"SAMs meet MEMS": surface modification with self-assembled monolayers for the dry-demolding of photoplastic MEMS/NEMS

In this contribution we demonstrate the use of self-assembled monolayers (SAMs) as anti-adhesion coating to assist the removal of photoplastic MEMS/NEMS with a patterned metal layer from the surface without wet chemical sacrificial layer etching, so-called 'dry-demolding'. The SAMs functionality here is to reduce the stiction between the surface and a thin evaporated metal film. The double-layer SAM/metal provides enough stability to support subsequent micromachining step

Photoplastic SU-8 probes for Near-Field Optical Applications

We propose a new attempt to solve the manufacturing problem of SNOM probes by a novel wafer-scale microfabrication process for sharp pyramidal and bright photoplastic probes. The probes are fabricated of a transparent photoplastic material (SU-8) which allows simple batch fabrication based on spin coating and subsequent near-ultraviolet exposure and development steps. SU-8 consists of the epoxy-based EPON SU-8 resin photosensitized with a triaryl sulfonium salt. The main interest for MOEMS applications is that SU-8 is transparent. These combined advantages are used here to define a sharp, transparent and high aspect ratio probe dedicated for near-field optical application

Micropositioning and microscopic observation of individual picoliter-sized containers within SU-8 microchannels

We describe the fabrication and application of a bioanalytical chip, made of SU-8 photoresist, comprising integrated, high aspect-ratio microfluidic channels, suitable to manipulate and investigate vesicles, cell fragments and biological cells. A central micrometer-sized aperture allows electrical particle counting and planar membrane experiments, microfluids allow (sub)micrometer-sized objects to be transported and addressed with different chemicals. Here we show how lipid vesicles are positioned with micrometer precision within the micro-channels by means of pressure and electrophoretic movement. Our approach is suited for controlling and investigating (bio)chemical synthesis and cellular signalling processes in ultrasmall individual vesicles by electro-optical technique

Fabrication of Miniaturized Shadow-mask for Local Deposition

A new tool of surface patterning technique for general purpose lithography was developed based on shadow mask method. This paper describes the fabrication of a new type of miniaturized shadow mask. The shadow mask is fabricated by photolithography and etching of 100-mm full wafer. The fabricated shadow mask has over 388 membranes with apertures of micrometer length scale ranging from 1 μm to 100s μm made on each 2mm x 2mm large low stress silicon nitride membrane. It allows micro scale patterns to be directly deposited on substrate surface through apertures of the membrane. This shadow mask method has much wider choice of deposit materials, and can be applied to wider class of surfaces including chemical functional layer, MEMS/NEMS surfaces, and biosensors

All-photoplastic microstencil with self-alignment for multiple layer shadow-mask patterning

A rapid and simple method to fabricate tiny shadow-masks and their use in multi-layer surface patterning with in situ micromechanical alignment is presented. Instead of using silicon micromachining with through-wafer etching to define the thin membrane with etched apertures, we are using photoplastic SU-8-based resist as structural material of both membrane and support rim. Two layers, 5 and 150um thick, are structured by lithography and finally released from the surface. The free-standing SU-8 membranes have apertures ranging from 6 to 300um. They are placed and mechanically fixed to the surface, which needs to be patterned. Deposition by evaporation of Cr, Au, Al or other material through the membrane apertures results in an accurate 1:1 replication of the aperture pattern. In view of multi-layer patterning, we used in situ micromechanical alignment pins or jigs and achieved an overlay precision of <2um in both x- and y-directions. The reusable shadow-masks allows for a low-cost surface patterning technique without the need for photolithography related process steps. It allows unconventional surfaces to be patterned in a rapid and vacuum-clean way on arbitrary surfaces

Options to correct local turbulent flux measurements for large-scale fluxes using an approach based on large-eddy simulation

