Microrobots have the potential to revolutionize many aspects of medicine. These untethered, wirelessly controlled and powered devices will make existing therapeutic and diagnostic procedures less invasive and will enable new procedures never before possible. The aim of this review is threefold: first, to provide a comprehensive survey of the technological state of the art in medical microrobots; second, to explore the potential impact of medical microrobots and inspire future research in this field; and third, to provide a collection of valuable information and engineering tools for the design of medical microrobots.

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Microrobots for Minimally Invasive Medicine

A wireless power transfer system using an inductive link has been demonstrated for implantable sensor applications. The system is composed of two primary blocks: an inductive power transfer unit and a backward data communication unit. The inductive link performs two functions: coupling the required power from a wireless power supply system enabling battery-less, long-term implant operation and providing a backward data transmission path. The backward data communication unit transmits the data to an outside reader using FSK modulation scheme via the inductive link. To demonstrate the operation of the inductive link, a board-level design has been implemented with high link efficiency. Test results from a fabricated sensor system, composed of a hybrid implementation of custom-integrated circuits and board-level discrete components, are presented demonstrating power transmission of 125 mW with a 12.5% power link transmission efficiency. Simultaneous backward data communication involving a digital pulse rate of up to 10 kbps was also observed.

/pdf/an-inductive-link-based-wireless-power-transfer-system-for-3aruxp72fw.pdf

An Inductive Link-Based Wireless Power Transfer System for Biomedical Applications

Flexible biodegradable electronics have the potential to serve as the centerpiece for temporary electronically active medical implants. Biodegradable electronics may exhibit many advantages over traditional chronic implants. Two important long-term goals for biodegradable electronics are (1) supplying sufficient power and (2) reducing the invasiveness of device deployment. Edible electronic devices are capable of addressing both challenges. Here, we introduce electrochemical electronic power sources that are compatible with non-invasive deployment strategies and are composed entirely of edible materials and naturally occurring precursors that are consumed in common diets. The current sources developed herein are powered by onboard sodium ion electrochemical cells. Potentials up to 0.6 V and currents in the range of 5–20 μA can be generated routinely. These devices could serve as an enabling platform technology for edible electronics used in non-invasive sensing and stimulation of tissues within the human body.

Self-deployable current sources fabricated from edible materials

Electronic medical devices have become an indispensable part of modern healthcare. Currently, a wide variety of electronic medical devices are being used to monitor physiological parameters of the body, perform therapy and supplement or even entirely replace complex biological functions. Cardiac pacemakers, cardioverter-defibrillators and cochlear implants are a few examples of such medical devices. Proper functionality of these devices relies heavily on the continuous supply of a sufficient amount of electricity to them. In this sense, a reliable, safe and convenient method for the provision of energy is very crucial. Various approaches have been developed to fulfil the divergent and challenging energy requirements of medical devices. In this article, we present a brief overview of the energy requirements of medical devices and review the existing and emerging energy sources for application in these devices, particularly wearable and implantable devices.

Energy sources and their development for application in medical devices

Magnetic resonance-based wireless power transfer system offers a promising solution to overcome power limitations typically encountered by capsule endoscopy. Despite of much attention in this area, aspects such as power stability and power transfer efficiency remain suboptimal and therefore investigation for further improvement is still required. This paper presents a method to improve power stability as well as power transfer efficiency for wireless capsule endoscopy. A new power transmission coil capable of producing uniform magnetic field is proposed to improve power stability through uniform field that at the same time minimizes the unnecessary peak electromagnetic exposure. To improve power transfer efficiency, a mixed resonance scheme is employed. Our experimental results show improvement over existing methods where the proposed system attained power stability of 94.62% and power transfer efficiency of 4.9% under worst position of the receiving coil. Furthermore, the proposed transmitting coil provides additional advantage, where it minimized the unnecessary peak electromagnetic exposure by 26% as compared to the conventional Helmholtz coil-based system. We believe the proposed system will open new direction for future wireless capsule endoscopy and can also be useful in other industrial applications.

Stable and High-Efficiency Wireless Power Transfer System for Robotic Capsule Using a Modified Helmholtz Coil

Much research on the development of a robotic capsule and microrobot for the diagnosis of gastrointestinal diseases has been carried out. The powering of these microsystems is becoming very important as the implementation of such systems is becoming more feasible by advances in relevant technologies. A wireless power transmission system employing two coils, based on inductive coupling, is discussed in this note. The coupling coefficient between the two coils was measured on axial, lateral and pitch misalignment. The power transmission efficiency was deduced and optimized by selecting proper tuning capacitors and transmission frequency. A serial resonant circuit (SRC) on a receiving side is more adaptive by comparison with parallel resonant circuit (PRC) topology. A multi-receiving coil structure was proposed and examined in an attempt to resolve the orientation indetermination problem of a receiving coil. Experiments show that a dc power level up to 170 mW, with an efficiency of 1.3%, could be steadily received when the receiving coil was placed at the center of the transmitting coil, which can meet the requirement for electric power of some microsystems.

https://iopscience.iop.org/article/10.1088/0967-3334/28/3/N01/pdf

He Xiu

Papers

Power transmission for gastrointestinal microsystems using inductive coupling.