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We present a multifunctional packaging technique for implantable microdevices. The packaging is composed of 3D printed bulk piezoelectric barium titanate (BaTiO3) ceramic with unique geometry shaped (i.e., regular convex polyhedrons; Platonic solid). The BaTiO3 ceramic provides not only a seamless packaging for essential electronics but also a power source for those electronics through the conversion of incoming ultrasound. Ultrasound has been an attractive powering source for many implantable microdevices [1]. However, most ultrasonic receivers are rectangular or disc, not in ideal form factors; ultrasound is often deflected within the path, and the miniature implants might shift and rotate, resulting in an angular misalignment. Tailoring a three-dimensional polyhedral architecture (i.e., Platonic solid) for an mm-scale ultrasonic receiver can dramatically enhance its omnidirectionality. Utilizing the 3D printing technique, we devised a dodecahedron shaped BaTiO3 ceramic with the center void space for electronics embodiment. As a proof of concept, an LC (inductor-capacitor pair) resonator is implemented as a representative implantable microdevice [2, 3]. The LC resonator has been utilized in physiological sensing by employing either a capacitive or inductive sensor. These sensors are typically powered by inductive coupling or batteries which can be impracticable when the implant is placed deep inside the tissues. Instead, the ultrasound-mediated interrogation scheme can compensate for these inadequacies. When ultrasound impacts the dodecahedron BaTiO3 ultrasonic receiver, it energizes the embedded LC oscillator, generating resonance radio frequency (RF) waves, which can be detected by an external antenna (Fig. 1).
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OMNIDIRECTIONAL POLYHEDRAL ULTRASOUND TRANSDUCER FOR POWERING IMPLANTABLE MICRODEVICES
Ultrasonic powering is an emerging power source for implantable microdevices due to its superior efficiency in energy transfer at millimeter-scale, long operation distance, and near omnidirectionality. In this paper, we investigate a novel polyhedral ultrasound transducer with emphasis on angular alignment between piezoelectric poling vector and incident waves. Three different polyhedrons (i.e., sphere, octahedron, and dodecahedron) are fabricated via 3D printing lead-free barium titanate ceramic. The maximum output voltage for a unit area occurred at 0° when the poling and waves direction aligned, which were measured to be 0.677±0.071,1.058±0.049 , and 0.709±0.092 V , respectively. At the extreme angular misalignment at 90° (poling and waves perpendicular to each other), only the dodecahedron could sustain the voltage output with 21% reduction, whereas sphere and octahedron dropped by 46%. The results imply that the geometry factor may overcome the poling vector, enabling omnidirectional ultrasonic powering for implantable microdevices.
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- Award ID(s):
- 2143723
- PAR ID:
- 10324514
- Date Published:
- Journal Name:
- 2021 21st International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers)
- Page Range / eLocation ID:
- 1404 to 1407
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/Transducers50396.2021.9495556
