Pickup heads

By exploiting these weU-estabUshed microfluidic liquid handling capabihties and coupling them with optical detection modules often akin to the pickup head of a conventional optical disc drive (ODD), a wide range of bioanalytical assays has been integrated and automated in a sample-to-answer fashion for point-of-care/ point-of-use scenarios on a user-friendly and cost-efficient LoaD platform. 

The term Bio-CD has been coined to refer to platforms which utilize the immobihzation of biological samples on a (semi-)reflective CD or DVD surface [8]. The main optical detection method associated with Bio-CDs is spinning disc interferometry while Bio-CD platforms also utilize ODD technology as a common method for readout via the ODD pickup head. 

An example of a LoaD platform utilizing ODD pickup head readout has been shown for microparticle and cell counting applications... 

Using the building blocks described above, we have built several optical systems on MEMS micro-optical benches. A femtosecond autocorrelator has been constructed to measure the pulse width of extremely short optical pulses (120 femtoseconds has been demonstrated experimentally). A single-chip optical disk pickup head has also been realized. 

The question at hand is in what format, hereafter called modulation, should the quantized samples be placed for faithful transmission through the channel and subsequent reproduction The answer depends on the channel. In the case of magnetic recording media, low-frequency response of the medium and recording and pickup heads is poor, so a type of modulation must be used that minimizes the low-frequency content of the signal being recorded. A myriad of formats is possible. We will discuss only a few. In Fig. 12.50, several possible formats are shown. 

Certain polymers, such as polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), possess special properties in the film form, caileApiezoelectricity and pyroelectricity. Piezoelectricity is electric polarization of a film produced by mechanical strain in some crystals. The polarization is proportional to the amount of strain and changes sign with it. The reverse is true and an electrical polarization induces a mechanical strain in piezoelectric sensors. Pyroelectricity is electric polarization of a film induced by thermal absorption in some polymer crystals. The induced polarization is proportional to the level of thermal change. These properties can be used in the manufacture of transducers, microphones, loudspeakers, pressure gauges, pickup heads, hydrophones, motion sensors, and other devices from biaxially oriented PVDF films. Table 13.37 gives the properties of a piezoelectric film of polyvinylidene fluoride. 

Another type of flow meter is the turbine flow meter This meter consists of a wheel with a set of curved blades (turbine blades) mounted inside a duct. The curved blades cause the wheel to rotate as liquid passes through them. The rate at which the wheel rotates is proportional to the rate of flow of the liquid. This rate of rotation is measured magnetically using a blade passing under a magnetic pickup mounted on the outside of the meter. The correlation between the pickup and the liquid rate of flow is calibrated into a readout. Turbine flow meters are also intrusive flow meters however, because rotation is facilitated by the curved blades, the head loss through the unit is small, despite its being intrusive. 

A. Iraqi and D. F. Pickup. Preparation and characterization of tractable regioregular head-to-tail poly(3-alkylthiophene)s with ferrocene substituents. Polym. Int. 55, 780-783 (2006). 

Magnetic flux was provided from a Mullard Ticonal Gn permanent magnet. The probe pin passes this flux through the pickup coil. Its head should be large to collect maximum flux, and since its shank must be shaped to accommodate the coil and finally be reduced to the diameter of the probe pin, a funnel shape is required. 

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