A novel structure for chronically implantable cortical electrodes using polyimide bio-polymer was devised, which provides both flexibility for micro-motion compliance between brain tissues and the skull and at the brain/implant interface and stiffness for better surgical handling. A 5–10 µm thick silicon backbone layer was attached to the tip of the electrode to enhance the structural stiffness. This stiff segment was then followed by a 1 mm flexible segment without a silicon backbone layer. The fabricated implants have tri-shanks with five recording sites (20 µm × 20 µm) and two vias of 40 µm × 40 µm on each shank. In vitro cytotoxicity tests of prototype implants revealed no adverse toxic effects on cells. Bench test impedance values were assessed, resulting in an average impedance value of ∼2 MΩ at 1 KHz. For a 5 µm thick silicon backbone electrode, the stiffness of polyimide-based electrodes was increased ten times over that of electrodes without the silicon backbone layer. Furthermore, polyimide-based electrodes with 5 µm and 10 µm thick silicon backbone layer penetrated pia of rat brain without buckling that has been observed in implants without silicon reinforcement.

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Gas-solid heterogeneous photocatalytic oxidation of trichloroethylene (TCE) in humid airstreams is achieved at high conversion levels in a bench-scale flat-plate fluidized-bed photoreactor, which provides efficient continuous contact of near-ultraviolet photons, silica-supported titania photocatalyst, and gaseous reactants. Silica-supported titania catalysts prepared through sol-gel methods require ~1 h on stream time to develop their maximum photocatalytic oxidation activity. Steady-state reaction rates as high as 0.8 µ of TCE (g of catalyst)"1 min™1 [2 µ (g of TÍO2)"1 min™1] and quantum efficiencies of 13% have been achieved over conditioned catalysts. High conversion of dilute levels (<10 ppm) of TCE can be sustained for extended periods of operation, although the catalyst reversibly deactivates during conversion of streams containing higher TCE concentrations. Once activated, the fluidized catalyst bed responds rapidly to step changes in feed flow rate, composition, and photon flux.

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