Figure 1.Schematic drawing of impedance based bacteria sensor for suspended (top) and attached cells (bottom). Reproduced with permission from reference [16].Carbonaro et al. have developed an on-chip artificial pore that could be used to detect bacterial pathogens [20]. The microfluidic chip was constructed with polydimethylsiloxane (PDMS) having a fluid channel (a pore) with cross-sectional dimension of 15 �� 15 ��m. The pore was functionalized with proteins that can specifically interact with cell-surface receptors. Cells suspended in a solution were introduced to the channel. The presence of cells blocks the current across the pore. The target cells that express receptors specific to the immobilized proteins stayed longer inside the pore than control cells.
Thus, the duration of the current pulse could discern the difference in the affinity of the cells to
In the last years, fiber Bragg grating (FBG) based sensors have been applied in a growing range of sensing applications, since their response to temperature or strain, or related measurands, is encoded as a linear or near-linear function of wavelength. Due to their extraordinary properties such as immunity to electromagnetic interference, remote sensing, stability in harsh environments, multiplexing capability, high sensitivity, wide dynamic range and simplicity FBG sensors offer solutions in situations where conventional sensors are unsuitable.In particular, underwater acoustic measurement is an important area of interest, and a number of FBG pressure sensor configurations have been demonstrated [1-3].
The operating principle of a FBG-based hydrophone is typically based on the intensity modulation of the laser light due to the shift of transmission power spectrum curve of the sensing element under the influence of the acoustic field. However, for practical use, the low sensitivity to acoustic pressure of the FBG based sensors limit their use in underwater applications, where piezoelectric transducers are widely used, despite their dimensions, complex signal processing and electronic front-end and difficult multiplexing. This limit is essentially due to the high Young module of the optical fiber material (tens of GPa) which converts the effects of a high pressures applied on the grating in weak deformations.
Recently, the authors have shown how it is possible to enhance the sensitivity of FBGs in pressure and acoustic detection by coating the grating region with a material of low elastic modulus [4]. For a given acoustic pressure, Drug_discovery the basic effect of the FBG coating is to enhance the dynamic strain experienced by the sensor of a factor given by the ratio between the fiber and the coating elastic modulus. According to this, an opportune coating can tailor the sensor directivity, the bandwidth and the acoustic sensitivity in water.