Design and Simulation of Implantable Blood Pressure Sensor Using COMSOL Multiphysics K.S.N. Murthy, M. Siva Kumar, K. Suma Bindu, K. Satyanarayana, D. Sivateja and G. Sai Hemanth Abstract This paper presents the design and simulation of blood pressure sensor for healthcare and biomedical applications. Generally blood pressure can be measured by using sensors externally, but here is an implantable sensor which is used for continuous monitoring of blood pressure. The software used is COMSOL Multiphysics, a general purpose software platform for modelling and simulating the advanced applications. This work describes the design of nanotube-based sensor with a basic known technology of MEMS. The main physics used in this design is solid mechanics and time-dependent analysis which is performed to certain values of pressure that is applied on the model. The pressure versus displacement analysis is performed, and it is observed that the pressure is directly proportional to displacement. The device performance is compared by using materials like Si and Au. The result shows that Au has good sensitivity than Si which is veriﬁed by calibration method. Keywords Blood pressure Displacement Biomedical applications COMSOL K.S.N. Murthy (&) M. Siva Kumar K. Suma Bindu K. Satyanarayana D. Sivateja G. Sai Hemanth Department of Electronics and Communication Engineering, K L University, Vaddeswaram, Andhra Pradesh, India e-mail: [email protected] M. Siva Kumar e-mail: [email protected] K. Suma Bindu e-mail: [email protected] K. Satyanarayana e-mail: [email protected] D. Sivateja e-mail: [email protected] G. Sai Hemanth e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2018 R. Singh et al. (eds.), Intelligent Communication, Control and Devices, Advances in Intelligent Systems and Computing 624, https://doi.org/10.1007/978-981-10-5903-2_117 1119 1120 K.S.N. Murthy et al. 1 Introduction An innovative technology, which has many attractions like miniaturization, low power consumption, performing multiple operations with single equipment, is MEMS. The technology of MEMS indicates that it produces the devices with the combination of both electrical and mechanical components . The main advantage of MEMS is its size which ranges between few micrometres to millimetres. MEMS devices have greater ability in many domains like sensing, actuating and controlling . The MEMS-based sensors can be used for biomedical applications also . Bio-MEMS devices can be manufactured based on the operation of various parameters like temperature, pressure, capacitance, voltage and current. This paper provides a brief idea about blood pressure detection using pressure as a sensing element . Pressure is an important parameter in real-life applications. It is deﬁned as force per unit area . The mathematical expression of pressure is Pressure ð pÞ = Force/Area ð1Þ Blood pressure measurement which is the most important routine check-up in order to have well-being health. The normal blood pressure can be expressed in terms of systolic over diastolic pressure as 120/80 (mmHg) . Systolic is the highest level of our blood pressure when the heart beats and diastolic is lowest level of our BP as heart relaxes between beats. This raise and fall of blood pressure leads to many diseases. 1. High BP leads to hypertension which causes heart attacks or strokes, trouble with memory. 2. Low BP causes hypotension which results in dizziness, fainting, diarrhoea, etc. In general, blood pressure can be measured by using some instruments like sphygmomanometer and some asculatory methods. But these instruments have a limitation that they cannot detect blood pressure when the body has mobility. So, a design of MEMS-based sensor is proposed to implant in a human body, which is used for continuous monitoring of blood pressure [4, 6]. This helps the doctor to provide an early detection and an efﬁcient treatment to the patients suffering with blood pressure. The implantable pressure sensor is interfaced to an external circuit for the wireless monitoring and digital display of blood pressure. The sensor is connected to RF microcontroller, a balun network and a chip antenna [4, 7] (Figs. 1 and 2). The total work is performed with the help of software named COMSOL Multiphysics. COMSOL Multiphysics is ﬁnite element analyser, solver and simulation software for various physics and engineering applications . The virtual blood pressure sensor model is designed using this tool followed by simulations. This paper describes a model for continuous monitoring of blood pressure using a nanotube-based design and also its analysis by using various parameters . Design and Simulation of Implantable Blood Pressure Sensor … 1121 Fig. 1 An asculatory method to measure blood pressure Fig. 2 Measurement of blood pressure using manometer 2 Design Procedure A virtual view of the model is designed in COMSOL , which has various physics and engineering applications. A 3D structure is developed by considering solid mechanics as the main physics which is a part of structural mechanics . There are many different analysers present in the tool among which the time-dependent analysis is selected as the variations in blood pressure are observed with respect to time. When the model is taken into consideration, the design is a nanotube-based sensor which is almost identical to cantilever sensor . A component needs to