Table of Contents

Title Page

Chapter 1: Introduction to Thermal Properties of Materials

1.1 Conventional Macroscale Heat Transfer
1.2 Micro/Nanoscale Heat Transfer
1.3 Bioinspired Thermal Materials
1.4 Perspective and Outlook
Acknowledgments
References

Chapter 2: The Engineering History of Thermal Materials

2.1 Introduction
2.2 Engineering History of Thermal Materials
2.3 Engineering Applications with Bioinspired Thermal Materials
2.4 Bioinspired Multiscale Wicks
2.5 Hybrid Superhydrophilic/Superhydrophobic Wicks
2.6 Flexible Heat Pipes with Integrated Bioinspired Design
References

Chapter 3: Bioinspired Surfaces for Enhanced Boiling

3.1 Introduction
3.2 Bioinspired Surfaces for Boiling
3.3 Surface-Structure-Enhanced Pool Boiling
3.4 Biphilic and Biconductive Surface-Enhanced Boiling
3.5 Surfactant-Enhanced Pool Boiling
3.6 Flow Boiling
3.7 Conclusions and Outlook
Acknowledgments
References

Chapter 4: Bioinspired Materials in Evaporation

4.1 Introduction
4.2 What Is Evaporation?
4.3 Bioinspired Materials in Evaporation
4.4 Summary and Perspectives
Acknowledgments
References

Chapter 5: Bioinspired Engineering of Photothermal Materials

5.1 Antireflection and Photothermal Biomaterials
5.2 Bioinspired Photothermal Materials
References

Chapter 6: Bioinspired Microfluidic Cooling

6.1 Introduction
6.2 Biological Heat Exchange
6.3 Wearable Fluidics
6.4 Fluidic-Based Windows and Facades for Buildings
6.5 Fabrication Methods for Large-Area Fluidic Networks
6.6 Summary
References

Chapter 7: Thermal Emissivity: Basics, Measurement, and Biological Examples

7.1 Terminology
7.2 Basic Radiation Laws
7.3 Direct Emissivity Measurements
7.4 Kirchhoff's Law
7.5 Measurements Using Kirchhoff's Law
7.6 Attenuated Total Reflectance
7.7 Ways to Determine Hemispherical Emissivity
7.8 Specular and Diffuse Reflectance
7.9 Problems with Sample Shape
7.10 Remote Sensing from Aircraft or Satellites
7.11 Examples of Emissivity Determinations of Biological Samples
References

Chapter 8: Bioinspired Thermal Detection

8.1 Introduction
8.2 Thermal Detection
8.3 Bioinspired Thermal Detection
8.4 Perspectives
References

Chapter 9: Bioinspired Thermal Insulation and Storage Materials

9.1 Introduction to Thermal Insulation Materials
9.2 Engineering of Thermal Insulation Materials
9.3 Bioinspired Thermal Insulation and Storage Materials
9.4 Summary and Outlook
Acknowledgments
References

Chapter 10: Bioinspired Icephobicity

10.1 Icing Nucleation of Sessile Drops
10.2 Literature Review – Icing of Water Drops on Surfaces
10.3 Icing of Stationary Water Drops
10.4 Icing of Water Drops Impacting Surfaces
References

Index

End User License Agreement

List of Illustrations

Chapter 1: Introduction to Thermal Properties of Materials

Figure 1.1 Schematic graphs of heat conductance and transfer.
Figure 1.2 Interface between liquid/solid/gas phase.
Figure 1.3 Various heat transfer cases on solid composite film, condensed liquid on the wall, oil–water solution and solid particles disperse in liquid, respectively.
Figure 1.4 Thermal capacity of various materials.
Figure 1.5 Thermal theories at different mass scales: at the known minimum scale of ∼10⁻³⁰ kg, the corresponding theory is the quantum mechanics that relates the reaction of electrons, proton, atoms, and electromagnetic waves; at larger levels (nanoscale 10⁻⁹ kg), the related molecular motion and particle reactions can be observed and predicted by manmade microscopic and other instruments. At the normal level of our daily life scale (∼1 kg), the classic theory of heat transfer involves the basic phenomena of conduction and convection. By applying thermal engineering at aerospace scale (∼10⁸ kg), the utilization of heat energy help us to better explore nature. At about the whole earth scale of 10²⁴ kg, the biological water recycling system in nature indicates the essentials of heat transfer.
Figure 1.6 Thermal theories at different length scales: For quantum motion problems such as electrons, proton, and atoms, the relative theory is the Schrodinger equation. For elastic bonding or collisions of atoms or molecules, the working principles can be described by Newton's law; for larger rigid particles problems in gaseous or occasionally liquid system, the most used statistical prediction tool is the Boltzmann equation. Furthermore, in integral structure, the motion or the vibration of liquid molecules and crystal can be solved by Navier–Stokes equation [3]
Figure 1.7 The solution of heat carrier collision (heat transfer) as a linear case in Boltzmann equation. (
Figure 1.8 A typical sample of aqueous molecules in the MD system.
Figure 1.9 Schematic principle of light-induced plasmonic heating on a gold nanoparticle.
Figure 1.10 The rapid charging of the thermal energy conversion and storage by Au NP–paraffin composite.
Figure 1.11 A large-scale, renewable, low-cost evaporational photothermal membrane.

