Nora Asyikin Binti Zulkifli. (2024). PDMS-based Magnetic Mechanical Sensors for Healthcare Devices - Design, Modeling & Integration. doi: 10.22677/THESIS.200000799236
Type
Thesis
Description
Mechanical sensor, pressure sensor, magnetic sensor, 3D printing, polydimethylsiloxane
Abstract
Within the realm of flexible and wearable electronics, mechanical sensors such as pressure sensors are among the most highly researched devices for both industrial and academia purposes, primarily due to their ease of operation and their broad range of usage. In the healthcare sector for instance, various wearable and portable mechanical sensors have found their way into diagnostic and monitoring devices, allowing patients to integrate these devices into their everyday lives with ease. In an effort to improve wearable devices for this particular application, this thesis introduces two versions of pressure sensor for various biomedical applications, including respiration measurement and pulse monitoring. To differentiate it from conventional, established sensor systems, the devices in this work utilize a magnetic sensor and simple 3D printing methodology. The elastomer polydimethylsiloxane (PDMS) was chosen to be one of the most essential elements and was thus studied in advance for finite element method (FEM) modeling. Detailed investigation on PDMS using FEM as well as creative structural design of the sensor played major parts in optimizing the sensors performance which were then demonstrated in actual healthcare monitoring processes. Keywords: Mechanical sensor, pressure sensor, magnetic sensor, 3D printing, polydimethylsiloxane|압력 센서와 같은 기계적 센서는 조작이 용이하고 광범위한 사용 범위를 가져, 유연하고 착용할 수 있는 디바이스로 산업 및 학계에서 많이 연구되고 있는 디바이스 중 하나이다. 예를 들어 의료 분야에서는 다양한 휴대용 웨어러블 기계식 센서가 진단 및 모니터링 장치로서 환자가 일상생활에 쉽게 사용할 수 있게 되었다. 본 논문에서는 이와 같은 웨어러블 디바이스에 적용하기 위한 방법으로, 호흡 측정과 맥박 모니터링과 같은 생체 신호의 측정이 가능한 바이오 메디컬 압력센서를 두 가지 형태로 시연하였다. 기존의 센서 시스템과 차별화하기 위해 자기 센서와 간단한 3D 프린팅 방법을 사용하였다. 탄성 폴리 디메틸실록산(polydimethylsiloxane; PDMS)는 디바이스의 핵심 재료 중 하나로 선택되었으며 유한 요소 방법 모델(FEM)을 통해 디바이스의 최적화된 형태가 모델링 되었다. FEM을 이용한 PDMS에 대한 심층 분석과 센서의 독창적인 구조 설계는 센서 성능의 최적화에 중요한 역할을 하였으며, 이는 실제 의료 모니터링 과정에서 입증되었다.
핵심어: 기계식 센서, 압력 센서, 자기 센서, 3D 프린팅, 폴리디메틸실록산
Table Of Contents
Abstract i List of contents iii List of tables vi List of figures vii
Ⅰ. Introduction 1.1 Wearable devices in the biomedical field 1 1.2 Mechanical sensors 1 1.2.1 Pressure sensors 2 1.3 Magnetic sensors 3 1.4 Sensor materials 5 1.4.1 Polylactic acid (PLA) 5 1.4.2 Polydimethylsiloxane (PDMS) 8 1.5 Sensor design 10 1.5.1 Implementation of microstructured surfaces 10 1.5.2 Multifunctionality from design detachability 12 1.6 Finite element method (FEM) 14 1.6.1 Structural analysis through simulation 14 1.6.2 Material modeling 15
IⅠ. Theoretical & Mathematical Development 2.1 Modeling of hyperelastic materials 17 2.1.1 Neo-Hookean model 19 2.1.2 Mooney-Rivlin 2 parameter model 19 2.1.3 Mooney-Rivlin 5 parameter model 19 2.1.4 Ogden model 20 2.1.5 Yeoh model 20
ⅠII. Experimental Methods & Materials 3.1 Magnetic sensor 21 3.1.1 Fabrication 21 3.1.2 Characterization 23 3.2 Polylactic acid (PLA) 26 3.2.1 Fabrication 26 3.3 Polydimethylsiloxane (PDMS) 27 3.3.1 Fabrication 28 3.3.1.1 For FEM 28 3.3.1.2 For the pressure sensor 31 3.3.1.3 For the respiration sensor 32 3.3.2 Characterization 33 3.3.2.1 For FEM 33 3.3.2.2 For the pressure sensor 35 3.3.2.3 For the respiration sensor 37 3.4 Finite element method (FEM) 38 3.4.1 COMSOL optimization module 38 3.4.2 COMSOL structural mechanics module 39
IV. Results & Discussion 4.1 Modeling of PDMS 41 4.1.1 Selection of material models 41 4.1.2 FEM simulations 48 4.1.3 Effects of combining different mechanical experiments 51 4.1.4 Varying the base to curing agent blend of PDMS samples 55 4.1.4 Experimental validation 57 4.2 Pressure Sensor 59 4.2.1 Conceptual design 59 4.2.2 Performance of the generic pressure sensor (mechanical loading) 62 4.2.3 Performance of the respiration sensor (air pressure loading) 68 4.2.4 FEA of microstructured PDMS layers 72 4.2.5 Health monitoring applications 78 V. Conclusion 91 Appendix 94 References 95
