Biological and Biologically Inspired Functional Nanostructures: Insights into Structural, Optical, Thermal, and Sensing Applications

Abstract

Biological materials developed over millennia consist of simple biogenic materials, yet exhibit exceptional functional properties. Leveraging design features from these structures with engineered nanomaterial components can lead to bio-inspired structures that demonstrate superior performance over traditional engineering materials. We describe nanoscale based architectures in biological systems, their role in enhancement of structural, optical, thermal and sensing properties, and their subsequent translation to bio-inspired structures. In structurally robust biological materials, we highlight nanoscale design features that enhance strength and stiffness, while retaining toughness. In optically active biological materials, we show how periodic nanostructures manipulate electromagnetic waves resulting in structural coloration as well as antireflective and camouflaging properties. Thermally regulating biological materials utilize nanopores and other nanostructural features to statically or dynamically control temperature. In addition, biological materials that are used in sensing utilize various nanostructures that enhance sensitivity by decreasing activation thresholds for signal transduction. We discuss challenges and opportunities including understanding control mechanisms in the formation of biological materials and leveraging advancements in self-assembly with new additive manufacturing techniques. The continued evaluation of organisms, including those that exhibit multifunctionality, provides not only new design features and pathways, but significant prospects for innovation in this ever-emerging field.

Keywords: biological materials; bio‐inspired materials; nanostructures; structure‐function relationships.

Figure 1

Overview of Biological and Bio‐inspired Nanomaterial Design. Summary of key biological models and their translation into functional nanomaterials across four domains: Structural, Optical, Thermal, and Sensing material design. Structural Materials: A) Nanoparticulate impact‐resistant architecture of the mantis shrimp, Odontodactylus scyllarus, dactyl club, inspiring durable protective coatings for multiple applications, including wind turbines. Reproduced with permission.^{[ 84 ]} Copyright 2020, Springer Nature. B) High‐performance radular nanofibers of chitons, informing bio‐inspired 3D printed nanostructures. Reproduced with permission.^{[ 16} , ^{17 ]} Copyright 2020, Springer Nature. Copyright 2017, Wiley. C) Brick‐and‐mortar nacre architectures, replicated in robust and stretchable hydrogels for space applications. Reproduced with permission.^{[ 85} , ^{86 ]} Copyright 2024, Wiley. Copyright 2005, Elsevier. Optical Materials: D) Structural coloration in Trigonophorus rothschildi varians, guiding the development of vivid, pigment‐free photonic materials. Reproduced with permission.^{[ 87 ]} Copyright 2004, Royal Society. E) Nanoporous silica shells of diatoms, enabling light‐trapping functionalities for photonic and energy applications. Reproduced with permission.^{[ 88 ]} Copyright 2015, Springer Nature. F) Anti‐reflective corneal nanostructures of moth eyes, adapted for high‐efficiency solar panel coatings. Reproduced with permission.^{[ 89 ]} Copyright 2018, Springer Nature. Thermal Materials: G) Thermoinsulating properties of polar bear fur, inspiring advanced textile insulation. Reproduced with permission.^{[ 90 ]} Copyright 2019, Elsevier B.V. H) Ultrabright scattering scales of Cyphochilus beetles, leading to heat‐reflective ceramic coatings and tiles. Reproduced with permission.^{[ 91 ]} Copyright 2023, AAAS. I) Cephalopod chromatophores with dynamic thermal modulation, informing sustainable buildings (e.g., energy‐efficient mechano‐thermochromic windows.). Reproduced with permission.^{[ 92 ]} Copyright 2020, Elsevier B.V. Sensing Materials: J) Infrared sensory organs of Melanophila acuminata, serving as models for IR detection devices. Reproduced with permission.^{[ 93 ]} Copyright 2015, MDPI. K) Chemosensory antennae of Bombyx mori, inspiring chemical sensing platforms. Reproduced with permissions.^{[ 94} , ^{95 ]} Copyright 2014, Frontiers. Copyright 2022, Elsevier. L) Mechanosensory nano‐slits of Cupiennius salei, guiding the development of vibration‐sensitive sensors. Reproduced with permissions.^{[ 96} , ^{97 ]} Copyright 2007, The Royal Society. Copyright 2014, Springer Nature. All other images used in this figure are licensed under public use licensess. (See Supplemental).

