Michael P. Kummer
ETH Zurich
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Publication
Featured researches published by Michael P. Kummer.
IEEE Transactions on Robotics | 2007
Jake J. Abbott; Olgaç Ergeneman; Michael P. Kummer; Ann M. Hirt; Bradley J. Nelson
We calculate the torque and force generated by an arbitrary magnetic field on an axially symmetric soft-magnetic body. We consider the magnetization of the body as a function of the applied field, using a continuous model that unifies two disparate magnetic models. The continuous torque and force follow. The model is verified experimentally, and captures the often neglected region between weak and saturating fields, where interesting behavior is observed. We provide the field direction to maximize torque for a given field magnitude. We also find an absolute maximum torque, for a given body geometry and material, which can be generated with relatively weak applied fields. This paper is aimed at those interested in systems-level analysis, simulation, and real-time control of soft-magnetic bodies.
international conference on robotics and automation | 2010
Bradley E. Kratochvil; Michael P. Kummer; Jake J. Abbott; Ruedi Borer; Olgaç Ergeneman; Bradley J. Nelson
We demonstrate five-degree-of-freedom (5-DOF) wireless magnetic control of a fully untethered microrobot (3-DOF position and 2-DOF pointing orientation). The microrobot can move through a large workspace and is completely unrestrained in the rotation DOF. We accomplish this level of wireless control with an electromagnetic system that we call OctoMag. OctoMags unique abilities are due to its utilization of complex nonuniform magnetic fields, which capitalizes on a linear representation of the coupled field contributions of multiple soft-magnetic-core electromagnets acting in concert. OctoMag was primarily designed to control intraocular microrobots for delicate retinal procedures, but it also has potential uses in other medical applications or micromanipulation under an optical microscope.
IEEE Sensors Journal | 2008
Olgaç Ergeneman; Gorkem Dogangil; Michael P. Kummer; Jake J. Abbott; Mohammad Khaja Nazeeruddin; Bradley J. Nelson
The influence of oxygen on various ophthalmological complications is not completely understood and intraocular oxygen measurements are essential for better diagnosis and treatment. A magnetically controlled wireless sensor device is proposed for minimally invasive intraocular oxygen concentration measurements. This device will make it possible to make measurements at locations that are currently too invasive for human intervention by integrating a luminescence optical sensor and a magnetic steering system. The sensor works based on quenching of luminescence in the presence of oxygen. A novel iridium phosphorescent complex is designed and synthesized for this system. A frequency-domain lifetime measurement approach is employed because of the intrinsic nature of the lifetime of luminescence. Experimental results of the oxygen sensor together with magnetic and hydrodynamic characterization of the sensor platform are presented to demonstrate the concept. In order to use this sensor for in vivo intraocular applications, the size of the sensor must be reduced, which will require an improved signal-to-noise ratio.
international symposium on experimental robotics | 2014
Bradley E. Kratochvil; Michael P. Kummer; Sandro Erni; Ruedi Borer; Dominic R. Frutiger; Simone Schürle; Bradley J. Nelson
The MiniMag is a magnetic manipulation system capable of 5 degree-of-freedom (5-DOF) wireless magnetic control of an untethered microrobot (3-DOF position, 2-DOF pointing orientation). The system has a spherical workspace with an intended diameter of approximately 10 mm, and is completely unrestrained in the rotational degrees-of-freedom. This is accomplished through the superposition of multiple magnetic fields, and capitalizes on a linear representation of the coupled field contributions of multiple softmagnetic- core electromagnets acting in concert. The prototype system consists of 8 stationary electromagnets with ferromagnetic cores, and is capable of producing magnetic fields in excess of 20 mT and field gradients in excess of 2 T/m at frequencies up 2 kHz.
medical image computing and computer assisted intervention | 2011
Christos Bergeles; Michael P. Kummer; Bradley E. Kratochvil; Carsten Framme; Bradley J. Nelson
The progress of wet age-related macular degeneration can now be controlled by intravitreal drug injection. This approach requires repeated injections, which could be avoided by delivering the drug to the retina. Intraocular implants are a promising solution for drug delivery near the retina. Currently, their accurate placement is challenging, and they can only be removed after a vitrectomy. In this paper, we introduce an approach for minimally invasive retinal drug delivery using magnetic intraocular inserts. We briefly discuss the electromagnetic-control system for magnetic implants and then focus on evaluating their ability to move in the vitreous humor. The mobility of magnetic intraocular implants is estimated in vitro with synthesized vitreous humors, and ex vivo with experiments on cadaver porcine eyes. Preliminary results show that with such magnetic implants a vitrectomy can be avoided.
