Efforts to impart elasticity and multifunctionality in nanocomposites focus mainly on integrating polymeric and nanoscale components. Yet owing to the stochastic emergence and distribution of ...strain-concentrating defects and to the stiffening of nanoscale components at high strains, such composites often possess unpredictable strain-property relationships. Here, by taking inspiration from kirigami—the Japanese art of paper cutting—we show that a network of notches made in rigid nanocomposite and other composite sheets by top-down patterning techniques prevents unpredictable local failure and increases the ultimate strain of the sheets from 4 to 370%. We also show that the sheets' tensile behaviour can be accurately predicted through finite-element modelling. Moreover, in marked contrast to other stretchable conductors, the electrical conductance of the stretchable kirigami sheets is maintained over the entire strain regime, and we demonstrate their use to tune plasma-discharge phenomena. The unique properties of kirigami nanocomposites as plasma electrodes open up a wide range of novel technological solutions for stretchable electronics and optoelectronic devices, among other application possibilities.
Progress towards the integration of technology into living organisms requires electrical power sources that are biocompatible, mechanically flexible, and able to harness the chemical energy available ...inside biological systems. Conventional batteries were not designed with these criteria in mind. The electric organ of the knifefish Electrophorus electricus (commonly known as the electric eel) is, however, an example of an electrical power source that operates within biological constraints while featuring power characteristics that include peak potential differences of 600 volts and currents of 1 ampere. Here we introduce an electric-eel-inspired power concept that uses gradients of ions between miniature polyacrylamide hydrogel compartments bounded by a repeating sequence of cation- and anion-selective hydrogel membranes. The system uses a scalable stacking or folding geometry that generates 110 volts at open circuit or 27 milliwatts per square metre per gel cell upon simultaneous, self-registered mechanical contact activation of thousands of gel compartments in series while circumventing power dissipation before contact. Unlike typical batteries, these systems are soft, flexible, transparent, and potentially biocompatible. These characteristics suggest that artificial electric organs could be used to power next-generation implant materials such as pacemakers, implantable sensors, or prosthetic devices in hybrids of living and non-living systems.
The potential use of poly(dimethylsiloxane) (PDMS) as an in vitro biomimetic analogue of the passive drug absorption process in the human gastrointestinal tract (GI) is assessed. PDMS is biomimetic ...because of similarities in small molecule transport, such as mechanism, ionization selectivity, lipophilicity. Nine molecular probes are used to evaluate the transport pathways and properties used to predict human oral absorption rates. The transport pathways through PDMS (bulk/pore) are analogous to transcellular (TCDT) and paracellular (PCDT) drug transport pathways. PDMS PCDT is assessed using positronium annihilation lifetime spectroscopy (PALS) and partition experiments; TCDT using diffusion and partition experiments. PALS determined that PDMS pores were uniform (D ∼ 0.85 nm), isolated, and void volume was unaffected by drug accumulation after equilibrium partitioning. Therefore, there is no PCDT or convective flow through PDMS. A strong linear correlation exists between predicted octanol–water partition coefficients and PDMS partition coefficients (LogK PDMS = 0.736 × LogP O–W – 0.971, R 2 = 0.981). The pH-partition hypothesis is confirmed in PDMS using ibuprofen over pH 2–12. Diffusivity through PDMS is a function of lipophilicity and polar surface area K × D PDMS = 4.46 × 10–8 × e 2.91×LogK PDMS (R 2 = 0.963) and K × D PDMS = 4.61 × 10 − 6 × ( P S A K PDMS ) − 1.20 (R 2 = 0.973). Varying the mass% of curing agent changed the lipophilicity and diffusivity (p < 0.02), but not practically (K × D = 2.23 × 10–5cm2s–1 vs 2.60 × 10–5cm2s–1), and does affect elastic modulus (3.2% = 0.3 MPa to 25% = 3.2 MPa).
Solar-tracking concentrators can potentially lead to low-cost photovoltaic modules that minimize the use of costly semiconductor materials by improving optical collection and coupling. However, solar ...concentrators and accompanying trackers have proven to be expensive, bulky, and heavy, thereby resulting in increased balance-of-system costs. Here we demonstrate a lightweight and low-profile, and potentially low-cost planar solar-tracking concentrator based on the ancient Japanese art of origami. The tightly packed hexagonal concentrator and tracker arrays are fabricated by cutting and folding thin reflecting sheets that capture and direct concentrated light onto a small, high-efficiency GaAs solar cell. The tracker enables single-axis solar tracking via a simple one-dimensional translational motion of an actuator with minimal energy expense (∼2.9 J/m2/day). Further, we demonstrate stable operation over 10 000 cycles. The solar concentrated cell achieves a 450% increase in diurnal energy output compared with an equivalent, unconcentrated cell. The potentially low cost and low profile of the origami concentrators may lead to their wide deployment on rooftops and other building-integrated applications.
