This chapter deals with designing CNT-based piezoresistive pressure sensors with different boss sizes and with different configurations designed for low pressure range. The purpose for this work is to show a NEMS-based pressure sensor, which was analyzed by using ANSYS 17 software. The different combination of the diaphragm shows the improved performance of the pressure sensor in the case of CNT as compare to the silicon. This chapter is organized in sections, where section 2 discusses the review of CNT based MEMS/NEM design process and applications, Section 3 elaborates the use of CNT materials for design piezoresistive pressure sensors, Section 4 discusses mathematical modeling and simulation of CNT-based piezoresistive pressure sensors, Section 5 examines the results and discussion in terms of linearity and sensitivity of designed sensor, and Section 6 consummates the chapter with the conclusion.
Top1. Introduction
1.1MEMS & NEMS Technology
MEMS has been observed as best growing technologies for the current century and has the capability to revolutionize both consumer and industrial products by combining CNT and silicon-based technology. NEMS (Nano Electro Mechanical) have the structure elements less than or below 100nm, this distinguishes NEMS from MEMS (Micro Electro Mechanical). There are different types of NEMS based devices, which are as from the simple stationary structure to the highly complex Nano system that contain the numbers of moveable parts under the control of integrated nanoelectronics. . The mostly used material for the NEMS and MEMS is the CNTs and Silicon because of its electrical properties, mechanical properties, physical properties as well as electromechanical properties.
1.2 MEMS & NEMS Components
MEMS represent integrated systems of very small size where the feature sizes are reducing to micron and nano dimensions. MEMS have unique features of sensing, actuation, manipulation, control and computation. Which all are integrated in the same system more important than this “size” characterization. Nano sensor, Nano electronics, Nano actuator, Nano structure are the main components of MEMS are given below in figure 1.Recently, NEMS and MEMS developers and researchers have demonstrated large number of Nano sensors, nanoactuators, micro sensors and micro actuators with improved performance. The size of MEMS device is in the range of 20 micrometers to millimeter and size of its sub-components is in the range of 1 to 100 micrometers whereas the size of NEMS devices are at the molecular level having the structure element less than or below 100nm. Typical active substrate material used for actuators and for sensors in microsystems or other MEMS components include silicon, gallium arsenide, germanium and quartz whereas the NEMS components includes the carbon Nano tubes, carbon Nano ribbons, graphene, etc. These are also beneficial for sensing devices, which can be good for the devices.
Figure 1. Schematic illustrations of MEMS & NEMS components
The functional elements of NEMS are miniaturized sensors, actuators, mechanical structure along with the microelectronics as shown in figure 1, among them Nano sensors and Nano actuators are the most notable elements.
2. Nano Sensor
Nano sensors are used to observe the intensity of certain biological, physical and chemical quantities in the environment of system. These Nano devices sense the fluctuation in their atmosphere and then pass the information for processing to the Nano electronics and in response produce an electrical signal as the input signal such as temperature, pressure, magnetic flux, chemical composition, sound and nuclear radiation (Hsu, 2008). Nowadays, the most commonly used Nano sensors are the thermal sensor, bio sensor, chemical sensor, pressure sensor and optical sensor (Tuantranont & Bright, 2000, p. 227-236). The pressure sensor is considered as the most notable and most interesting sensor (Yunus et al., 2015). The front part of the NEMS device is the sensing element. The diaphragm of silicon material with four piezo resistors of CNT material are good for stress and deformation detection.
2.1 Nanoelectronics
Nanoelectronics is the major processing unit of the device or of the system same as brain, which gets information and then process it accordingly. In the MEMS the information begins from the Nano sensors. The processed information is then passed by the process unit to Nano actuators which leads to some fluctuations in its atmosphere.
2.2 Nanoactuator
Nanoactuator is a device which converts an electrical signal to the mechanical signal especially the Nano scale movement (Yunus et al., 2015). The end part of the MEMS device is the Nano actuating that leads by moving, rotating, positioning, regulating, pumping and filtering, for controlling the atmosphere for some kind of purpose or results of device.