Flexible piezoresistive pressure sensors for smart textiles (original) (raw)
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Sensors, 2015
The piezoresistive characteristics of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) pressure sensors with inter-digitated (IDE) and cross-point electrode (CPE) structures have been investigated. A small variation of the resistance of the pressure sensors with IDE without bottom indium-tin-oxide (b-ITO) film and with CPE structures was observed owing to the single carrier-conducting pathway. For the IDE pressure sensors with b-ITO, the piezoresistive characteristics at low and high pressure were similar to those of the pressure sensors with IDE without b-ITO and with CPE structures, respectively, leading to increased piezoresistive pressure sensitivity as the PEDOT:PSS film thickness decreased. A maximum sensitivity of more than 42 kΩ/Pa was achieved. When the normal pressure was applied, the increased number of conducting points or the reduced distance between the PEDOT oligomers within the PEDOT:PSS film resulted in a decrease of the resistance. The piezoresistive pressure sensors with a single carrier-conducting pathway, i.e., IDE without b-ITO and CPE structures, exhibited a small relaxation time and a superior reversible operation, which can be advantageous for fast piezoresistive response applications.
A Novel Approach to a Piezoelectric Sensing Element
Journal of Sensors, 2010
Piezoelectric materials have commonly been used in pressure and stress sensors; however, many designs consist of thin plate structures that produce small voltage signals when they are compressed or extended under a pressure field. This study used finite element methods to design a novel piezoelectric pressure sensor with a C-shaped piezoelectric element, and determine if the voltage signal obtained during hydrostatic pressure application was enhanced compared to a standard thin plate piezoelectric element. The results of this study demonstrated how small deformations of this C-shaped sensor produced a large electrical signal output. It was also shown that the location of the electrodes for this sensor needs to be carefully chosen and that the electric potential distribution varies depending on the poling of the piezoelectric element. This study indicated that the utilization of piezoelectric materials of different shapes and geometries embedded in a polymer matrix for sensing applications has several advantages over thin plate solid piezoelectric structures.
IJERT-A Review on Evolution, Current Trends and Future Scope of MEMS Piezoresistive Pressure Sensor
International Journal of Engineering Research and Technology (IJERT), 2016
https://www.ijert.org/a-review-on-evolution-current-trends-and-future-scope-of-mems-piezoresistive-pressure-sensor https://www.ijert.org/research/a-review-on-evolution-current-trends-and-future-scope-of-mems-piezoresistive-pressure-sensor-IJERTV4IS110384.pdf Piezoresistive pressure sensors are the first MEMS devices to be commercialized. They work on the principle of change in resistivity of materials due to applied pressure. Literature reports lot of work and development in this area of sensing mechanisms. This paper provides a review on evolution of these sensors right from thin metal film based technology to the semiconductor technology. The paper presents the current trends in the design and use of piezoresistive pressure sensor. The paper also presents the future scope form these sensors which, will be around the extensive use of materials like SOI, SiC, DLC, CNT and Silicon Nanowires.
Study and Analysis of the Effective Geometries for the Piezoresistive Pressure Sensors
Turkish Journal of Computer and Mathematics Education, 2021
ABSTRACT:THE REPORTED WORK IS ON THE DESIGN AND SIMULATION OF MICROELECTROMECHANICAL SYSTEMS (MEMS) BASED SILICON PIEZORESISTIVE PRESSURE SENSOR DEPLOYED TOSENSE PRESSURE IN THE RANGE OF 0 TO 1.1 BAR. THE PRESSURE IS APPLIED ON THE DIAPHRAGM CONSISTING OF FOUR PIEZORESISTORS CONNECTED IN THE WHEATSTONE BRIDGE CONFIGURATION. THE INDUCED STRESS AS A RESULT OF THE PRESSURE CAUSES CHANGE IN RESISTANCE OF PIEZORESISTORS DUE TO PIEZORESISTIVE EFFECT. THE DESIGN AND SIMULATION OF THE SENSORS PRIOR TO FABRICATION HELPS US TO OPTIMIZE THE DIAPHRAGM THICKNESS AND SIZE. MEANDER SHAPED PIEZORESISTORS WITH DIFFERENT NUMBER OF TURNS ARE STUDIED IN ORDER TO FIND OUT THE BEST CONFIGURATION FOR HIGH SENSITIVITY AND LINEARITY. THE DESIGN AND SIMULATION IS CARRIED OUT USING FEM (FINITE ELEMENT METHOD) BASED COMSOLMULTIPHYSICS. BASED ON THE SIMULATION RESULTS, THE TWO-TURN CONFIGURATION IS FOUND TO HAVE THE BEST SENSITIVITY OF 4.181 MV/V/BAR AND THE ONE TURN CONFIGURATION GIVES THE LEAST NON-LINEARITY OF 0.5051 % Keywords: MicroElectroMechanical Systems; Piezoresistivity; Pressure sensor; Finite element method.
