Actuators that can convert environmental stimuli into mechanical work are widely used in intelligent systems, robots, and micromechanics. To produce robust and sensitive actuators of different ...scales, efforts are devoted to developing effective actuating schemes and functional materials for actuator design. Carbon‐based nanomaterials have emerged as preferred candidates for different actuating systems because of their low cost, ease of processing, mechanical strength, and excellent physical/chemical properties. Especially, due to their excellent photothermal activity, which includes both optical absorption and thermal conductivities, carbon‐based materials have shown great potential for use in photothermal actuators. Herein, the recent advances in photothermal actuators based on various carbon allotropes, including graphite, carbon nanotubes, amorphous carbon, graphene and its derivatives, are reviewed. Different photothermal actuating schemes, including photothermal effect–induced expansion, desorption, phase change, surface tension gradient creation, and actuation under magnetic levitation, are summarized, and the light‐to‐heat and heat‐to‐work conversion mechanisms are discussed. Carbon‐based photothermal actuators that feature high light‐to‐work conversion efficiency, mechanical robustness, and noncontact manipulation hold great promise for future autonomous systems.
This review highlights the recent advances in carbon‐based photothermal actuators. Physical properties and light‐to‐heat conversion mechanisms of various carbon‐based functional materials are summarized. Photothermal actuating schemes such as photothermal expansion, desorption, phase change, surface tension effect, and magnetic susceptibility are reviewed. The current challenges and future perspectives of this field are also discussed.
An unexpected interaction between a long non-coding RNA locus and a genetic insulator called Fub-1 has an important role in gene regulation during development in Drosophila.
Natural musculoskeletal systems have been widely recognized as an advanced robotic model for designing robust yet flexible microbots. However, the development of artificial musculoskeletal systems at ...micro-nanoscale currently remains a big challenge, since it requires precise assembly of two or more materials of distinct properties into complex 3D micro/nanostructures. In this study, we report femtosecond laser programmed artificial musculoskeletal systems for prototyping 3D microbots, using relatively stiff SU-8 as the skeleton and pH-responsive protein (bovine serum albumin, BSA) as the smart muscle. To realize the programmable integration of the two materials into a 3D configuration, a successive on-chip two-photon polymerization (TPP) strategy that enables structuring two photosensitive materials sequentially within a predesigned configuration was proposed. As a proof-of-concept, we demonstrate a pH-responsive spider microbot and a 3D smart micro-gripper that enables controllable grabbing and releasing. Our strategy provides a universal protocol for directly printing 3D microbots composed of multiple materials.
Muscles and joints make highly coordinated motion, which can be partly mimicked to drive robots or facilitate activities. However, most cases primarily employ actuators enabling simple deformations. ...Therefore, a mature artificial motor system requires many actuators assembled with jointed structures to accomplish complex motions, posing limitations and challenges to the fabrication, integration, and applicability of the system. Here, a holistic artificial muscle with integrated light‐addressable nodes, using one‐step laser printing from a bilayer structure of poly(methyl methacrylate) and graphene oxide compounded with gold nanorods (AuNRs), is reported. Utilizing the synergistic effect of the AuNRs with high plasmonic property and wavelength‐selectivity as well as graphene with good flexibility and thermal conductivity, the artificial muscle can implement full‐function motility without further integration, which is reconfigurable through wavelength‐sensitive light activation. A biomimetic robot and artificial hand are demonstrated, showcasing functionalized control, which is desirable for various applications, from soft robotics to human assists.
A holistic artificial muscle with integrated light‐addressable nodes, using one‐step laser printing from a bilayer structure of poly(methyl methacrylate) and graphene oxide compounded with gold nanorods, is reported. The artificial muscle can implement full‐function motility without further integration, which is reconfigurable through wavelength‐sensitive light activation. A biomimetic robot and artificial hand is demonstrated, showcasing functionalized control, which is desirable for various applications.
