Light-emitting p-i-n GaP/GaPAs NW encapsulated in a flexible PDMS membrane

Our work is aimed at the method of fabricating arrays of semiconductor III-V NWs transferred into a flexible polymer membrane made of polydimethylsiloxane. GaP/GaPAs NWs with an axial p-i-n structure were synthesized by molecular beam epitaxy. The synthesized NW arrays on substrates were encapsulated into a silicone membrane by the G-coating method in a swinging-bucket centrifuge. After membranes were treated in a plasma mixture of O2/CF2 gases to open the NWs tops, which ensured the application of conductive transparent contacts - single-walled carbon nanotubes obtained by aerosol chemical method. At the last technological stage, the membranes were separated from substrates by peeling with a razor blade and the second carbon nanotubes contact was formed. The obtained LED NW/silicone membranes were characterized by I-V and the electroluminescence spectroscopy measurements.

Resistance of a Silicone Membrane to Long-term UV and Moisture Aging in Light of Climate Change

Three room-temperature fluid-applied silicone membranes intended for application in the building envelope were studied in this work. The membranes were subjected to 5000 hours of accelerated UV and moisture aging to evaluate their resistance to long-term aging. The properties of the membranes were studied to understand any degradation mechanisms that might happen during accelerated aging. The weight loss, wetting propensity, cracking and oxidation resistance, and storage modulus were measured at different intervals during the 5000 hours of aging. Based on the material characterization results, the silicone membranes proved to be resilient under aggressive accelerated UV radiation and moisture aging, conditions which can be expected as a result of climate change.

Transstadial Transmission from Nymph to Adult of Coxiella burnetii by Naturally Infected Hyalomma lusitanicum

Coxiella burnetii (Derrick) Philip, the causative agent of Q fever, is mainly transmitted by aerosols, but ticks can also be a source of infection. Transstadial and transovarial transmission of C. burnetii by Hyalomma lusitanicum (Koch) has been suggested. There is a close relationship between this tick species, wild animals and C. burnetii but the transmission in a natural environment has not been demonstrated. In this study, we collected 80 engorged nymphs of H. lusitanicum from red deer and wild rabbits. They moult to adults under laboratory conditions and we feed them artificially through silicone membranes after a preconditioning period. C. burnetii DNA was tested in ticks, blood and faeces samples using real-time PCR. The pathogen was found in 36.2% of fed adults, demonstrating that transstadial transmission from nymph to adult occurs in nature. The presence of DNA in the 60.0% of blood samples after artificial feeding confirms that adults transmit the bacteria during feeding. Further studies are needed about co-feeding and other possible transmission routes to define the role of this tick species in the cycle of C. burnetii.

Transstadial Transmission from Nymph to Adult of Coxiella burnetii by Naturally Infected Hyalomma lusitanicum

Coxiella burnetii (Derrick) Philip, the causative agent of Q fever, is mainly transmitted by aerosols, but ticks can also be a source of infection. Transstadial and transovarical transmission of C. burnetii by Hyalomma lusitanicum (Koch) has been suggested. There is a close relationship between this tick species, wild animals and C. burnetii but the transmission in a natural environment has not been demonstrated. In this study, we collected 80 engorged nymphs of H. lusitanicum from red deer and wild rabbits. They molt to adults under laboratory conditions and we feed them artificially through silicone membranes after a preconditioning period. C. burnetii DNA was tested in ticks, blood and feces samples using real-time PCR. The pathogen was found in 36.25% of fed adults demonstrating that transstadial transmission from nymph to adult occurs in nature. The presence of DNA in the 60% of blood samples confirms that adults transmit the bacteria during feeding. Further studied are needed about co-feeding and other possible transmission routes to define the role of this tick species in the cycle of C. burnetii.

Mechanical Behaviour of Silicone Membranes Saturated with Short Strand, Loose Polyester Fibres for Prosthetic and Rehabilitative Surrogate Skin Applications

Silicone-based elastomers saturated with embedded, short-strand fibres are used for their ability to mimic the aesthetic qualities of skin in clinical and theatrical maxillofacial appliance design. Well-known to prostheses fabricators and technicians, the mechanical impact of fibre addition on elastomeric behaviour endures as tacit, embodied knowledge of the craft, almost unknown in the literature. To examine mechanical changes caused by fibre addition, 100 modified polydimethylsiloxane (PDMS) elastomeric compounds containing incremental amounts of loose polyester fibres were prepared and examined in a variety of mechanical tests. It was found that elasticity and strain percentage at breaking point was reduced by increasing fibre content, but Young’s modulus and ultimate tensile strength (UTS) increased. As fibre content was increased, strain hardening was seen at low strain rates, but exaggerated plastic deformation at high strain rates. PDMS hardness increased by 5 degrees of hardness (Shore-00 scale) for every additional percentage of fibres added and a strong positive linear coefficient (0.993 and 0.995) was identified to reach the hardness values given in the literature for living human skin. The apparent reorienting of loose fibres in the PDMS interrupts and absorbs stress during the loading process similar to the organic response to soft tissue loading, except in extension.

Fiber Embroidery of Self-Sensing Soft Actuators

Natural organisms use a combination of contracting muscles and inextensible fibers to transform into controllable shapes, camouflage into their surrounding environment, and catch prey. Replicating these capabilities with engineered materials is challenging because of the difficulty in manufacturing and controlling soft material actuators with embedded fibers. In addition, while linear and bending motions are common in soft actuators, rotary motions require three-dimensional fiber wrapping or multiple bending or linear elements working in coordination that are challenging to design and fabricate. In this work, an automatic embroidery machine patterned Kevlar™ fibers and stretchable optical fibers into inflatable silicone membranes to control their inflated shape and enable sensing. This embroidery-based fabrication technique is simple, low cost, and allows for precise and custom patterning of fibers in elastomers. Using this technique, we developed inflatable elastomeric actuators embedded with a planar spiral pattern of high-strength Kevlar™ fibers that inflate into radially symmetric shapes and achieve nearly 180° angular rotation and 10 cm linear displacement.

Effects of uniaxial stretching on tenocyte migration behaviour

It is widely known that tendon tissues are subjected to repeated cyclic mechanical load which influences cellular processes. The involvement of principles of mechanics in tissue engineering contributes to the investigations of the connection between mechanical and biological parameters in cellular processes and as well as to the development of new approaches for specific treatment methods. The healing process of injured tendons includes tenocyte migration which occurs from intact regions of tendon into the wound site. The aim of the present study is to investigate and enhance the migration characteristics of tenocytes under uniaxial mechanical stretching using an in-house tensile bioreactor system. Uniaxial mechanical stretching is applied to tenocyte-seeded silicone as well as collagen membranes, which possess different material properties. Tenocyte-seeded silicone membranes were investigated under three different loading conditions, including unstimulated (control), 3% and 5% strain, at frequency of 0.5 Hz. Tenocyte-seeded collagen membranes were investigated using three different frequencies, including unstimulated (control), 0.1 Hz and 0.5 Hz at strain of 4%. The main finding in this study is that uniaxially mechanical stretching at 3% strain enhances the cell migration more than 5% strain on silicone membranes.