Search

In this paper, we study the effect of acoustic agitation on the penetration force for microinjections in Drosophila embryos for genome-wide RNA interference (RNAi) screens, using an integrated optical MEMS force encoder for in vivo characterization of the dynamic penetration forces. Two modes of operation are investigated. In the first mode of operation, the injector is brought into contact and acts on the embryo with a fixed force, and the vibration amplitude of the microinjector is increased till penetration occur. We observed a linear decrease in the penetration force of 1.6 [micro]N with every 0.1 m/s tip velocity increase. In the second mode of operation, the vibration amplitude is kept constant and the injector is pushed into the embryo until penetration. We simulate the optical force encoder eigenmodes and measure the injection force over the frequency range from 0 to 16 kHz with actuation voltages up to 150 V. Among the eight encoder eigenmodes with resonant frequency up to 16 kHz, the longitudinal vibration along the injector is shown to dominate the force reduction at 14 kHz. Two other modes, both involving significant out-of-plane injector motion, reduce the penetration force by 52% around 3.1 kHz. The average penetration force is calculated based on injections into multiple embryos for each experimental condition. For each microinjection, the peak (or average) penetration force can be derived from the peak (or average) relative displacement of the two gratings upon penetration. The achieved minimum peak penetration force was 15.6 [micro]N (~29.7% of the static penetration force), while the minimum average penetration force was 2.7 [micro]N (5.1% of the static penetration force). [1547] Index Terms--Drosophila embryo, force sensor, microsurgery, optical encoder, vibratory microinjection.

Electrical through-wafer interconnects (ETWI) which connect devices between both sides of a substrate are critical components for microelectromechanical systems (MEMS) and integrated circuits (IC), as they enable three-dimensional (3-D) structures and permit new packaging and integration geometries. Previously demonstrated ETWI are very difficult to integrate with standard semiconductor fabrication processes, not compatible with released sensors, do not permit extensive processing on both sides of the wafer, and are in general very application specific. This work describes the design, fabrication, and characterization of an ETWI technology for silicon substrates that can be broadly integrated with MEMS and IC processes. This interconnect is a passively isolated electrical through-wafer polysilicon plug, with a 20 [micro]m diameter, 10-14 [OMEGA] resistance, and less than 1 pF capacitance. Plasma etching from both sides of the wafer is used to achieve a high-aspect ratio via (20:1 through 400 [micro]m). The process is compatible with standard lithography, standard wafer handling, subsequent high-temperature processing, and released sensors integration. N-type and p-type versions are demonstrated, and isolated ground planes are added to provide shielding against substrate noise. Electrical properties of these ETWI are measured and analytically modeled. These ETWI are appropriate for integration with devices with impedances much greater than the ETWI, such as piezoresistive and capacitive sensor arrays. [850] Index Terms--Electrical through-wafer interconnects (ETWI), MEMS and IC integration, through-wafer via deep silicon plasma etch.

We present a fabrication method for silicon nitride solid immersion lenses (SILs) integrated with atomic force microscope (AFM) cantilevers. We demonstrate a scanning optical microscope based on the microfabricated SIL that operates in reflection and transmission modes at a wavelength of [lambda] = 400 nm. In this microscope, light is focused to a spot in a high refractive index SIL held close to the sample. The minimum spot size of a SIL-based microscope, which determines the transverse optical resolution, is [lambda]/(2n) where n is the refractive index of the SIL. This is smaller than the minimum spot size of [lambda]/2 in air. The SIL, therefore, makes possible optical resolution better than the diffraction limit in air. The full-width at half-maximum (FWHM) spot size of the SIL-based microscope is measured to be ~ 133 nm in transmission mode, which is ~ 1.98 times better than the spot size measured without the SIL (264 nm). This improvement factor is close to the refractive index of the silicon nitride SIL (n = 1.96). [797] Index Terms--Atomic force microscopy (AFM), microlens, near-field scanning optical microscopy, scanning probe microscopy, solid immersion lens (SILs).

