Keratin composites enable animals to hike with hooves, fly with feathers, and sense with skin. Mammalian whiskers are elongated keratin rods attached to tactile skin structures that extend the animal's sensory volume. We investigated the whiskers that cover Asian elephant (Elephas maximus) trunks and found that they are geometrically and mechanically tailored to facilitate tactile perception by encoding contact location in the amplitude and frequency of the vibrotactile signal felt at the whisker base. Elephant whiskers emerge from armored trunk skin and shift from a thick, circular, porous, stiff base to a thin, ovular, dense, soft tip. These functional gradients of geometry, porosity, and stiffness independently tune the neuromechanics of elephant trunk touch to facilitate highly dexterous manipulation while ensuring whisker durability.

Aquatic environments are often contaminated with biopersistent pharmaceuticals, such as the β-blocker metoprolol. The quantitative determination of such pollutants is crucial for environmental monitoring. Therefore, a highly sensitive integrated photonic biosensor for the detection of minute concentrations of metoprolol is presented here. The sensor is based on a thermally robust ring resonator with a hydrogel coating for metoprolol adsorption. Hydrogels consisting of gelatin methacryloyl enabled an increase in the concentration of metoprolol ions in the vicinity of the photonic chip, resulting in high sensitivity of the sensor setup. Compared to an uncoated chip, an increase in sensitivity of up to a factor of 20 was observed. In combination with software-implemented signal processing, the setup showed a detection limit of less than 1 × 10–4 μmol mL–1. The combination of functional coating, thermally insensitive design, and applied digital signal postprocessing makes the system introduced here an attractive approach toward sensor-based wastewater analysis and monitoring.

Hydrogels containing functional groups are highly interesting for sensor applications as they can change their physical properties by interaction with their environment. In this study, it is demonstrated that by monitoring the conductance of two different functional hydrogels, the concentrations of two different drugs in aqueous solution can be selectively and quantitatively measured simultaneously based on non-specific interactions. Detailed characterization of the competitive drug adsorption on the hydrogels allows the description of both hydrogel conductances as a function of the drug concentrations based on physical models. The result is a system of non-linear equations that can be solved for the drug concentrations. The different affinities and conductance responses of the hydrogels for the two drugs is a prerequisite, which is usually achieved with different materials. This approach is demonstrated with hydrogels based on poly(ethylene glycol), functionalized with the ionic monomers [2-(acryloyloxy)ethyl] trimethylammonium chloride (AETA) and 3-sulfopropyl acrylate potassium salt (SPA), and the drugs diclofenac and metoprolol. The hydrogel conductance is found to be linear with drug concentration in the hydrogels, which in turn is described by a non-linear Langmuir-type competitive adsorption isotherm. The proposed approach thus shows potential for future studies on more complex mixtures by including a larger variety of functional hydrogels.

Whiskers are so named because these hairs often actuate circularly, whisking, via collagen wrapping at the root of the hair follicle to increase their sensing volumes. Elephant trunks are a unique case study for whiskers, as the dorsal and lateral sections of the elephant proboscis have scattered sensory hairs that lack individual actuation. We hypothesize that the actuation limitations of these non-whisking whiskers led to anisotropic morphology and non-homogeneous composition to meet the animal's sensory needs. To test these hypotheses, we examined trunk whiskers from a 35-year-old female African savannah elephant (Loxodonta africana). Whisker morphology was evaluated through micro-CT and polarized light microscopy. The whiskers from the distal tip of the trunk were found to be axially asymmetric, with an ovular cross-section at the root, shifting to a near-square cross-section at the point. Nanoindentation and additional microscopy revealed that elephant whiskers have a composition unlike any other mammalian hair ever studied: we recorded an elastic modulus of 3 GPa at the root and 0.05 GPa at the point of a single 4-cm-long whisker. This work challenges the assumption that hairs have circular cross-sections and isotropic mechanical properties. With such striking differences compared to other mammals, including the mouse (Mus musculus), rat (Rattus norvegicus), and cat (Felis catus), we conclude that whisker morphology and composition play distinct and complementary roles in elephant trunk mechanosensing.

The discovery of the high maximum energy product of 59 MGOe for NdFeB magnets is a breakthrough in the development of permanent magnets with a tremendous impact in many fields of technology. This value is still the world record, for 40 years. This work reports on a reliable and robust route to realize nearly perfectly ordered L1_0-phase FePt nanoparticles, leading to an unprecedented energy product of 80 MGOe at room temperature. Furthermore, with a 3 nm Au coverage, the magnetic polarization of these nanomagnets can be enhanced by 25% exceeding 1.8 T. This exceptional magnetization and anisotropy is confirmed by using multiple imaging and spectroscopic methods, which reveal highly consistent results. Due to the unprecedented huge energy product, this material can be envisaged as a new advanced basic magnetic component in modern micro and nanosized devices.