Figure 2

Impact surface and structure of the mantis shrimp dactyl club. a) Photograph of a mantis shrimp and its dactyl club, indicated with white arrows. b) Optical micrograph of the transverse section of an intact dactyl club showing the impact surface, impact region, and periodic region. c) SEM micrograph of a transverse section of an intermolted dactyl club. Inset: nanoparticles ≈60 nm in diameter are found within the impact surface. d) Primary grains were found assembled within a single ≈60 nm secondary particle. The white dots marked with red arrows suggest a second phase. Inset: the arcs in the FFT pattern indicate the misalignment of primary grains. e) Grain boundaries of adjacent grains, indicated by FFT spectroscopy. Inset: HRTEM demonstrating the disordered grain boundary adjacent to the (100) planes of HAP crystals. The second phase found in a is outlined in green. f) Misalignment (≈1.5°) of two adjacent grains. g) AFM phase map of a coronal section of the impact surface showing the network of two different phases. The angle (color scale) refers to the phase change/lag during the AFM tests. The phase change thus reflects changes in mechanical properties. Inset: high‐resolution image illustrating the two different phases. h) HRTEM of stained samples showing chitin molecules surrounding a HAP crystal lattice. Proteins are stained as dark spots. Inset: FFT pattern of the chitin‐wrapped HAP nanoparticles. Diffraction spots represent HAP crystals and the broad diffuse ring represents the chitin macromolecules. i) HRTEM image shows the organic network within the HAP crystalline network. The green dashed lines indicate areas that have organic phase, as suggested by the expanded d spacings of the lattice. Inset: FFT pattern. j) HRTEM of HAP particles after heat treatment at 800 °C. k) Schematic of the dactyl club highlighting the impact surface and illustrating its location and hierarchical nature. From left to right: drawing of the dactyl club, with the transverse cutaway highlighted in color; impact surface and impact region from the transverse section; HAP nanoparticles embedded in an organic matrix on the impact surface; bi‐continuous network of the HAP nanoparticles within an organic phase (bottom); oriented attachment of HAP nanocrystals, in which the lattice mismatch and organics embedded within the HAP crystal lattice are illustrated (top). Adapted with permission.^{[ 84 ]} Copyright 2020, Springer Nature.

Figure 3

Representative biological macromolecules in structural biological materials. a–c) Hierarchical structure of wood and cellulose fibers. Crystalline and non‐crystalline regions are shown. a) Reproduced with permission.^{[ 127 ]} Copyright 2021, Wiley. b,c) Adapted with permission.^{[ 121 ]} Copyright 2007, American Chemical Society. d–g) Mineralized iron oxide onto a chitin scaffold. Hierarchical structure of nanorods results in robust mechanical properties. Adapted with permissions.^{[ 17} , ³⁸ , ^{160 ]} Copyright 2013, Wiley. Copyright 2010, Elsevier. Copyright 2022, Wiley. h–j) Skin and collagen fibers at the nanoscale. Skins show resistance to crack propagation. Adapted with permission.^{[ 122 ]} Copyright 2015, Springer Nature. k–p) Bighorn sheep horns and keratin fibers inside keratinized cells. Crystalline intermediate filaments are indicated. Adapted with permissions.^{[ 123} , ^{124 ]} Copyright 2017, Elsevier. Copyright 2019, Wiley.

Figure 4

Schematic of A) the hierarchical crossed‐lamellar structure observed in the conch shells. Adapted with permission.^{[ 144 ]} Copyright 2025, Wiley. B) Plot of the crack tip opening displacement as a function of crack extension in conch and single crystal aragonite. Adapated with permission.^{[ 149 ]} Copyright 2016, Springer Nature. C) Crack is shown traveling straight through the “weak” direction and being deflected within the next layer. Adapted with permission.^{[ 150 ]} Copyright 2004, Elsevier. D) Schematic of different energy dissipation mechanisms in the platelet sliding process. Adapted with permission.^{[ 54 ]} Copyright 2015, Springer Nature. E) Experimental tensile stress‐strain curve for nacre and F) schematics associated with deformation modes. Adapted with permission.^{[ 154 ]} Copyright 2007, Elsevier. SEM microscopy of nacreous structures exhibiting: G) platelet pullout and H) presence of interlocking between platelets. Adapted with permission.^{[ 86 ]} Copyright 2006, Elsevier.

