精微電加工法開發內皮層陣列腦波探針研究

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2014

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本研究旨在針對擷取腦波訊號的內皮層陣列探針,提出一種複合式精微電加工(Hybrid micro electro-machining)的製程技術,此項技術包含兩部分:螺旋式放電加工(Spiral EDM)及鍍銀技術(Silver plating)。研究之初,以外徑ψ300μm碳化鎢棒材,對鉻銅(Cu-Cr)棒材進行螺旋式微孔放電,製成具陣列式微孔電極。再令鉻銅電極倒置夾持,對黃銅(Brass)電極(腦波探針素材)進行螺旋式放電,透由電極搖動、啄鑽運動與一系列精微放電加工參數的實驗,以獲得精確的內皮層陣列腦波探針,探針之尺寸規劃為:5×5陣列針數、探針高度350μm、探針尖端外徑50μm、探針錐率1:7。由實驗得知,採用兩段式電容放電加工,可獲得一適當的表面粗糙度Ra2.9μm,此表面粗糙度恰能提供針體對腦部皮層組織足夠的摩擦力,使探針不易脫落。完成的陣列探針,再輔以銀電法快速覆層,以便提高探針表面的電導度。實驗也證實,以批量式放電製作內皮層腦波陣列探針,可獲得最快的成形時間:3.1分/顆,比起單顆探針製作(5.8分/顆),約僅一半的加工時間。完成的內皮層陣列腦波探針進行腦波擷取實驗,所獲得的腦波訊號(α波, β波, θ波, δ波),包括波形強度及波形重現性,皆證實優於市售的腦波電極;而探針使用壽命經1000次插拔及50次的側向搖動測試後,發現探針仍能維持其原有的形狀精度,證實本研究所開發的內皮層陣列探針能精確應用於腦波訊號的量測,並且,所提複合式精微電加工法著實能應用於生醫領域。
This study presents the development of hybrid micro electro-machining technique in which spiral electrical discharge machining (EDM) and silver plating are employed to fabricate a penetrating intra-cortical probe array for detecting human brain activity. The probe owns a design of 5×5array micro pillar. The height, tip diameter, taper rate of each micro pillar and the inter-pillar spacing are 350µm, 50µm,1:7 and 550µm,respectively. A micro-holes array is first formed on a small rod-shaped copper-chromium (Cu-Cr) workpiece by using spiral EDM and micro tungsten carbide electrode with a 300μmdiameter. Spiral EDM operation is again employed to machine the penetrating intra-cortical probe array on a rod-shaped brass workpiece by applying the finished Cu-Cr electrode. After a series of spiral EDM experiments, it is found that two-step capacity discharge can achieve a surface roughness of Ra2.9μmon the pillar surface, which provides sufficient friction between the contact interfaces. Also, experimental results confirmed that batch spiral EDM can speed the fabrication of probe array up to 3.1 minutes each piece. This time is approaching half of the machining time for single probe array(5.8 minutes). To increase the conductivity of the probe array, silver plating process with 1μmin coating thickness is implemented. Experiment in human brain activity detection is conducted and obtained as α, β, θ and δ activities via the finished penetrating intra-cortical probe array. It was verified that the developed probe array used in the intensity and repeatability of the signal activity is superior to that of the existing commercial probe. After life tests with inserting/pulling out of 1000 times and waggling of 50 times, the form accuracy of the probe can still be kept demonstrated that the developed probe can really be used in measurement of human brain activity. Also, the proposed micro electro-machining technique can contribute significantly to the bio-medical field.

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內皮層陣列腦波探針, 複合式精微電加工, 螺旋式放電加工, 鍍銀技術, 腦波波形

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