Multilayered nano film fabrication using geometric electrodes and free-standing electrospinning technology = 자유지지 필름 형성을 위한 기하표면상 전기방사 기법을 이용한 다층나노 구조물 형성

다국어 초록 (Multilingual Abstract)

Electrospinning is a nano-scale fiber production method with various polymer materials. This technique allows simple fiber diameters control by changing the physical conditions such as applied voltage and polymer solution viscosity during the fabrication process. The electrospun polymer fibers form a thin porous film with high surface area to volume ratio. Due to these unique characteristics, it is widely used for many application fields such as textiles, filters, biomedicine, drug delivery, energy, and sensors. For the electrospun film fabrication, typical electrospinning process is based on planar substrate equipment. In planar substrate based electrospinning method purpose to produce fiber with regular diameter that is necessary to uniform electric field on planar surfaces. Planar substrate based electrospinning process has obstacles to apply non-planar and conductive material surface. To solve this problem, substrate-free electrospinning method has to be developed. In the electrospinning history, various wire-based electrodes have been proposed for specific nano-porous film fabrication and applications. A simple physics in electrospinning technique offer the possibilities for using wire-based electrodes such as circle, rectangular, parallel wires and so on. However, experimental approaches are limited due to difficulties to find exact working condition and control the physical variables. Here, we investigate a circle electrode in the electrospinning process for the fabrication of substrate-free, freestanding nanofiber films. Circle electrode-based electrospinning is controlled by varying the applied voltage and the metal needle tip-to-collector distance. A hollow cylinder is used as the circle electrode to ensure stable electrostatic conditions on the top surface of the cylinder collector. Numerical simulation is used to determine the electric field in the electrospinning process for quantitative analysis. The freestanding electrospun film can be transferred as a coating to a non-planar surface without using additional processes. Thus, the electrospinning process using the circle electrode collector was successfully optimized for freestanding film fabrication. Substrate-free electrospun films can be applied to multifunctional filters for dust filtration with humidity blocking. Regarding future applications, the circle electrode-based electrospinning process verified the potential for integrating freestanding electrospun films into organs-on-chip, biochemical sensors, and microfluidic analysis systems.

목차 (Table of Contents)

• List of schematics i
• Abstract iv
• Chapter 1. Introduction 1
• 1.1 Research background 1
• 1.2 Research purpose 4
• Chapter 2. Experimental 6
• 2.1 Materials 6
• 2.2 Electrospinning 6
• 2.2.1 Experimental set up 6
• 2.2.2 Electrospinning process 7
• 2.2.3 Film transferring process 10
• 2.3 Characterization measurement 11
• Chapter 3. Numerical modeling 12
• 3.1 Electrospinning condition for optimized film fabrication 12
• 3.2 Numerical modeling of electrospinning 14
• 3.3 Analysis of electrical properties 14
• Chapter 4. Results and discussion 23
• 4.1 Film surface energy variation 23
• 4.1.1 Analysis of PVDF film morphologies 23
• 4.1.2 Surface energy of zeolite embedded PVDF film 24
• 4.1.3 Effect of TCD and zeolite ratio for ES film morphologies 27
• 4.2 Film characteristics by collector shape 32
• 4.2.1 Electrospun film fabrication on circle electrode collector 32
• 4.2.2 Characterization of ES film 35
• 4.2.3 Permeability test of the ES film 41
• 4.3 Film fabrication for the multifunctional film application 44
• 4.3.1 Water absorption property of zeolite embedded ES film 44
• 4.3.2 Humidity removal test of ES multilayer film 48
• Chapter 5. Conclusions 53
• References 55
• Abstracts in Korean 65