS), a technique that gives a considerably enhanced surface sensitivity. Experiments have been carried out at or near the critical angle of the layer. It is shown that, because C and Ag show no mutual solubility, a demixing occurs during the co-deposition process and silver clusters form within an amorphous carbon matrix. Using different incident angles of the X-ray beam, it is demonstrated that two populations of clusters are present in the layer: some large and nearly spherical on the surface, others smaller and elongated along the direction of the growth of the thin film in the bulk. In the case of a C/C–Ag bilayer, the surface diffusion is avoided just after the co-deposition process and it is shown that only the small and elongated clusters in the bulk are formed. In the case of a very thin Ag/C layer, there is only surface diffusion and it is shown that large silver islands are formed on the carbon surface. Such experiments demonstrate that the growth mechanism that takes place during the co-deposition process involves mainly a surface diffusion of silver and carbon atoms, as opposed to a volume diffusion.

Electron Transport in Graphene with One-dimensional Local Strain

2012 ◽  
Author(s):  
H. Tomori ◽  
H. Karube ◽  
Y. Ootuka ◽  
A. Kanda
Keyword(s):  
Electron Transport ◽  
Local Strain ◽  
One Dimensional

Three-Dimensional Strain Fields in a Uniform Osteotomy Gap

1986 ◽  
Vol 108 (3) ◽  
pp. 273-280 ◽  
Author(s):  
A. M. DiGioia ◽  
E. J. Cheal ◽  
W. C. Hayes
Keyword(s):  
Longitudinal Strain ◽  
Large Strain ◽  
Geometric Analysis ◽  
Local Strain ◽  
Material Model ◽  
Nonlinear Material ◽  
In Vivo Study ◽  
Strain Fields ◽  
Longitudinal Strains

Stable internal fixation usually results in a unique histological healing pattern which involves direct cortical reconstruction and an absence of periosteal bridging callus. While it has been suggested that longitudinal interfragmentary strain levels control this healing pattern, the complex, multiaxial strain fields in the interfragmentary region are not well understood. Based on an in-vivo study of gap healing in the sheep tibia by Mansmann et al. [13], we used several finite element models of simplified geometry to: 1) explore modeling assumptions on material linearity and deformation kinematics, and 2) examine the strain distribution in a healing fracture gap subjected to known levels of interfragmentary strain. We found that a general nonlinear material, nonlinear geometric analysis is necessary to model an osteotomy gap subjected to a maximum longitudinal strain of 100 percent. The large displacement, large strain conditions which were used in the in-vivo study result in complex, multiaxial strain fields in the gap. Restricting the maximum longitudinal strain to 10 percent allows use of a linear goemetric formulation without compromising the numerical results. At this reduced strain level a linear material model can be used to examine the extent of material yielding within a homogeneous osteotomy gap. Severe local strain variations occurred both through the thickness of the gap and radially from the endosteal to periosteal gap surfaces. The bone/gap interface represented a critical plane of high distortional and volumetric change and principal strain magnitudes exceeded the maximum longitudinal strains.

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

2013 ◽  
Vol 1 (1) ◽  
Author(s):  
Michael A. Cullinan ◽  
Martin L. Culpepper
Keyword(s):  
Carbon Nanotube ◽  
Dynamic Range ◽  
Flicker Noise ◽  
Sensor System ◽  
Strain Sensitivity ◽  
Mems Devices ◽  
Noise Mitigation ◽  
Piezoresistive Sensors ◽  
Piezoresistive Sensor ◽  
Total Noise

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.

Sign in / Sign up

Export Citation Format

Share Document