Artificial Soft Cilia with Asymmetric Beating Patterns for Biomimetic Low‐Reynolds‐Number Fluid Propulsion

In nature, liquid propulsion in low‐Reynolds‐number regimes is often achieved by arrays of beating cilia with various forms of motion asymmetry. In particular, spatial asymmetry, where the cilia follow a different trajectory in their effective and recovery strokes, is an efficient way of generating flow in low Reynolds regimes. However, this type of asymmetry is difficult to mimic and control artificially. In this paper, an artificial soft cilium that comprises two pneumatic actuators that can be controlled individually is developed. These two independent degrees of freedom allow for the first time adjustment and study of spatial asymmetry in the cilium's beating pattern. Using low‐Reynolds‐number flow measurements, it is confirmed that spatial asymmetry allows for the generation of fluid propulsion. These two‐degree‐of‐freedom soft cilia provide a platform to study ciliary fluid transport mechanisms and to mimic biologic viscous propulsion.     

Biomimetic Composites: Protein Localization in Silica Nanospheres Derived via Biomimetic Mineralization (Adv. Funct. Mater. 18/2010)

Lysozyme‐templated precipitation of silica synthesized by sol‐gel chemistry produces a composite material with antimicrobial properties. This study investigates the structural properties of the composite material that allow for retention of the antimicrobial activity of lysozyme. Scanning (SEM) and transmission (TEM) electron microscopy reveal that the composite has a hierarchical structure composed of quasi‐spherical structures (～450 nm diameter), which are in turn composed of closely packed spherical structures of ～8–10 nm in diameter. Using small‐angle neutron scattering (SANS) with contrast variation, the scattering signatures of the lysozyme and silica within the composite were separated. It was determined that the lysozyme molecules are spatially correlated in the material and form clusters with colloidal silica particles. The size of the clusters determined by SANS agrees well with the structural architecture observed by TEM. BET analysis revealed that the surface area of the composite is relatively low (4.73 m²/g). However, after removal of the protein by heating to 200 °C, the surface area is increased by ～20%. In addition to demonstrating a well organized sol‐gel synthesis which generates a functional material with antimicrobial applications, the analysis and modeling approaches described herein can be used for characterizing a wide range of mesoporous and ultrastructural materials.     

A Flexible and Biomimetic Olfactory Synapse with Gasotransmitter-Mediated Plasticity (Adv. Funct. Mater. 18/2023)

Neuromorphic electronics has demonstrated great promise in mimicking the sensory and memory functions of biological systems. However, synaptic devices with desirable sensitivity, selectivity, and operational voltage imitating the olfactory system have rarely been reported. Here, a flexible and biomimetic olfactory synapse based on an organic electrochemical transistor (OECT) coupled with a breath-figure derived porous solid polymer electrolyte (SPE) is proposed. The device demonstrates excellent sensitivity with a ppb-level response limit and desirable selectivity toward hydrogen sulfide (H₂S) over other gases, and successfully achieves wireless real-time detection of excessive concentration of H₂S from rotten eggs. H₂S-mediated synaptic plasticity is accomplished with the device and typical synaptic behaviors are realized, including short-term memory (STM), long-term memory (LTM), transition from STM to LTM, etc., enabling the imitation of potential cumulative damages upon H₂S exposure. The proposed device paves new ways toward next-generation olfactory systems capable of sensing and memorizing functionalities mimicking neurobiological systems, offering critical materials strategies to accomplish intelligent artificial sensory systems.