Chapter 2: The Engineering History of Thermal Materials

Figure 2.1 History of aviation.
Figure 2.2 Copper and stainless steel identical bars of rectangular cross section.
Figure 2.3 Temperature distribution for the copper and stainless steel bars.
Figure 2.4 Thermal conductivity of numerous materials at different temperatures.
Figure 2.5 Schematic of the Balandin et al. experiment showing the excitation laser light concentrated on a graphene layer suspended across a trench. The focused laser light produces a local hot spot and generates a heat wave inside SLG propagating toward heat sinks.
Figure 2.6 A large-scale scanning electron microscopy (SEM) image of a microfabricated suspended device. The scale bars represent 100 and 1 μm (for the enlarged central part) [5, 6].
Figure 2.7 Schematic heat transfer model of the suspended device with a sample across the two legs.
Figure 2.8 The change in resistance of the heater resistor (R_h) and sensor resistor (R_s) as a function of the applied power to the heater resistor. Upper inset: SEM image of the suspended islands with an MWNT bundle across the device. The scale bar represents 1 μm.
Figure 2.9 SEM image of the suspended islands with a bridging individual MWNT [5]. The diameter of the MWNT is 14 nm. The inset shows the top view of the device. The scale bar represents 10 μm.
Figure 2.10 The thermal conductance of an individual MWNT of 14 nm diameter. The solid lines represent linear fits of the data in a logarithmic scale at different temperature ranges. The slopes of the line fits are 2.50 and 2.01, respectively.
Figure 2.11 Bioinspired modification of h-BN for high thermal conductive composite films coating.
Figure 2.12 (a) A water droplet on a hydrophobic solid surface (contact angle greater than 90°) and (b) a water droplet on a hydrophilic solid surface (contact angle less than 90°).
Figure 2.13 When the gaseous phase of a substance is exposed to a surface at a temperature below the saturation temperature, condensation in the form of droplets (dropwise condensation) or a liquid film (film condensation) takes place on the surface.
Figure 2.14 The motion of droplets from the hydrophobic to hydrophilic side of a surface gradient is shown. The creation of a surface energy gradient by varying the surface concentration of molecules with low surface energy is also illustrated.
Figure 2.15 Environmental scanning electron microscope (ESEM) images of the condensation of water vapor on a superhydrophobic surface comprising of an array of hydrophobic square posts with width, edge-to-edge spacing, and aspect ratio of 15, 30, 7 μm, respectively. (a) Dry surface. (b–d) Snapshots of the condensation phenomenon on the surface.
Figure 2.16 Illustration of heat pipe operation.
Figure 2.17 Hierarchical multiscale structures in the human lung.
Figure 2.18 SEM image of biporous sintered Cu powder wick.
Figure 2.19 Converging wick structure. Thick wick fingers deliver liquid to the thin wick sections between the fingers where evaporation takes place. Vapor escapes through the spaces between the fingers.
Figure 2.20 Cylindrical post wick structure. Tall sintered wick posts deliver liquid to the thin wick sections between the posts where evaporation takes place. Vapor escapes through the spaces between the posts.
Figure 2.21 Pictures of low coefficient of thermal expansion (CTE) high heat flux flat heat pipes using bioinspired converging and cylindrical post wick structures fabricated by ACT.
Figure 2.22 Engineered nanostructures for high thermal conductivity TGP substrates.
Figure 2.23 The water-capturing wing surface of a Namib desert beetle: (a) Optical image of the adult female beetle, (b) hydrophilic region (bordered) found on the peak of each ‘bump’ on the elytra beetle's back, (c) SEM for hydrophobic region found in the troughs between “bumps” on the beetle's back. Scale bars: (a) 10 mm; (b) 0.2 mm; (c) 10 μm.
Figure 2.24 A schematic cross section of the flexible heat pipe and a photograph of the fabricated flexible heat pipe [35].