Figure 5

Helicoidal architecture in biological systems. a) Hierarchical structure of the lobster cuticle: a, I) N‐acetyl‐glucosamine molecules, a, II) antiparallel chains of ɑ‐chitin, a, III) chitin‐protein nanofibrils, a, IV) chitin‐protein fibers in a mineral‐protein matrix (not shown), a, V) cuticle with pore canal system (in‐plane cross‐section), a, VI) twisted plywood structure, and a, VII) three‐layered cuticle. Reproduced with permission.^{[ 175 ]} Copyright 2010, Wiley. b,c) Helicoidal structural motif consisting of chitinous fibers surrounded by an amorphous calcium phosphate matrix within the periodic region (periodicity: ≈75 µm) of the dactyl club of the mantis shrimp, Odontodactylus scyllarus. b) A generalized three‐dimensional model of a helicoid and accompanying SEM fractograph from the periodic region. c) Backscattered (BEI, left) and charge‐contrast secondary (SEI, right) scanning electron micrographs of a transverse cross section through the dactyl club, indicating crack‐arrest near the impact surface (IR: Impact Region) and at interfaces within the periodic region (PR). Adapted with permission.^{[ 176 ]} Copyright 2012, AAAS. d–f) Helicoid structures within the cuticle of the Diabolical iron‐clad beetle (DIB), Phloeodes diabolicus. d) Image of DIB, e) false colored SEM of fractured section of beetle elytra. f) Helicoidal microstructure of chitin fibers, surrounded by a protein matrix, in the endocuticle. Adapted with permission.^{[ 177 ]} Copyright 2020, Springer Nature. g) Nanoindentation curves of geological fluorapatite in comparison to the dactyl club outer layer (DOL) and dactyl club inner layer (DIL). Adapted with permission.^{[ 178 ]} Copyright 2015, Springer Nature. h, i) Schematic illustration of a twisting crack behind an initial flat crack in the Bouligand structure in this study with interlayer spacing d (distance between adjacent fiber layers) and h, ii) pitch angle γ (difference in orientation of adjacent fiber layers). h, iii) The twisting crack is represented by a twisting surface. Adapted with permission.^{[ 179 ]} Copyright 2017, Elsevier. i) (Top) Digital Image correlation strain distribution measured from 3D printed helicoid samples with a 0° (left) and 5° (right) misalignment between layers. (Bottom) Comparison with computational models. Adapted with permission.^{[ 180 ]} Copyright 2018, Elsevier.

Figure 6

Bio‐inspired designs of strong and tough fiber materials. a) Schematic showing hierarchical structure of wool keratin and transition from α‐helix to β‐sheet that is feasible under strain. b) Schematic representing the water‐triggered shape memory mechanism. c) Mechanical tests and toughening mechanisms of keratin fibers. Adapted with permission.^{[ 270 ]} Copyright 2021, Springer Nature. e) Schematic of fabricating strong and tough cellulose macrofibers based on bacterial cellulose. f–h) SEM images of the as‐fabricated cellulose fibers. m,n) Comparison of mechanical properties and Ashby plot. Adapted with permission.^{[ 268 ]} Copyright 2017, Wiley.

Figure 7

a) Orientation of Si₃N₄ (blue) and h‐BN (green) laminates. b) Four‐point bend test load vs displacement for biomimetic ceramic. Adapted with permission.^{[ 279 ]} Copyright 2013, Elsevier. c) Mono‐lamellar Ag‐NW film was separated from the porous MCE substrate in water. d) Crack extension characterization of 5‐lamellar Ag NW film. High magnification SEM image shows typical debonding and pullout of Ag‐NW in the fracture surface of a freestanding ultrathin Ag‐NW film. White arrows indicate the direction of load redistribution. Blue arrows indicate the path of crack propagation. Inset image shows a schematic diagram of crack propagation. e) Typical sawtooth pattern on the load‐displacement curve in mechanical tearing tests. f) Ashby diagram of toughness versus tensile strength for disordered and 5‐lamellar Ag‐NW films. Adapted with permission.^{[ 286 ]} Copyright 2024, ACS Publications.

Figure 8

a) Digital photograph of a large area (100 cm × 25 cm) layered composite film fabricated by blade coating. b) SEM image of the cross‐section of the conductive nacre showing lamellar structure. c) SEM image of the cross‐section of the conductive nacre is taken using backscattered electrons. d) Flexural stress‐strain curves of the natural nacre, artificial nacre, and conductive nacre. e) Comparison of flexural strength and flexural modulus of the natural nacre, artificial nacre, and conductive nacre. f) Rising crack extension resistance curves (R‐curves) of the natural nacre, artificial nacre, and conductive nacre showing the resistance to failure in terms of the fracture toughness (K_JC) as a function of crack extension (Δa). g) Comparison of fracture toughness and electrical conductivity of the natural nacre and conductive nacre. Adapted with permission.^{[ 18 ]} Copyright 2024, Wiley. Nacre‐biomimetic structure design and fabrication of ceramic aerogels. h) Conceptual structure design principle inspired by nacre. i) Stress distribution of the laminated structural model showed stress transfer and in‐plane stress delocalization. j) Weak to strong interface structure design concept for biomimetic ceramic aerogels. k) Fabrication process of biomimetic ceramic aerogels with laminated structure and interfacial topology interlocking. Reproduced with permission.^{[ 85 ]} Copyright 2024, Wiley. l) Partially demineralized biogenic and m) a single layer of artificial nacre, showing the crystalline domain boundaries. n) SEM image showing early‐stage crystallization through single PVP pores in a trilayer of calorg/organic/calorg (scale bar, 500 nm). o) Optical micrograph showing 5–35 µm birefringent crystalline domains (right: though crossed polarizers) (scale bar, 25 µm). p)The plain strain moduli for the two natural and three man‐made samples as a function of the indentation depth. Adapted with permission.^{[ 290 ]} Copyright 2012, Springer Nature.

