傳統的印刷電路板製程需經過上光阻、曝光、顯影及蝕刻等步驟，步驟繁瑣且蝕刻會產生廢液，若將噴墨印刷技術應用在印刷電路板等電子工業上，則能簡化步驟且不會有蝕刻所產生的廢液。目前奈米銀墨水發展較為成熟，一來銀本身的導電性佳二來對氧的活性較小，但是銀價格較高且離子遷移(Ion migration)較嚴重。銅的導電性與銀相近、價格便宜且離子遷移沒有銀嚴重，具有發展的潛力，但銅較容易氧化，若能克服容易氧化的問題，奈米銅墨水就可以取代奈米銀墨水。
本研究將氫氧化銅及異硬脂酸於正庚烷中合成異硬脂酸銅(Copper Isostearate, Cu(ISt)2)，並以其為前驅物，聚乙烯吡咯烷酮(PVP)為保護劑，維生素C為還原劑，甲醇及無水酒精為溶劑，於還原過程中引入高壓二氧化碳形成二氧化碳膨脹液體，能在溫和的條件下(41 °C及CO2壓力736 psi)短時間(5分鐘)得到粒徑小(平均粒徑12 nm)的奈米銅。
製備之奈米銅應用部分分為銅墨水及高壓流體反溶劑法成膜。銅墨水方面為將製備之奈米銅懸浮溶液以離心去除雜質，再加入無水酒精及乙二醇以超音波震盪再分散，將之旋轉塗佈於玻璃片上，於燒結後能得到電阻率7.9×10-6 Ω·m之導電銅膜。而高壓流體反溶劑法成膜則是直接將製備好的奈米銅懸浮溶液以高壓二氧化碳為反溶劑沉積在玻璃上並乾燥，於燒結後能得到電阻率6.46×10-3 Ω·m之導電銅膜。

The traditional printed circuit board process involves coating photoresist, exposure, development, etching and so on. It includes many steps and etching will produce waste. If the inkjet printing technology can be used in printed circuit boards and other electronic industries, the process can be simplified and there will be no waste produced by etching. At present, the development of silver inks is more mature. The first reason is that silver is the most conductive metal. The second reason is that silver is stable under ambient atmospheric conditions. But the price of silver is higher and ion migration is more serious. The conductivity of copper is close to silver, but it’s cheaper and ion migration is not as serious as silver. Copper has the potential to be used in inkjet printing technology, but copper is easier to oxidize. If we can overcome the problem about oxidation, copper inks can replace silver inks.
In this study, we can synthesize copper isostearate from copper hydroxide and isostearic acid in heptane. We use copper isostearate as precursors, PVP as capping agents, vitamin C as reducing agents, methanol and absolute alcohol as solvents. In the process of reducing reaction, we introduce high-pressure CO2 to form CO2-expanded liquids, so that small copper nanoparticles (average particle size 12 nm) can be obtained in a short time (5 minutes) under mild conditions (41 ° C and CO2 pressure 736 psi).
The application parts of copper nanoparticle suspensions can be divided into copper ink and preparation of copper films by compressed fluid anti-solvent. To prepare copper ink, first we remove impurities by centrifugation, and then mix copper nanoparticles with absolute alcohol and ethylene glycol. After oscillating the mixed solution using ultrasonic waves, the well- dispersed solutions are copper inks. After sintering the spin-coated film, we can get a conductive copper film with the resistivity of 7.9×10-6 Ω·m. The preparation of copper films by compressed fluid anti-solvent can directly precipitate copper nanoparticles on the glass by high pressure CO2 as anti-solvent and open the valve to leak the liquid. Then dry the film by scCO2. After sintering, we can get a conductive copper film with the resistivity of 6.46×10-3 Ω·m.

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