Chapter 3: Bioinspired Surfaces for Enhanced Boiling

Figure 3.1 A schematic of a typical boiling curve with controlled surface temperature. Heat flux q versus superheat ΔT, where ΔT = T_w − T_sat. The solid arrow indicates the critical heat flux (CHF). In a system with controlled heat flux, the boiling curve typically follows the dashed arrow when transitioning from nucleate boiling to film boiling.
Figure 3.2 Schematics of (a) a hydrophilic surface with a contact angle <90°, (b) a hydrophobic surface with a contact angle >90°, (c) a superhydrophilic surface with an apparent contact angle = 0°, and (d) a superhydrophobic surface with an apparent contact angle >150°.
Figure 3.3 SEM images of hierarchical structured superhydrophobic surfaces in plants. (a) The lotus and (b) Euphorbia myrsinites leaves composed of microscale papillose cells with nanoscale wax crystals. (c–e) Salvinia oblongifolia hairs composed of the multicellular hair with nanoscale wax crystals.
Figure 3.4 SEM images of superhydrophilic structured surfaces in plants. (a) Calathea zebrina and (b) Ruellia devosiana.
Figure 3.5 (a) A schematic of a vapor bubble growing from a surface cavity. (b) Prediction of the range of active cavity sizes using Hsu's theory [33] when the thermal boundary layer is 0.25 mm, the contact angle is 30°, and the liquid is saturated water at atmospheric pressure.
Figure 3.6 SEM images of (a) silicon nanowires and (b) copper nanowires.
Figure 3.7 (a) TEM image of a Tobacco mosaic virus. (b) SEM image of the self-assembled Tobacco mosaic viruses coated with nickel.
Figure 3.8 Images of a hydrophilic network (a), and a hydrophobic network (b) sample from Betz et al. Pool boiling performance curves from the same study showing the boiling curve (c), and the heat transfer coefficient (HTC) (d) for the various samples investigated; note that p indicates the pitch of the biphilic islands in micrometers.
Figure 3.9 Super biphilic surfaces for enhanced pool boiling with water. (a) Image of the superhydrophilic network with superhydrophobic regions/dots; top insets show the behavior of sessile droplets on the superhydrophilic (left) and superhydrophobic (right) regions, and bottom inset shows an SEM image of the nanoscale structures. Heat transfer enhancement achieved with super biphilic surfaces over biphilic, superhydrophilic, and hydrophilic surfaces are shown: (b) the boiling curve and (c) the heat transfer coefficient curve.
Figure 3.10 Concept of biconductive surface-enhanced boiling is shown in (a) and a sample fabricated biconductive surface, which is a combination of a copper substrates with interspersed low thermal conductivity epoxy stripes, is shown in (b)–(d). Optimization of the boiling performance, that is, the CHF (e) and HTC (f) of the biconductive surfaces in terms of the Bond number and the epoxy division pitch P.
Figure 3.11 Surfactant-enhanced pool boiling with water. Schematic representation of effects of surfactant on surface wettability: (a) no surfactant, hence surface is hydrophilic; (b) surfactant adsorption on the surface reduces wettability and activates the larger of two nucleation sites; and (c) higher surfactant adsorption on the surface due to applied electric field activates smaller nucleation site.
Figure 3.12 Tuning the performance of surfactant-enhanced boiling via electric fields. Transient response of the surface temperature and the HTC to changes in the applied electric field for (a) SDS, a negatively charged surfactant and (b) DTAB, a positively charged surfactant.
Figure 3.13 Boiling curves for (a) NaBr, a nonsurfactant salt, and (b) MEGA-10, a nonionic surfactant, showing that the applied electric field does not affect the boiling performance. Boiling curves for (c) SDS and (d) DTAB, two ionic surfactants, demonstrating the potential of tuning boiling performance (high HTC or high CHF) based on prevailing conditions.
Figure 3.14 Schematics of (a) side view and (b) cross-sectional view of flow boiling in a micro- or minichannel. (c) Multichannels with silicon nanowires covering the bottom wall. (d) Reduced temperature fluctuation of nanowire-coated channels compared to plain surface channels at a mass flux G of 571 kg/m² s and a heat flux q of 80 W/cm².
Figure 3.15 (a) SEM image of the cross section of a channel with magnified view of the micropillars (left inset) and a sidewall at the bottom corner (right inset). (b) Midpoint channel backside surface temperature and pressure drop across a smooth surface channel and a structured surface channel (d = 5 μm, h = 25 μm, and l = 15 μm) at q = 315 W/cm² and q = 615 W/cm² (G = 300 kg/m² s). (c) Optical images of a smooth bottom channel surface and a structured bottom channel surface (d = 5 μm, h = 25 μm, and l = 15 μm). (d) The boiling curve of a smooth surface channel and three structured surface channels (Sample 1: d = 5 μm, h = 25 μm, and l = 10 μm, Sample 2: d = 5 μm, h = 25 μm, and l = 15 μm, Sample 3: d = 10 μm, h = 25 μm, and l = 30 μm).