High-resolution atomic force microscopy (AFM) of soft or fragile samples requires a cantilever with a low spring constant and a sharp tip. We have developed a novel process for making such cantilevers from silicon nitride with oxidation-sharpened silicon tips. First, we made and sharpened silicon tips on a silicon wafer. Next, we deposited a thin film of silicon nitride over the tips and etched it to define nitride cantilevers and to remove it from the tips so that they protruded through the cantilevers. Finally, we etched from the back side to release the cantilevers by removing the silicon substrate. We characterized the resulting cantilevers by imaging them with a scanning electron microscope, by measuring their thermal noise spectra, and by using them to image a test sample in contact mode. A representative cantilever had a spring constant of ~0.06 N/m, and the tip had a radius of 9.2 nm and a cone angle of 36[degrees] over 3 [micro]m of tip length. These cantilevers are capable of higher resolution imaging than commercially available nitride cantilevers with oxidation-sharpened nitride tips, and they are especially useful for imaging large vertical features. [735] Index Terms--Atomic force microscopy (AFM), microfabricated cantilevers, microfabricated tips, micromachining, oxidation sharpening.

The materials and physical properties of high-quality, single-walled nanotunes (SWNTs) can be measured, following progress in the synthesis of SWNTs. Individual nanotubes have to be connected, maipulated, isolated and synthesized if nanotubes and conventional microstructures are to be integrated. A strategy for producing high-qualit SWNTs on an individual basis on patterned silicon wafers has been developed using chemical vapor deposition with methane gas.

We present the microfabrication of a solid immersion lens from silicon for scanning near-field optical microscopy. The solid immersion lens (SIL) achieves spatial resolution better than the diffraction limit in air without the losses associated with tapered optical fibers. A 15-[micro]m-diameter SIL is formed by reflowing photoresist in acetone vapor and transferring the shape into single-crystal Si with reactive ion etching. The lens is integrated onto a cantilever for scanning, and a tip is fabricated opposite the lens to localize lens-sample contact. Using the Si SIL, we show that microfabricated lenses have greater optical transparency and less aberration than conventional lenses by focusing a plane wave of 633-nm light to a spot close to a wavelength in diameter. Microlenses made from absorbing materials can be used when the lens thickness is comparable to the penetration depth of the light. Tolerance to errors in curvature and thickness is improved in micromachined lenses, because spherical aberrations decrease with lens diameter. We demonstrate scanning near-field optical microscopy with the Si SIL and achieve spatial resolution below the diffraction limit in air by resolving 200-nm lines with 633-nm light. [648] Index Terms--Atomic force microscopy, microelectromechanical devices, micromatching, microscopy, optical imaging.

In this paper, we study the effect of acoustic agitation on the penetration force for microinjections in Drosophila embryos for genome-wide RNA interference (RNAi) screens, using an integrated optical MEMS force encoder for ill vivo characterization of the dynamic penetration forces. Two modes of operation are investigated, in the first mode of operation, the injector is brought into contact and acts on the embryo with a fixed force, and the vibration amplitude of the microinjector is increased till penetration occur. We observed a linear decrease in the penetration force of 1.6 μN with every 0.1 m/s tip velocity increase, in the second mode of operation, the vibration amplitude is kept constant and the injector is pushed into the embryo until penetration. We simulate the optical force encoder eigenmodes and measure the injection force over the frequency range from 0 to 16 kHz with actuation voltages up to 150 V. Among the eight encoder eigenmodes with resonant frequency up to 16 kHz, the longitudinal vibration along the injector is shown to dominate the force reduction at 14 kHz. Two other modes, both involving significant out-of-plane injector motion, reduce the penetration force by 52% around 3.1 kHz. The average penetration force is calculated based on injections into multiple embryos for each experimental condition. For each microinjection, the peak (or average) penetration force can be derived from the peak (or average) relative displacement of the two gratings upon penetration. The achieved minimum peak penetration force was 15.6 μN (∼29.7% of the static penetration force), while the minimum average penetration force was 2.7 μN (5.1% of the static penetration force). [ABSTRACT FROM AUTHOR]