The eddy-covariance method provides the most direct estimates for fluxes between ecosystems and the atmosphere. However, dispersive fluxes can occur in the presence of secondary circulations, which can inherently not be captured by such single-tower measurements. In this study, we present options to correct local flux measurements for such large-scale transport based on a non-local parametric model that has been developed from a set of idealized large-eddy simulations. This method is tested for three real-world sites (DK-Sor, DE-Fen, and DE-Gwg), representing typical conditions in the mid-latitudes with different measurement heights, different terrain complexities, and different landscape-scale heterogeneities. Two ways to determine the boundary-layer height, which is a necessary input variable for modelling the dispersive fluxes, are applied, which are either based on operational radio soundings and local in situ measurements for the flat sites or from backscatter-intensity profiles obtained from co-located ceilometers for the two sites in complex terrain. The adjusted total fluxes are evaluated by assessing the improvement in energy balance closure and by comparing the resulting latent heat fluxes with evapotranspiration rates from nearby lysimeters. The results show that not only the accuracy of the flux estimates is improved but also the precision, which is indicated by RMSE values that are reduced by approximately 50 %. Nevertheless, it needs to be clear that this method is intended to correct for a bias in eddy-covariance measurements due to the presence of large-scale dispersive fluxes. Other reasons potentially causing a systematic underestimated or overestimation, such as low-pass filtering effects and missing storage terms, still need to be considered and minimized as much as possible. Moreover, additional transport induced by surface heterogeneities is not considered

Fabrication and application of a full wafer size micro/nanostencil for multiple length-scale surface patterning

A tool and method for flexible and rapid surface patterning technique beyond lithography based on high-resolution shadow mask method, or nanostencil, is presented. This new type of miniaturized shadow mask is fabricated by a combination of MEMS processes and focused ion beam (FIB) milling. Thereby apertures in a 100-500 nm thick low-stress silicon nitride membrane in the size range from 100 mum were made. The stencil device is mechanically fixed on the surface and used as miniature shadow mask during deposition of metal layers. Using this method, aluminum micro- and nanostructures as small as 100 nm in width were patterned. The deposited micro- and nano-scale structures were used as etch mask and transferred into a sub-layer (in our case silicon nitride) by dry plasma etching. High-resolution shadow masking can be used to create micro/nanoscale patterns on arbitrary substrates including mechanically fragile or chemically active surfaces. (C) 2003 Elsevier Science B.V. All rights reserved

Thermal analysis, design and fabrication of microfluidic device with local temperature controls

This paper reports a microfluidic device with local temperature controls to stimulate bio-cells by heat. Thermal analysis on temperature distributions of microheaters as well as inside of fluidic channels was carried out. Moreover, temperature in microfluidic device was measured by on-chip resistive thermometers

Nanomechanical structures with 91 MHz resonance frequency fabricated by local deposition and dry etching

We report an all-dry, two-step, surface nanoengineering method to fabricate nanomechanical elements without photolithography. It is based on the local deposition through a nanostencil of a well-defined aluminum pattern onto a silicon/silicon-nitride substrate, followed by plasma etching to release the structures. The suspended 100-nm-wide, 2-mum-long, and 300-nm-thick nanolevers and nanobridges have natural resonance frequencies of 50 and 91 MHz, respectively. The fabrication method is scalable to a full wafer and allows for a variety of materials to be structured on arbitrary surfaces, thus opening new types of nanoscale mechanical systems

Photoplastic near-field optical probe with sub-100 nm aperture made by replication from a nanomould

Polymers have the ability to conform to surface contours down to a few nanometres. We studied the filling of transparent epoxy-type EPON SU-8 into nanoscale apertures made in a thin metal film as a new method for polymer/metal near-field optical structures. Mould replica processes combining silicon micromachining with the photo-curable SU-8 offer great potential for low-cost nanostructure fabrication. In addition to offering a route for mass production, the transparent pyramidal probes are expected to improve light transmission thanks to a wider geometry near the aperture. By combining silicon MEMS, mould geometry tuning by oxidation, anti-adhesion coating by self-assembled monolayer and mechanical release steps, we propose an advanced method for near-field optical probe fabrication. The major improvement is the possibility to fabricate nanoscale apertures directly on wafer scale during the microfabrication process and not on free-standing tips. Optical measurements were performed with the fabricated probes. The full width half maximum after a Gaussian fit of the intensity profile indicates a lateral optical resolution of approximate to 60 nm