Chapter 4: Bioinspired Materials in Evaporation

Figure 4.1 (a, b) Simulated temperature distribution of liquid by interfacial heating (a) and bulk heating from bottom (b) after 15 min under the input heat flux of 600 W/m². (c, d) Heat flux changes of surfaces as a function of time for interfacial heating (c) and bulk heating (d) under the same input heat flux of 600 W/m².
Figure 4.2 (a) Schematic illustration of solar steam generation through plasmonic heating. The nanoparticles convert light to heat, raising their surface temperature above the boiling point of the liquid. Bubbles are formed around the particle and transported to the air–liquid interface, where the vapor is released into the air.
Figure 4.3 (a) Schematic illustration of plasmonic heating induced by purely absorptive AuNPs and purely scattering PSNPs enhanced light absorbing. (b) Evaporation performance of 10 nm aqueous AuNP solution with different concentration under the illumination of 532 nm laser light. It shows a saturation zone where the evaporation rate does not rise up as the concentration of particles increases. The insets are IR images showing the side-view temperature. (c) Evaporation rate of 10 nm AuNPs and 200 nm PSNPs mixing solution as a function of AuNP concentration. (d) Bar graph shows the enhancement of evaporation rate due to the addition of PSNPs. Pure AuNP solution is used as standard.
Figure 4.4 Bioinspired surface evaporation. (a) Schematic illustration of the perspiration process of human skin. (b) Schematic illustration of surface-efficient evaporation through plasmonic heating of self-assembled free-floating AuNP film at air/water interface, inspired by sweating process. (c, d) IR side-view images of free-floating AuNP film and aqueous AuNP solution at 10.18 W/cm² of laser illumination, respectively. (e) Evaporation rate after 20 min illumination under different laser power. (a–e)
Figure 4.5 Surface wettability modification. (a) Schematic illustration of a free-floating double-layer film (top: light-to-heat conversion layer; bottom: supporting layer) with varying wettability. (b, c) Optical images of the hydrophilic leaf of Osmanthus fragrans and hydrophobic leaf of cactus. (d) Schematic of preparation procedure of AAO-based AuNP film (AANF) with different wettability. (e) Evaporation weight change of HLN-HLA, HBN-HLA, HLN-HBA, HBN-HBA, HLA, and HBA as a function of time under Xenon lamp with a power density of ∼3.2 kW/m². (a–e)
Figure 4.6 Skin-mimic evaporative cooling system. (a) Schematic illustration of heat dissipation from human skin. (b) Schematic illustration of heat dissipation from the bioinspired cooling porous membrane.
Figure 4.7 Evaporation-driven distillation processes of ethanol–water and 1-propanol–water mixtures. (a) Liquid–vapor distillation diagram of ethanol–water mixtures with nanoshells under laser illumination (red dots), and using a conventional thermal approach (blue curve). (b) Time-dependent evaporation mass. change of ethanol–water mixtures with different mole fractions under 5 W laser illumination. The inset shows the linear relationship between evaporation rate and ethanol mole fraction in liquid phase. (c) Liquid–vapor distillation diagram of 1-propanol–water mixtures with nanoparticles under laser illumination (red dots), and standard equilibrium distillation curve using a conventional thermal approach (blue curve). (d) The 1-propanol mole fraction in liquid mixtures of 0.57 M fraction separates into two phases induced by nanoshells under laser illumination.
Figure 4.8 Design of solar autoclaves and their sterilization behaviors. (a) Schematic illustration and photograph of the closed-loop autoclave. I–III show the steam generation module, connection module, and sterilization module, respectively. (c) Schematic illustration and photograph of the open-loop autoclave. i–iii show the solar concentrator, heat collector, and sterilization chamber. (b, d) The time-dependent steam temperature in the closed-loop (b) and open-loop (d) autoclaves. The red, blue, and green plots indicate the temperature at the top, bottom, and surroundings, respectively. The dashed line and red region indicate the sterilization temperature and the sterilization regime (115 °C for 20 min and 132 °C for 4.6 min).
Figure 4.9 (a) Schematic illustration of an existing solar still under natural solar illumination. (b) Desalination weight change and output of PGF at the top/bottom of a beaker and solar absorption layer at the bottom. The maximum output efficiency reaches over twice that with the conventional approach.
Figure 4.10 Fabrication of bifunctional membrane (a–c). (a) Cross-sectional SEM image of bilayer Au–AAO membrane. (b) Cross-sectional SEM image of trilayer TiO₂–Au–AAO membrane. (c) Schematic illustration of the preparation process of a bifunctional membrane. (d) Photocatalytic degradation performance of RhB with TiO₂–Au–AAO, TiO₂–AAO, Au–AAO membranes and blank group. (e) Repeat test of RhB photocatalytic degradation with bifunctional membrane for eight continuous cycles. (f) Evaporation weight loss of TiO₂–Au–AAO, TiO₂–AAO, Au–AAO membranes under simulated solar light illumination. (g) Photographs of contaminated water, partial purified water degraded by bifunctional membrane, and condensed pure water collected after evaporation. (

