Ti1−Ag electrodes deposited on polymer based sensors

Abstract

Piezoelectric materials are interesting for the development of sensors and actuators for biomedical applications in areas such as smart prosthesis, implantable biosensors and biomechanical signal monitoring, among others. For acquiring or applying the electrical signal from/to the piezoelectric material, suitable electrodes can be produced from Ti based coatings with tailored multifunctional properties: conductivity and antibacterial characteristics through Ag inclusions. This work reports on Ti 1-x Ag x electrodes with different Ag/Ti atomic ratios deposited by d. c. and pulsed magnetron sputtering at room temperature on poly(vinylidene fluoride), PVDF. The X-Ray Diffraction (XRD) results revealed that the deposition conditions preserve the polymer structure and suggested the presence of crystalline Tiβ phase in pure titanium coating and fcc-Ag phase in pure silver coating. According to the results obtained from scanning electron microscopy (SEM) analysis, the coatings are homogeneous and no clusters were found; since β-PVDF is anisotropic, the deposited coatings replicate the underlying substrate surface. Sheet resistivity values show a typical behavior of a binary alloy system, with low resistivity values for coatings of zone 1 (Ti rich) and zone 3 (Ag rich) and a slightly higher resistivity values in zone 2. The piezoelectricity of the different samples show similar values.

PVD-grown antibacterial Ag-TiN films on piezoelectric PVDF substrates for sensor applications

“…composition versus deposition parameters, of the similar samples, can be found elsewhere [22,23]. For the TiN-Ag x series, with increasing nitrogen flow, the piezoelectricity response tends to decrease.…”

“…However, this slight variation does not compromise the piezoelectric response for the required application. Further discussion and details can be seen elsewhere [22,23]. The XRD pattern of Ag/Ti (0.11)R coating indicates that the most intense peak is located at ∼38.1°, which is very close to the TiAg (111) and Ag (111) peak (see figure 1b).…”

“…The XRD pattern of Ag/Ti (0.11)R coating indicates that the most intense peak is located at ∼38.1°, which is very close to the TiAg (111) and Ag (111) peak (see figure 1b). Previous studies of TiAg coatings deposited by magnetron sputtering suggested the formation of the TiAg crystalline phase, although it is difficult to identify Ag, Ti-β and TiAg phases since they show very similar diffraction patterns [9,22,23]. Together with the TiAg phase, the presence of the Ti (002) peak can also be identified, which suggests that the coating is composed by a mixture of crystalline TiAg and Ti phases.…”

“…In fact, the high temperatures associated with the sputtering process represent the major limitation in the development of functional electrode coatings on piezoelectric PVDF substrates, due to the inevitable structural changes promoted by temperature as well as eventual depolarization of the sample, which leads to the loss of the piezoelectric response. Two recent studies [22,23], show the successful deposition of Ti 1-x Ag x and Ag-TiN x coatings by sputtering on PVDF substrates, maintaining the piezoelectric response of the polymer.…”

“…Since the amount of Ti present in the coating is high (93 at. %), TiAg phase is formed until the Ag is consumed and the remaining titanium forms a crystalline Ti phase [22,23].…”