Jef Thoné

Wireless powering for a self-propelled and steerable endoscopic capsule for stomach inspection

This paper describes the integration of an active locomotion module in a wirelessly powered endoscopic capsule. The device is a submersible capsule optimized to operate in a fluid environment in a liquid-distended stomach. A 3D inductive link is used to supply up to 400mW to the embedded electronics and a set of 4 radio-controlled motor propellers. The design takes advantage of a ferrite-core in the receiving coil-set. This approach significantly improves the coupling with the external field source with respect to earlier work by the group. It doubles the power that can be received with a coreless coil-set under identical external conditions. The upper limit of the received power was achieved complying with the strict regulations for safe exposure of biological tissue to variable magnetic fields. The wireless transferred power was proven to be sufficient to achieve the speed of 7cm/s in any directions. An optimized locomotion strategy was defined which limits the power consumption by running only 2 motors at a time. A user interface and a joystick controller allow to fully drive the capsule in an intuitive manner. The device functionalities were successfully tested in a dry and a wet environment in a laboratory set-up.

Wireless power and data transmission strategies for next-generation capsule endoscopes

Capsular endoscopy is becoming increasingly popular as an alternative to traditional gastro-intestinal (GI) examination techniques. However, the breakthrough of these devices is hindered by the limited amount of power that can be stored in a tiny pill. Most commercial devices use two watch batteries that can only provide an average power of 25 mW for about 6 h, certainly not sufficient for advanced robotic features. A dedicated inductive powering system, operating at 1 MHz to limit the human body absorption, has been developed which was proven to support the transfer of over 300 mW. The system relies on a condensed set of orthogonal ferrite coils, embedded in the capsule, and an external unit based on a Helmholtz coil driven by a class E amplifier. Control data can be sent through the inductive link by modulating the power carrier, whereas a dedicated high data rate RF link is used to transfer the images from the capsule to the base station. Besides evaluating the compatibility with radio transmission, several demonstrators were assembled combining the wireless powering system with various locomotion strategies and LED illumination. This paper describes the design and implementation of the inductive powering system, its combination with data transmission techniques and the testing activity with other capsule-dedicated modules.

Wireless Power and Data Transmission for Robotic Endoscopic Capsules

Robotic capsular endoscopy is nowadays a really hot topic. Scientists are fascinated by the idea of developing an integrated tool that travels through the human body while sending images, measuring biomedical parameters and performing therapeutic activity. Doctors actively support this futuristic solution aiming at non invasive examination and therapy. Patients appreciate the idea of swallowing a capsule that performs medical examinations without any pain or discomfort. Although technology has obtained results unthinkable only a few years ago, the main issue is the dramatic lack of energy in the capsule. Up to date commercial capsules are purely passive devices relying on batteries that provide a mere 25 mW for 6 to 8 hours. A promising approach to overcome energy shortage is wireless powering. A condensed set of orthogonal coils inside the capsule can retrieve more than 300 mW from an external magnetic field, without any time limitation. This solution allows the integration in the capsule of highly consuming modules such as diagnostic tools, actuators, a better camera and a high data-rate transmitter. This work presents an overview of this powering solution and proposes a few examples of system integration.

Short Distance Wireless Communications

Since the publication of the first biomedical swallowable telemetry device in 1957, an immense evolution has taken place in biomedical monitoring, stimulation and instrumentation, that would have been impossible without the use of wireless information transmission. The first section gives an overview of wireless methods for transmitting information to and from biomedical implants, followed by a practical introduction on analog and digital modulation methods, in a historical perspective. Next, methods are presented briefly for compressing the amount of transmitted information, as well as rendering the transmitted information more error-resistant. Being a design hurdle in many biomedical telemetry designs, the trade-off between antenna sizing and carrier selection is discussed. Finally, an overview is given of several published or commercial biomedical telemetry applications, with a focus on wireless transmission.

On-chip high performance magnetics for point-of-load high-frequency DC-DC converters

This paper presents the design, fabrication, and characterization of on silicon integrated micro-transformers for high frequency power applications. The microtransformer device is used and tested in DC-DC converter application at high switching frequency. This device has stable L vs. f characteristic up to 50 MHz. The design is improved regarding to the electrical resistance and current capability. The microtransformer shows an inductivity of about 60 nH, resistance of 350 mΩ and can be applied for current up to 1.5 A.

A 650 V, 3 A three-phase fully-integrated BLDC motor driver with charge pump and level shifters

A 650 V three-phase IGBT motor driver is presented in this article. Apart from the power transistors and predrivers, also freewheeling diodes are present in the output power stage to drive inductive loads. The 15 V overdrive voltage as well as all other floating supplies are generated on-chip by means of a charge pump and cascoded current mirrors. The input signals for all switches are at ground level and level-shifted internally. Each half-bridge is able to switch at 20 kHz a 1.5 A current at 600 V and a 3 A current at 300 V. The ground connection contains a current shunt and a sense-amplifier, which can be used as a feedback signal in the BLDC control loop. The system is implemented in a 1 μm SoI technology with 650 V IGBT transistors.