Figure 9

a) Photographs showing damage (from top to bottom) in unidirectional, quasi‐isotropic, small‐angle, medium‐angle, and large‐angle carbon fiber reinforced composites after 100J drop tower testing. b) Dent depth measurements for each sample as percentage reduction in dent depth listed for helicoidal samples. c) Photographs of damage in (from top to bottom) quasi‐isotropic, small‐angle, medium‐angle, and large‐angle composites after compression tests. d) Residual strength calculated from compressive data, with percentage change listed for helicoidal samples. Ultrasonic C‐scan images showing internal damage fields in the e) quasi‐isotropic, f) small‐angle, g) medium‐angle, and h) large‐angle composites after drop tower testing, showing the increase of in‐plane damaged area after a 100J impact. Adapted with permission.^{[ 304 ]} Copyright 2014, Elsevier. i) Schematic diagram of the controlled alignment of carbon nanotubes by the rotation of electrodes immersed in a photocurable resin bath. Progressive rotation of electrodes and curing of resin by a digital micromirror device (DMD) produces structures in j) with helicoidal arrangement. k) Compression tests of the printed samples with different fiber clocking angles, where N = 1 is a rotation angle of 45°, N = 15 is 12°, N = 30 is 6°, and N = 90 is 2°. Adapted with permission.^{[ 310 ]} Copyright 2017, Wiley. l) Schematic illustration of electrospinning setup with patterned collector and programmable voltage collector used to fabricate a periodic helicoidal microstructure within a transparent impact resistant film. Reproduced with permission.^{[ 311 ]} Copyright 2019, ACS. Schematic illustration and digital micrographs showing high‐efficiency ‘brushing and laminating’ strategies for flexibly fabricating biomimetic macroscopic 3D bulk materials. Adapted with permission.^{[ 312 ]} Copyright 2018, Oxford University Press.

Figure 10

Schematic illustration of a) poly (vinyl alcohol)/cellulose nanocrystals (CNC/PVA) composite lamellar hydrogel fabrication process with the helicoid multiscale structure. b) Fabrication of CNC/PVA hydrogels by salting out sodium citrate solutions of varying concentrations. c) Modulus and toughness of CNC₅/PVA hydrogels after salting‐out in sodium citrate solutions of varying concentrations. d) Modulus and toughness of CNC/PVA hydrogels with varying CNC concentrations. e) Fracture energy and shear strength of CNC/PVA hydrogels with varying CNC contents. Adapted with permission.^{[ 316 ]} Copyright 2024, ACS. f) Schematic representation of the development of helically ordered chitin/CaCO₃ hybrid materials. g) SEM micrographs of the cross sections of the chitin/PAA organic template sample, and the films after the CaCO₃ crystallization processes for h) 1 day and i) 7 days. Adapted with permission.^{[ 317 ]} Copyright 2015, Wiley.

Figure 11

Structural arrangement and light‐scattering analysis of Coeligena feather barbules. A) Microscopic image showing the gorget feather of C. helianthea. B) SEM image of a longitudinal section of C. violifer barbules, corresponding to the dashed area in (A). C) Equivalent section for C. prunellei. D) TEM image of a cross‐sectioned barbule from C. helianthea. E) Schematic representation of a feather barb with two barbules, indicating lamina (L) and side wall (S). The lamina is inclined by an angle δ relative to the barb's axis. F) Angular reflectance spectra (normalized) for barbules from C. violifer, C. helianthea, C. wilsoni, and C. prunellei. G) Schematic of the scatterometry setup, featuring ellipsoidal mirror (E), diaphragm (D), and lens (L); two parallel rays strike opposite barbule surfaces. H–K) Transverse sections of barbs from different Coeligena species. L–O) Their corresponding scatterograms, with arrows indicating the direction of incident rays as in (G). Red circles in (L–O) denote scattering angles of 5°, 30°, 60°, and 90°. Scale bars: A) 2 mm; B,C) 50 µm; D) 5 µm; H–K) 150 µm. Adapted with permission.^{[ 339 ]} Copyright 2021, Royal Society.

