Mobility Experiments With Microrobots for Minimally Invasive Intraocular Surgery

Purpose.: To investigate microrobots as an assistive tool for minimally invasive intraocular surgery and to demonstrate mobility and controllability inside the living rabbit eye. / Methods.: A system for wireless magnetic control of untethered microrobots was developed. Mobility and controllability of a microrobot are examined in different media, specifically vitreous, balanced salt solution (BSS), and silicone oil. This is demonstrated through ex vivo and in vivo animal experiments. / Results.: The developed electromagnetic system enables precise control of magnetic microrobots over a workspace that covers the posterior eye segment. The system allows for rotation and translation of the microrobot in different media (vitreous, BSS, silicone oil) inside the eye. / Conclusions.: Intravitreal introduction of untethered mobile microrobots can enable sutureless and precise ophthalmic procedures. Ex vivo and in vivo experiments demonstrate that microrobots can be manipulated inside the eye. Potential applications are targeted drug delivery for maculopathies such as AMD, intravenous deployment of anticoagulation agents for retinal vein occlusion (RVO), and mechanical applications, such as manipulation of epiretinal membrane peeling (ERM). The technology has the potential to reduce the invasiveness of ophthalmic surgery and assist in the treatment of a variety of ophthalmic diseases

A photopatternable superparamagnetic nanocomposite: Material characterization and fabrication of microstructures

A superparamagnetic nanocomposite obtained by dispersing superparamagnetic magnetite nanoparticles in the epoxy SU-8 is used to fabricate microstructures by photolithography. The dispersion of the nanoparticles and the level of agglomerations are analyzed by optical microscopy, TEM (transmission electron microscope), SAXS (small-angle X-ray scattering), XDC (X-ray disc centrifuge) and XRD (X-ray diffraction). Two different phosphate-based dispersing agents are compared. In order to obtain a high-quality nanocomposite, the influence of particle concentration 1–10 vol.% (4–32 wt.%) on composite fabrication steps such as spin coating and UV exposure are systematically analyzed. Features with narrow widths (down to 1.3 μm) are obtained for composites with 5 vol.% particle concentration. Mechanical, magnetic and wetting properties of the nanocomposites are characterized. These nanocomposites exhibit superparamagnetic properties with a saturation magnetization up to 27.9 kA m⁻¹ for10 vol.%. All nanocomposites show no differences in surface polarity with respect to pure SU-8, and exhibit a moderate hydrophobic behavior (advancing dynamic contact angles approximately 81°). Microcantilevers with particle concentrations of 0–5 vol.% were successfully fabricated and were used to determine the dynamic Young's modulus of the composite. A slight increase of the Young's modulus with increased particle concentration from 4.1 GPa (pure SU-8) up to 5.1 GPa (for 5 vol.%) was observed

Wireless Microrobotic Oxygen Sensing for Retinal Hypoxia Monitoring

This paper presents a luminescence oxygen sensor for retinal-hypoxia monitoring. The sensor coats a wirelessly controlled magnetic microrobot that will operate in the human eye. The coating embodies Pt(II) octaethylporphine (PtOEP) dyes as the luminescence material and polystyrene as a supporting matrix. It is deposited on the microrobot as a thin film and this film is experimentally evaluated using a custom optical setup. Due to the intrinsic nature of luminescence lifetimes, oxygen concentration was determined using a frequency-domain lifetime measurement approach. © 2012 ICST Institute for Computer Science, Social Informatics and Telecommunications Engineering

Hermetically-coated superparamagnetic Fe<inf>2</inf>O<inf>3</inf> particles with SiO<inf>2</inf> nanofilms

Magnetic nanoparticles are frequently coated with SiO2to improve their functionality and bio-compatibility in a range of biomedical and polymer nanocomposile applications. In this paper, a scalable flame aerosol technology is used to produce highly dispersible, superparamagnetic iron oxide nanoparticles hermetically coaled with silica to retain full magnetization performance. Iron oxide particles were produced by flame spray pyrolysis (FSP) of iron acelylacetonale in xylene/acetonitrile solutions, and the resulting aerosol was in situ coaled with SiO2 by oxidation of swirling hexamethlydisiloxane vapor. The process allows independent control of the core Fe2O3, particle properties and the thickness of their silica coaling film. This ensures that the non-magnetic SiO2 layer can be closely controlled and minimized. The optimal SiO2 content for complete (hermetic) encapsulation of the magnetic core particles was determined by isopropanol chemisorption. The magnetization of Fe2O3 coated with about 2 nm thin SiO2 layers was nearly identical lo that of uncoated, pure Fe2O3 nanoparlicles

Assembly and Disassembly of Magnetic Mobile Micro-Robots towards 2-D Reconfigurable Micro-Systems

Abstract A primary challenge in the field of reconfigurable robotics is scaling down the size of individual robotic modules. We present a novel set of permanent magnet modules that are 900 µm × 900 µm × 270 µm in size, called Mag-µMods, for use in a reconfigurable micro-system. The module is actuated by oscillating external magnetic fields less than 5 mT in strength, and is capable of locomoting on a 2-D surface. Multiple modules can be controlled by using an electrostatic anchoring surface, which can selectively prevent specific modules from being driven by the external field while allowing others to move freely. We address the challenges of both assembling and disassembling two modules. Assembly is performed by bringing two modules sufficiently close that their magnetic attraction causes them to combine. Disassembly is performed by electrostatically anchoring one module to the surface, and applying magnetic forces or torques from external sources to separate the unanchored module.

When nothing is constant but change: Adaptive and sensorial materials and their impact on product design

This article is the preface to the Special Issue of the Journal of Intelligent Material Systems and Structures on occasion of the Symposium A53 'MEMS/NEMS for Sensorial and Actorial Materials' held at the Euromat 2011 Conference, Montpellier, France, September 12-15, 2011. The authors outline the concept of material-integrated sensing and intelligence, which is summarized in the term sensorial materials. Such materials are understood to incorporate sensing, signal and data processing as well as communication facilities to autonomously evaluate their own condition and/or their environment. To achieve these capabilities, bottom-up as well as top-down approaches are currently being discussed. The latter is highlighted in this work. Research efforts towards it range from materials science to sensor and microelectromechanical system (MEMS)/nanoelectromechanical system (NEMS) technology, microelectronics and computer science and were covered in the underlying Euromat symposiu m. As a specific aspect linked to the envisaged autonomy and a resulting adaptivity, for example, of internal self-representation and data interpretation, potential consequences for engineering design are sketched