電紡織收集器與順向性

收集板除了收集纖維外時常於文獻中看到許多研究團隊結合不同方法，¹⁸製 成可得順向纖維收集器，利用方法為：外力滾動收集板促使高速轉動、收集板電 荷分布改變、可變電場、可變磁場等等皆可製得新型順向纖維收集器。表八為常 見順向收集器。(A)、(C)型收集器，皆是利用滾輪快速轉動使落下纖維可以纏繞 在滾輪或紡輪上，造成順向排列，一般轉動速率的快慢可決定順向程度。其它類 型收集器皆是利用電場以及電荷分布改變造成纖維可收集於預訂區域。

圖十三代表了不同收集器與電場方向示意圖，我們可從電場方向了解其纖維 順向收集原因，圖十三(A)收集器利用多重電場輔助，最後可造成電場集中於收 集板上，使纖維可更有效收集。圖十三(C)之收集器，兩細長金屬棒可改變其間 距造成不同程度電場電荷分布改變，纖維最後必須於金屬棒上做收集，並除去電 荷(decharge)，其可使纖維於兩金屬棒間收集且具有順向性。圖十三(E)滾動金屬 盤收集器，即是結合滾輪特性以及唯一接地區域，迫使纖維沉積於金屬盤上，並 加速旋轉金屬盤可得順向纖維。

圖十三、不同收集器與電場方向示意圖¹⁸

下圖十四為四極板收集器，其亦可收集到順向纖維於各個極板間，原理如同 兩金屬棒收集器，利用兩導體誘導電場於兩者接觸面上集中，當纖維沉積於兩極 板間時則可具有順向排列，此些極板間距十分關鍵，唯有最適當距離下才能收集 順向程度最高纖維。

圖十四、四極板收集器及收集纖維順向圖¹⁸

除了改變電場或滾輪輔助外，文獻上亦有利用可變磁場誘使順向纖維收集方 法，在一收集板週遭放置磁鐵造成磁場如圖十五所示，由於纖維尚未接觸收集板 前皆帶有電荷，根據弗萊明右手定則，¹⁶一電流方向在磁場中將會受一同方向外 力，此收集板即是利用此原理，使纖維受磁場影響最終可有序地排列於收集板 上。如下圖十五所示，可於磁場輔助下獲得高順向排列纖維。

圖十五、磁場輔助順向收集方法¹⁷

表八、常見收集器表¹⁸ Collector type Advantages/Disadvantages A. Rotating drum Advantage

Simple set-up

Large area of aligned fibres can be fabricated Disadvantage

Highly aligned fibrous assemblies are difficult to fabricate Fibre breakage may occur if rotating speed is too high (Matthews et al 2002, Kimet al 2004, Chew et al 2005, Wannatong et al 2004)

B. Parallel electrodes Advantage Simple set-up

Highly aligned fibres are easy to obtain

Aligned fibres are easily transferable to another substrate Disadvantage

Thicker layer of aligned fibres are not possible There is a limit in the length of the aligned fibres (Li et al 2003)

C. Rotating wire drum collector

Advantage Simple set-up

Highly aligned fibres are possible Disadvantage

Thicker layer of aligned fibres are not possible

Fibres may not be aligned throughout the whole assembly (Katta et al 2004)

D. Disc collector Advantage Simple set-up

Highly aligned fibres are possible

Able to fabricate arrayed fibres by attaching a rotatable table

on the edge of the disc Disadvantage

Unable to retain high fibre alignment at the same rotating speed when the deposited fibres are thicker

Small area of fibre alignment

(Theron et al 2001, Inai et al 2005, Xu et al 2004)

表八、常見收集器表¹⁸ Collector type Advantages/Disadvantages E. Array of

counter-electrodes

Advantage Simple set-up Disadvantage

Fibre patterning is not consistent throughout the assembly

Area of the assembly is limited

Thicker fibrous assembly is not possible (Li et al 2004)

F. Blade placed in line

Negative high voltage

Advantage Simple set-up

Yarn can be easily removed from the collector Collected yarn is highly aligned

Disadvantage

Fabricated yarn is of limited length

Deposited fibres have to be dipped in water first before yarn is formed

(Teo and Ramakrishna 2005) G. Ring collector placed in

parallel

Advantage Simple set-up

Twisted yarn can be fabricated Disadvantage

Fabricated yarn is of limited length

One of the rings has to be rotated to twist the fibres that are deposited into yarn

(Dalton et al 2005) H. Controlled deposition

using ring electrodes

Advantage

Positive high voltage Negative high voltage

Area where fibres are deposited can be minimized Disadvantage

Complicated set-up

Rings have to be given a positive charge (Deitzel et al 2001a)