We have developed an integrated microfluidic platform for producing 2-[(18)F]-fluoro-2-deoxy-D-glucose ((18)F-FDG) in continuous flow from a single bolus of radioactive isotope solution, with constant product yields achieved throughout the operation that were comparable to those reported for commercially available vessel-based synthesisers (40-80%). The system would allow researchers to obtain radiopharmaceuticals in a dose-on-demand setting within a few minutes. The flexible architecture of the platform, based on a modular design, can potentially be applied to the synthesis of other radiotracers that require a two-step synthetic approach, and may be adaptable to more complex synthetic routes by implementing additional modules. It can therefore be employed for standard synthesis protocols as well as for research and development of new radiopharmaceuticals.
Using a commercial finite-element simulation tool, this work considers some of the electromechanical effects commonly neglected during the analysis of electrostatically actuated fixed–fixed beams. These structures are used in many applications of micromechanical systems, from relay switches and RF resonators to thin film characterization tests, but much of the analytical modelling of the device behaviour disregards the effects of electrostatic field fringing, plane-strain conditions and anchor compliance. It is shown that the cumulative total of these errors can be substantial, and may lead to large discrepancies in the expected operational characteristics of the device. We quantify the influence of these effects on the electrostatic pull-in of fixed–fixed beams, and illustrate some of the limitations of ideal pull-in theory. In order to more accurately predict the pull-in voltage for a real structure, a model is developed that combines ideal case theory with anchor compliance correction factors extracted using finite-element analysis. Three common anchor types (ideal, step-up and cup-style) are characterized. The final model takes account of the compliance of the beam anchors, electrostatic field fringing and plane-strain effects, and agrees well with simulated results.
As microelectromechanical systems (MEMS) move rapidly towards
commercialization, the issue of mechanical characterization has emerged as a
major consideration in device design and fabrication. It is now common to include
a set of test structures on a MEMS wafer for extraction of thin film material
properties (in particular, residual stress, stress gradient and Young’s modulus),
and for process and device monitoring. These structures usually consist of
micromachined beams and strain gauges. Measurement techniques include tensile
testing, scanning electron microscopy (SEM) imaging, atomic force microscopy
(AFM) analysis, surface profiling and Raman spectroscopy. However, these tests
are often destructive and may be difficult to carry out at the wafer scale.
Instead of these methods, this paper uses white-light interferometry surface
profiling for material characterization and device inspection. Interferometry
is quick, non-destructive, non-contact, and can offer a high density
lateral resolution with extremely high sensitivities to the surface in the
z-direction—all
essential requirements for high volume manufacturing. A range of devices is
employed to illustrate the capabilities of white-light interferometry as a
measurement and process characterization tool.It is shown that residual stress
may be determined by using electrostatic actuation to pull fixed–fixed beams
towards the substrate, and interferometry to record the beam deflection profile.
Finite-element simulation software is employed to model this deflection, and to
estimate the material properties which minimize the difference between the
measured and simulated profiles. The results agree well with blanket film
measurements.
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