A smart window that dynamically modulates light transmittance is crucial for building energy efficiently, and promising for on‐demand optical devices. The rapid development of technology brings out different categories that have fundamentally different transmittance modulation mechanisms, including the electro‐, thermo‐, mechano‐, and photochromic smart windows. In this review, recent progress in smart windows of each category is overviewed. The strategies for each smart window are outlined with particular focus on functional materials, device design, and performance enhancement. The advantages and disadvantages of each category are summarized, followed by a discussion of emerging technologies such as dual stimuli triggered smart window and integrated devices toward multifunctionality. These multifunctional devices combine smart window technology with, for example, solar cells, triboelectric nanogenerators, actuators, energy storage devices, and electrothermal devices. Lastly, a perspective is provided on the future development of smart windows.

Soft machines typically exhibit slow locomotion speed and low manipulation strength because of intrinsic limitations of soft materials. Here, we present a generic design principle that harnesses mechanical instability for a variety of spine-inspired fast and strong soft machines. Unlike most current soft robots that are designed as inherently and unimodally stable, our design leverages tunable snap-through bistability to fully explore the ability of soft robots to rapidly store and release energy within tens of milliseconds. We demonstrate this generic design principle with three high-performance soft machines: High-speed cheetah-like galloping crawlers with locomotion speeds of 2.68 body length/s, high-speed underwater swimmers (0.78 body length/s), and tunable low-to-high-force soft grippers with over 1 to 103 stiffness modulation (maximum load capacity is 11.4 kg). Our study establishes a new generic design paradigm of next-generation high-performance soft robots that are applicable for multifunctionality, different actuation methods, and materials at multiscales.

Many natural fruits and vegetables adopt an approximately spheroidal shape and are characterized by their distinct undulating topologies. We demonstrate that various global pattern features can be reproduced by anisotropic stress-driven buckles on spheroidal core/shell systems, which implies that the relevant mechanical forces might provide a template underpinning the topological conformation in some fruits and plants. Three dimensionless parameters, the ratio of effective size/thickness, the ratio of equatorial/polar radii, and the ratio of core/shell moduli, primarily govern the initiation and formation of the patterns. A distinct morphological feature occurs only when these parameters fall within certain ranges: In a prolate spheroid, reticular buckles take over longitudinal ridged patterns when one or more parameters become large. Our results demonstrate that some universal features of fruit/vegetable patterns (e.g., those observed in Korean melons, silk gourds, ribbed pumpkins, striped cavern tomatoes, and cantaloupes, etc.) may be related to the spontaneous buckling from mechanical perspectives, although the more complex biological or biochemical processes are involved at deep levels. morphogenesis ͉ nonlinear mechanics ͉ pattern formation ͉ physical geometry S pontaneous buckling of thin films on compliant substrates can achieve numerous highly ordered patterns due to mismatched deformation (1-6), which can be manipulated in different ways (1, 7-9). Buckling may also play an important role in the morphogenesis of some plant parts, including phyllotactic pattern in compressed tunica (10, 11), primordium initiation in sunflower capitulum (12), and Fibonacci patterns resembling those in some flowering cactus and pine cones (2), among others, in a way that is similar to the energy-minimizing buckling of a compressed shell on an elastic foundation (10).Many natural fruits and vegetables can be approximated as spheroidal stiff exocarp (shell)/compliant sarcocarp (core) systems, which exhibit intriguing buckle-like profiles. For example, the Korean melon (yellow melon) and ridged gourd (or silk gourd, luffa acutangula) are distinguishable by 10 equidistant longitudinal ridges that run from stem to tip. Small pumpkins, acorn squashes, and carnival squashes often have ϳ10 uniformly spaced ribs, whereas the large pumpkins often have ϳ20 or more ridges. Similar undulating morphologies found in varieties of cucumis melons, gourds, striped cavern tomatoes, bell peppers, and other fruits and vegetables underpin their distinctive appearances. Although pattern formation in plants usually involves various complex biological and biochemical processes (11,13,14), such distinctive yet simple features make one wonder whether there exist other relatively simpler mechanisms contributing to the morphogenesis at the macroscopic scale, and the possibility of stress-driven buckling is explored in this study.Consider a model spheroidal core/shell system where the shell is characterized by (x 2 ϩ y 2 )/a 2 ϩ z 2 /b 2 ϭ 1 with equator...

Programmable kirigami metamaterials with controllable local tilting orientations on demand through prescribed notches are constructed through a new approach of kiri-kirgami, and their actuation of pore opening via both mechanical stretching and temperature, along with their potential application as skins for energy-saving buildings, is discussed.

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The delamination buckling approach provides a facile means to dynamically control the optical transmittance of extremely flexible and stretchable graphene oxide coatings with fast response time. Such graphene oxide coatings can be deposited by scalable solution-processing methods for potential applications in dynamic glazing.

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Ordered herringbone patterns with deterministic long and short wavelengths are created using a sequential wrinkling strategy (SWS). Patterns with a prescribed zig-zag turning angle less than 90° are obtained upon sequential wrinkling of non-equi-biaxial prestrain for the first time. SWS provides a new method for measuring thin-film mechanical properties simply through the wrinkling metrology without measurement of film thickness.