Chapter 5: Bioinspired Engineering of Photothermal Materials

Figure 5.1 Structure and effective refractive index profiles of various types of AR coating. (a–c) Homogeneous single-layer, digital, and multilayer AR coatings; (d–f) inhomogeneous single-layer, structured, and complex AR coatings.
Figure 5.2 Corneal nipple arrays in the peacock (Inachis io), a nymphalid butterfly, as revealed by SEM. (a) The complete eye. (b) The nipple array in one facet lens. (c) Details showing the local arrangement of domains with highly ordered nipple arrays.
Figure 5.3 (a) Reflectance of nipple arrays with paraboloid type of nipples for normally incident light. The spectra were calculated with a model multilayer, consisting of 100 layers with thickness h/100, where h is the height of the paraboloid nipples. The height was varied from 50 to 250 nm in steps of 50 nm. The width parameter p was taken to be 0.53. The reflectance for 50 nm high nipples approximates the value 0.043, predicted by the Fresnel equations, at longer wavelengths. (b,c) Dependence of the reflectance on polarization and angle of incidence. The corneal nipples were assumed to be paraboloids that touch each other at their base (p = 0.53), and the nipple height was varied from 50 to 250 nm. The light wavelength was 500 nm. (b) The reflectance of TE (s-) polarized light is strongly reduced with increasing nipple height. (b) With TM (p-) polarized light, the strong reflectance reduction only occurs at angles of incidence below 50°.
Figure 5.4 (a) Measured and simulated total hemispherical reflectance (total R%) spectrum as a function of wavelength for the cicada wing.
Figure 5.5 (a) The reflection spectra and (b) absorption spectra of the forewings of T. helena (T_FW) over the wavelength range of 300–2500 nm, respectively.
Figure 5.6 (a) Model for FDTD simulation of T_FW with microribs; maps of electromagnetic field energy flux density amplitude of T_FW with microribs when the wavelength of the incident light is fixed under (b) 470 nm and (c) 980 nm.
Figure 5.7 Process of synthesis of morph-genetic metal, metal/semiconductor function material.
Figure 5.8 (a) Optical microscopy image of the wing scales of the T_FW; (b) SEM images of the T_FW; (c) cross-sectional TEM image of T_FW. (d) Optical microscopy image of the Au–CuS_T_FW; (e) SEM images of the Au–CuS_T_FW; (f) cross-sectional SEM image of the Au–CuS_T_FW.
Figure 5.9 (a,b) TEM images of Au–CuS_T_FW; (c,d) HRTEM images of Au–CuS_T_FW; (e) XRD result of Au–CuS_T_FW; and (f) the SAED pattern of the Au–CuS_ T_FW.
Figure 5.10 XPS spectra of (a) Cu 2p and (b) S 2p regions for CuS_T_FW.
Figure 5.11 XPS spectra of (a) Cu 2p and (b) S 2p regions for Au–CuS_T_FW.
Figure 5.12 (a) XPS spectra of Cu 2p regions for CuS_T_FW and Au–CuS_T_FW, respectively; (b) XPS spectra of S 2p regions for CuS_T_FW and Au–CuS_T_FW, respectively.
Figure 5.13 XPS spectra of Au 4f regions for Au NPs.
Figure 5.14 (a) The absorption spectra of the Au–CuS_T_FW, CuS_T_FW, Au_T_FW, T_FW, BlueTec eta plus_Cu, and (Au + CuS)_T_FW over the wavelength range of 300–2500 nm. (b) The absorption spectra of the Au–CuS_T_FW, CuS_T_FW, Au_T_FW, T_FW, and BlueTec eta plus_Cu over the wavelength range of 2.5–15 μm. The inset of (a) is the absorption spectra in the red rectangular region at a higher magnification.
Figure 5.15 (a) The temperature elevation of the system with photothermal conversion material (Au–CuS_T_FW, CuS_T_FW, Au_T_FW, T_FW, and BlueTec eta plus_Cu, respectively) irradiated with a 980 nm laser (0.439 W/cm²). (b) The time constant for heat transfer from the system (Au–CuS_T_FW) was determined to be τ_s = 195 s by applying the linear time data from the heating period (20 min) versus the negative natural logarithm of 1 subtracted from the driving force temperature. The inset is the schematic illustration of the setup for the measurement of the photothermal conversion properties.
Figure 5.16 The temperature elevation of the Au–CuS_T_FW_APCF flat plate solar collector and BlueTec eta plus_Cu flat plate solar collector irradiated with simulated sunlight (AM 1.5, 1000 W/m²), in which the irradiation lasted for 30 min and then the solar simulator was shut off. The insets are the schematic illustration of the simple flat plate solar collector and the temperature elevation on irradiation with simulated sunlight for the first 1.2 min at a higher magnification, respectively.
Figure 5.17 SEM images of (a) T_FW, (b) chitin-matrix Ni wing, and (c) CNMF_6h (via Ni NP deposition for 6 h), respectively; (d) XRD pattern of CNMF_6h. Insets show morphologies at higher magnification.
Figure 5.18 (a) The temperature elevation of CNMF_1h (via Ni NP deposition for 1 h), CNMF_6h (via Ni NP deposition for 6 h), CNMF_10h (via Ni NP deposition for 10 h), electroplating of the Ni NPs onto silver sheet (Electroplate_Ni), and the Ag sheet. The values were presented as the mean ± variance from triplicate samples. The inset of (a) is the temperature elevation of CNMF_1h and CNMF_10h over the time range of 400–600 s at a higher magnification. (b) Magnetization intensity versus temperature at the level of the magnetizing field H = 5000 Oe for the CNMF_6h. (c) Magnetic hysteresis loops of the CNMF_6h at temperatures of 25, 40, and 60 °C. The inset of Figure 5.6c shows the magnetic hysteresis loops over the magnetic field range of 2–5 kOe at a higher magnification.
Figure 5.19 AFM–MFM images performed using a magnetic probe on CNMF_6h. Panels (a) and (c) are the AFM images of CNMF_6h at the temperatures of 25 and 40 °C, respectively. Panels (b) and (d) are the MFM images of CNMF_6h at the temperatures of 25 and 40 °C, respectively.