Figure 12

A) SEM Micrograph of the diatom Coscinodiscus walesii and B) morphometric details of its pore ultrastructure. A,B) Adapted with permission.^{[ 343 ]} Copyright 2009, Elsevier. C) Simplified 3D structure of the unit cell of diatom frustule with a thickness of the three layers: Cribellum t₁ = 50 nm, Cribrum t₂ = 300 nm, Internal Plate t₃ = 1000 nm. D) Left: top view of cribellum, the lattice constant p₁ = 200 nm and the hole size d₁ = 50 nm. Middle: top view of cribrum, the lattice constant p₂ = 400 nm and the hole size d₂ = 250 nm. Right: top view of internal plate, the lattice constant p₃ = 2 µm and the hole size d₃ = 1.3 µm. E) FDTD simulated absorption spectra of the simplified diatom frustule model with the 50 nm thick active layer, case 1 (a), in which the light enters from the valve side, and case 2 (e), in which the light enters from the girdle band side. And normalized electric‐field‐intensity |E/E ₀|² distribution on the Y‐Z plane at λ_b (b), λ_c (c), and λ_d (d) for case 1, λ_f (f), λ_g (g), and λ_h (h) for case 2. Stacking sequence of case 1 (From top to bottom: air, cribellum, cribrum, internal plate, active layer, and substrate), stacking sequence of case 2 (From top to bottom: air, internal plate, cribrum, cribellum, active layer, and substrate). F, a) Schematic representation of a PTB7:PC₇₁BM‐based thin film with the diatom frustules on the top layer. F, b) experimental absorption spectrum for the model of planar active layer without diatom frustule on top (black curve) and with diatom frustule (red curve), with the experimetnal absorption enhancement curve for diatom frustule (green dashed curve). C–F) Reproduced with permission.^{[ 88 ]} Copyright 2015, Springer Nature. G) 3D model and SEM images showing square and hexagonal lattice arrangements in diatom girdle bands, including a schematic diagram of photonic stopband formation in periodic pore structures. H) Simulated reflectance curves showing the increase in stopband intensity with increasing number of periodic pores along the z‐direction. The data highlight how precise control of pore number/geometry directly influences optical performance. Reproduced with permission.^{[ 346 ]} Copyright 2025, Spinger Nature.

Figure 13

A) Trigonophorus rothschildi varians and B) macroscopically observed colors of the elytra: violet, green, and orange. C) Reflectance of the elytra (circle, orange; square, violet; and triangle, green). D) Micrographs of the elytra cross sections with the calculated averaged period p of the one‐dimensional photonic crystals and the position of the reflectance maxima λ for normal incidence. E) Micrographs of the nanoarchitected 5X (SiO/SiGe) multilayer with random hole distribution (upper) and regular square hole pattern (bottom) (scale bar 1 µm). F) Photographs showing the same fabricated nanoarchitectures under different illumination angles. Adapted with permission.^{[ 87 ]} Copyright 2010, Springer Nature.

Figure 14

A) Photo of moth, B) the compound eye, and C) the sub‐wavelength array structure constituting the ommatidia. D) Schematics of refractive index variations: i) flat UV‐curable resin coating, ii) columnar sub‐wavelength structure, iii) triangular sub‐wavelength structure, and iv) conical sub‐wavelength structure. E) Micrograph of the poly(dimethylsiloxane) (PDMS) prepolymer female mold and hardness variation of the mold with different curing times under 110 °C. B–E) Adapted with permission.^{[ 89 ]} Copyright 2018, Springer Nature. F, a) Natural moth compound eye with anti‐reflective nanostructures and b) schematic of the developed BAC‐eye system, where microlenses are optically coupled to a flat base via index‐matched waveguides. G) Illustration of the fabrication process involving microfluidic‐assisted 3D printing of hemispherical molds. H) Image of a single row of ommatidia formed on the curved surface, where post height variation reflects the spatial distribution of forces during fabrication. I) Experimental and simulated results showing the distribution of post height across the hemispherical surface as a function of rotation rate. J) Cross‐sectional image of the BAC‐eye substrate showing internal tapered waveguides connecting microlenses to a flat output panel. J, a–j) Optical performance of the fabricated artificial ommatidia. a) Simulated light intensity profiles illustrating crosstalk between adjacent ommatidia with different angular orientations: (α = 64.8°, β = 0°), (α = 72°, β = 0°), and (α= 79.2°, β = 0°). b,c) Experimental setup and output image used to evaluate the spatial separation and light delivery from three curved silicone waveguides. d) Quantified light distribution at the output facet. e–h) Ray tracing simulations in ommatidia with orientations of e,f) (α = 0°, β = 0°) and g,h) (α = 36°, β = 0°) for light incident at different angles, demonstrating how orientation modulates intensity at the waveguide output. i,j) Angular sensitivity functions of the ommatidia with orientations of (α = 0°, β = 0°) and (α = 36°, β = 0°) derived from both experimental data (red points) and Gaussian fitting (grey surface), indicating directional optical response. Together, these data demonstrate how precise control of nanostructure geometry and optical alignment enables the fabrication of scalable, high‐performance, bioinspired imaging systems. F–J) Adapted with permission.^{[ 364 ]} Copyright 2021, Springer Nature.

