1,721,030 research outputs found
A systematic review of proton therapy in the treatment of chondrosarcoma of the skull base
No full textAbstract
Chondrosarcoma (CSA) of the skull base (SB) is an uncommon, slowly growing, neoplasm comprising approximately 0.1% of all intracranial tumors and 6% of SB lesions. Even though its growth is slow, CSA is a potentially lethal tumor. The therapeutic approach to CSA of the SB is still controversial and clinical experience is limited because of the relative rarity of this tumor. The use of proton therapy (PT) after maximal surgery is widely accepted, but there are no controlled studies demonstrating the need of PT and its superiority in comparison to radiotherapy with photons. We conducted a systematic review of the scientific literature published during the period between January 1980 and June 2008 on data regarding irradiation of CSA of the SB with PT and a series of inclusion criteria. During August 2008, two independent reviewers (M.A. and D.A.), by applying the key words "skull base", "chondrosarcoma", and "proton therapy" selected those studies from the PubMed database in which a minimum of ten patients received palliative, radical, or postoperative irradiation with protons and which furnished a minimum of 24 months of follow-up. Forty nine reports were retrieved. There were no prospective trials (randomized or nonrandomized) but just nine uncontrolled single-arm studies for PT mainly related to advanced and frequently incompletely resected tumors. According to the inclusion criteria, only four articles, reporting the most recent updated results of the publishing institution, were included in the analysis providing clinical outcomes for 254 patients in total. Therapeutic approach to CSA of the SB has traditionally relied on surgical control. Radiation therapy has demonstrated to be a valuable modality for local control in the postoperative setting or in advanced/inoperable cases treated with definitive intent. The use of PT following maximal surgical resection shows a very high probability of medium- and long-term cure with a relatively low risk of significant complications
Soft robots in surgery
No full textMinimally Invasive Surgery (MIS) represents the gold standard in the majority of abdominal operations, although some fundamental limitations are still present and are far to be really addressed despite emerging robotic solutions. Flexible endoscopes can exploit their high flexibility to reach the surgical target while being inserted remotely or by a natural orifice. However endoscopes may lack stability that rigid tools normally provide. Novel surgical instrumentation is being developed in order to provide higher dexterity and flexibility to the surgeon, but unlike traditional surgical manipulators, here we report the approach followed in the development of the STIFF-FLOP manipulator. The main idea is based on the exploitation of soft materials to be intrinsically flexible and safe while combining different fluidic actuation technologies to enable high dexterity and selective stiffness variability. In this chapter, the functional evolution of the robot is reported highlighting advantages and drawbacks that steered the development of a manipulator which in the end demonstrated to be effective in overcoming mobility limitations experienced with standard rigid tools
Plant-Inspired Soft Bistable Structures Based on Hygroscopic Electrospun Nanofibers
Full text linkThe tissue composition and microstructures of plants have dynamic morphologies that change according to their environments. Recently, multifunctional responsive materials and smart structures also took inspiration from these plants' features. Dionaea muscipula leaves provide a remarkable example of an optimized structure that, owing to the synergistic integration of bistability, material, and geometrical properties, permits to overcome the performance limits of purely diffusive processes. In this paper, a hygroscopic bistable structure (HBS) inspired by the Venus flytrap leaves is presented, obtained by bonding prestretched poly(dimethylsiloxane) (PDMS) layers prior to depositing electrospun polyethylene oxide (PEO) nanofibers. A hygroresponsive bilayer (HBL) is also obtained by electrospinning of PEO on an unstretched PDMS layer. The hygroscopic material (Young's modulus and hygroscopic expansion) is mechanically characterized so as to predict the response time of a bending HBL in response to a step humidity variation. The HBS response time (≈1 s) is sensibly lower than the one of purely diffusive HBL (≈10 s) thanks to bistability. An illustrative implementation is also presented, exploiting an HBS to trigger the curvature of a PDMS optical focusing system. The developed plant-inspired soft bistable structure can also be used for sensing (e.g., humidity), energy harvesting, as well as advanced soft robotics applications
Design methodology for the development of variable stiffness devices based on layer jamming transition
Full text linkVariable stiffness mechanisms as Jamming Transition draw huge attention recently in Soft Robotics. This paper proposes a comprehensive design methodology for developing variable stiffness devices based on layer jamming. Starting from pre-existing modelling, we highlight the design parameters that should be considered, extracting them from literature and our direct experience with the phenomenon. Then we validated the methodology applying the design process to previous layer jamming cases presented in literature. The comparison between the results obtained from our methodology and those presented in the analyzed previous works highlights a good predictive capability, demonstrating that this methodology can be used as a valid tool to design variable stiffness devices based on layer jamming transition. Finally, in order to provide the scientific community with an easily usable tool to design variable stiffness structures based on layer jamming transition, we have elaborated a Matlab script that guides the user through the main design parameters implementing the proposed methodology in an interactive process