Origami and kirigami (the folding and cutting of paper, respectively, to achieve a desired shape) have been used in engineering to develop airbags, optical components, deployable spaceborne solar ...arrays, reprogrammable metamaterials, and load-bearing metal structures. Despite these efforts however, little has been shown beyond the packaging and load-bearing advantages of these three-dimensional approaches to structural design. This dissertation describes the use of dynamic, three-dimensional design principles to develop multifunctional mechanical and optoelectronic devices with improved performance, decreased fabrication costs, and greater economic value. First, we introduce a novel method of integrated, low-profile solar tracking whereby a simple kirigami pattern in thin-film gallium-arsenide solar cells enables tracking at the substrate level simply by stretching the sheet. The new tracker is inherently lightweight and very low profile; it is less susceptible to wind loading, which greatly reduces tracking system complexity, size, and cost, while also enabling new applications. System performance is considered as a function of cut geometry, materials selection, and geographic location, and optimized trackers are shown to generate up to 40% more energy per solar cell area over the course of a day relative to a stationary, flat panel module. Electrical and mechanical robustness are also considered with implications towards long-term solar tracking applications (i.e. >10,000 actuation cycles). Subsequently, we discuss a multifunctional system that combines kirigami solar tracking and integrated concentration optics to further reduce the overall cost of solar electricity. Optical design, mechanical response, and materials selection are considered to maximize optical and power concentration factor while also maintaining a simple design philosophy. The final system is shown to provide ~60x solar concentration, and further modifications will enable power concentration factors greater than 100x. Finally, similar design principles are extended to develop new applications including textured surfaces for flow manipulation and drag steering, kirigami patterns for tunable antennas, and origami tessellations for novel forms of electrochemical energy storage.
Squamates present a unique challenge to the homology and evolution of tooth attachment tissues. Their stereotypically pleurodont teeth are fused in place by a single “bone of attachment”, with ...seemingly dubious homology to the three‐part tooth attachment system of mammals and crocodilians. Despite extensive debate over the interpretations of squamate pleurodonty, its phylogenetic significance, and the growing evidence from fossil amniotes for the homology of tooth attachment tissues, few studies have defined pleurodonty on histological grounds. Using a sample of extant squamate teeth that we organize into three broad categories of implantation, we investigate the histological and developmental properties of their dental tissues in multiple planes of section. We use these data to demonstrate the specific soft‐ and hard‐tissue features of squamate teeth that produce their disparate tooth implantation modes. In addition, we describe cementum, periodontal ligaments, and alveolar bone in pleurodont squamates, dental tissues that were historically thought to be restricted to extant mammals and crocodilians. Moreover, we show how the differences between pleurodonty and thecodonty do not relate to the identity of the tooth attachment tissues, but rather the arrangements of homologous tissues around the teeth.
A look into the teeth and jaws of modern lizards reveal similar tooth attachment tissues to those in mammals. This challenges over a century of assumptions about dental evolution.
The first histological study of an entire hadrosaurid dental battery provides a comprehensive look at tooth movement within this complex structure. Previous studies have focused on isolated teeth, or ...in-situ batteries, but this is the first study to examine an entire dental battery of any dinosaur. The absence of direct tooth-to-tooth contact across the entire battery and a unique arrangement of the dental tissues in hadrosaurids led us to compare their teeth with the ever-growing incisors of mammals. The similarity in the distributions of tissues along the incisor, coupled with continuous eruption, make for helpful comparisons to hadrosaurid teeth. The mammalian ever-growing incisor can be used as a model to extrapolate the soft tissue connections and eruptive mechanisms within the hadrosaurid dental battery. Serial sections across the adult dental battery reveal signs of gradual ontogenetic tooth migration. Extensive remodeling of the alveolar septa and the anteroposterior displacement of successive generations of teeth highlight the gradual migration of tooth generations within the battery. These eruptive and ontogenetic tooth movements would not be possible without a ligamentous connection between successive teeth and the jaws, underscoring the dynamic nature of one of the most unique and complex dental systems in vertebrate history.
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