Resonant magnetoelastic microstructures for wireless actuation of liquid flow on 3D surfaces and use in glaucoma drainage implants

Magnetoelastic resonators made from metal alloy foils are widely used for miniature wireless anti-theft tags and have also been explored for use in various sensing applications.Through annealing within three-dimensional(3D)molds,these foils can be formed into curved structures.Consequently,magnetoelastic materials present an opportunity for the development of a new class of wireless,actuators that have small form factors and low surface profiles and that can conform to curved surfaces.This paper describes passive,wireless,resonant magnetoelastic actuators intended for the generation of fluid flow on the surfaces of implantable Ahmed glaucoma drainage devices.The actuators are remotely excited to resonance using a magnetic field generated by external coils.The fluid flow is intended to limit cellular adhesion to the surface of the implant,as this adhesion can ultimately lead to implant encapsulation and failure.The actuators are micromachined from planar 29-μm-thick foils of Metglas 2826MB(Fe_(40)Ni_(38)Mo_(4)B_(18)),an amorphous magnetoelastic alloy,using photochemical machining.Measuring 10.3×5.6 mm^(2),the planar structures are annealed in 3D molds to conform to the surface of the drainage device,which has an aspherical curvature.Six actuator designs are described,with varying shapes and resonant mode shapes.The resonant frequencies for the different designs vary from 520 Hz to 4.7 kHz.Flow velocities of up to 266μm s^(−1) are recorded at a wireless activation range of 25–30 mm,with peak actuator vibration amplitudes of 1.5μm.Integrated actuators such as those described here have the potential to greatly enhance the effectiveness of glaucoma drainage devices at lowering eye pressure and may also be useful in other areas of medicine.

A fully electronic microfabricated gas chromatograph with complementary capacitive detectors for indoor pollutants

This paper reports a complete micro gas chromatography(μGC)system in which all the components are lithographically microfabricated and electronically interfaced.The components include a bi-directional Knudsen pump,a preconcentrator,separation columns and a pair of capacitive gas detectors;together,these form the iGC3.c2 system.All the fluidic components of the system are fabricated by a common three-mask lithographic process.The Knudsen pump is a thermomolecular pump that provides air flow to theμGC without any moving parts.The film heaters embedded in the separation columns permit temperature programming.The capacitive detectors provide complementary response patterns,enhancing vapor recognition and resolving coeluting peaks.With the components assembled on printed circuit boards,the system has a footprint of 8×10 cm^(2).Using room air as the carrier gas,the system is used to experimentally demonstrate the analysis of 19 chemicals with concentration levels on the order of parts per million(p.p.m.)and parts per billion(p.p.b.).The tested chemicals include alkanes,aromatic hydrocarbons,aldehydes,halogenated hydrocarbons and terpenes.This set of chemicals represents a variety of common indoor air pollutants,among which benzene,toluene and xylenes(BTX)are of particular interest.

Portable comprehensive two-dimensional microgas chromatography using an integrated flowrestricted pneumatic modulator

Two-dimensional(2D)gas chromatography(GC)provides enhanced vapor separation capabilities in contrast to conventional one-dimensional GC and is useful for the analysis of highly complex chemical samples.We developed a microfabricated flow-restricted pneumatic modulator(FRPM)for portable comprehensive 2D micro-GC(μGC),which enables rapid ^(2)D injection and separation without compromising the ^(1)D separation speed and eluent peak profiles.^(2)D injection characteristics such as injection peak width and peak height were fully characterized by using flow-through micro-photoionization detectors(μPIDs)at the FRPM inlet and outlet.A ^(2)D injection peak width of~25 ms could be achieved with a ^(2)D/^(1)D flow rate ratio over 10.The FRPM was further integrated with a 0.5-m long ^(2)D μcolumn on the same chip,and its performance was characterized.Finally,we developed an automated portable comprehensive 2D μGC consisting of a 10m OV-11D μcolumn,an integrated FRPM with a built-in 0.5m polyethylene glycol ^(2)D μcolumn,and two μPIDs.Rapid separation of 40 volatile organic compounds in~5 min was demonstrated.A hybrid 2D contour plot was constructed by using both ^(1)D and ^(2)D chromatograms obtained with the two μPIDs at the end of the ^(1)D and ^(2)D μcolumns,which was enabled by the presence of the flow resistor in the FRPM.