Model-based compensation of rate-dependent hysteresis in a piezoresistive strain sensor
No full textThis paper is concerned with modeling of smart textiles, aimed at compensating their intrinsic nonlinearities. In particular, a new model is proposed to compensate for hysteresis and relaxation in strain sensors made of Electrolycra. These sensors are increasingly employed in emerging areas such as wearable electronics and soft robotics for their simple transduction mechanism and low cost. However, being intrinsically nonlinear, the signals measured from these devices need some processing, in order to increase their sensing accuracy. Here, we propose a new model for the compensation of the main distortions intrinsic to these soft sensors, which are mainly caused by hysteresis and relaxation, whose combined effect produces rate-dependent hysteresis. The model capabilities are tested on experimental data measured on Electrolycra. The comparisons with the results obtained with two different models witness the good behavior of the proposed model
I-support soft arm for assistance tasks: a new manufacturing approach based on 3D printing and characterization
No full textSoft robotics is an emerging scientific field well known for being widespread employed in several applications where dexterity and safe interaction are of major importance. In particular, a very challenging scenario in which it is involved concerns bio-medical field. In the last few years, several soft robotic devices have been developed to assist elderly people in daily tasks. In this paper, the authors present a new manufacturing approach for the fabrication of I-SUPPORT, a soft arm used to help needful people during shower activities. The proposed I-SUPPORT version, based on pneumatic and cable-driven actuation, is manufactured using Fused Filament Fabrication (FFF), the most common and inexpensive Additive Manufacturing (AM) technology. The advantages offered by FFF technology compared to traditional manufacturing methods regard: (i) the possibility to increase the automation degree of the process by reducing manual tasks, (ii) the decrease of assembly operations and (iii) an improvement in terms of supply chain. Moreover, the constitutive I-SUPPORT elements have been printed separately to save time, reduce materials and optimize the waste in case of failure. Afterwards, the proposed soft robotic arm has been tested to evaluate the performances and of the chambers, module and the whole I-SUPPORT manipulator
A piezoresistive flexible sensor to detect soft actuator deformation
Full text linkA textile-based strain sensor for measuring the length of a McKibben pneumatic actuator has been developed. McKibben actuators are flexible, lightweight, and widely used in all those applications where compliance and safety are required, e.g. soft robotics and power assisting device. The actuator length needs to be measured to control the device accurately. However, properties such as flexibility and lightness might be lost if rigid sensors such as potentiometers or linear encoders are directly attached to the actuators. For this reason, flexible and stretchable sensors are necessary. In this study, a flexible sensor using conductive textile is proposed to actively measure the length of manufactured McKibben actuators. Firstly, the electro-mechanical characteristics of the proposed sensor were obtained and a model to compensate its nonlinearities was evaluated. Secondly, an estimation of the accuracy was performed during dynamic actuator contractions. The results showed that, using this sensor, a direct measurement of the actuator axial displacement can be obtained within 20% error, without affecting its performances in terms of contraction
Evolving optimal swimming in different fluids: A study inspired by batoid fishes
No full textFor their efficient and elegant locomotion, batoid fishes (e.g. the manta ray) have been widely studied in biology, and also taken as a source of inspiration by engineers and roboticists willing to replicate their propulsion mechanism in order to build efficient swimming machines. In this work, a new model of an under-actuated compliant wing is proposed, exhibiting both the oscillatory and undulatory behaviors underlying batoid propulsion mechanism. The proposed model allowed an investigation of the co-evolution of morphology and control, exploiting dynamics emergent from the interaction between the environment and the mechanical properties of the soft materials. Having condensed such aspects in a mathematical model, we studied the adaptability of a batoid-like morphology to different environments. As for biology, our main contribution is an exploration of the parameters linking swimming mechanics, morphology and environment. This can contribute to a deeper understanding of the factors that led various species of the batoid group to phylogenetically adapt to different environments. From a robotics standpoint, this work offers an additional example remarking the importance of morphological computation and embodied intelligence. A direct application can be an under-water soft robot capable of adapting morphology and control to reach the maximum swimming efficiency. © 2014 Springer International Publishing
Controllable Multibending Soft Actuator for Surgical Applications
No full textSoft actuators offer great versatility in terms of design and applications. Their compliance affords them greater dexterity as compared to rigid structures, and also permits the possibility to adapt their shape as per need. However compliance makes it difficult for them to sustain loads. As a step towards resolving this conundrum, a low melting point alloy based stiffening methodology is proposed to be integrated with a soft actuator designed for minimally invasive surgical use. This integration not only increases the load capacity but also helps motion control by selectively rigidifying parts of the actuator. The actuator design may be tweaked by using FEM based models, with a possibility to increase the overall stiffness up to 30 times
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