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Protein redox is responsible for many crucial biological processes; thus, the ability to modulate the redox proteins through external stimuli presents a unique opportunity to tune the system. In this work, we present an acousto-nanodevice that is capable of oxidizing redox protein under ultrasonic irradiation via surface-engineered barium titanate (BTO) nanoparticles with a gold half-coating. Using cytochrome c as the model protein, we demonstrate nanodevice-mediated protein oxidation. BINased on our experimental observations, we reveal that the electron transfer occurs in one direction due to the alternating electrical polarization of BTO under ultrasound. Such unique unidirectional electron transfer is enabled by modulating the work function of the gold surface with respect to the redox center. The new class of ultrasonically powered nano-sized protein redox agents could be a modulator for biological processes with high selectivity and deeper treatment sites. 

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).