Figure 15

a) Silver ant. b) SEM and c) cross‐sectional view of the hairs and d) 2D distribution of a light field around a triangular hair for three exemplary Mie resonances. e) Schematic diagram showing the interaction between visible and NIR light and a hair at different incidence angles. a–e) Adapted with permission.^{[ 373 ]} Copyright 2015, AAAS. f) Thermal energy flow in a typical passive daytime radiative cooling system. Reproduced with permission.^{[ 378 ]} Copyright 2022, Wiley‐VCH. g) Photograph of the dorsal side of the male butterfly. h) IR image of the butterfly above the heating device (set at 60 °C) with the ambient temperature at 25 °C. Top‐view (i) and cross‐sectional view (j) SEM images of the non‐scent patch scales and the scent patch scales on the Rapala dioetas hindwing. k) Cross‐sectional view of a two‐dimensional normalized light field intensity distribution at wavelength = 8 µm inside the simulation model of a scent patch scale. h–k) Adapted with permission.^{[ 385 ]} Copyright 2021, AIP Publishing.

Figure 16

Schematic of thermal insulation in a) polar bear hairs and b) encapsulated aerogel fibers. SEM images of c) a polar bear hair and d) encapsulated aerogel fibers. a–d) Adapted with permission.^{[ 380 ]} Copyright 2023, AAAS. e) Yak on the Tibetan Plateau (>4000 m), f) raw yak hairs with guard and down hairs, g) naturally crimped yak hair, h) stretched yak hair showing extended length. e–h) Adapted with permission.^{[ 90 ]} Copyright 2019, Elsevier B.V.

Figure 17

a) Schematic illustration of the preparation of the TAG and BAG samples and flexible films. b) Rooftop measurement and thermal images of the bare bottle and the bottle covered by TAG. c) Thermal image of the watchband areas covered and uncovered by TAG. a–c) Adapted with permission.^{[ 395 ]} Copyright 2020, Elsevier B.V. d) The optical and e) cross‐sectional SEM image of a Cyphochilus scale. f) SEM images of a fabricated cooling ceramic sample showing the hierarchically porous structure. g) Variation in the surface temperature. d–g) Adapted with permission.^{[ 91 ]} Copyright 2023, AAAS.

Figure 18

a) Image of a space blanket on a human arm. b) Schematic of the space blanket. c) Image of a squid. d) Schematic of squid skin layer. e) Composite material on arm in wearable form. f) Schematic of the composite. g) Heat flux through the composite without (left) and with (right) actuation. h) Temperature increase of forearms with space blanket‐ and composite‐based sleeves under 0%, 10%, 30%, and 50% strain. a–h) Adapted  with permission.^{[ 396 ]} Copyright 2019, Springer Nature. i) Squid in expanded (left) and contracted (right) states. j) Strain‐induced transition of metal domains from abutted (left) to separated (right). k,l) Reflectance and transmittance spectra of composite under 0%, 30%, and 50% strain. m) Coffee‐filled cup covered with composite. n) Thermal camera time‐lapse images. o,p) External and internal temperature differences after 90 min for material‐covered vs. bare cups. i–p) Adapted with permission.^{[ 397 ]} Copyright 2022, Springer Nature.

