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

Protective coatings for intraocular wirelessly controlled microrobots for implantation : corrosion, cell culture, and in vivo animal tests

Grup: Gnm3 FundingDiseases in the ocular posterior segment are a leading cause of blindness. The surgical skills required to treat them are at the limits of human manipulation ability, and involve the risk of permanent retinal damage. Instrument tethering and design limit accessibility within the eye. Wireless microrobots suturelessly injected into the posterior segment, steered using magnetic manipulation, are proposed for procedures involving implantation. Biocompatibility is a prerequisite for these procedures. This paper investigates the use of cobalt-nickel microrobots coated with polypyrrole, and gold, which has been used as an ocular implant material. Polypyrrole has well-established biocompatibility properties, but no reports concerning its ocular implantation is available. Coated and uncoated microrobots were investigated for their corrosion properties, and solutions that had contained coated and uncoated microrobots for one week were tested for cytotoxicity by monitoring NIH3T3 cell viability. None of the microrobots showed significant corrosion currents and corrosion potentials were as expected in relation to the intrinsic nobility of the materials. NIH3T3 cell viability was not affected by the release medium, in which coated/uncoated microrobots were stored. In vivo tests inside rabbit eyes were performed using coated microrobots. There were no significant inflammatory responses during the first week after injection. An inflammatory response detected after two weeks was likely due to a lack of longer-duration biocompatibility. The results provide valuable information for those who work on implant technology and biocompatibility. Coated microrobots have the potential to facilitate a new generation of surgical treatments, diagnostics and drug-delivery techniques, when implantation in the ocular posterior segment will be possible

Modelling aerosol transport and virus exposure with numerical simulations in relation to SARS-CoV-2 transmission by inhalation indoors

We provide research findings on the physics of aerosol and droplet dispersion relevant to the hypothesized aerosol transmission of SARS-CoV-2 during the current pandemic. We utilize physics-based modeling at different levels of complexity, along with previous literature on coronaviruses, to investigate the possibility of airborne transmission. The previous literature, our 0D-3D simulations by various physics-based models, and theoretical calculations, indicate that the typical size range of speech and cough originated droplets (dPeer reviewe

Metapopulations revisited: the area‐dependence of dispersal matters

The metapopulation concept initiated a paradigm shift in ecology and conservation biology, recognizing the eminent role of dispersal and colonization as fundamental processes contributing to species’ long-term persistence. Early models made ad hoc assumptions about a positive area dependency of dispersal (i.e., total number of emigrants), which persisted in the theoretical literature; however, numerous empirical examples of negative area dependencies of dispersal have been reported. Here, we first give a qualitative overview for different area dependencies of dispersal in empirical systems. Then, using a spatially realistic Levins model, we show that extending assumptions on the area dependence of dispersal (ADD) to include all empirically supported parameter space, specifically also negative ADD, alters predictions on several conservation-relevant patterns. Importantly, we find that small patches could be of similar importance as large ones if dispersal decreases inversely with patch area, a result contrasting with previous findings based on a positive ADD. This leads to context-dependent strategies to preserve metapopulations. If dispersal is positively correlated with patch area, efforts should be devoted to preserving large patches and the total habitat area. If dispersal is negatively correlated with patch area, the most efficient strategy is to preserve a high number of patches, including small ones. Our results have direct implications for management decisions in the context of destruction, deterioration, and protection of habitat patches

Magnetic microrheometry of tumor-relevant stiffness levels and probabilistic quantification of viscoelasticity differences inside 3D cell culture matrices.

The progression of breast cancer involves cancer-cell invasions of extracellular matrices. To investigate the progression, 3D cell cultures are widely used along with different types of matrices. Currently, the matrices are often characterized using parallel-plate rheometry for matrix viscoelasticity, or liquid-like viscous and stiffness-related elastic characteristics. The characterization reveals averaged information and sample-to-sample variation, yet, it neglects internal heterogeneity within matrices, experienced by cancer cells in 3D culture. Techniques using optical tweezers and magnetic microrheometry have measured heterogeneity in viscoelasticity in 3D culture. However, there is a lack of probabilistic heterogeneity quantification and cell-size-relevant, microscale-viscoelasticity measurements at breast-tumor tissue stiffness up to ≃10 kPa in Young's modulus. Here, we have advanced methods, for the purpose, which use a magnetic microrheometer that applies forces on magnetic spheres within matrices, and detects the spheres displacements. We present probabilistic heterogeneity quantification using microscale-viscoelasticity measurements in 3D culture matrices at breast-tumor-relevant stiffness levels. Bayesian multilevel modeling was employed to distinguish heterogeneity in viscoelasticity from the effects of experimental design and measurement errors. We report about the heterogeneity of breast-tumor-relevant agarose, GrowDex, GrowDex-collagen and fibrin matrices. The degree of heterogeneity differs for stiffness, and phase angle (i.e. ratio between viscous and elastic characteristics). Concerning stiffness, agarose and GrowDex show the lowest and highest heterogeneity, respectively. Concerning phase angle, fibrin and GrowDex-collagen present the lowest and the highest heterogeneity, respectively. While this heterogeneity information involves softer matrices, probed by ≃30 μm magnetic spheres, we employ larger ≃100 μm spheres to increase magnetic forces and acquire a sufficient displacement signal-to-noise ratio in stiffer matrices. Thus, we show pointwise microscale viscoelasticity measurements within agarose matrices up to Young's moduli of 10 kPa. These results establish methods that combine magnetic microrheometry and Bayesian multilevel modeling for enhanced heterogeneity analysis within 3D culture matrices

Localized viscoelasticity measurements with untethered intravitreal microrobots

Microrobots are a promising tool for medical interventions and micromanipulation. In this paper, we explore the concept of using microrobots for microrheology. Untethered magnetically actuated microrobots were used to characterize one of the most complex biofluids, the vitreous humor. In this work we began by experimentally characterizing the viscoelastic properties of an artificial vitreous humor. For comparison, its properties were also measured using special microcantilevers in an atomic force microscope (AFM) setup. Subsequently, an untethered device was used to study the vitreous humor of a porcine eye, which is a valid ex-vivo model of a human eye. Its viscoelasticity model was extracted, which was in agreement with the model of the artificial vitreous. The existing characterization methodology requires eye and vitreous humor dissection for the microrheology measurements. We envision that the method proposed here can be used in in vivo