RESUMEN
Microelectromechanical system-based microphones demand high ingress protection levels with regard to their use in harsh environment. Here, we develop environmental protective components comprising polyimide nanofibers combined onto polyether ether ketone fabric meshes and subsequently appraise their impact on the electroacoustic properties of high signal-to-noise-ratio microelectromechanical system-based microphones via industry-standard characterizations and theoretical simulations. Being placed directly on top of the microphone sound port, the nanofiber mesh die-cut parts with an inner diameter of 1.4 mm result in signal-to-noise-ratio and insertion losses of (2.05 ± 0.16) dB(A) and (0.30 ± 0.11) dBFS, respectively, in electroacoustic measurements. Hence, a high signal-to-noise-ratio value of (70.05 ± 0.17) dB(A) can be maintained by the mesh-protected microphone system. Due to their high temperature stability, acoustic performance, environmental robustness, and industry-scale batch production, these nanofibrous meshes reveal high potential to be practically implemented in high-market-volume applications of packaged microelectromechanical system-based microphones.
RESUMEN
Sulphur hexafluoride (SF(6)) plasma treatments and hexamethyl disiloxane (HMDSO) plasma polymerisation were performed on poly(ethylene terephthalate) (PET) meshes and the resulting wettability against liquids having very different surface tensions were investigated at the light of a possible use of the materials in the fuel/water separation technology. Surface modification of the meshes owing to HMDSO plasma polymerisation followed by SF(6) plasma treatment was also investigated. Hydrophobic performances were characterised refining the conventional Wilhelmy dynamic contact angle (DCA) technique, using several reference solutions having the surface tension values between 20-72 mN/m. Measurements of the water intrusion pressure (WIP) of the treated samples were also performed. Surface modifications on the plasma treated meshes were investigated by means of Fourier-transform infrared absorption spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis. SF(6) and HMDSO plasma treatments decrease the surface energy of the PET meshes, lowering the liquid surface tension at which the wettable/unwettable transition occurs and increasing the WIP. Moreover, an increase in hydrophobic performances was achieved with HMDSO plasma polymerisation followed by SF(6) plasma treatment.
RESUMEN
This work deals with the optimization of argon plasma-induced graft-polymerization of polyethylene glycol acrylate (PEGA) on polypropylene (PP) films in order to obtain surfaces with a reduced protein adsorption for possible biomedical applications. To this end, we examined the protein adsorption on the treated and untreated surfaces. The graft-polymerization process consisted of four steps: (a) plasma pre-activation of the PP substrates; (b) immersion in a PEGA solution; (c) argon plasma-induced graft-polymerization; (d) washing and drying of the samples. The efficiency of these processes was evaluated in terms of the amount of grafted polymer, coverage uniformity and substrates wettability. The process was monitored by contact angle measurements, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS) and atomic force microscopy (AFM) analyses. The stability of the obtained thin films was evaluated in water and in Phosphate Buffer Saline (PBS) at 37 degrees C. The adsorption of fibrinogen and green fluorescent protein (GFP)--taken as model proteins--on the differently prepared surfaces was evaluated through a fluorescence approach using laser scanning confocal microscopy with photon counting detection. After plasma treatments of short duration, the protein adsorption decreases by about 60-70% with respect to that of the untreated film, while long plasma exposure resulted in a higher protein adsorption, due to damaging of the grafted polymer.