No abstract

The optical transduction of acoustic emission signals offers many advantages over piezoelectric devices. These include high bandwidth, no modification to the signal as well as providing contactless measurement. The major difficulties associated with optical devices are stability against low frequency vibrations and the generally complex nature of an optical interferometer. This paper describes the attempts to miniaturize a Michelson interferometer while at the same time overcoming some of the stability problems associated with these devices.Active stability of an interferometric transducer with dimensions of ~ 5cm (2") cube has been achieved over 8 fringes of red light at 100Hz and 4 fringes at 300Hz. The range of active stabilization of the interferometer is limited by the frequency response of the large amplitude piezoelectric element and the filter characteristics of the feedback electronics. A sensitivity of 0.5R (0.5 x 10-lOm) has been achieved.

Radio frequency (RF) biosensors are an expanding field of interest because of the ability to design noninvasive, label-free, low-production-cost sensing devices. Previous works identified the need for smaller experimental devices, requiring nanoliter to milliliter sampling volumes and increased capability of repeatable and sensitive measurement capability. The following work aims to verify a millimeter-sized, microstrip transmission line biosensor design with a microliter well operating on a broadband radio frequency range of 1.0–17.0 GHz. Three successive experiments were performed to provide evidence for (1) repeatability of measurements after loading/unloading the well, (2) sensitivity of measurement sets, and (3) methodology verification. Materials under test (MUTs) loaded into the well included deionized water, Tris-EDTA buffer, and lambda DNA. S-parameters were measured to determine interaction levels between the radio frequencies and MUTs during the broadband sweep. MUTs increasing in concentration were repeatably detected and demonstrated high measurement sensitivity, with the highest error value observed being 0.36%. Comparing Tris-EDTA buffer versus lambda DNA suspended in Tris-EDTA buffer suggests that introducing lambda DNA into the Tris-EDTA buffer repeatably alters S-parameters. The innovative aspect of this biosensor is that it can measure interactions of electromagnetic energy and MUTs in microliter quantities with high repeatability and sensitivity.

An ideal ultrasonic transducer will be one which responds accurately to an ultrasonic waveform. Information contained within the original waveform should be easily obtained from the output of such a transducer. This will require the transducer to have a number of characteristics: i) Wide bandwidth-for some measurements response up to lOMHz is required. ii) High sensitivity-gives the ability to detect defects at a distance.