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

Abstract

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 Â 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 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.

Translational Applications of Hydrogels

“…Novel properties that may further enhance these coatings include the ability to undergo wettability changes for self-cleaning 576 and the use of mechanical vibration to displace the attachment of proteins, cells, and bacteria. 577,578 5.2.3. Hydrogels as Anti-Fouling Coatings.…”

“…Continued development of these materials against virulent bacterial strains is critical and will need to exploit all the properties hydrogels have to offer: meshes that can encapsulate drugs over long terms (at least days); mechanics that affect adhesion of the gel to the device; and the ability to respond dynamically to stimuli (e.g., temperature and inflammation). Novel properties that may further enhance these coatings include the ability to undergo wettability changes for self-cleaning and the use of mechanical vibration to displace the attachment of proteins, cells, and bacteria. , …”

Microfluidics in the eye: a review of glaucoma implants from an engineering perspective

“…5e, Pepakayala and colleagues have proposed to attach passive, wireless, resonant magnetoelastic actuators to the endplate body, which is intended for the generation of fluid flow on the surfaces of the AGV, thus limiting cellular adhesion and FC formation. 150 The actuators can be remotely excited to resonate using a magnetic field generated by external coils. However, it is unfriendly to use for the patients since they will need an external device to continually excite the actuators.…”

Implantable Sensors for Regenerative Medicine

“…Magnetoelastic materials can also be deployed as implantable actuators [77,78]. By incorporating a high-strain magnetoelastic material such as Terfenol-D to orthopedic implants, it is possible to produce a mechanically active, externally controlled fixation device for bone fracture repair.…”