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

Venkatram Pepakayala,Joshua Stein,Yogesh Gianchandani

doi:10.1038/micronano.2015.32

Venkatram Pepakayala, Joshua Stein + Show 1 more

Open Access

https://doi.org/10.1038/micronano.2015.32

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Abstract

AbstractMagnetoelastic 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 (Fe40Ni38Mo4B18), an amorphous magnetoelastic alloy, using photochemical machining. Measuring 10.3 × 5.6 mm2, 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 266 μm s−1 are recorded at a wireless activation range of 25–30 mm, with peak actuator vibration amplitudes of 1.5 μm. 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.

Highlights

Magnetoelastic devices have wide appeal for use in applications that demand passive, wireless operation
This paper describes the design and fabrication of actuators from amorphous magnetoelastic materials and results from in vitro experiments performed with these actuators
Each actuator was placed in an aqueous suspension of 3.1-μm-diameter particles (Fluoro-Max dyed green aqueous fluorescent particles, Thermo Fisher Scientific Inc., Waltham, MA, USA) at a concentration of 6 ng ml−1

Summary

Introduction

Magnetoelastic devices have wide appeal for use in applications that demand passive, wireless operation. Linear and rotary actuators have been reported[8,9], as have passive sensors that detect occlusions in biliary and peripheral artery stents[10,11]. Whereas the vast majority of reported magnetoelastic devices have been planar, a few curved structures have been described for use in sensing applications[10,14,15]. These three-dimensional (3D), out-of-plane geometries have been achieved by thermal annealing or by inducing elastic or plastic deformations. Sensors reported for detecting occlusions in biliary stents had tubular curvatures to match stent geometry[10]

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