The development of high quality seals for silicon patch-clamp chips.

International audiencePlanar patch-clamp is a two-dimensional variation of traditional patch-clamp. By contrast to classical glass micropipette, the seal quality of silicon patch-clamp chips (i.e. seal resistance and seal success rate) have remained poor due to the planar geometry and the nature of the substrate and thus partially obliterate the advantages related to planar patch-clamp. The characterization of physical parameters involved in seal formation is thus of major interest. In this paper, we demonstrate that the physical characterization of surfaces by a set of techniques (Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), surface energy (polar and dispersive contributions), drop angles, impedance spectroscopy, combined with a statistical design of experiments (DOE)) allowed us discriminating chips that provide relevant performances for planar patch-clamp analysis. Analyses of seal quality demonstrate that dispersive interactions and micropore size are the most crucial physical parameters of chip surfaces, by contrast to surface roughness and dielectric membrane thickness. This multi-scale study combined with electrophysiological validation of chips on a diverse set of cell-types expressing various ion channels (IRK1, hERG and hNa(v)1.5 channels) unveiled a suitable patch-clamp chip candidate. This original approach may inspire novel strategies for selecting appropriate surface parameters dedicated to biochips

Free-carrier effects in polycrystalline silicon-on-insulator photonic devices

Photonic systems integrated into microelectronic systems using the well established integrated chips fabrication technologies offer immense opportunity in overcoming the bandwidth and power limitations IC faces. The use of deposited polycrystalline silicon in the fabrication of photonic devices has the potential of offering monolithic integration, promising electrical and optical properties, under optimized micro-fabrication, and lower costs. In this thesis, the design, fabrication and optical testing of waveguide devices on polycrystalline silicon platform is presented. Single mode polysilicon waveguide devices were fabricated at the RIT SMFL. The polysilicon waveguides fabricated successfully coupled and guided light. The transmission was measured over several lengths and the cut back method was used to quantify the free carrier absorption and propagation losses of polysilicon at 1550 nm wavelength. Comparisons were made with data for crystalline silicon. The absorption coefficient for polysilicon was found to be 25.9% higher than that of crystalline silicon

ULTRA-LOW-LOSS SILICON NITRIDE WAVEGUIDE GRATINGS AND THEIR APPLICATIONS IN ASTROPHOTONICS

Recent progresses in silicon photonics have enabled many exciting applications in data communications, sensing, quantum information, and astrophotonics. Astrophotonics is an emerging research field which aims to apply the fast-evolving photonics technology to astronomy. Compared with the silicon-on-insulator (SOI) based silicon photonics, silicon nitride (SiN) based silicon photonics inherits many prominent characteristics such as CMOS compatibility and fabrication flexibility. Furthermore, SiN-based photonics excels in applications strongly associated with low loss level and wide transparent window. All these features are all very attractive for astronomical instrumentation. Typical applications of astrophotonic components are photonic lanterns, frequency combs, highly selective optical filters, and on-chip spectroscopy. Specifically, the scope of this dissertation covers the astrophotonic filters and spectroscopy, from the design, fabrication to characterization. The photonic components which they are based on are ultra-low-loss SiN waveguide and waveguide gratings. The fabrication techniques of ultra-low-loss SiN photonic devices will be first discussed. I will demonstrate several methods to reduce the waveguide and grating losses, including the optimization of SiN deposition, e-beam lithography, etching, cladding oxide deposition, and thermal annealing. In the third chapter, an efficient waveguide characterization approach is developed for measuring losses in on-chip waveguides. This approach is based on measuring the transmission of a Fabry-Perot Bragg grating cavity formed by two highly reflective and low loss Bragg grating mirrors. In the fourth chapter, I will discuss on the design and characterization of a high performance integrated arbitrary filter from 1450 nm to 1640 nm. The filter’s target spectrum is chosen to suppress the night-sky OH emission lines, which is critical for ground-based astronomical telescopes. To reduce the device footprint, the designed 50-mm-long 55-notch filter is mapped to a compact spiral waveguide. The last topic of this dissertation is on-chip spectroscopy with arrayed waveguide grating (AWG). Different with conventional AWG used in WDM telecommunication applications, this astrophotonic spectroscopic AWG particularly needs a large free spectral range (FSR) and a flat focal-plane for the following up free-space cross disperser. The basic principle and preliminary experimental results of AWG will be first presented, followed by discussions of two AWG designs with flat output-plane