Patterning electrodes using

The sputtering technique has been used in the preparation of SOFC electrodes, and is generally combined with photolithography in the production of thin-lilm patterned electrodes that are mainly used in fundamental reactivity and mechanistic studies [120], Although it is a versatile technique that allows for excellent control of composition and morphology, and relatively low temperatures that help to prevent unwanted reactivity observed at higher temperatures, its major limitations lie in the equipment costs and in the slow deposition rates ( 5 pm/h) [120],... 

Radhakrishnan R, Virkar AV, and Singhal SC. Estimation of charge-transfer resistivity of Pt cathode on YSZ electrolyte using patterned electrodes. J. Electrochem. Soc. 2005 152 A927-A936. 

Figure 3. LEED pattern of the Pt(lll) electrode used for the reported research. The beam energy was 65 eV.

Figure 7.8 Schematic representation of a typical wall-jet electrode used for electroanalytical measurements (a) contact to Pt disc electrode (the shaded portion at the centre of the figure) (b) contact to ring electrode (c) AgCl Ag reference electrode (d) Pt tube counter electrode (e) cell inlet (f) cell body (made of an insulator such as Teflon), (b) A typical pattern of solution flow over the face of a wall-jet electrode, showing why splash back does not occur. Part (a) reproduced from Brett, C. M. A. and Brett, A. M. O., Electroanalysis, 1998, 1998, by permission of Oxford University Press.

An example of a microelectroporation device [51,52] fabricated on a silicon substrate is shown in Figure 8.25. It consisted of patterned electrode blocks separated by a 5-p.m gap. The blocks of electrodes were separated by parylene. First, the cells and the medium were pumped into the channel. Next, the cells were attracted to the sharp point of the electrode by dielec-trophoretic force using ac voltage in the frequency range of a few hundred kilohertz to a few megahertz. Then they were lysed by a pulsed electric field. The electrode was designed to have sharp edges, so that the electric field was concentrated there. 

Figure 21.7 Transmission electron micrograph (a) (x 88000) and electron diffraction pattern (b) of the composition graded transitional buffering fdm layered by double-graded process (1 copper electrode used 2 silver electrode used).

Fig. 2. Illustration of the concept of the active-area density used to describe patterned electrode surfaces (A) bare, flat electrode, (B and C) flat electrodes covered by resist patterns of different density, (D) electrode with topographic pattern. (Reprinted by permission of the publisher. The Electrochemical Society, Inc. [25]).

To address this we have recently developed unique optofluidic based on chip SERS devices. The chip exploits our previously developed electro-active microwells [11] which are used here to enhance mixing for DNA hybridization and concentration for sample enrichment (Fig. 7). The chip comprises of a glass substrate with lithographically patterned electrodes. The substrate and electrodes are covered with an electrically insulating polyimide layer into which 10 pm diameter wells and microfluidic system are etched. After completion we align and bond the PDMS cover to the bottom substrate such that the wells align with the spaces in the upper electrodes. 

In order to fuUy exploit the scalability of DE actuators, it necessary to be able to pattern electrodes on the micro scale as well. Rosset el al have explored the use of ion implanted metal electrodes in PDMS [221-224]. Their results show that conductivity can be maintained for strains up to 175% and can remain conductive over 10 cycles at 30% strain. This is of particular importance for MEMS microfluidic devices where the DE micro-actuators could be used as micro-pumps. The ion-implanted films maintained high breakdown fields (>100 MV m ) while the Young s modulus increased by 50-200% depending on the dose. 

Figure 5 shows the surface morphology of a polycrystalline Ti02 after photoetching at 4-1.0 V versus SCE, which is about 1.2 V anodic with respect to photocurrent onset at the electrode. The electrode used is a pellet prepared by sintering at 1300 C for six hours in N2 atmosphere and subsequently reduced at 700 °C for four hours in 10% H2/N2 gas to get n-type semiconductivity. These SEM pictures show that the characteristic etching pattern... 

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