Mini Review: Comparison of Bio-Inspired Adhesive Feet of Climbing Robots on Smooth Vertical Surfaces

Developing climbing robots for smooth vertical surfaces (e.g., glass) is one of the most challenging problems in robotics. Here, the adequate functioning of an adhesive foot is an essential factor for successful locomotion performance. Among the various technologies (such as dry adhesion, wet adhesion, magnetic adhesion, and pneumatic adhesion), bio-inspired dry adhesion has been actively studied and successfully applied to climbing robots. Thus, this review focuses on the characteristics of two different types of foot microstructures, namely spatula-shaped and mushroom-shaped, capable of generating such adhesion. These are the most used types of foot microstructures in climbing robots for smooth vertical surfaces. Moreover, this review shows that the spatula-shaped feet are particularly suitable for massive and one-directional climbing robots, whereas mushroom-shaped feet are primarily suitable for light and all-directional climbing robots. Consequently, this study can guide roboticists in selecting the right adhesive foot to achieve the best climbing ability for future robot developments

A study of shape memory polymers and their usage in the development of directional dry adhesives

This thesis first introduces shape memory polymers and their unique phase-changing and recoverability properties. The underlying thermodynamic explanations along with their fundamental governing equations is presented. A few possible potential areas of interest for applications of this unique polymer are presented, but the one of particular interest is biomimetic dry adhesives. In this thesis, a shape memory polymer (SMP) surface with geometrically asymmetric micro-wedge array is fabricated as a reversible directional dry adhesive through a double exposure angled lithography technique. The unique shape fixing and recovery properties of SMPs and surface microstructuring enable highly reversible adhesion strength upon thermo-mechanical loading, and the tilted wedge geometry gives rise not only to its capability for varying adhesion strength based on loading direction, but also the reduction of strain energy input necessary to achieve contact area saturation with the opposing surface. To characterize the directional adhesion strength of the fabricated micro-wedge surface, adhesion tests are performed in the forward shear, backward shear, and normal directions based on the tilting direction of the micro-wedges. The adhesion strength is measured as a function of the applied preload for the three directions investigated, and is compared to a computational analysis by modeling the adhesive failure as the initiation of crack growth in linear elastic fracture mechanics. Additionally, reversibility is demonstrated by heating the micro-wedge surface above its T g , allowing the structure to recover its original shape after being deformed, resulting in almost zero adhesion strength. The adhesion tests demonstrate that the forward shear direction is capable of adhesion strengths that are greater than that of the backward shear direction by a factor of over 3, confirming its capability for directional adhesion. Finally, additional novel shapes are introduced, taking advantage of the angled exposure technique and properties of negative photoresist to "cleave" a unique wedge pattern based on the shape of the patterns on the photomask used in fabrication

Développement d'un drone percheur pour atterrissage et grimpe sur des surfaces verticales

Ce projet visait le développement du premier drone à aile fixe capable de se percher de façon autonome sur des surfaces verticales et d'en décoller. Inspiré par les oiseaux, l'avion développé utilise une manoeuvre de cabrage assistée par la poussée pour rapidement ralentir avant de se poser. Des microgriffes sont utilisées pour permettre à l'avion de s'accrocher à des surfaces rugueuses, alors que le contrôle de la manoeuvre est entièrement embarqué. L'effet de la poussée aérodynamique sur l'enveloppe d'atterrissage de l'avion est analysée et un contrôleur de vitesse verticale est proposé pour créer des descentes fluides et robustes vers un mur. Plusieurs atterissages ont été testé, à travers une plage de conditions de vol. La poussée aérodynamique de l'avion est également utilisée pour grimper le long de surfaces verticales. Des modèles aérodynamiques sont utilisés pour prédire les performance de l'avion dans plusieurs régimes de grimpe aérienne, et sélectionner un contrôleur pour le maintien d'une distance fixe avec un mur en montée verticale. La manœuvre de grimpe est testée à l'intérieur et à l'extérieur, pour des grimpes courtes et longues

Musculoskeletal adaptation to PWS

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2007.Includes bibliographical references.As human spaceflight extends in both duration and scope, it is critical to better understand the physiologic effects of this novel environment. In the weight bearing structures of the body, bone loss and muscle atrophy far in excess of age-related declines are hallmarks of microgravity adaptation. However, while the physiological effects of such disuse unloading are well-described, the effects of partial weight bearing, such as expected on the moon (16% of Earth's gravity) and Mars (38% of Earth's gravity), have yet to be quantified. In these environments, the risks of musculoskeletal atrophy and accompanying orthopedic injury are uncertain, and a means of further investigation is needed. To address this need, we developed a novel model of Partial Weight Suspension (PWS) that supports investigation of the physiologic effects of chronically reduced quadrupedal loading in mice. Validation of the PWS system was conducted using a gait analysis treadmill and high-precision force platform. These studies showed that peak ground reaction forces were significantly reduced under conditions of partial weightbeari:ng, and changes in gait dynamics were consistent with previous studies of human locomotion. Using the PWS system, we conducted the first known studies of chronic musculoskeletal adaptation to Mars and lunar levels of weight bearing. Adult female BALB/cByJ mice underwent 21 days of partial weight bearing or control treatment. Relative to controls, suspended animals showed significant bone and muscle loss. In particular, bone formation rate was decreased, leading to deterioration of both cortical and trabecular bone structure in mice exposed to weight bearingtbearing. Although material properties of the bone were largely unaffected, structural and geometric changes resulted in lower bone strength.weight bearinged weight bearing at Mars and lunar levels led to similar losses of muscle and bone relative to controls. Comparison with previous literature suggests that adaptation to partial weight-bearing associated with both Mars and lunar loading provided some protection relative to the deconditioning seen in full unloading. Although additional studies are needed, the data also indicated that the musculoskeletal deterioration was not linearly related to the degree of unloading. Altogether, this model provides a validated, controlled system for investigaweight bearingof partial weightbearing and countermeasures on musculoskeletal deconditioning. Our initial findings have practical applications for bioastronautics, suggesting that physiological investigations on the surface of the moon may not be fully predictive for future Mars exploration.by Erika Brown Wagner.Ph.D

Special oils for halal and safe cosmetics

Three types of non conventional oils were extracted, analyzed and tested for toxicity. Date palm kernel oil (DPKO), mango kernel oil (MKO) and Ramputan seed oil (RSO). Oil content for tow cultivars of dates Deglect Noor and Moshkan was 9.67% and 7.30%, respectively. The three varieties of mango were found to contain about 10% oil in average. The red yellow types of Ramputan were found to have 11 and 14% oil, respectively. The phenolic compounds in DPKO, MKO and RSO were 0.98, 0.88 and 0.78 mg/ml Gallic acid equivalent, respectively. Oils were analyzed for their fatty acid composition and they are rich in oleic acid C18:1 and showed the presence of (dodecanoic acid) lauric acid C12:0, which reported to appear some antimicrobial activities. All extracted oils, DPKO, MKO and RSO showed no toxic effect using prime shrimp bioassay. Since these oils are stable, melt at skin temperature, have good lubricity and are great source of essential fatty acids; they could be used as highly moisturizing, cleansing and nourishing oils because of high oleic acid content. They are ideal for use in such halal cosmetics such as Science, Engineering and Technology 75 skin care and massage, hair-care, soap and shampoo products

Life Sciences Program Tasks and Bibliography for FY 1997

This document includes information on all peer reviewed projects funded by the Office of Life and Microgravity Sciences and Applications, Life Sciences Division during fiscal year 1997. This document will be published annually and made available to scientists in the space life sciences field both as a hard copy and as an interactive internet web page