Chapter 6: Bioinspired Microfluidic Cooling

Figure 6.1 (a) Blood is transported through highly branched vascular networks to sustain the tissues and organs in our bodies.
Figure 6.2 Vascularized thermoregulatory appendages: (a) Caribou antlers are grown and shed annually. Through the summer months these appendages are soft and highly vascularized, and are used as heat exchangers.
Figure 6.3 (a) Shuttle LCG.
Figure 6.5 Wearable fluidic devices of various fabrication techniques. (a) Silicone-molded Paxman™ cooling cap. (b) Integrated tubing Veskimo™ Personal Microclimate Body Cooling Vest [28]. (c) Radio frequency welded plastic Genesis neonatal cooling cap.
Figure 6.4 DigniCap® scalp cooling technology to reduce chemotherapy-induced alopecia. (a) Fitting the cooling cap. (b) Cooling and control unit. (c) Silicone cooling cap.
Figure 6.6 A wearable microfluidic device designed to monitor biochemical markers in sweat. (a) Schematic of device. (b) Illustration of the top, middle, and back sides of the device. Black and white markers on the top side calibrate the imaging software. The colorimetric assay reagents (water, lactate, chloride, glucose, and pH) are contained in microfluidic channels in the middle. On the bottom side are the inlets for harvesting sweat, and adhesive. (c) Cross section as defined by the dashed lines in the top side illustration in (b). (d) Photo of device on skin. (e) The results of finite element analysis (FEA) stress analysis and corresponding photos for various mechanical distortions: stretching at 30% strain, bending with 5 cm radius, and twisting.
Figure 6.7 Mushtari, from the Wanderers collection. Designed by Neri Oxman. In collaboration with Christoph Bader and Dominik Kolb; produced by Stratasys on the Objet500 Connex3 3D Production System. Photo credit: Paula Aguilera and Jonathan Williams (a). Yoram Reshef (b).
Figure 6.8 Example of an integrated fluidic network within the floors and building façade.
Figure 6.9 (a,b) Phase change materials contained as a suspension within a supported polyethylene fluidic layer.
Figure 6.10 Thermal IR images of the Diamond 1 PDMS channel layer for input water temperature of 0 °C. (a) Effect of flow rate, at steady state. (b) Effect of time, at high flow rate (10 mL/min). In all images, inlet is on the right and output on the left; flow is from right to left.
Figure 6.11 Basis of the 1D steady-state heat transfer model developed by Hatton et al. [32].
Figure 6.12 Optical properties of adaptive fluidic networks.
Figure 6.16 Micro Molding of channel master: (a) the master is molded using compliant elastomer, (b) a thin sheet is created by spin coating a flat plate, (c) the two sections are bonded together, (d) EGaln fills the channels, (e) leads are attached to measure changes in electrical resistance, (f) a force post is attached, and (g) the pressure sensor is complete.
Figure 6.13 Embedded 3D Printing Technique. (a) Schematic of the fabrication process for an elastic microfluidic stretch sensor. (b) An immiscible neutrally buoyant conductive ink is directly written into a monolithic liquid elastomer by a computer numerically controlled extruding nozzle. (c) The resultant patch with fingers for scale. (d) When stretched, the cross section of the channels decreases and their length increases, reducing the conductivity of the ink pathways.
Figure 6.14 Schematic of RF-welding system.
Figure 6.15 CNC machining of microchannels where (a) channels are carved by endmill into poly(methyl methacrylate) (PMMA) substrate, (b) serpentine pattern distributes fluid over surface. (c) Thermal bonding of secondary PMMA sheet with aligned end holes; (d) connection of inlet and outlet hosing.
Figure 6.17 (a) Photo series: stages of growth of the hollow channels as air displaces liquid silicone. The experimenter (coauthor CK) injects air using a 200 cm³ syringe into a Hele-Shaw cell filled with liquid silicone. A suction cup is used to pull the top surface and guide the channel growth. (b) Photo series: Post-curing, the hollow channels remain an inclosed and integrated part of a single piece of silicone. They are then inflated and deflated with red-dyed water.
Figure 6.18 Wearable liquid cooling and warming garment invented by CK.
Figure 6.19 Silicone membrane produced using the technique of viscous fingering for use in solar water disinfection and rooftop solar thermal mitigation.
Figure 6.20 View from above the Hele-Shaw cells. Top circular glass plate of diameter 26″ is closely spaced (∼0.4 mm) with dyed glycerine in between. Air is injected in the center at a pressure of ∼150 mbar. Branch angle depends on underlying etched groove pattern. (a) No grooves. (b) Rectangular grid. (c) Triangular grid. (d) Randomly etched grid with no spacing between top and bottom plates.

Chapter 7: Thermal Emissivity: Basics, Measurement, and Biological Examples

Figure 7.1 Three-lid method for emissivity determination [2].
Figure 7.2 Bruker Vertex 70 FTIR spectrophotometer with integrating sphere and MCT detector cooled by liquid nitrogen [4].
Figure 7.3 ET-100 thermal handheld emissometer from the Surface Optics Corporation.
Figure 7.4 Comparison of an average of 10 emissivity spectra to a calculated average emissivity derived from directional-hemispherical reflectance spectra of a fused silica sample [8].
Figure 7.5 The instrument described by Hameury et al. [17] (1) sample; (2) detector; (3) set of four mirrors with spherical surface; (4) rotating plane mirror; (5) fixed plane mirrors for the selection of the angle of incidence; (6) field stop and aperture limiting stop; (7) polarizer; (8) grating monochromator; (9) mechanical chopper; (10) lamp source; (11) blackbody source; (12) interference filter; and (13) flat mobile mirrors for selection of the monochromator or the interference filters.
Figure 7.6 A schematic representation of the emissivity measurement setup of Maynard [18]. (1) Sample strip; (2) adjustable top of the sample holder; (3) fixed sample holder support; (4) thermocouple connector; (5) Type K thermocouple wire; (6a) and (6b) electrical feed-throughs; (7) ceramic mounting post for thermocouple connectors; (8a) and (8b) Type K thermocouple feed throughs; (9) base plate for the bell jar; (10) dead weight to keep the test specimen from flexing at high temperature; (11) flexible, low-impedance electrical cable; (12) turbomolecular pump; (13) mechanical roughing pump; (14) power supply; (15) electrical resistor; (16) bell jar base well with eight vacuum feed-throughs and turbomolecular pump connection; (17) vacuum bell jar; and (18) pressure readout.
Figure 7.7 Comparison of measurements taken on two test sites in California, from space with MODIS and ASTER instruments, and in the laboratory [25].
Figure 7.8 Emissivity according to ASTER's Band 12 (8.925–9.275 µm) for Earth's land surfaces. Highest emissivity values are in red, lowest are in blue; and yellow and green are in between. The Sahara and Rub al'Khali exhibit the lowest values due to quartz absorption band [26].
Figure 7.9 The diurnal dynamics of temperature and emissivity on 1 June 2013. Gaps in the graph are the result of missing data due to clouds. Notice that the variation range in the 8.7 µm channel was one order of magnitude larger than those in the 10.8 and 12 µm cannels [41].

