本研究使用那菲翁(Nafion®)製作一平面型離子交換膜連接兩微管道於一微逆電透析發電裝置。兩不同濃度之鹽溶液(氯化鈉)分別填充於於此微逆電透析發電裝置的兩微管道中，實驗結果證實了此微逆電透析發電裝置可成功地將吉伯斯混合自由能(或所謂的擴散電流及電位)轉換為電能。
本研究亦探討了鹽溶液濃度比及溶液酸鹼值對於擴散電位(或所謂的開路電壓)及微逆電透析發電效能的影響。實驗結果顯示當鹽溶液的濃度比落於區間100-1000時(即10 mM | 0.1 mM ~ 100 mM | 0.1 mM)，此微逆電透析發電裝置可產生最高之擴散電位值。另外，當鹽溶液較酸(擁有較低pH值)時，微逆電透析發電裝置將獲得較低之擴散電位。此原因可歸咎於較酸的鹽溶液通常使得陽離子交換膜內之奈米孔洞表面擁有較少表面電荷密度，即陽離子傳遞數較小。一般而言，擁有較大之陽離子傳遞數將擁有較高之擴散電位及輸出電功，此亦表示偏酸性鹽溶液將使得陽離子交換膜微逆電透析發電裝置擁有較差之轉換效率。本研究的實驗結果顯示此微逆電透析發電裝置在鹽溶液濃度比為 10 mM | 0.1 mM 及pH值為7.6時，產生了最大輸出電功為122皮瓦特，其對應之輸出電壓及轉換效率分別為45微伏特及30%左右。
由於非常小的接觸面積產生於交換膜與鹽溶液之間，使得此微逆電透析發電裝置產生非常小的輸出電功，為了獲取一較實用的電功值，足夠大的交換膜與鹽溶液間接觸面積在未來將被必須製作於此類型微發電裝置。

In this study, we employed the Nafion® as a planar ion-exchange membrane to bridging two parallel microchannels in a micro-reverse electrodialysis (RED) device. The two microchannels were filled with two different salt concentrations (sodium chloride solution). Then, the electric power generation from the Gibbs free energy of mixing (i.e., diffusion current and diffusion potential) in this micro-RED device has been successfully demonstrated.
The effects of the salt concentration ratio and the pH value of the salt solution on the diffusion potential (i.e., open-circuit voltage) and the performance of this micro-RED device have been studied. The experimental results showed that a highest value of the diffusion potential always is obtained when the salt concentration ratio falls in the range of 100-1000 (i.e., 10 mM | 0.1 mM ~ 100 mM | 0.1 mM). In addition, the smaller diffusion potential was obtained when the salt solution has a lower pH value. This is attributed to a lower pH value usually indicates a smaller transference number of the counter-ion (or surface charge density) inside the cation-exchange membrane. A larger transference number of the counter-ion reveals a higher diffusion potential and a higher output power. This also implies that the lower pH value has the lower conversion efficiency in a RED device with a cation-exchange membrane. The highest output power of this micro-RED device was found to be approximately 122 pW when the salt concentration ratio is 10 mM | 0.1 mM and the pH value is 7.6. The corresponding output voltage and conversion efficiency are estimated to be 45mV and 30%, respectively.
The low output power was harvested in this work is due to a very small contact area of the Nafion® membrane and the salt solution was created in our micro-RED device (i.e., a very thin membrane 7μm was coated on the glass surface). In order to harvest a more practical electric power from a micro-RED device, an ion-exchange membrane with an enough large contact area (or thickness) will be created in the future.

