• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1422-1424
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• 1994

This paper deals with piezoresistive humidity sensor using polycrystalline silicon (Poly-Si ) with membrane in sensors of semiconductor. Poly-Si piezoresistors which have no temperature dependancy are deposited on silicon wafer, membrane is formed with micromachining technology, then polyimide is formed as a hygroscopic layer. Whereas the principle of conventional humidify sensors are based on the change in electrical properties of the material, the humidity induced volume change of a polyimide layer leads to a deformation of a silicon membrane in this case. This deformation is transformed into an output voltage by Poly-Si piezoresistive. Wheatstone bridge. Fabricated piezoresistive humidity sensors showed good linearity, response time, and long term stability.

• Journal of Sensor Science and Technology
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• v.11 no.4
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• pp.191-199
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• 2002

This paper presents the design concept, theoretical investigation, and fabrication of a six-degree of freedom (6-DOF) turbulent flow micro sensor utilizing the piezoresistive effect in silicon. Unlike other flow sensors, which typically measure just one component of wall shear stress, the proposed sensor can independently detect six components of force and moment on a test particle in a turbulent flow. By combining conventional and four-terminal piezoresistors in Si (111), and arranging them suitably on the sensing area, the total number of piezoresistors used in this sensing chip is only eighteen, much fewer than the forty eight piezoresistors of the prior art piezoresistive 6-DOF force sensor.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.1
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• pp.19-24
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• 2005

In this paper, the fabrication process of Si pressure sensors utilizing piezoresistive effect was optimized. The efficiency(yield) of the fabrication process for Si piezoresistive pressure sensors was improved by conducting Si anisotrophic etching process after processes of piezoresistors and AI circuit patterns. The position and process parameters for piezoresistors were determined by ANSYS and SUPREM simulators, respectively. The measured thickness of p-type Si piezoresistors from the boron depth-profile measurement was in good agreement with the simulated one from SUPREM simulation. The Si anisotrohic etching process for diaphragm was optimized by adding ammonium persulfate(AP) to tetramethyl ammonium hydroxide (TMAH) solution.

• Computers and Concrete
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• v.30 no.5
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• pp.301-310
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• 2022

Cement-based sensors have been widely used as structural health monitoring systems, however, their long-term sensing performance have not actively investigated. In this study, a deep learning-based methodology is adopted to predict the long-term piezoresistive properties of cement-based sensors. Samples with different multi-walled carbon nanotube contents (0.1, 0.3, and 0.5 wt.%) are fabricated, and piezoresistive tests are conducted over 10,000 loading cycles to obtain the training data. Time-dependent degradation is predicted using a modified long short-term memory (LSTM) model. The effects of different model variables including the amount of training data, number of epochs, and dropout ratio on the accuracy of predictions are analyzed. Finally, the effectiveness of the proposed approach is evaluated by comparing the predictions for long-term piezoresistive sensing performance with untrained experimental data. A sensitivity of 6% is experimentally examined in the sample containing 0.1 wt.% of MWCNTs, and predictions with accuracy up to 98% are found using the proposed LSTM model. Based on the experimental results, the proposed model is expected to be applied in the structural health monitoring systems to predict their long-term piezoresistice sensing performances during their service life.

• Smart Structures and Systems
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• v.18 no.2
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• pp.217-231
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• 2016

The present work aims to develop piezoresistive sensors of excellent piezoresistive response attributable to change in nanoscale structures of multi-wall carbon nanotube (MWNT) embedded in cement. MWNT was distributed in a cement matrix by means of polymer wrapping method in tandem with the ultrasonication process. DC conductivity of the prepared samples exhibited the electrical percolation behavior and therefore the dispersion method adopted in this study was deemed effective. The integrity of piezoresistive response of the sensors was assessed in terms of stability, the maximum electrical resistance change rate, and sensitivity. A composite sensor with MWNT 0.2 wt.% showed the lowest stability and sensitivity, while the maximum electrical resistance change rate exhibited by this sample was the highest (96 %) among others and even higher than those found in the literature. This observation was presumably attributed by the percolation threshold and the tunneling effect. As a result of the MWNT content (0.2 wt.%) of the sensor being near the percolation threshold (0.25 wt.%), MWNTs were close to each other to trigger tunneling in response of external loading. The sensor with MWNT 0.2 wt.% was able to maintain the repeatable sensing capability while sustaining a vehicular loading on road, demonstrating the feasibility in traffic flow sensing application.

• Journal of Sensor Science and Technology
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• v.14 no.1
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• pp.56-61
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• 2005

This paper present characteristics of chromium oxide thin-film as piezoresistive sensors, which were deposited on Si substrates by DC reactive magnetron sputtering in an argon-Oxide atmosphere for high temperature applications. The chemical composition, physical and electrical properties and thermal stability ranges of the $CrO_{x}$ sensing elements have studied. $CrO_{x}$ thin films with a linear gauge factor(GF${\fallingdotseq}$15), high electrical resistivity (${\rho}$ = $340{\mu}{\Omega}cm$) and TCR<-55 ppm/$^{\circ}C$ have been obtained. These $CrO_{x}$ thin films may allow high temperature pressure sensor miniaturization to be achieved.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1055-1056
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• 2011

• Journal of Sensor Science and Technology
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• v.14 no.3
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• pp.156-159
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• 2005

Liposomes are microscopic spherical vesicles that form when lipids are hydrated and have been widely used for biochemical assay, drug delivery and molecular imaging. In particular, they are well known for artificial cell membranes to study cellular functions such as cell fusions and membrane proteins. Here, we firstly report the detection of liposomes by the highly sensitive microfabricated piezoresistive cantilever sensor chip and the phosphatidylserine recognition protein C2A which is chemically immobilized on the sensor surface. The signal created from the bending motion of piezoresistive cantilever after the liposome attachment has been monitored in real time.

• Elastomers and Composites
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• v.48 no.1
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• pp.76-84
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• 2013

The term 'Piezoresistive effect' describes a change in the electrical resistance of the material from deformed to its original shape by the external pressure, e.g., elongation, compression, etc. This phenomenon has various applications of sensors for monitoring pressure, vibration, and acceleration. Although there are many materials which have the piezoresistive effect, rubber (nano)composites with conductive fillers have attracted a great deal of attention because the piezoresistive effect appears at the various range of pressure by controlling the type of filler, particle size, particle shape, aspect ratio of particles, and filler content. Especially one can obtain the composites with elasticity and flexibility by using the rubber as a matrix. This paper aims to review the piezoresistive effect itself, their basic principles, and the various conductive rubber-composites with piezoresistive effect.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.3
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• pp.573-577
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• 2009

Piezoresistive pressure sensor have become the successfully-commercialized MEMS product and the related technologies have been well developed over the past decades. Regarding the design methodology, however, the coupled-physics FEM analyses of the transducer itself and the signal-processing circuitry design based on the conventional EDA are separated and both of the analyses were sequentially processed for the full design of the pressure sensor. For the fast and effective R&D, new design methodology is proposed in this paper where the FEM results are linked to the EDA environment and therefore most of the design works can be done in the EDA environments, which means the time-consuming FEM analyses can be minimized. In order to verify the proposed approach, a typical piezoresistive pressure sensor having the silicon diaphragm and piezoresistors was modeled and analyzed based on the proposed methodology. The verification results showed that the simulated results were matched well with the measured data within the 7% difference while the simulation time was reduced less than 5% compared to the conventional methodology. Through the proposed approach, various types of the piezoresistive pressure sensors can be developed in more effective way.