Smart-Cut Layer Transfer of Single-Crystal SiC Using Spin-on-Glass

The authors demonstrate “smart-cut”-type layer transfer of single-crystal silicon carbide (SiC) by using spin-on-glass (SoG) as an adhesion layer. Using SoG as an adhesion layer is desirable because it can planarize the surface, facilitate an initial low temperature bond, and withstand the thermal stresses at high temperature where layer splitting occurs (800–900 °C). With SoG, the bonding of wafers with a relatively large surface roughness of 7.5–12.5 Å rms can be achieved. This compares favorably to direct (fusion) wafer bonding, which usually requires extremely low roughness (\u3c2 Å rms), typically achieved using chemical mechanical polishing (CMP) after implantation. The higher roughness tolerance of the SoG layer transfer removes the need for the CMP step, making the process more reliable and affordable for expensive materials like SiC. To demonstrate the reliability of the smart-cut layer transfer using SoG, we successfully fabricated a number of suspended MEMS structures using this technology

Communication and control system for a 15-channel hermetic retinal prosthesis

A small, hermetic, wirelessly-controlled retinal prosthesis has been developed for pre-clinical studies in Yucatan minipigs. The device was attached conformally to the outside of the eye in the socket and received both power and data wirelessly from external sources. Based on the received image data, the prosthesis drove a subretinal thin-film polyimide array of sputtered iridium oxide stimulating electrodes. The implanted device included a hermetic titanium case containing a 15-channel stimulator and receiver chip and discrete circuit components. Feedthroughs in the hermetic case connected the chip to secondary power- and data-receiving coils, which coupled to corresponding external power and data coils driven by power amplifiers. Power was delivered by a 125 kHz carrier, and data were delivered by amplitude shift keying of a 15.5 MHz carrier at 100 kbps. Stimulation pulse strength, duration and frequency were programmed wirelessly from an external computer system. The final assembly was tested in vitro in physiological saline and in vivo in two minipigs for up to five and a half months by measuring stimulus artifacts generated by the implant's current drivers.United States. Dept. of Veteran AffairsUnited states. Dept. of Veterans Affairs. Boston Healthcare SystemNational Institutes of Health (U.S.)United States. Dept. of DefenseMassachusetts Lions Foundatio

An Integrated-Photonics Optical-Frequency Synthesizer

Integrated-photonics microchips now enable a range of advanced functionalities for high-coherence applications such as data transmission, highly optimized physical sensors, and harnessing quantum states, but with cost, efficiency, and portability much beyond tabletop experiments. Through high-volume semiconductor processing built around advanced materials there exists an opportunity for integrated devices to impact applications cutting across disciplines of basic science and technology. Here we show how to synthesize the absolute frequency of a lightwave signal, using integrated photonics to implement lasers, system interconnects, and nonlinear frequency comb generation. The laser frequency output of our synthesizer is programmed by a microwave clock across 4 THz near 1550 nm with 1 Hz resolution and traceability to the SI second. This is accomplished with a heterogeneously integrated III/V-Si tunable laser, which is guided by dual dissipative-Kerr-soliton frequency combs fabricated on silicon chips. Through out-of-loop measurements of the phase-coherent, microwave-to-optical link, we verify that the fractional-frequency instability of the integrated photonics synthesizer matches the $7.0*10^{-13}$ reference-clock instability for a 1 second acquisition, and constrain any synthesis error to $7.7*10^{-15}$ while stepping the synthesizer across the telecommunication C band. Any application of an optical frequency source would be enabled by the precision optical synthesis presented here. Building on the ubiquitous capability in the microwave domain, our results demonstrate a first path to synthesis with integrated photonics, leveraging low-cost, low-power, and compact features that will be critical for its widespread use.Comment: 10 pages, 6 figure

Rapid metal‐free macromolecular coupling via In Situ nitrile oxide‐activated alkene cycloaddition

Nitrile oxide 1,3 dipolar cycloaddition is a simple and powerful coupling methodology. However, the self-dimerization of nitrile oxides has prevented the widespread use of this strategy for macromolecular coupling. By combining an in situ nitrile oxide generation with a highly reactive activated dipolarophile, we have overcome these obstacles and present a metal-free macromolecular coupling strategy for the modular synthesis of several ABA triblock copolymers. Nitrile oxides were generated in situ from chloroxime terminated poly(dimethylsiloxane) B-blocks and coupled with several distinct hydrophilic (poly(2-methyloxazoline) and poly(ethylene glycol)), and poly(N-isopropylacrylamide) or hydrophobic (poly(L-lactide) A-blocks terminated in activated dipolarophiles in a rapid fashion with high yield. This methodology overcomes many drawbacks of previously reported metal-free methods due to its rapid kinetics, versatility, scalability, and ease of introduction of necessary functionality. Nitrile oxide cycloaddition should find use as an attractive macromolecular coupling strategy for the synthesis of biocompatible polymeric nanostructures

