Magnetic Field-Based Technologies for Lab-on-a-Chip Applications

In the last decades, LOC technologies have represented a real breakthrough in the field of in vitro biochemical and biological analyses. However, the integration of really complex functions in a limited space results extremely challenging and proper working principles should be identified. In this sense, magnetic fields revealed to be extremely promising. Thanks to the exploitation of external magnetic sources and to the integration of magnetic materials, mainly high aspect ratio micro-/nanoparticles, non-contact manipulation of biological and chemical samples can be enabled. In this chapter, magnetic field-based technologies, their basic theory, and main applications in LOC scenario will be described by foreseeing also a deeper interaction/integration with the typical technologies of microrobotics. Attention will be focused on magnetic separation and manipulation, by taking examples coming from traditional LOC devices and from microrobotics

A Power-efficient Propulsion Method for Magnetic Microrobots

Current magnetic systems for microrobotic navigation consist of assemblies of electromagnets, which allow for the wireless accurate steering and propulsion of sub-millimetric bodies. However, large numbers of windings and/or high currents are needed in order to generate suitable magnetic fields and gradients. This means that magnetic navigation systems are typically cumbersome and require a lot of power, thus limiting their application fields. In this paper, we propose a novel propulsion method that is able to dramatically reduce the power demand of such systems. This propulsion method was conceived for navigation systems that achieve propulsion by pulling microrobots with magnetic gradients. We compare this power-efficient propulsion method with the traditional pulling propulsion, in the case of a microrobot swimming in a micro-structured confined liquid environment. Results show that both methods are equivalent in terms of accuracy and the velocity of the motion of the microrobots, while the new approach requires only one ninth of the power needed to generate the magnetic gradients. Substantial equivalence is demonstrated also in terms of the manoeuvrability of user-controlled microrobots along a complex path

PDMS and DLC-coated unidirectional valves for artificial urinary sphincters: Opening performance after 126 days of immersion in urine

In this work, unidirectional valves made of bare polydimethylsiloxane (PDMS) and PDMS provided with a micrometric diamond-like carbon (DLC) coating were fabricated and characterized, in terms of surface properties and opening pressure. The valve performance was also tested over 1250 repeated cycles of opening/closure in water, finding a slight decrease in the opening pressure after such cycles (10%) for the PDMS valves, while almost no variation for the PDMS + DLC ones. The valves were then immersed in urine for 126 days, evaluating the formation of encrustations and the trend of the opening pressure over time. Results showed that PDMS valves were featured by a thin layer of encrustations after 126 days, but the overall encrustation level was much smaller than the one shown by PDMS in static conditions. Furthermore, the opening pressure was almost not affected by such a thin layer of crystals. DLC-coated valves showed even less encrustations at the same time-point, with no significant loss of performance over time, although they were featured by a higher variability. These results suggest that most encrustations can be removed by the mechanical action of the valve during daily openings/closures. Such a self-cleaning behavior with respect to a static condition opens exciting scenarios for the long-term functionality of mobile devices operating in the urinary environment

A discrete-time localization method for capsule endoscopy based on on-board magnetic sensing

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Studio elettromagnetico per la localizzazione e il controllo di capsule endoscopiche

Il seguente progetto di tesi si è posto l’obiettivo di realizzare strategie di controllo e di localizzazione attraverso l’uso di campi elettromagnetici per capsula endoscopica magnetica a locomozione attiva e fa parte di una collaborazione instaurata tra il laboratorio CRIM della Scuola Superiore Sant’Anna e il dipartimento di Sistemi Elettrici e Automazione della facoltà di Ingegneria dell’Università di Pisa. In particolare, i principali obiettivi sono stati lo studio, il dimensionamento e la realizzazione di un sistema di bobine per la locomozione magnetica di capsule endoscopiche e l’integrazione all’interno della capsula endoscopica di un sensore di campo magnetico per la sua localizzazione e il suo orientamento. Per quanto riguarda il primo aspetto, sono state elaborate simulazioni per determinare la configurazione ottimale, le correnti richieste e le strategie di controllo necessarie alla locomozione e all’orientamento della capsula endoscopica. Per quanto riguarda invece il secondo aspetto, l’integrazione di un sensore di campo magnetico per la localizzazione è stata fondamentale per restituire al medico il feedback sensoriale necessario a chiudere il loop di controllo. Gli sviluppi futuri per questo aspetto riguarderanno la miniaturizzazione dei sensori in modo da ridurre gli ingombri e rendere quindi l’endocapsula realmente accettabile dal punto di vista clinico

Magnetically-controlled artificial urinary sphincters for severe urinary incontinence

Urinary incontinence (UI) is a dysfunction related to an involuntary urine leakage, mainly caused by a deficient action of the urethral sphincter muscles. When UI is particularly severe, it must be managed via invasive surgical procedures. The most popular artificial urinary sphincters (AUS) are surgically placed around the urethra (i.e. extra-urethral AUS) and they squeeze it whenever necessary to restore continence. Current solutions do not present a unisex design and are constituted of several components, which must be installed in a rather invasive way and which imply a non-comfortable device management and control. The aim of this paper is i) to present the design of novel AUS prototypes, all of them magnetically controlled and actuated, ii) to focus on a unisex design suitable for both female and male anatomies, and iii) to reduce device dimensions and to minimize the implantation invasiveness. Preliminary results demonstrated that magnetically-controlled AUS could be appropriate solutions for different typologies of patients and requirements, depending on endo-or extra-urethral design approach