近場電紡絲技術應用於可控制多根奈米纖維生成、選擇性沉積及奈米流道之製備

Application of near-filed electrospinning in controlled formation of multiple jets, selective nanofiber deposition and fabrication of monolithic polymer nanofluidic channels

許宏碩(Hung-Shuo Hsu)

指導教授 ： 傅尹坤

國立中央大學/工學院/機械工程學系/碩士(2012年)

摘要

本論文主要在近場電紡絲技術中，研究纖維的形成、發展控制技術以及應用，主要重點為(1)近場電紡絲技術中可控制的多根奈米纖維生成及奈米纖維沉積，(2)利用微機電系統所製作出的結構增強近場電紡絲技術的選擇性沉積，(3)經由近場電紡絲技術所生產的奈米纖維作為犧牲模板，製作陣列的奈米流體流道。

(1)近場電紡絲技術中可控制的多根奈米纖維生成技術
我們在連續近場電紡絲 (Near-field Electrospinning, NFES) 製程中發展一種簡單且可控制多條射流形成技術，能有效的同時射出一、二和三條的奈米纖維。此研究中成功的展示在連續近場電紡絲製程中，使用機械力拉伸和直寫 (direct-write) 在收集器 (基板) 的方法來控制多條射流形成。其觸發機制為使用一或多個鎢探針針尖去戳聚合物液滴，當應用的電場超過帶電的聚合物液滴表面張力，則奈米纖維開始拉伸，接著在距離500 μm到1 mm (針頭到收集器) 的基板上開始沉積。奈米纖維直徑範圍為40到140 nm，經由一條、二條和三條射流所生產的奈米纖維，平均尺寸和變異範圍分別為: 64 ± 14 nm、79 ± 15 nm和76 ± 20 nm。此技術可進一步發展成大面積沉積纖維，如在微電子領域沉積有序奈米纖維的不織布、微機電系統結構和奈米結構的組織工程支架。

(2)利用微機電系統製作的結構增強近場電紡絲技術的選擇性沉積
這篇研究利用微機電系統 (Micro-Electrical Mechanical System, MEMS) 方法製作的微結構，增強近場電紡織技術所生產纖維的選擇性沉積。我們使用微米尺度範圍的六角錐形狀MEMS結構作為基板，沉積奈米纖維。並以有限元素 (Finite Element Method, FEM) 進行模擬(COMSOL 4.0)，模擬之主要條件包含施加電壓800 V，針頭與微結構收集器為500 μm，並將微結構作正反擺放模擬電場效應。模擬結果與實際近場電紡織技術製作奈米纖維之集中電場效應吻合。

(3)經由近場電紡絲技術所生產的奈米纖維作為犧牲模板，製作陣列的奈米流體流道
這篇研究提出了一種簡單無光罩的方法製作陣列的奈米流體流道，利用近場電紡織技術沉積奈米纖維作為模板與聚二甲基矽氧烷 (polydimethylsiloxane, PDMS) 翻模技術。製備奈米流道通過三個主要步驟: (1)使用近場電紡織技術直寫陣列的奈米纖維在矽基板上，(2)陣列的奈米纖維圖案利用PDMS翻模，(3)使用O2 plasma表面改質，增加PDMS與基板黏合的黏結力。這篇研究中所製作的奈米流道寬度範圍為500 nm – 1300 nm，深度為70 - 500 nm。奈米流道尺寸主要依據奈米纖維直徑尺寸，近場電紡織技術能夠控制直徑~50 nm的奈米纖維。結果顯示，整合近場電紡絲技術可在低成本下快速的製作陣列奈米流道，而奈米流道圖形與尺寸主要由近場電紡織的直寫與定位方法控制。

關鍵字

近場電紡絲技術 ； 奈米流體流道 ； 選擇性沉積 ； 多根纖維生成

並列摘要

This paper mainly research formation of nanofiber, controlled technology and application in near-field electrospinning. The focus of the study is (1) Controlled formation of multiple jets and nanofibers deposition via near-field electrospinning process, (2) MEMS/NEMS-enhanced selective nanofiber deposition via near-field electrospinning, (3) Fabrication of monolithic polymer nanofluidic channels via near-field electrospun nanofibers as sacrificial templates.

(1) Controlled formation of multiple jets and nanofibers deposition via near-field electrospinning process.
A simple yet powerful technique to form multiple jets using continuous near-field electrospinning (NFES) has been developed, and it can effectively create one, two and three nanofibers deposition in a controlled manner. In this study, we successfully demonstrate controlled formation of multiple jets using the mechanical drawing and direct-write on the collector via continuous NFES process. The triggering mechanism of proposed electrospinning process is using one or several tungsten probe tips to poke the polymer droplet, and when the surface tension of charged polymer solution is surpassed by applied electrical fields, the nanofibers are initially stretching and controllably depositing on the substrate at a needle-to-collector distance of 500 μm to 1 mm. The deposited nanofibers have diameters in the range of 40 to 140 nm, which arithmetic means and variances range from 64 ± 14 nm for one jet, 79 ± 15 nm for two jets and 76 ± 20 nm for three jets. This novel and reproducible technique can further expand the application of NFES in building up large area such as ordered nonwoven nanofibers in the field of microelectronics, MEMS structures and nano-featured scaffolds of tissue engineering.

(2) MEMS enhanced selective nanofiber deposition via near-field electrospinning.
MEMS structure with pyramidal cross-section and hexagonal shapes is first used to deposit nanofibers in micron meter range. A microstructure places front- and back- side to simulate electric field effect via finite element method (FEM) simulation (COMSOL 4.0) under applied voltage at 800 V and needle-to-collector at 500 μm. The simulation and experimental results are found in good in agreement.

(3) Fabrication of monolithic polymer nanofluidic channels via near-field electrospun nanofibers as sacrificial templates.
This paper reports a facile and maskless method for fabricating nanofluidic channel arrays using near-field electrospinning (NFES) templates with prescribed patterns and the polydimethylsiloxane (PDMS) molding technique. Nanochannels were fabricated monolithically through three main steps: (1) direct-writing nanofiber arrays onto a silicon substrate using NFES, (2) PDMS molding of the prescribed nanofibers patterns, and (3) plasma treating PDMS substrate to promote the adhesion and bonding process. The nanochannels fabricated in this study had channel widths ranging from 500 nm – 1300 nm and depths of 70 - 500 nm, and were patterned in a fashion similar to the wire bonding process routinely used in the semiconductor industry. The nanochannel dimensions were predominately dictated by electrospun nanofibers, showing that NFES is capable of depositing nanofibers with a diameter down to ~50 nm. Results show that reliable and repeatable nanofluidic channel arrays were speedily fabricated at a very low cost, while nanofluidic patterns and dimensions are predominantly controlled by NFES in a direct-write, addressable manner.

並列關鍵字

Near-field electrospinning (NFES) ； Nanofluidic channel ； Selective deposition ； Formation of multiple jets

參考文獻

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