Nanoscale surface texturing, drilling, cutting, and spatial sculpturing, which are essential for applications, including thin-film solar cells, photonic chips, antireflection, wettability, and ...friction drag reduction, require not only high accuracy in material processing, but also the capability of manufacturing in an atmospheric environment. Widely used focused ion beam (FIB) technology offers nanoscale precision, but is limited by the vacuum-working conditions; therefore, it is not applicable to industrial-scale samples such as ship hulls or biomaterials, e.g., cells and tissues. Here, we report an optical far-field-induced near-field breakdown (O-FIB) approach as an optical version of the conventional FIB technique, which allows direct nanowriting in air. The writing is initiated from nanoholes created by femtosecond-laser-induced multiphoton absorption, and its cutting "knife edge" is sharpened by the far-field-regulated enhancement of the optical near field. A spatial resolution of less than 20 nm (
/40, with
being the light wavelength) is readily achieved. O-FIB is empowered by the utilization of simple polarization control of the incident light to steer the nanogroove writing along the designed pattern. The universality of near-field enhancement and localization makes O-FIB applicable to various materials, and enables a large-area printing mode that is superior to conventional FIB processing.
With high thermal and mechanical stability, glass artificial compound eyes have great potential applications in wide field‐of‐view (FOV) imaging and fast detection. However, the rapid fabrication of ...large‐area, high integration, uniform, and well‐designed three‐dimensional (3D) glass compound eyes is still a great challenge. Here, a dry‐etching‐assisted femtosecond laser machining (DE‐FsLM) technology is proposed for fabrication of cm‐sized concave compound eye from a curved sapphire substrate, with which the fabrication efficiency can be improved by over two orders of magnitude compared with direct laser ablation. With high hardness and thermal stabilities, the sapphire concave compound eyes can be used as high‐temperature and hard‐casting templates for the replication of convex compound eyes on K9 glass. The replicated cm2‐size all‐glass compound eye consists of a spherical macrolens (1 cm diameter and 2.3 mm height) and over 190 000 close‐packed ommatidia (≈20 µm diameter and 1.5 µm height). The compound eyes exhibit excellent optical properties with wide FOV (up to 90°) imaging and focusing. These results indicate that the DE‐FsLM and casting replication technology will open new opportunities in micro‐/nanofabrication of hard materials.
Dry‐etching‐assisted femtosecond laser machining is proposed for the rapid fabrication of large‐scale uniform and smooth sapphire concave compound eye templates. K9 glass compound eyes are fabricated by high‐temperature casting replication from the sapphire concave compound eyes, which exhibit a wide field‐of‐view (up to 90°) for practical applications.
The “China Dream” is an “Urban Dream”. Urbanization is an inevitable requirement for promoting social progress. The Chinese government sees sustainable urbanization as an engine of modernization and ...economic growth. And the country's urbanization has followed a unique course and is perhaps the greatest human-resettlement experiment in the world history, unprecedentedly transforming the Chinese society in a very short period of time. Yet problems have arisen during the historical process, China's unique path to urbanization has avoided many of pitfalls existing in the developing countries in Africa, Asia and South America. This paper attempts to conclude the good jobs as well as problems in China's urbanizing process which might provide successful experience for the underdeveloped nations and regions to promote urbanization. The most brilliant achievement of urbanization in China is that thousands of years' agriculture-dominated country has ended and a new urbanized country has formed, which only consumed several decades. The country's urban infrastructure, living conditions and public service for urban residents have made great improvements. The fostering urban agglomerations are considered to lead the country's socio-economic transformation and possess the greatest potential for the urbanization and economic growth in the coming decades. In general, the traditional land-centered urbanization in China is a typical “incomplete urbanization” and “low-quality urbanization”, presenting impressive characteristics of “four highs and five lows”—high investment, consumption, emission and expansion, and low level, quality, harmony degree, inclusiveness and sustainability. Undoubtedly, the traditional urbanization of China is increasingly difficult to continue and the transformation process should be speeded up as soon as possible. The country should actively explore a people-oriented new-type urbanization way, i.e. an intensive, efficient, rural-urban integration, harmonious and sustainable urbanization model.