[1] Wick G.L., “Power from salinity gradients”, Energy 3 95-100 1978
[2] Długołęcki P.E., “Mass transport in reverse electrodialysis for sustainable energy generation”, PhD Thesis, University of Twente, The Netherlands
[3] Feynman. R.P., “There’s Plenty of Room at the Bottom”, Journal of Microelectromechanical Systems 1 60-66 1992
[4] Petersen K.E., “Silicon as a mechanical material Proc”, IEEE 70 420–456 1982
[5] Seidel H., “The mechanism of anisotropic silicon etching and its relevance for micromachining”, In Transducers ’87 Dig. Tech. Pap. Int. Conf. Solid-State Sensors Actuators, 4th, Tokyo, 120–125 1987
[6] Ristic L., “Sensor Technology and Devices”, Boston: Artech House. 524 1994
[7] Manz A., Graber N., Widmer H.M., “Miniaturized total chemical analysis systems: A novel concept for chemical sensing”, Sensors and Actuators B, Vol. 244-248 1990
[8] Pennathur S., Eijkel J.C.T., van den Berg A., “Energy conversion in microsystems: is there a role for micro/nanofluidics?”, Lab on a Chip 7 1234–1237 2007
[9] Majumdar A., Tien CL., “Micro power devices”, Microscale Thermophysical Engineering 2 67–69 1998
[10] Van der Heyden F.H.J., Bonthuis D.J., Stein D., Meyer C., Dekker C., “ Electro-chemo-mechanical energy conversion in nanofluidicchannels”, NanoLetters 7 1022–1025 2007
[11] Veerman J., Saakes M., Metz SJ., Harmsen GJ., “Reverse electrodialysis: performance of a stack with 50 cells on the mixing of sea and river water”, Journal of Membrane Science 327 136–144 2009
[12] Pattle R.E., “Production of electric power by mixing fresh and salt water in the hydroelectric pile”, Nature 174 660 1954
[13] Weinstein J.N., Leitz F.B., “Electric power from differences insalinity: the dialytic battery”, Science 191 557–559 1976
[14] Audinos R., “Electric power produced from two solutions of unequal salinity by reverse electrodialysis”, Indian Journal of Chemistry 348‐354 1992
[15] Lacey R.E., “Energy by Reverse Electrodialysis”, Ocean Engineering 7 147 1980
[16] Joseph Jagur-Grodzinski R.K., “Novel Process for Direct Conversion of Free Energy of Mixing into Electric Power”, Industrial Engineering Chemistry Process 443-449 1986
[17] Audinos R., “Inverse electrodialysis: study of electric energy obtained starting with two solutions of different salinity”, Journal of Power Sources 10 203–217 1983
[18] Turek M., Bandura B., “Renewable energy by reverse electrodialysis”, Desalination 205 67-74 2007
[19] Suda F., Matsuo T., Ushioda D., “Transient changes in the power output from the concentration difference cell (dialytic battery) between seawater and river water”, Energy 32 165-173 2007
[20] Koter S., “Influence of the layer fixed charge distribution on the performance of an ion‐exchange membrane”, Journal of Membrane Science 108 177-183 1995
[21] Jiang L., Wang Y., Zhu D., Song Y., Xue J., Ma W., Nie F.Q., Xia J., Cao L., Guo W., “Energy Harvesting with Single-Ion-Selective Nanopores: A Concentration-Gradient-Driven Nanofluidic Power Source”, Advanced Functional Materials 20 1339-1344 2010
[22] Kim D.K., Duan C., Chen Y.F., Majumdar A., “Power generation from concentration gradient by reverse electrodialysis in ion-selective nanochannels”, Microfluidics and Nanofluidics 9 1215-1224 2010
[23] Jönsson M., Lindberg U., “A planar polymer microfluidic electrocapture device for bead immobilization”, Journal of Micromechanics and Microengineering 16 2116-2120 2006
[24] Han J., Song Y.K., Lee J.H., “Multiplexed proteomic sample preconcentration device using surface-patterned ion-selective membrane”, Lab on a Chip 8 596-601 2008
[25] Probstein R.F., “Physicochemical hydrodynamics: an introduction (New York: John Wiely & Sons)”, 1994
[26] Pu Q., Yun J., Temkin H., Liu S., “Ion-Enrichment and Ion-Depletion Effect of Nanochannel Structures”, Nano Letters 1099‐1103 2004
[27] Schoch R.B., Han J., Renaud P., “Transport phenomena in nanofluidics”, Reviews of Modern Physics 839-883 2008
[28] Martin C. R., Szentirmay M.N., “Ion-Exchange Selectivity of Nafion® Films on Electrode Surfaces”, Analytical Chemistry 56 1898-1902 1984
[29] Moore R. B., Mauritz K.A., “State of Understanding of Nafion®”, Chemical Reviews 104 4535-4585 2004
[30] MicroChem “NANOTM SU-8 Negative Tone Photoresist Formulations 2–25”, Datasheet Rev.