In situ electroporation of mammalian cells through SiO2 thin film capacitive microelectrodes

Electroporation is a widely used non-viral technique for the delivery of molecules, including nucleic acids, into cells. Recently, electronic microsystems that miniaturize the electroporation machinery have been developed as a new tool for genetic manipulation of cells in vitro, by integrating metal microelectrodes in the culture substrate and enabling electroporation in-situ. We report that non-faradic SiO2 thin film-insulated microelectrodes can be used for reliable and spatially selective in-situ electroporation of mammalian cells. CHO-K1 and SH-SY5Y cell lines and primary neuronal cultures were electroporated by application of short and low amplitude voltage transients leading to cell electroporation by capacitive currents. We demonstrate reliable delivery of DNA plasmids and exogenous gene expression, accompanied by high spatial selectivity and cell viability, even with differentiated neurons. Finally, we show that SiO2 thin film-insulated microelectrodes support a double and serial transfection of the targeted cells.

Tuning the Electrical Parameters of p-NiOx-Based Thin Film Transistors (TFTs) by Pulsed Laser Irradiation

We utilized laser irradiation as a potential technique in tuning the electrical performance of NiOx/SiO2 thin film transistors (TFTs). By optimizing the laser fluence and the number of laser pulses, the TFT performance was evaluated in terms of mobility, threshold voltage, on/off current ratio and subthreshold swing, all of which were derived from the transfer and output characteristics. The 500 laser pulses-irradiated NiOx/SiO2 TFT exhibited an enhanced mobility of 3 cm2/V-s from a value of 1.25 cm2/V-s for as-deposited NiOx/SiO2 TFT, subthreshold swing of 0.65 V/decade, on/off current ratio of 6.5 × 104 and threshold voltage of −12.2 V. The concentration of defect gap states as a result of light absorption processes explains the enhanced performance of laser-irradiated NiOx. Additionally, laser irradiation results in complex thermal and photo thermal changes, thus resulting in an enhanced electrical performance of the p-type NiOx/SiO2 TFT structure.

Deposition and Characterization of RP-ALD SiO2 Thin Films with Different Oxygen Plasma Powers

In this study, silicon oxide (SiO2) films were deposited by remote plasma atomic layer deposition with Bis(diethylamino)silane (BDEAS) and an oxygen/argon mixture as the precursors. Oxygen plasma powers play a key role in the quality of SiO2 films. Post-annealing was performed in the air at different temperatures for 1 h. The effects of oxygen plasma powers from 1000 W to 3000 W on the properties of the SiO2 thin films were investigated. The experimental results demonstrated that the SiO2 thin film growth per cycle was greatly affected by the O2 plasma power. Atomic force microscope (AFM) and conductive AFM tests show that the surface of the SiO2 thin films, with different O2 plasma powers, is relatively smooth and the films all present favorable insulation properties. The water contact angle (WCA) of the SiO2 thin film deposited at the power of 1500 W is higher than that of other WCAs of SiO2 films deposited at other plasma powers, indicating that it is less hydrophilic. This phenomenon is more likely to be associated with a smaller bonding energy, which is consistent with the result obtained by Fourier transformation infrared spectroscopy. In addition, the influence of post-annealing temperature on the quality of the SiO2 thin films was also investigated. As the annealing temperature increases, the SiO2 thin film becomes denser, leading to a higher refractive index and a lower etch rate.

Optical Constant and Conformality Analysis of SiO2 Thin Films Deposited on Linear Array Microstructure Substrate by PECVD

SiO2 thin films are deposited by radio frequency (RF) plasma-enhanced chemical vapor deposition (PECVD) technique using SiH4 and N2O as precursor gases. The stoichiometry of SiO2 thin films is determined by the X-ray photoelectron spectroscopy (XPS), and the optical constant n and k are obtained by using variable angle spectroscopic ellipsometer (VASE) in the spectral range 380–1600 nm. The refractive index and extinction coefficient of the deposited SiO2 thin films at 500 nm are 1.464 and 0.0069, respectively. The deposition rate of SiO2 thin films is controlled by changing the reaction pressure. The effects of deposition rate, film thickness, and microstructure size on the conformality of SiO2 thin films are studied. The conformality of SiO2 thin films increases from 0.68 to 0.91, with the increase of deposition rate of the SiO2 thin film from 20.84 to 41.92 nm/min. The conformality of SiO2 thin films decreases with the increase of film thickness, and the higher the step height, the smaller the conformality of SiO2 thin films.