Velocity Profiles in Pores with Undulating Opening Diameter and Their Importance for Resistive-Pulse Experiments

[Image: see text] Pores with undulating opening diameters have emerged as an analytical tool enhancing the speed of resistive-pulse experiments, with a potential to simultaneously characterize size and mechanical properties of translocating objects. In this work, we present a detailed study of the characteristics of resistive-pulses of charged and uncharged polymer particles in pores with different aspect ratios and pore topography. Although no external pressure difference was applied, our experiments and modeling indicated the existence of local pressure drops, which modified axial and radial velocities of the solution. As a consequence of the complex velocity profiles, pores with undulating pore diameter and low-aspect ratio exhibited large dispersion of the translocation times. Distribution of the pulse amplitude, which is a measure of the object size, was not significantly affected by the pore topography. The importance of tuning pore geometry for the application in resistive-sensing and multipronged characterization of physical properties of translocating objects is discussed

Velocity profiles in pores with undulating opening diameter and their importance for resistive-pulse experiments.

Pores with undulating opening diameters have emerged as an analytical tool enhancing the speed of resistive-pulse experiments, with a potential to simultaneously characterize size and mechanical properties of translocating objects. In this work, we present a detailed study of the characteristics of resistive-pulses of charged and uncharged polymer particles in pores with different aspect ratios and pore topography. Although no external pressure difference was applied, our experiments and modeling indicated the existence of local pressure drops, which modified axial and radial velocities of the solution. As a consequence of the complex velocity profiles, pores with undulating pore diameter and low-aspect ratio exhibited large dispersion of the translocation times. Distribution of the pulse amplitude, which is a measure of the object size, was not significantly affected by the pore topography. The importance of tuning pore geometry for the application in resistive-sensing and multipronged characterization of physical properties of translocating objects is discussed

The Boston retinal prosthesis a 15-channel hermetic wireless neural stimulator

A miniaturized, hermetically-encased, wirelessly-operated retinal prosthesis has been developed for pre-clinical studies in Yucatan minipig animal models. The prosthesis attaches conformally to the outside of the eye and drives a microfabricated thin-film polyimide stimulating electrode array with sputtered iridium oxide electrodes. This array is implanted in the subretinal space using a specially-designed ab externo surgical technique that uses the retina to hold the array in place while leaving the bulk of the prosthesis outside the eye. The implanted device includes a hermetic titanium case containing a 15-channel stimulator chip and discrete circuit components. Feedthroughs from the case connect to secondary power- and data-receiving coils. In addition, long-term in vitro pulse testing was performed on the electrodes to ensure that their lifetime would match that of the hermetic case. The final assembly was tested in vitro to verify wireless operation of the system in biological saline using a custom RF transmitter circuit and primary coils. Stimulation pulse strength, duration and frequency were programmed wirelessly using a custom graphical user interface. Operation of the retinal implant has been verified in vivo in two pigs for up to five and a half months by measuring stimulus artifact on the eye surface using a contact lens electrode.Center for Innovative Visual Rehabilitation (U.S.)National Institutes of Health (U.S.) (EY016674-01)National Science Foundation (U.S.) (IIS-0515134)Catalyst FoundationMOSIS Servic

Realization of a 15-channel, hermetically-encased wireless subretinal for the blind

A miniaturized, hermetically-encased, wirelessly-operated retinal prosthesis has been developed for implantation and pre-clinical studies in Yucatan mini-pig animal models. The prosthesis conforms to the eye and drives a microfabricated polyimide stimulating electrode array with sputtered iridium oxide electrodes. This array is implanted in the subretinal space using a specially-designed ab externo surgical technique that affixes the bulk of the prosthesis to the surface of the sclera. The implanted device includes a hermetic titanium case containing a 15-channel stimulator chip and discrete power supply components. Feedthroughs from the case connect to secondary power- and data-receiving coils. In addition, long-term in vitro pulse testing was performed on the electrodes to ensure their stability for the long lifetime of the hermetic case. The final assembly was tested in vitro to verify wireless operation of the system in biological saline using a custom RF transmitter circuit and primary coils. Stimulation pulse strength, duration and frequency were programmed wirelessly using a custom graphical user interface. Operation of the retinal implant has been verified in vivo in one pig for more than three months by measuring stimulus artifacts on the eye surface using a contact lens electrode.National Science Foundation (IIS-0515134)National Institutes of Health (EY016674-01)MOSIS ServiceCatalyst FoundationUnited States Dept. of Veteran Affairs. Center for Innovative Visual Rehabilitatio