New Insights into the Biosensing of Parkinson's Disease Biomarkers: A Concise Review

Background: Parkinson's disease (PD) is a long-term, degenerative, and neurological disease in which a person loses control of certain body functions. The formulation of novel effective therapeutics for PD as a neurodegenerative disease requires accurate and efficient diagnosis at the early stages. Objective: Analyzing data gathered by measurable signals converted from biological reactions allows for qualitative and quantitative evaluations. Among various approaches reported so far, biosensors are powerful analytical tools that have been used in detecting the biomarkers of PD. Methods: Biosensor’s biological recognition components include antibodies, receptors, microorganisms, nucleic acids, enzymes, cells and tissues, and biomimetic structures. This review introduces electrochemical, optical, and optochemical detection of PD biomarkers based on recent advances in nanotechnology and material science, which resulted in the development of high-performance biosensors in this field. Conclusion: The development of novel biosensors is required for the early diagnosis of PD as sensitive, rapid, reliable, and cost-effective systems.

The kapok petal: superhydrophobic surface induced by microscale trichomes

The Kapok petal is reported for the first time that it shows a superhydrophobic characteristic with a static water contact angle higher than 150°. Intriguingly, there exist single-scale micro-trichomes and no more nanocrystals on a kapok petal in contrast to most natural superhydrophobic surfaces with hierarchical morphologies, such as lotus leaf and rose petal. Experiment results show that kapok petal has an excellent self-cleaning ability either in air or oil. Further scanning electron microscope characterization demonstrates that the superhydrophobic state is induced by densely-distributed microscale trichomes with an average diameter of 10.2 μm and a high aspect ratio of 17.5. A mechanical model is built to illustrate that the trichomes re-entrant curvature should be a key factor to induce the superhydrophobic state of the kapok petal. To support the proposed mechanism, gold-wire trichomes with a re-entrant curvature are fabricated and the results show that a superhydrophobic state can be induced by microstructures with a re-entrant curvature surface. Taking the scalability and cost-efficiency of microstructure fabrication into account, we believe the biomimetic structures inspired by the superhydrophobic kapok petal can find numerous applications that require a superhydrophobic state.

An extended family of perforated submicrometer hollow or core-shell plasmonic particles as antireflective synthetic brochosomes

We investigated different biomimetic structures inspired by natural brochosome powders which appear on the bodies and wings of leafhoppers (insects from the Cicadellidae family). All structures we analyzed are roughly spherical, with diameters 200 nm to 1000 nm, with a core and a shell made of different materials and the core perforated with subwavelength holes with diameters of the order of tens of nanometers. We extended the range of possible designs, geometries and materials of synthetic brochosomes, inspired by their natural counterparts found as powders secreted by various species of leafhoppers. We performed simulation of the optical properties of the structures using the finite element method. We found out that our approach ensures the design of highly efficient omnidirectional ultra-antireflective diffractive powders with subwavelength apertures. The reflectivity of 600 nm diameter holey spheres does not exceed 0.02% in 500-600 nm range. We showed that planar arrays of plasmonic-based artificial brochosomes exhibit a rich optical behavior, including effective refractive index below unity and even below zero at longer wavelengths. Such metamaterial-like behavior contributes to the multifunctionality of our synthetic brochosomes which can already serve as antireflective, superhydrophobic and highly porous structures controllable by design. This kind of versatility shows potentials for numerous practical uses. A major part of the novel functionalities stems from the use of nanocomposites containing free-electron conductors (plasmonic materials). Thus we arrived at a toolbox for the design of highly customizable antireflective layers. Potential fields of use include photodetectors, photoelectrochemistry, photocatalysis and general microoptoelectromechanical (MOEMS) systems.

