Resonant ultrasonic wireless power transmission for bio-implants

Abstract

In this paper, we present the ultrasonic wireless power transmission system as part of a brain-machine interface (BMI) system in development to supply the required electric power. Making a small-size implantable BMI, it is essential to design a low power unit with a rechargeable battery. The ultrasonic power transmission system has two piezoelectric transducers, facing each other between skin tissues converting electrical energy to mechanical vibrational energy or vice versa. Ultrasound is free from the electromagnetic coupling effect and medical frequency band limitations which making it a promising candidate for implantable purposes. In this paper, we present the design of piezoelectric composite transducer, the rectifier circuit, and rechargeable battery that all packaged in biocompatible titanium can. An initial prototype device was built for demonstration purpose. The early experimental results demonstrate the prototype device can reach 50% of energy transmission efficiency in a water medium at 20mm distance and 18% in animal skin tissue at 18mm distance, respectively.

A Wireless 32-Channel Implantable Bidirectional Brain Machine Interface

“…Wireless power transmission is an attractive alternative to batteries in low-power biomedical implants and has received increasing research interest in recent years [33,34]. Radio frequency (RF), ultrasound [15,35], infrared light and low-frequency magnetic field are considered as viable wireless power transfer options. Wireless power charging technologies, such as magnetic resonance and induction coupling, have limited applications because of their short transfer distance compared to device size and the magnetic field intensity limitation for the safety of body exposure.…”

“…As an alternative, the biocompatible wireless power transfer using ultrasonic resonance developed in a collaborating study offers a smaller circuit size and no heat dissipation. In this study, we used the wireless power transfer technique fully described in [15] to deliver power to the implantable BBMI system as demonstrated in Figure 3. Also illustrated in Figure 3, ultrasonic wireless power transmission is composed of converting electrical energy to ultrasonic energy and vice versa.…”

“…Since the wireless BBMI system we proposed would be placed as a skull implant, the scalp is the only object that lies between the ultrasonic transmitter and the receiver. The detailed implementation of the ultrasonic power transmitter and the receiver is presented in our previous work [15]. The key parameters of the novel ultrasonic power transfer module are listed in Table 1.…”

“…Based on the brain activity report, the system can induce stimulation to the brain and record neural activity as a response to the stimulus. The system utilizes the ultrasonic power transfer technique developed in a collaborative study [15] for wirelessly charging an on board battery. The hardware and component-based software platform we developed were validated through in vivo tests and adapted by other research groups.…”

Through-Metal-Wall Power Delivery and Data Transmission for Enclosed Sensors: A Review

“…Acoustic waves, especially ultrasonic waves, have widely been used in fields such as underwater acoustic communications [ 23 , 24 ], industrial detection and health monitoring of structures [ 25 ]. Wireless ultrasonic power transfer has been used to power biomedical implants through human tissues [ 26 , 27 , 28 , 29 ], so this should be a favorable solution for power delivery and data transmission through metal walls by means of ultrasound. However, this field is less well developed than areas such as underwater acoustic communications.…”