be created which has many designing facilities like geometry, deﬁnitions, materials, physics used and meshing. In geometry, a cylindrical structure is designed with some dimensions like height and radius. Similarly, another cylindrical structure is designed and placed inside the ﬁrst cylinder by using Booleans and partitions in 1122 K.S.N. Murthy et al. geometry. The structure has ﬁxed base at one end and free suspension at other end. Since it is an implantable sensor, the size is an important parameter . The structure is designed in micrometres (µm), as the diameter of the blood vessels where the sensor is placed is in micrometre range. A height of 8 µm and radius of 2 µm are used for design. After the structural design is performed, the sensing ability should be developed. As pressure is the main sensing parameter, some load like boundary or point load is applied to the design with the help of deﬁnitions in the tool. The materials like silicon (Si) and gold (Au) are opted by selecting the required domains in the model. In material analysis, the Young’s modulus and Poisson ratio of Si and Au are considered. For silicon, 1. Poisson ratio = 0.17 2. Young’s modulus = 150 GPa For gold, 1. Poisson ratio = 0.42 2. Young’s modulus = 79 GPa Meshing is performed which is a ﬁnite element analyser. Some parameters like pressure and displacement are created by entering certain values of pressure in Pa/kPa. The ranges of values between 5 and 11 kPa are provided. The model is simulated for a required amount of selected time. After computation, the displacement is recorded with the variation of pressure. 3 Simulation and Analysis Using COMSOL The designed model is simulated with the help of COMSOL, and analysis is performed by varying dimensions of the sensor, material and pressure. Some values of pressure that is higher and lower to normal blood pressure 120/80 are given to the model. Different boundary loads are applied at the free end, and their displacements are recorded simultaneously. The graphical analysis is also performed along with the simulation result. 3.1 3.1.1 Analysis Material Analysis Using Si and Au The working performance of the sensor changes with change in material. The model is simulated by using silicon and gold materials. The operating conditions change when different values of pressure are applied. The simulations and values of displacement for different values of pressure are recorded (Figs. 3 and 4; Table 1). Design and Simulation of Implantable Blood Pressure Sensor … Fig. 3 Simulation of nano tube sensor for blood pressure sensor using silicon Fig. 4 Simulation of blood pressure sensor using gold 1123 1124 K.S.N. Murthy et al. Table 1 Variation of displacement with pressure for Si and Au Pressure (Pa) Materials used Silicon displacement (lm) Gold displacement (lm) 11,000 9500 8000 6500 5000 0.58 0.505 0.425 0.346 0.266 1.4 1.21 1.02 0.826 0.635 3.1.2 Pressure versus Displacement Analysis The boundary loads and point loads are applied to the model for the variation in pressure. The ranges of values are in between 5 and 11 kPa. After computation of the model, it is observed that there is an increase of displacement with increase of pressure. This shows that displacement is directly proportional to blood pressure. Thus, the blood pressure can be calibrated in terms of displacement of the sensor. The graphical representation of pressure versus displacement is shown in Fig. 5. Fig. 5 Graph showing the variation of displacement with pressure Design and Simulation of Implantable Blood Pressure Sensor … 3.1.3 1125 Calibration of the Sensor The difference in displacement for 1500 Pa when Si material is used: Between the pressure 11000–9500 Pa = 0.575 µm Between the pressure 9500–8000 Pa = 0.080 µm Between the pressure 8000–6500 Pa = 0.079 µm Between the pressure 6500–5000 Pa = 0.080 µm The difference in displacement for 1500 Pa when Au material is used: Between the pressure 11000–9500 Pa = 0.190 µm Between the pressure 9500–8000 Pa = 0.190 µm Between the pressure 8000–6500 Pa = 0.794 µm Between the pressure 6500–5000 Pa = 0.191 µm The calibrated value of pressure sensor for 1 Pa with respect to silicon and gold materials is 1.566e−4 and 2.2733e−4 µm, respectively. 4 Conclusion The analysis shows that there is an increase in displacement as pressure increases. So displacement is directly proportional to pressure. When materials are considered, the calibrated value of pressure sensor for 1 Pa to the silicon is 1.566e−4 and to the gold is 2.2733e−4. This shows that gold has good accuracy and sensitivity when compared to other materials. So it is concluded that gold is the preferred material for the implantation of blood pressure sensor. 5 Future Scope Similar to blood pressure detection, protein concentration can also be detected since the displacement of nanotube is based on number of substances which is directly proportional to the protein concentration. So protein concentration can be detected by addition of some materials. References 1. R. U. Sonje, S. V. Borde, “Micro-Electromechanical Systems (Mems)”, IJMER, Vol. 4 Iss. 3 (Mar. 2014), 2249–6645, Page no: 1, 2. 2. Dr. Prasanna Kumar S.C., Jyothsna D., “Biomedical Applications Of Mems & Nems Pressure Transducers/ Sensors”, IJIRD, Vol 2 Issue (5 May, 2013), 2278–0211, Page no: 6. 3. Nurul Amziah Md. 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