Chapter 8: Bioinspired Thermal Detection

Figure 8.1 (a–d) Circuit formation of thermocouples. A, B, and C are three different metals. T₁, T₂, and T₃ are three different temperatures.
Figure 8.2 A representative schematic of the Schlieren method for detecting gas and flame temperatures.
Figure 8.3 (a) Reflection spectra of original butterfly wing (BW); amination of the wing is realized though alkali treatment. After treatment, the peak of the sample shifts due to the change of the refractive index of the sample. (b) Reflectance spectra of PNIPAm-co-AAC-PC sample at temperature of 26, 31, and 36 °C. (c) The peak values of the reflection spectrum (λ_max) are dependent on temperature. The peak position displays blue shift following the increase of temperature. Volume phase transition of PNIPAm-co-AAc-PC happens in a narrow range, corresponding to a dramatic shift of peaks as temperature changes from about 29 to 32 °C. (d) λ_max versus the cycles of heating and cooling. The curve represents the reversible and durable properties of the PNIPAM-co-AAc-PC sample.
Figure 8.4 The synthesis of the diphenylalanine (FF) nanotubes and the scanning electron microscopy (SEM) images corresponding to each morphology: (a) the original microtubes; (b) after treatment, the sample remains large with a step-like shape; (c) falling nanotubes from the microtubes. The insert shows that the lengths of some short nanotubes are less than 300 nm.
Figure 8.5 (a) The change of photoluminescence (PL) and (b) time-resolved photoluminescence (TRPL) spectra of the FF nanotubes varied with temperatures. The IRF is the instrumental response function. (c) The average PL lifetime (black square responding to left y axis) and average PL intensity (blue circle responding to right y axis) of three independent measurements at different temperatures. The black line is the fitted curve of experimental lifetime versus temperature. The inserted table contains the constant values and the corresponding standard errors of the fitting function. The error bars that indicate the standard deviations from the average values are shown in the Figure (d) The three PL decay curves of the FF nanotubes as a function of concentrations. The Figure shows that lifetime values of the FF nanotubes are independent on FF concentrations.
Figure 8.6 The use of DNA as a temperature stress sensor. (a) The morphological alteration of DNA supercoiling induced by heat stress or cold shock. (b) DNA curvature change of the local structure when temperature varies.
Figure 8.7 The mechanism of RNA thermal detection. At low temperatures, the SD sequence is combined with the AUG initiation codon and generates a hairpin structure in the 5′ untranslated region (UTR). When temperature rises, the structure becomes instable and 30S and 50S ribosomal subunits are available for binding, leading to the initialization of gene transcription.
Figure 8.8 (a) The combination of tsGFP1 and tsGFP2. (b)The structure and fluorescence change of green fluorescent protein-based thermosensors (tsGFPs) subjected to heating or cooling. (c) The fluorescence excitation spectra of tsGFP1, tsGFP2, and GFP as a function of temperature.
Figure 8.9 The mechanism of lipid–protein thermosensor. The fluidity and thickness of the membrane significantly influence the interaction of the lipid and the protein because of the increasing temperature and render the signal inactive.
Figure 8.10 Schematic of the two-step replication process of rice leaf structures. (i) Negative replication of the morphology form by solidifying PDMS using regular replica molding (REM) method. (ii) Transformation of the surface of PDMS template to PNIPAm in hot water. (iii) Positive PNIPAm replica of rice leaf after the separation of the PDMS mold.
Figure 8.11 Schematic of microcontact printing (µCP) of a sensor-grown biomembrane on silicon wafer and the formation of two patterns upon different pressures. The size of the membrane is 5 mm × 5 mm.
Figure 8.12 Sol–gel phase change property of HA/Pluronic hydrogels (HA-dopamine conjugates: 5 wt%) characterized by detecting elastic (G′) and viscous (G″) modulus, depending on the increasing temperatures by 0.25 °C. The Plu-SH concentrations are (a) 11.3 wt%, (b) 12.5 wt%, and (c) 13.8 wt%. (d) 5 wt% HA and 13.8 wt% Pluronic F127 physical mixture act as a control. Overlapped points of elastic modulus G′ and viscous modulus G″ correspond to the gelation temperature.
Figure 8.13 Sensory fiber endings inside glabrous skin.
Figure 8.14 Thermoresistive sensor arrays with excellent flexibility. The inset displays the interdigitated copper electrode (top) and deposited graphite–PDMS composite on the electrode (bottom).
Figure 8.15 Resistance changes of the graphite–PDMS composites with temperature. The platinum thin film serves as a temperature sensor that is presented for comparison. 15% and 25% are the volume fractions of graphite power in the graphite–PDMS composites.
Figure 8.16 The structure of liposome and functional design for drug delivery.
Figure 8.17 (a) Fluorescence signal image indicating a 200 mM carboxyfluorescein (CF), which is encapsulated in a solution going through a polycarbonate microchannel. The solution contains a mole fraction of 5 mol% cholesterol and 95 mol% 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes with 0.5 M Tris buffer. The microchannel has a temperature gradient of 20–64 °C and is 2 mm long, but the graph only shows 1.7 mm of the microchannel. The volumetric flow rate of the solution is 100 µL/h. (b) The same as (a), but false color of fluorescence signal image. (c) Normalized fluorescence intensity and temperature versus the position in microchannel corresponding to (a).
Figure 8.18 (a) Fluorescence signal image indicating a 1 mg/mL ethidium bromide, which is encapsulated in a 100 mol% DPPC solution is mixed with 0.1 unit/mL calf thymus DNA and goes through a fused-silica capillary. The microchannel has a temperature gradient of 20–80 °C and is 2 mm long. The volumetric flow rate of the solution is 100 µL/h. (b) Normalized fluorescence intensity at different positions in the microchannel corresponding to (a).

