Plastic Chip Sensor

The chip sensor (27 x 7 x 6 mm) was constructed of Plexiglas (see Fig. 3). The rectangular enzyme cell (5 x 3 x 0.5 mm) and the inlet and outlet parts were 

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Figure 3.21 — (A) Integrated FET with two hydrogen ion-sensitive FET elements. (B) Structure of enzyme-modified FET sensor S plastic card FET enzyme-modified FET chip lUM, immobilized urease membrane. (C) Flowthrough cell Bl fixed sensor cell block B2 movable sensor cell block SC flowthrough cell EC electrical connector RP silicone rubber sheet AMP amplifier. (Reproduced from [151] with permission of Elsevier Science Publishers).

Figure 12 shows the CTL-based sensor element. The platinum ribbon wire (0.2 mm in width and 0.02 mm in thickness) is spot-welled on the screen-printed substrate as heater lead wires, and the sensor chip is suspended on a plastic frame by the lead wires. In order to measure the catalyst temperature, very thin thermocouple wires are fixed on the substrate using ceramic cement. 

The relatively small measurement effect limits the achievable resolution to about 0.5 °/s and requires the operation of the sensor in a vacuum. The sensor system is packaged in a PLCC(Plastic Leaded Chip Carrier)-housing (Fig. 7.2.16). 

Although to date grating couplers have been used in SPR to a lesser extent than have prism couplers, they offer some very attractive features. Most importantly, as gratings can be fabricated by techniques such as replication into plastic substrates, grating-based SPR chips provide an avenue to low-cost SPR sensors. 

Bisphenol A (BPA) is a compound which is currently not regulated, but as it exhibits weak estrogenic properties it is a suspected endocrine disrupter [33]. BPA is widely used as a plasticizer in plastics such as polycarbonate and epoxy resins and thus it is a concern for water quahty. Soh et al. developed an SPR immunosensor based on inhibition assay to detect BPA [34]. They used a SPR-20 sensor instrument (DKK, Japan) with the sensor chip modified with thiol monolayer on which BPA was immobilized through BPA succinimidyl ester. Using a monoclonal antibody, detection of BPA in buffer at concentrations as low as 10 ngmL was achieved. Detection time was approximately 30 min and the sensor was demonstrated to be regenerable using... 

In summary, the combination of flexible light sources and photodetectors with microfluidic chips fabricated from elastomers such as polydimethylsilox-ane can enable the fabrication of low-cost all-plastic sensors that are ideally suited to low-cost point-of-care applications. 

Eiometric package—A package where the die is exposed but the interconnections are protected by a window frame and plastic encapsulant. Developed by Harris Corporation (Melbourne, FL) in 1996 for a sensor chip used to recognize a person s fingerprint. 

It should be noted that a hybrid approach to design gas-sensing devices on plastic substrates can be used as well. In particular, a surface acoustic wave (SAW) chip, which require substrates with very different properties, can be transferred onto a plastic substrate Cobianu et al. (2007). Another interesting and new approach is the coating of passive (no power source on board) conventional RFID (radiofrequency identification) tags with chemically sensitive films to form a chemical sensor (Potyrailo and Morris 2007). The detection of several vapors of industrial, health, law enforcement, and security... 

Wire bonding is the technology for contacting the optical sensors. The silicon chips are first located mechanically on the substrate by an adhesive. Metallized plastic pins produced just like the conductor tracks directly in the injection-molding process are the contacts to the periphery. 

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