Ultrasound‐Induced Wireless Energy Harvesting for Potential Retinal Electrical Stimulation Application

Abstract

Retinal electrical stimulation for people with neurodegenerative diseases has shown to be feasible for direct excitation of neurons as a means of restoring vision. In this work, a new electrical stimulation strategy is proposed using ultrasound-driven wireless energy harvesting technology to convert acoustic energy to electricity through the piezoelectric effect. The design, fabrication, and performance of a millimeter-scale flexible ultrasound patch that utilizes an environment-friendly lead-free piezocomposite are described. A modified dice-and-fill technique is used to manufacture the microstructure of the piezocomposite and to generate improved electrical and acoustic properties. The as-developed device can be attached on a complex surface and be driven by ultrasound to produce adjustable electrical outputs, reaching a maximum output power of 45 mW cm −2 . Potential applications for charging energy storage devices and powering commercial electronics using the device are demonstrated. The considerable current signals (e.g., current >72 µA and current density >9.2 nA µm −2 ) that are higher than the average thresholds of retinal stimulation are also obtained in the ex vivo experiment of an implanted environment, showing great potential to be integrated on implanted biomedical devices for electrical stimulation application.

3D-Printing Piezoelectric Composite with Honeycomb Structure for Ultrasonic Devices

“…Both sides of the sputtered device were connected with copper wires, and then the combined components were encapsulated with Ecoflex resin to form the final ultrasonic device ( Figure 7 b). Finally, an ultrasound test system consisting of a 1 MHz ultrasound transmitter, a function generator, an amplifier, and an oscilloscope was used to evaluate the ultrasound sensing performance of the device [ 22 ].…”

“…Both sides of the sputtered device were connected with copper wires, and then the combined components were encapsulated with Ecoflex resin to form the final ultrasonic device (Figure 7b). Finally, an ultrasound test system consisting of a 1 MHz ultrasound transmitter, a function generator, an amplifier, and an oscilloscope was used to evaluate the ultrasound sensing performance of the device [22]. To characterize the sensing capability of the manufactured ultrasonic device, the ultrasound transmitter generates ultrasound under various input voltages at a frequency of 1 MHz, and then the ultrasound directly propagates to the area of the device.…”

“…The energy induced by ultrasound or kinetic energy has promising potential in various medical applications, especially in the development of piezoelectric energy harvesters or ultrasonic sensors. For example, a flexible energy harvester with outstanding acoustic, electrical, and mechanical properties was recently implanted wirelessly into eyeballs for the electric stimulation of nerves, in which the piezoelectric part was induced by ultrasound that is harmless to the human body [22]. In general, piezoelectric materials can be classified into the three categories: inorganic materials, organic materials, and composites of both.…”

“…Moreover, the honeycomb structure could be fabricated as a composite material by introducing low-permittivity epoxy. As a result, the voltage coefficient (g 33 = d 33 /ε) can be augmented by lowering the permittivity, effectively improving the sensitivity of the piezocomposite to sense ultrasound [22]. Kim et al also showed the 3D-printed honeycomb structure could be optimized to achieve better material properties, such as excellent electric properties, mechanical strength, and larger specific surface area [37][38][39].…”

Modeling of a Rope-Driven Piezoelectric Vibration Energy Harvester for Low-Frequency and Wideband Energy Harvesting

“…In recent years, the great demand for micro-energy harvesting devices has been continuously increasing with the wide application of wearable device and wireless sensors due to the limited life-span and disposal pollution of the battery [ 1 , 2 , 3 ]. Mechanical vibration energy has been one of the major energy sources due to its ubiquity in the environment.…”