Woosub Youm

Biocompatible wireless power transferring based on ultrasonic resonance devices

To increase application area of implantable devices for medical treatment including implantable cardiac defibrillator or deep brain stimulator, wireless power transfer is highly required. Previous technologies such as magnetic resonance and induction coupling have limited applications because of short transfer distance compared to device size and magnetic field intensity limitation for the safety of body exposure. The biocompatible wireless power transferring technology is proposed using ultrasonic resonance method. In power transfer through tissue, since the distance between transmitter and receiver is not adjustable, the optimum power transfer condition is changed. For efficient power transferring, operating frequency should be adjusted based on acoustic radiation and spatial pressure distribution. The ultrasonic resonance transmitter and receiver are manufactured with 50mm diameter and 250 kHz resonance frequency. In case of water medium, since it is easy to adjust frequency at fixed distance, it bring...

A Wireless 32-Channel Implantable Bidirectional Brain Machine Interface.

All neural information systems (NIS) rely on sensing neural activity to supply commands and control signals for computers, machines and a variety of prosthetic devices. Invasive systems achieve a high signal-to-noise ratio (SNR) by eliminating the volume conduction problems caused by tissue and bone. An implantable brain machine interface (BMI) using intracortical electrodes provides excellent detection of a broad range of frequency oscillatory activities through the placement of a sensor in direct contact with cortex. This paper introduces a compact-sized implantable wireless 32-channel bidirectional brain machine interface (BBMI) to be used with freely-moving primates. The system is designed to monitor brain sensorimotor rhythms and present current stimuli with a configurable duration, frequency and amplitude in real time to the brain based on the brain activity report. The battery is charged via a novel ultrasonic wireless power delivery module developed for efficient delivery of power into a deeply-implanted system. The system was successfully tested through bench tests and in vivo tests on a behaving primate to record the local field potential (LFP) oscillation and stimulate the target area at the same time.

Resonant ultrasonic wireless power transmission for bio-implants

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.

Biocompatible wireless power transferring and charging based on ultrasonic resonance devices

To increase application area of implantable devices for medical treatment including implantable cardiac defibrillator or deep brain stimulator, the rechargeable battery module is highly requested. The previous Li-type battery has limited current sources, so that the patient is forced to have surgery just for changing battery. Previous technologies such as magnetic resonance and induction coupling have limited applications because of its short transfer distance compared to device size and magnetic field intensity limitation for the safety of body exposure. As an alternative, the biocompatible wireless power transferring and charging technology is proposed using ultrasonic resonance devices. For the high efficient power transferring, optimal transfer frequency is calculated based on the acoustic radiation and damping effect. Then, the optimal load resistance is selected for matching power condition in receiver. And, transmitter is designed to match the optimal transfer frequency. The ultrasonic resonance tr...

Extraction and Analysis of Respiratory Motion Using Wearable Inertial Sensor System during Trunk Motion

Respiratory activity is an essential vital sign of life that can indicate changes in typical breathing patterns and irregular body functions such as asthma and panic attacks. Many times, there is a need to monitor breathing activity while performing day-to-day functions such as standing, bending, trunk stretching or during yoga exercises. A single IMU (inertial measurement unit) can be used in measuring respiratory motion; however, breathing motion data may be influenced by a body trunk movement that occurs while recording respiratory activity. This research employs a pair of wireless, wearable IMU sensors custom-made by the Department of Electrical Engineering at San Diego State University. After appropriate sensor placement for data collection, this research applies principles of robotics, using the Denavit-Hartenberg convention, to extract relative angular motion between the two sensors. One of the obtained relative joint angles in the “Sagittal” plane predominantly yields respiratory activity. An improvised version of the proposed method and wearable, wireless sensors can be suitable to extract respiratory information while performing sports or exercises, as they do not restrict body motion or the choice of location to gather data.