Figure 19

Main olfactory sensory organs of the silk moth, Bombyx mori, and the fruit fly, Drosophila melanogaster. a) Single antennal branch at higher magnification showing the different sensillum types. Scale bar: 25 µm. Adapted with permission.^{[ 460 ]} Copyright 2005, Springer. b) Schematic diagram of an olfactory sensillum showing the detailed configuration of ORNs and accessory cells with respect to cuticular specializations. Adapted with permission.^{[ 461 ]} Copyright 2004, Springer. c) Airflow at the antenna of the male moth Antheraea polyphemus. Air was blown from a glass tube toward the antenna. Scheme of the glass tube, antenna, and thermistor positions drawn to scale. By means of a thermistor (0.2 mm diameter) the airstream velocity was measured without the antennae (open squares and dashed lines), in front of the antenna (open circles), and behind the antenna (dots). Reproduced with permission.^{[ 446 ]} Copyright 2009, Springer. d) Dose‐dependent increases in the bombykol (red) or Z11‐16:Ald (blue)‐induced spike frequency of BmOR1‐GAL4IUAS‐PxOR1 male moths. Error bars represent ± SEM (n = 10). Adapted with permission.^{[ 462 ]} Copyright 2011, PLoS Genet. e) Current trace with application of the indicated concentrations of bombykol. Bombykol was sequentially applied to the same oocytes. Adapted with permission.^{[ 463 ]} Copyright 2005, AAAS. f) Schematic representation of Drosophila olfactory organ. Adapted with permission.^{[ 464 ]} Copyright 2019, Cell Press. g−i) Cross‐sections through various subtypes of sensilla basiconica (sb) on the antenna of Drosophila with pores labeled (P) and arrows indicating pore tubules. SB: small sb. TB‐2: thin sb. TB*: thin sb with relatively thick cuticular wall and different internal morphology. Adapted with permission.^{[ 465 ]} Copyright 1999, Elsevier. j) Recording responses with a capillary tip containing the stimulus. Left, schematic of stimulus presentation showing a capillary tip containing material; r indicates the radius at which the impulse rate exceeds the spontaneous rate by more than 20 impulses s⁻¹. Right top, response of the T1 neuron to an intermediate dose of cis‐vaccenyl acetate. Approach of the stimulus to the sensillum, the time of sensillum contact, and stimulus removal are indicated. Right bottom, control stimulus. Adapted with permission.^{[ 466 ]} Copyright 2007, Cell Press.

Figure 20

a,b) Biological design features of flexible tactile sensors. b) Adapted with permission.^{[ 490 ]} Copyright 2022, MDPI. c) Deflection of tarsus by an angle 𝛼 exceeding 25° leads to pressure on the pad in front of the vibration receptor. d) SEM micrograph of the metatarsal organ of C. salei circled in (c). Arrow indicates nanoslits of the lyriform structure. e) Frequency dependence of Young's modulus (filled symbols) and of sensory thresholds of the lyriform vibration sensor (open circles). c–e) Adapted with permission.^{[ 96 ]} Copyright 2007, The Royal Society.

Figure 21

Infrared (IR) organ of Melanophila acuminata. a) Dome‐shaped IR sensilla at the base of the organ (inset: whole organ). Each sensillum is accompanied by a smaller wax gland (wg) characterized by tiny pores. Bar: 15 µm (Inset 100 µm). b) Cross‐section of single IR sensillum prepared by focused ion beam (FIB). Specimen was air‐dried; therefore, only the cuticle is preserved. Microcavities (mc) of the intermediate layer and the inner pressure chamber (ipc) can be discerned inside the sphere. exo: exocuticular outer dome. Bar: 5 µm. c) Schematic drawing of a photomechanic IR sensillum covered by an outer dome of hard exocuticle (exo). The tip of the dendrite (d) is suspended by fine filaments inside the inner pressure chamber (ipc), which communicates with the fluid in the microcavities (mc) of the intermediate layer. Any increase in fluid pressure is transferred onto the dendritic membrane. (ls): lamellated exocuticular shell of the sphere. (a‐c) Reproduced with permission.^{[ 93 ]} Copyright 2015, MDPI. d) Experimental setup used for electrophysiological recordings. Inset: emission characteristic of the ORIEL IR element when supplied with 9W. Note that the maximum is at 3 µm (i.e., like that of a typical forest fire). e) Response of pit organ exposed to unfiltered IR stimulus (1), 1.65 µm long pass filter inserted into the camera shutter (2), and 2.4 µm longpass filter inserted into the camera shutter (3). d,e) Adapted with permission.^{[ 505 ]} Copyright 1998, Springer.

Figure 22

a) Transmission electron microscopy (TEM) micrographs of a magnetotactic bacterium and b) its magnetic particles. Adapted with permission.^{[ 508 ]} Copyright 2008, RSP. c) Magnetic particles form a chain‐like 1D structure within the bacterium and are postulated to function as biological compass needles that enable the bacterium to migrate along oxygen gradients in aquatic environments under the influence of the Earth's geomagnetic field lines. d) Formation of magnetic particles using various biomimetic surfaces with biomineralization protein Mms6. Reproduced with permission.^{[ 511 ]} Copyright 2016, RSC. e) Cryo‐EM reconstruction of MamK filaments. A, section of a micrograph of MamK filaments. B, three‐dimensional reconstruction of the MamK filament. C, homology model of MamK fitted into the cryo‐EM reconstruction. Dashed brackets indicate regions shown in greater detail in D and E. Reproduced with permission.^{[ 512 ]} Copyright 2016, RSC.