Soft robots controlled by different actuation schemes are flourishing owing to the continued development of smart materials. However, most of the existing actuators are powered by a single source ...with predetermined mechanical properties and motion characteristics. Speed, power, and efficiency of these actuators are thus far inferior to their conventional counter parts. How to preload or alter the internal energy distribution and trigger rapid kinetic energy release combined with re‐programmability is a challenge and corresponding solutions will extend the practical use of soft robotics. Herein, a hybrid magnetically and photothermally responsive actuator with high degrees of freedom by using a coupled‐field manipulation strategy is proposed. As a proof‐of‐concept, a crab robot (CraBot) that contains uniformly distributed superparamagnetic particles and localized light‐responsive joints is produced. The spatial magnetic field exerts force on the robot, leading to real‐time adjustment of energy distribution within the entire robot. Meanwhile, the focused light field enables selective deformation of specific joints, releasing the accumulated energy into kinetic energy of motion for quick actuation. The directional accumulation and addressable release of elastic energy enables the CraBot to walk efficiently with improved power and speed. Such a hybrid‐field manipulation strategy holds great promise for sophisticated actuation of soft robots.
Soft actuators with improved flexibility are demonstrated by synergistic magnetic and light fields manipulation. The magnetic field adjusts the overall energy distribution, and the light field enables directional release of the accumulated energy at specific point. A crab‐shaped robot can walk freely according to the proposed driving strategy.
Compound eyes are natural multiaperture optical imaging systems and have substantial potential in the field of modern optics. However, both natural and artificial compound eyes are composed of ...ommatidia with fixed focal lengths, and thus incapable of variable‐focus imaging. In this study, inspired by the tunable crystalline lens of human eyes, smart stimuli‐responsive compound eyes based on the bovine serum album (BSA) protein are fabricated via femtosecond laser direct writing. Due to the swelling and shrinking effect of BSA under different pH conditions, a tunable field of view (FOV, 35°–80°) and variable focal length of ommatidia are achieved. In addition to the direct prototyping of an entire protein‐based compound eye, the ability to flexibly integrate the smart protein ommatidia with a conventional optical lens (an SU‐8 lens in this study) to form a composite compound eye is shown. The composite compound eye achieves nearly 400% of focal length tuning at a fixed FOV. It is anticipated that femtosecond laser fabrication and the integration of smart protein‐based compound eyes may emerge as an enabler for fabricating miniature tunable imaging systems.
Smart artificial compound eyes with the combined advantages of both insect compound eyes and human eyes are fabricated based on a pH‐responsive protein via femtosecond laser direct writing, demonstrating variable fields of view and focal lengths for tunable imaging. In addition to direct prototyping of entire compound eyes, flexible integration of tunable ommatidia with given micro‐optical components is realized.
For the simple and versatile fabrication of nanosmooth finished microlens arrays on hard materials, an approach combining femtosecond laser modification with subsequent ion beam etching is ...demonstrated. This method is based on the dependence of the plasma etching rate on the laser fluence used to modify the surface. The fabricated microlenses exhibit a low surface roughness of approximately 2.5 nm, due to the high precision of the plasma etching and benefit from the smooth interface between the laser‐modified and pristine subsurface regions. Microlenses with focal lengths ranging from 60 to 100 µm are realized by controlling the laser fluence, exposure dose, and etching time. Uniform square and hexagonal microlens arrays are fabricated on both hard and ultrahard materials and glasses (fused silica, GaAs, SiC, diamond) by the same process and deliver high‐quality focusing and imaging.
Femtosecond laser modification followed by ion beam etching is proposed for simple and versatile fabrication of nanosmooth finished microlens arrays on hard materials. The fabricated microlenses exhibit a low surface roughness of approximately 2.5 nm. Uniform square and hexagonal microlens arrays are fabricated on fused silica, GaAs, SiC, and diamond by the same process and deliver high‐quality focusing and imaging.
PDF