Design Analysis and Sensitivity Enhancement of Piezoresistive Micro Pressure Sensors
March 29-30, 2015 Singapore, 2015
Piezoresistive micro pressure sensors are widely used for pressure measurement. There are a few design issues need to be addressed like temperature sensitivity, placement of piezoresistive element on the membrane, design of element size, etc. For better sensitivity the length of piezoresistor needs to be increased whereas the thickness needs to be reduced. For a square membrane, the maximum stress value occurs at the center of the edge and decreases rapidly towards the center of the membrane. Increase in length of the piezoresistor beyond a limit will develop huge design error, since the localized stress variations are not considered in the design. The solution could be breaking down the resistance into smaller pieces and connecting them in series and positioning them in the maximum stress region. This paper discusses about the design of such a piezoresistive micro pressure sensor with optimized position placement and element size. Initially, a square diaphragm piezoresistive pressure using classical governing equations is designed. Since, three of the physics such as structural mechanics, piezoresistive physics and electrical physics are involved in the design; Comsol Multiphysics 4.3 is used to make a comparative study of the model with analytical design. The stress variation over the diaphragm is analyzed and the length of the piezoresistive element is designed by restricting the element in the maximum stress region. A Matlab code is written to find the optimum element size, and number of elements to be connected in series. The material properties, dimensions of the membrane, initial resistance and sheet resistance of the piezoresistor are considered as variables and obtained as user inputs.
MEMS Piezoresistive Pressure Sensor: A Survey
Piezoresistive pressure sensors are one of the very first products of MEMS technology, and are used in various fields like automotive industries, aerospace, biomedical applications, and household appliances. Amongst various transduction principles of pressure sensor piezoresistive transduction mechanism is widely used. Over a decade therehas been tremendous improvement in the development of the design of piezoresistive pressure sensor starting with the invention of piezoresistance in the silicon to the recent piezoresistive pressure sensor materials. Because of its high sensitivity, high gauge factor, independent to the temperature, linear operation over a wide range of pressure, and many more advantages. This paper provides survey of piezoresistive pressure sensor including their pressure sensing mechanism, evolution, materials, design considerations, performance parameter that to be considered and the fabrication process used
. Polysilicon piezoresistive MEMS pressure sensor- ICCSP2017 Camera Ready paper
Pressure measurement is a key part of many commercial and industrial systems. Piezoresistive pressure sensors are simpler to integrate with electronics, they are inherently shielded from RF noise and their response is more linear while compared to capacitive pressure sensors. And piezoresistive devices have always dominated the pressure sensor market. The analyticals that are typically used to model the diaphragm of the pressure sensor have been analysed by many researchers. To optimize the pressure sensor for parameters like linearity and sensitivity, the Finite Element Method (FEM) is incorporated. The selection of appropriate parameters of piezoresistors such as the shape and the position of the piezoresistor on the pressure sensor diaphragm, thickness of diaphragm are important. This study shows the scope of using analytical solutions and design techniques for a piezoresistive pressure sensor.
Effect of Process Deviations on Performance of Piezoresistive Pressure Sensors
IEEE Transactions on Semiconductor Manufacturing, 2014
Diaphragm thickness and the corresponding piezoresistor locations change due to over or under etching in bulk micromachined piezoresistive pressure sensor which intern influences the device performance. In the present work, variation of sensitivity and nonlinearity of a micro electro mechanical system low pressure sensor is investigated. The sensor is modeled using finite element method to analyze the variation of sensitivity and nonlinearity with diaphragm thickness. To verify the simulated results, the sensors with different diaphragm thicknesses are fabricated. The models are verified by comparing the calculated results with experimental data. This study is potentially useful for the researchers as most of the times the diaphragm is either over-etched or under-etched due to inherent variation in wafer thickness and involving manual operations.