Figure 23

A) Schematic illustration of Bombyx mori antenna. B) Schematic demonstration of the multiscale 3D bioinspired hierarchical Si‐MPs@TiO2‐NRs@FeO(OH)‐NBs core‐shell superstructures on a microcantilever where a) a Si pillar corresponds to an antennal stem, b) TiO2 NRs on Si‐MPs correspond to antennal branches, and c) FeO(OH) NBs on Si‐MPs@TiO2‐NRs are associated to sensilla. SEM images of a nanostructured microcantilever decorated with C) Si‐MPs@TiO₂‐NRs and with D) Si‐MPs@TiO₂‐NRs@FeO(OH)‐NBs, with d) top views and e) side views. Adapted with permission.^{[ 95 ]} Copyright 2022, Elsevier.

Figure 24

Hexagonal nanoporous MoS₂ FET‐based EtOH sensor mimicking the Drosophila olfactory system. a) Schematic of Drosophila (left), close‐up view of the head with antennae and maxillary palp (left inset), schematic of antenna containing olfactory organs (middle), hexagonal nanoporous MoS₂ bio‐FET for detection of VOCs using LUSH (right). b) 3D representation of hexagonal nanoporous MoS₂ with selective edge functionalization. c) STEM micrograph of hexagonal nanoporous array (scale bar 20 nm); EDX elemental mapping of d) Mo L and e) S K peaks in hexagonal nanoporous MoS₂ (scale bar 20 nm). f) Cross‐sectional STEM micrograph of throughout perforation of hexagonal nanoporous MoS₂ (scale bar 20 nm). g) Schematic images of energy barrier height corresponding to bare hexagonal nanopore (left), immobilized LUSH (middle), and EtOH coupled with LUSH (right) at the edges of the hexagonal nanopore. Reproduced with permission.^{[ 523 ]} Copyright 2023, American Chemical Society.

Figure 25

Electronic whiskers. a) Schematic showing the design of an e‐whisker device with 5 and 30 wt.% AgNP composite lines patterned on the top and bottom surfaces of a PDMS fiber, respectively. Adapted with permission.^{[ 406 ]} Copyright 2014, PNAS. b) SEM micrograph of nanoslits on the spider‐inspired sensor. c) E (yellow), A (green), D (blue), and G (red) strings played open (with no finger stopping) produce different wavefunctions. Collected using a spider‐inspired nanoscale crack sensor. d) The measured sound waves of music playing (Salut d'Amour; excerpt shown at top). e) Comparisons of the acoustic waveform and auditory spectrogram changes measured by electrical resistance using the nanoscale crack sensor (left‐hand image) and a standing microphone (right‐hand image) in a noisy (≈92 dB) environment. b–e) Adapted with permission.^{[ 97 ]} Copyright 2014, Springer Nature. f) The resistance change of a nanocrack when the crack opens. g) The NCBEW mechanosensor responds to the applied force with a wide range from 0 to 67.5 µN. h) The linear relationship between the applied force and relative resistance changes within the range from 0 to 5.5 µN. Considering the noise level, the minimum resolution for force detection is as low as 72.2 nN. i) The scanning results of the NCBEW mechanosensor on the samples with a stage height of 32 µm. The blue line and red line indicate the data obtained by the NCBEW device and surface profilometer, respectively. j) The profiling results of a 30‐nm‐thick Au stripe on a glass substrate obtained from the NCBEW mechanosensor. Adapted with permission.^{[ 527 ]} Copyright 2023, Springer Nature.

Figure 26

a) Cartoon describing the thermally driven nanoactuation of the PNIPAM brushes in the nanopore as demonstrated by Azzaroni's group. Reproduced with permission.^{[ 533 ]} Copyright 2009, Wiley. b) Temperature dependence of the ionic current through the PNIPAM‐modified single nanopore as demonstrated by Jiang's group. The inset cartoons illustrate the gate‐like temperature‐responsive change in effective pore size. c,d) I–V curves measured on single conical gold‐coated nanopores with and without PNIPAM modification, respectively. b–d) Adapted with permission.^{[ 540 ]} Copyright 2010, Wiley. e,f) Cartoon of a microcavity sealed with a freely suspended nanomembrane in the planar state at room temperature (e) and in deformed states (f). g) SEM micrograph of the silicon substrate with a uniform array of microcavities; and h) higher magnification SEM image showing the smooth edges of the microcavity and the trenches separating the individual cavities. Reproduced with permission.^{[ 542 ]} Copyright 2006, American Chemical Society.