Chapter 9: Bioinspired Thermal Insulation and Storage Materials

Figure 9.1 Thermal conductivity of porous insulation materials as a function of density.
Figure 9.2 Classification of conventional thermal insulation materials.
Figure 9.3 Aerogel-based advanced thermal insulation materials: (a) schematic of aerogel fabrication process, (b) polymer-reinforced silica aerogels, and (c) mechanically compressible and recoverable polyurea-reinforced silica aerogels.
Figure 9.4 Application of thermal insulation materials: (a) building insulation, (b) spacecraft cryogenic insulation, (c) subsea pipeline thermal management, and (d) clothing thermal insulation and fire protection.
Figure 9.5 Penguins with thermally insulating feathers: (a) a photograph of emperor penguin Aptenodytes forsteri colony in Antarctic, (b) infrared images of a pair of emperor penguins, and (c) hierarchical microstructure of Pygoscelis papua penguin feathers.
Figure 9.6 Polar bear inspired thermal insulation systems: (a) a photograph of a polar bear, (b) yellow fur and black skin of polar bear, (c) schematic for solar-thermal functions of polar bear fur, (d) biomimetic spacer fibers for solar-thermal harvest, and (e) schematic for solar heat harvesting and thermal transportation system.
Figure 9.7 Optical photograph of Papilio paris butterfly and the microstructure of their wings: (a–c) black male and (d–f) blue male.
Figure 9.8 Rapid optical charging of solar-thermal energy storage materials inspired by black butterflies: (a) conventional heat-diffusion-based thermal charging, (b) bioinspired optical charging, and (c) time-sequential infrared images of gel wax charged by thermal charging and gel wax dispersed with gold nanoparticles charged by optical charging.

Chapter 10: Bioinspired Icephobicity

Figure 10.1 A sessile pure water drop on a smooth substrate surface. The entire system is at a temperature T lower than the equilibrium freezing temperature T_e. Nucleation takes place at the W—S interface.
Figure 10.2 Critical radius of water-to-ice nucleation versus supercooling temperature.
Figure 10.3 Nondimensional nucleation rate per unit volume versus contact angle for two supercooling temperatures.
Figure 10.4 Freezing of a water drop on a surface.
Figure 10.5 IR thermoimaging analysis of a 6 µl water drop freezing on a silicon substrate (θ = 44^°) during constant cooling at a rate of 20 °C/min. (a) IR image of water drop and conductive black tape. (b) Temperature of the water drop (red) and Si surface (black). (c) Magnification of the phase transition regime.
Figure 10.6 Topmost temperature of a 21 µL water drop on the hydrophilic surface being cooled at 10 °C/min. Four processes are identified: (1) liquid cooling; (2) recalescence; (3) freezing; and (4) solid cooling. The temperature during recalescence and freezing is enlarged and shown as a continuous curve in the inset graph.
Figure 10.7 The surface temperature was measured when a sessile drop with the same volume on a surface was cooled at 5 °C/min. Three surfaces with different contact angles were tested.
Figure 10.8 Topmost temperatures of 21 µL water drop on the hydrophilic surface and a 7.2 µL drop on the hydrophobic surface for varied cold plate cooling rates.
Figure 10.9 Propagation of freezing boundary along the vertical centerline of the drop. The vertical axis is the distance from the drop base normalized by the drop center height.
Figure 10.10 Transient temperatures of 4 µL water drop freezing on (a) hydrophilic (44°), (b) hydrophobic (109°), and (c) superhydrophobic (145°) substrates. In all cases, room temperature drops were impinged on the −20 °C substrates.
Figure 10.11 The impact of the drop on the hydrophobic surface.
Figure 10.12 The impact and icing of a water drop on a plasma-treated Si wafer with contact angle 11°. The surface was maintained at −20 °C.

Bioinspired Engineering of Thermal Materials

Edited by Tao Deng

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