Fabrication of a gold microelectrode for amperometric detection on a polycarbonate electrophoresis chip by photodirected electroless plating

Abstract

A novel method of photoresist-free micropatterning coupled with electroless gold plating is described for the fabrication of an integrated gold electrode for electrochemical detection (ED) on a polycarbonate (PC) electrophoresis microchip. The microelectrode layout was photochemically patterned onto the surface of a PC plate by selective exposure of the surface coated without photoresist to 254 nm UV light through a chromium/quartz photomask. Thus, the PC plate was selectively sensitized by formation of reactive chemical moieties in the exposed areas. After a series of wet chemistry reactions, the UV-exposed area was activated with a layer of gold nanoparticles that served as a seed to catalyze the electroless plating. The gold microelectrode was then selectively plated onto the activated area by using an electroless gold plating bath. Nonselective gold deposition on the unwanted areas was eliminated by sonication of the activated PC plate in a KSCN solution before electroless plating, and the adhesion of the plated electrodes to the PC surface was strengthened with thermal annealing. Compared with the previously reported electroless plating technique for fabrication of microelectrodes on a microchip, the present method avoided the use of a membrane stencil with an electrode pattern to restrict the area to be wet-chemically sensitized. The CE with integrated ED (CE-ED) microchip was assembled by thermal bonding an electrode-plated PC cover plate to a microchannel-embossed PC substrate. The novel method allows one to fabricate low-cost, electrode-integrated, complete PC CE-ED chips with no need of a clean room. The fabricated CE-ED microchip was demonstrated for separation and detection of model analytes, including dopamine (DA) and catechol (CA). Detection limits of 0.65 and 1.03 microM were achieved for DA and CA, respectively, and theoretical plate number of 1.4 x 10(4) was obtained for DA. The plated gold electrode can be used for about 4 h, bearing usually more than 100 runs before complete failure.

Gold nanoparticle-based biosensors

“…While bulk gold is chemical inert, recent studies show that nanosized GNPs exhibit extraordinary catalytic activity [102][103][104], which is utilized by several studies in electrochemical biosensing [105][106][107][108][109]. The catalytic properties of GNPs, which are believed to originate from the quantum scale dimension [110], the large surface-to-volume ratio and the interface-dominated properties [111,112], can decrease overpotentials of many analytically important electrochemical reactions, realize the reversibility of some redox reactions, and might even allow fabrication of enzyme-free biosensors.…”

A high‐performance polycarbonate electrophoresis microchip with integrated three‐electrode system for end‐channel amperometric detection

“…The procedure employed for fabrication of gold microelectrodes using the photo-directed electroless gold plating was as described in our previous report [30]. Briefly, a PC sheet of 4065062 mm was exposed to UV light in atmosphere for 3 h through a quartz glass photomask, the electrode pattern on the mask being transferred to the UV-exposed area through photolysis.…”

“…To achieve this, researchers have used an inchannel detection mode in combination with an electricallyisolated potentiostat or power supply [4,5], while others have applied an off-channel detection mode in conjunction with a field decoupler, such as a membrane decoupler [6,7] or Pd/ Pt cathode decouplers [8][9][10][11][12][13][14]. Most reports, however, have adopted an end-channel detection mode [3,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], because of its simpler in-chip fabrication protocols and/or instrumentation in comparison to the off-channel and in-channel detection modes. Two approaches are commonly used in end-channel detection to diminish the HV-field interference with ED using a separation channel with sufficiently small inner dimensions, and/or placing the working electrode 10-60 mm away from the exit of the separation channel.…”

“…Challenge associated with fabricating metal electrodes on polymers using standard lithographic techniques is that the solvents used for the photoresist or that used for removal of the resist can be non-compatible with the underlying polymer substrate [36,37]. In our previous work [30], we used a novel photoresist free micropatterning technique coupled with electroless plating [38] to fabricate a micro gold working electrode on a PC plate, which was assembled with a channel-structured PC substrate to form a complete PC CE-ED microchip with an integrated working electrode. This novel technique, referred to as photo-directed electroless plating, can be used to fabricate a variety of different metal electrodes onto polymer substrates, without the need for lithographic processing or the concern of non-compatibility with the underlying substrate.…”

Region-selective Metalization of Poly(methylmethacrylate) Surface Based on UV/ozone Surface Modification

“…在前期工作中, 我们采用紫外光区域改性结合化 学镀的方法在聚碳酸酯(PC) [5] 、聚苯乙烯(PS) [6] 、聚对苯 二甲酸乙二醇酯(PET) [7] 的微流控电泳芯片上成功制备 了安培检测微电极. 金永龙等 [8] 、 唐红肖等 [9] 也采用紫外 光改性结合化学镀法, 分别在聚萘二甲酸乙二醇酯 (PEN)上制备铜微电极 [8] 和在 PET 上制备微银薄膜图 形 [9] .…”