本論文利用STM針尖局部電場會被放大的特性，將針尖作為電極的一端以產生強大的電流，我們發現在施加AC電場作用下，流體會於針尖周圍產生類似於經典點力所驅動Landau-Squire噴流現象。據我們所知，這是首次透過AC電場所實現的點力驅動流動，但機理與Landau-Squire噴流的完全不同。藉由調整電壓以及頻率條件來辨別這些不同流動所發生的範圍，分別為交流電熱(AC electrothermal, ACET)噴流、歐姆交流電滲(Ohmic AC electro-osmotic, Ohmic ACEO)衝擊流、電化學交流電滲(Faradaic AC electro-osmotic, Faradaic ACEO)噴流。更重要的是，測量這些不同流動的流速發現皆會與距離成反比之關係，這呈現出與Landau-Squire噴流有相同的表徵。
在第四章中，我們組裝了一種T字型的電極對裝置，其中包含了由鎢絲透過電蝕刻而形成的錐形針尖，而另一端則是以未經處理的鎢線來做為電極。實驗選用純水並添加粒徑適當的追蹤劑來觀察施加不同電壓及AC頻率下的流動現象。我們發現在高頻(>1 MHz)時針尖周圍會形成ACET噴流現象。而在中高頻(10-100kHz)時將會產生由Ohmic ACEO所驅動的逆時針衝擊流，其流速會快於高頻的ACET噴流，當頻率低於1 kHz時，將出現速度極快的Faradaic ACEO噴流從針尖噴出。這些不同流態的流線會在靠近針尖時會呈現朝針尖吸引，隨後再被針尖排開的驟降現象，並在針尖附近的流速呈現出1/r的依賴性。以上結果皆指出這是一種新的Landau-Squire流動現象。當頻率調至不同流態的範圍邊界時，常會有流態共存的現象，譬如針尖處有ACET噴流，但會受到周圍Ohmic ACEO逆向渦流的干擾進而抑制其流速表現；或者是同時出現Ohmic ACEO及Faradaic ACEO這兩種不同方向的渦流在彼此競爭。
在第五章中，為了要檢驗導電度對這些不同AC流動的響應，實驗溶液換用食鹽水溶液，其導電度值約為純水的100倍。我們發現這些流動形成的範圍會發生在更高頻的情況，但流速仍然存有1/r的依賴性。而在此條件下的ACET，並未如所預期的，會受到更強的焦耳熱(Joule heating)效應而形成較快的流動，反倒是表現出更慢的流速。
在第六章中，為了更深入地探討在第四、五章所觀察到的流動現象，我們以物理角度建立了數種理論模型。爾後驗明這AC噴流現象在高頻時確實是歸因於在針尖處由局部焦耳加熱作用所致的ACET主導，造成電力會集中於針尖處，這使得局部噴流速度表現出隨針尖距離成反比的結果。與此同時，發現ACET噴流流速會更趨近於與電壓成三次方的正比關係，而非經典理論中所示的會正比於電壓四次方。此外以經典的電動學理論來闡明在中高頻所產生的逆向Ohmic ACEO衝擊流，確實流速是呈現出正比於電壓平方的關係。至於在低頻所觀察到極快的Faradaic ACEO噴流，是因電化學反應所形成的強大電流引起，進而使流速會正比於V^(3/2)logV。

In this thesis, we report experimentally that a new class of Landau-Squire flows can be achieved in a purely electrohydrodynamic manner at microscales without pump discharge using nanotubes or nanopores. Utilizing the local diverging electric field near a sharp conducting tip under the actions of ac voltages, we are able to generate a variety of electrohydrodynamic flows that display point-force-like 1/r decay at distance (r) to the tip. These flows are AC electrothermal (ACET) jet, Ohmic AC electro-osmotic (Ohmic ACEO) impinging flow, and Faradaic AC electro-osmotic (Faradaic ACEO) jet, depending on the applied voltage and frequency. In the MHz regime, an ACET jet can emit from the tip that becomes a local hotspot undergoing heated capacitive charging. The resulting electric force thus becomes point-like but varies as V^3 instead of V^4 commonly reported by literature, where V is the driving voltage. At 1–100 kHz, a reversal Ohmic ACEO impinging flow takes place and varies as V^2 in its speed. At even lower frequencies, the impinging flow turns into a jet-like electro-osmotic streaming due to an intensified Faradaic reaction around the tip. The speed of such Faradaic ACEO streaming is found to vary as V^(3/2)logV resulted by the balance between the Faradaic leakage current and tangential conduction, markedly different from (logV)^2 found for planar electrodes.

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