Bio-inspired aquatic propulsion using piezoelectric effect

Underwater propulsion of fishes have inspired many biomimetic structures. Generally, the bio-inspired structures mimics the flapping behaviour of various control surfaces/fins in fishes. The present study mimics the flapping behaviour using a piezoelectric structure. The system is analyzed as a fluid structure interaction problem. The dynamic behaviour of a cantilever beam surrounded by a bounded fluid domain open at top is analyzed. The structure is modeled as a Euler-Bernoulli beam and the fluid is modeled using potential flow theory. The influence of domain size on the wet natural frequencies of the system was analyzed. The dimensions of the fluid domain wherein the variation in wet natural frequencies becomes insensitive were determined. The influence of added mass on the wet natural frequency was parametrized based on Non-dimensional Added Mass Increment (NAVMI) factor. The NAVMI factors were observed to be relatively higher for lower wet modes of the structure. Therefore, the peizo-beam was analyzed by exciting the lower wet modes. The thrust generated at different excitation frequencies were determined using tip velocity of the cantilever beam following Lighthill’s analogy. The results from the study indicated that higher propulsive thrust was produced for lower modes of excitation of the structure.

A Strategy towards Light-Absorbing Coatings Based on Optically Black Nanoporous Alumina with Tailored Disorder

This work provides a conceptually new way of thinking about the light-absorbing mechanism in additive-free black porous anodic alumina (black PAA, or b-PAA) layers obtained via “burning” anodizing regime. The new insight into the controllable photonic effects in PAA allows the implementation of the optical blackening method based on the deliberate randomization of the initially well-ordered nanopore arrangement. The proposed black coloration mechanism rests solely on the destructive interference of light after its multiple scattering. Similar effects have been earlier considered for some natural or artificially created biomimetic structures (e.g., the so-called “moth eye effect”, or the coloration mechanism in the Neurothemis tullia dragonfly wings). Comprehensive analysis confirmed that the chemical composition of b-PAA has only a minor influence on the color changes and the optical density increase, and that the light-absorbing properties most likely result from the structural effects. The new functional 2D materials exhibit strong adhesion to aluminum surface, are cost-effective and suitable for application under harsh thermal or UV-light conditions. They are potentially useful for manufacturing of optical devices or heat-resistant coatings in aerospace technologies, as well as solid supports for biological filtration and fluorescence imaging.

Nature-Inspired Structures Applied in Heat Transfer Enhancement and Drag Reduction

Heat exchangers are general equipment for energy exchange in the industrial field. Enhancing the heat transfer of a heat exchanger with low pump energy consumption is beneficial to the maximum utilization of energy. The optimization design for enhanced heat transfer structure is an effective method to improve the heat transfer coefficient. Present research shows that the biomimetic structures applied in different equipment could enhance heat transfer and reduce flow resistance significantly. Firstly, six biomimetic structures including the fractal-tree-like structure, conical column structure, hybrid wetting structure, scale structure, concave-convex structure and superhydrophobic micro-nano structure were summarized in this paper. The biomimetic structure characteristics and heat transfer enhancement and drag reduction mechanisms were analyzed. Secondly, four processing methods including photolithography, nanoimprinting, femtosecond laser processing and 3D printing were introduced as the reference of biomimetic structure machining. Finally, according to the systemic summary of the research review, the prospect of biomimetic heat transfer structure optimization was proposed.

Mastering of NIL Stamps with Undercut T-Shaped Features from Single Layer to Multilayer Stamps

Biomimetic structures such as structural colors demand a fabrication technology of complex three-dimensional nanostructures on large areas. Nanoimprint lithography (NIL) is capable of large area replication of three-dimensional structures, but the master stamp fabrication is often a bottleneck. We have demonstrated different approaches allowing for the generation of sophisticated undercut T-shaped masters for NIL replication. With a layer-stack of phase transition material (PTM) on poly-Si, we have demonstrated the successful fabrication of a single layer undercut T-shaped structure. With a multilayer-stack of silicon oxide on silicon, we have shown the successful fabrication of a multilayer undercut T-shaped structures. For patterning optical lithography, electron beam lithography and nanoimprint lithography have been compared and have yielded structures from 10 µm down to 300 nm. The multilayer undercut T-shaped structures closely resemble the geometry of the surface of a Morpho butterfly, and may be used in future to replicate structural colors on artificial surfaces.