We report on the calibration and testing of a fiber Bragg grating (FBG)-based 2D-shape sensing strip for real-time monitoring of the position and orientation of the human spine during gait. The strip is evaluated for its use as an input for control of an exoskeleton for patients with spinal cord injury. By measuring the torsion and bending of the back, walking movements can be reconstructed. The 3D-printed strip has nine embedded fiber Bragg gratings that are located at specific places with respect to the vertebral column. Three FBGs are placed opposite to the thoracic vertebrae T6–T9, these FBGs are sensitive for measuring the bending of the spine during the gait cycle. Torsion is measured at two locations: at thoracic vertebra, T3 and at lumbar vertebra, L3. At these locations, the width of the strip is reduced to have a larger sensitivity for torsion. The strain at each FBG is measured using an interrogator. This leads to the radius of curvature and torsion as a function of time. The Frenet-Serret formulae are used to calculate the shape of the strip during the gait cycle. We have calibrated this FBG strip for curvature by bending it at known radius of different curvatures. We found a linear dependence between the strain and curvature. For torsion calibration we have rotated the strip with a stepper motor at different angles and monitored the strain. We, again, found a linear dependence with a small hysteresis. We mounted the strip on a healthy test subject and monitored their gait cycle. The FBG strip shows similar results when compared to a motion capture system based on multiple cameras. Although the fixation of the strip to a garment or on the back directly strongly influences the measured response, it does show a periodic and reproducible signal during the gait cycle.
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This paper introduces the design principle of legibility as means to examine the epistemic and ethical conditions of sensing technologies. Emerging sensing technologies create new possibilities regarding what to measure, as well as how to analyze, interpret, and communicate said measurements. In doing so, they create ethical challenges for designers to navigate, specifically how the interpretation and communication of complex data affect moral values such as (user) autonomy. Contemporary sensing technologies require layers of mediation and exposition to render what they sense as intelligible and constructive to the end user, which is a value-laden design act. Legibility is positioned as both an evaluative lens and a design criterion, making it complimentary to existing frameworks such as value sensitive design. To concretize the notion of legibility, and understand how it could be utilized in both evaluative and anticipatory contexts, the case study of a vest embedded with sensors and an accompanying app for patients with chronic obstructive pulmonary disease is analyzed.
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This study explores the shape-morphing behavior of 4D-printed structures made from Polylactic Acid (PLA), a prominent bio-sourced shape-memory polymer. Focusing on the response of these structures to thermal stimuli, this research investigates how various printing parameters influence their morphing capabilities. The experimental approach integrates design and slicing, printing using fused deposition modeling (FDM), and a post-printing activation phase in a controlled laboratory environment. This process aims to replicate the external stimuli that induce shape morphing, highlighting the dynamic potential of 4D printing. Utilizing Taguchi’s Design of Experiments (DoE), this study examines the effects of printing speed, layer height, layer width, nozzle temperature, bed temperature, and activation temperature on the morphing behavior. The analysis includes precise measurements of deformation parameters, providing a comprehensive understanding of the morphing process. Regression models demonstrate strong correlations with observed data, suggesting their effectiveness in predicting responses based on control parameters. Additionally, finite element analysis (FEA) modeling successfully predicts the performance of these structures, validating its application as a design tool in 4D printing. This research contributes to the understanding of 4D printing dynamics and offers insights for optimizing printing processes to harness the full potential of shape-morphing materials. It sets a foundation for future research, particularly in exploring the relationship between printing parameters and the functional capabilities of 4D-printed structures.
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Katheterablatie is een medische ingreep om een abnormale elektrische verbinding te onderbreken of om een structuur in het hart zodanig te wijzigen dat geen ritmestoornissen meer optreden. Hartritmestoornissen kunnen leiden tot hartfalen of hartstilstand. Katheterablatie is een zeer effectieve methode om hartritmestoornissen te verhelpen die in Nederland gemiddeld 30 keer per dag uitgevoerd. Katheterablatie wordt uitgevoerd met röntgendoorlichting om de positie van de katheter te controleren. De röntgenstraling is schadelijk voor zowel de patiënt als de operateur. Het Haga ziekenhuis in Den Haag heeft een nieuwe unieke faciliteit waar ablaties uitgevoerd kunnen worden in een MRI scanner. Met dit project willen we onderzoeken hoe de positie en vorm van het uiteinde van de katheter ook tijdens een ablatie in de MRI real-time bepaald kan worden, zodat de operateur de operatie efficiënt kan laten verlopen. Optische sensoren lenen zich hier heel goed voor omdat ze niet verstoord worden door het sterke magneetveld van de MRI. Er bestaan systemen die met behulp van glasvezels de vorm en positie van katheters kunnen weergeven, maar deze zijn zeer kostbaar en niet toegespitst op het gebruik bij disposable ablatie-katheters in een MRI. In dit project onderzoeken wij de potentie van een voor deze toepassing specifieke glasvezel-gebaseerde oplossing, waarmee alleen de vorm van het uiteinde van de katheter wordt gemeten en gevisualiseerd, en die bruikbaar is in combinatie met een MRI. Het beoogde resultaat is een prototype van een systeem dat tegen lagere kosten met optische sensoren de vorm en positie van de katheter in een MRI kan weergeven. De projectpartners dragen met hun expertise bij aan de realisatie van dit prototype: fotonica in medische toepassingen (Haagse Hogeschool), sensoren gebaseerd op FBGs (VanderHoekPhotonics), en de medische praktijk en testfaciliteiten (Haga Ziekenhuis ablatiecentrum).