international conference of the ieee engineering in medicine and biology society | 2007
Michael P. Kummer; Jake J. Abbott; Sandro Dinser; Bradley J. Nelson
In this paper we present a protocol to create artificial vitreous humor phantom tissue to be used as a test bed for in vitro experiments. The artificial vitreous consists of water, agar, and hyaluronic acid. Unlike existing vitreous replacement substances, this dummy tissue exhibits viscoelastic characteristics of in vivo natural vitreous humor. We are able to prepare artificial vitreous with a range of viscoelastic properties, which will allow us to account for the variation seen in human vitreous that comes with aging. The artificial vitreous will primarily serve as an experimental test bed for wireless magnetic control and vision-based tracking of assembled-MEMS microrobots. These microrobots will someday enable minimally invasive surgical and diagnostic intraocular procedures.
international conference on robotics and automation | 2007
Michael P. Kummer; Jake J. Abbott; Karl Vollmers; Bradley J. Nelson
Microrobots experience physical phenomena that are difficult to model analytically and that are not completely captured with macro-scale prototypes. In this paper we present a reconfigurable robotic measurement system to characterize the magnetic and hydrodynamic properties of assembled-MEMS microrobots. The system consists of a powerful permanent magnet that is position controlled with a linear stage. The magnetic field is accurately characterized. Precision sensors are used to measure magnetic force as a function of applied field. The system is first used to validate an existing model for the magnetic force on a soft-magnetic ellipsoid. Next, the magnetic force on a soft-magnetic assembled-MEMS microrobot as a function of the applied field is measured experimentally. Finally, a vision tracking system is integrated with the setup to measure the hydrodynamic properties of the microrobot. The coefficient of viscous friction for the microrobot is obtained experimentally.
Surgical robotics : systems, applications and visions | 2011
Olgaç Ergeneman; Christos Bergeles; Michael P. Kummer; Jake J. Abbott; Bradley J. Nelson
Many current and proposed retinal procedures are at the limits of human performance and perception. Microrobots that can navigate the fluid in the interior of the eye have the potential to revolutionize the way the most difficult retinal procedures are conducted. Microrobots are typically envisioned as miniature mechatronic systems that utilize MEMS technology to incorporate sensing and actuation onboard. This chapter presents a simpler alternative approach for the development of intraocular microrobots consisting of magnetic platforms and functional coatings. Luminescence dyes immobilized in coatings can be excited and read wirelessly to detect analytes or physical properties. Drug coatings can be used for diffusion-based delivery, and may provide more efficient therapy than microsystems containing pumps, as diffusion dominates over advection at the microscale. Oxygen sensing for diagnosis and drug therapy for retinal vein occlusions are presented as example applications. Accurate sensing and therapy requires precise control to guide the microrobot in the interior of the human eye. We require an understanding of the possibilities and limitations in wireless magnetic control. We also require the ability to visually track and localize the microrobot inside the eye, while obtaining clinically useful retinal images. Each of these topics is discussed.
international conference on advanced intelligent mechatronics | 2007
Jake J. Abbott; Olgaç Ergeneman; Michael P. Kummer; Ann M. Hirt; Bradley J. Nelson
We calculate the torque and force generated by an arbitrary magnetic field on an axially symmetric soft-magnetic body. We consider the magnetization of the body as a function of the applied field, using a continuous model that unifies two disparate magnetic models. The continuous torque and force follow. The model is verified experimentally, and captures the often-neglected region between weak and saturating fields, where interesting behavior is observed. We provide the optimal field direction for a given field magnitude. We find a maximum possible torque, which can be generated with relatively weak applied fields. This paper facilitates systems-level analysis, simulation, and real-time control of soft-magnetic bodies.
IEEE Transactions on Robotics | 2010
Michael P. Kummer; Jake J. Abbott; Bradley E. Kratochvil; Ruedi Borer; Ali Sengul; Bradley J. Nelson