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1.
Nature ; 597(7877): 503-510, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34552257

RESUMO

Large, distributed collections of miniaturized, wireless electronic devices1,2 may form the basis of future systems for environmental monitoring3, population surveillance4, disease management5 and other applications that demand coverage over expansive spatial scales. Aerial schemes to distribute the components for such networks are required, and-inspired by wind-dispersed seeds6-we examined passive structures designed for controlled, unpowered flight across natural environments or city settings. Techniques in mechanically guided assembly of three-dimensional (3D) mesostructures7-9 provide access to miniature, 3D fliers optimized for such purposes, in processes that align with the most sophisticated production techniques for electronic, optoelectronic, microfluidic and microelectromechanical technologies. Here we demonstrate a range of 3D macro-, meso- and microscale fliers produced in this manner, including those that incorporate active electronic and colorimetric payloads. Analytical, computational and experimental studies of the aerodynamics of high-performance structures of this type establish a set of fundamental considerations in bio-inspired design, with a focus on 3D fliers that exhibit controlled rotational kinematics and low terminal velocities. An approach that represents these complex 3D structures as discrete numbers of blades captures the essential physics in simple, analytical scaling forms, validated by computational and experimental results. Battery-free, wireless devices and colorimetric sensors for environmental measurements provide simple examples of a wide spectrum of applications of these unusual concepts.

2.
Adv Mater ; 33(37): e2102684, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34342056

RESUMO

Three-dimensional (3D) flexible electronics represent an emerging area of intensive attention in recent years, owing to their broad-ranging applications in wearable electronics, flexible robots, tissue/cell scaffolds, among others. The widely adopted 3D conductive mesostructures in the functional device systems would inevitably undergo repetitive out-of-plane compressions during practical operations, and thus, anti-fatigue design strategies are of great significance to improve the reliability of 3D flexible electronics. Previous studies mainly focused on the fatigue failure behavior of planar ribbon-shaped geometries, while anti-fatigue design strategies and predictive failure criteria addressing 3D ribbon-shaped mesostructures are still lacking. This work demonstrates an anti-fatigue strategy to significantly prolong the fatigue life of 3D ribbon-shaped flexible electronics by switching the metal-dominated failure to desired polymer-dominated failure. Combined in situ measurements and computational studies allow the establishment of a failure criterion capable of accurately predicting fatigue lives under out-of-plane compressions, thereby providing useful guidelines for the design of anti-fatigue mesostructures with diverse 3D geometries. Two mechanically reliable 3D devices, including a resistance-type vibration sensor and a janus sensor capable of decoupled temperature measurements, serve as two demonstrative examples to highlight potential applications in long-term health monitoring and human-like robotic perception, respectively.

3.
Proc Natl Acad Sci U S A ; 118(11)2021 03 16.
Artigo em Inglês | MEDLINE | ID: mdl-33836614

RESUMO

Structures that significantly and rapidly change their shapes and sizes upon external stimuli have widespread applications in a diversity of areas. The ability to miniaturize these deployable and morphable structures is essential for applications in fields that require high-spatial resolution or minimal invasiveness, such as biomechanics sensing, surgery, and biopsy. Despite intensive studies on the actuation mechanisms and material/structure strategies, it remains challenging to realize deployable and morphable structures in high-performance inorganic materials at small scales (e.g., several millimeters, comparable to the feature size of many biological tissues). The difficulty in integrating actuation materials increases as the size scales down, and many types of actuation forces become too small compared to the structure rigidity at millimeter scales. Here, we present schemes of electromagnetic actuation and design strategies to overcome this challenge, by exploiting the mechanics-guided three-dimensional (3D) assembly to enable integration of current-carrying metallic or magnetic films into millimeter-scale structures that generate controlled Lorentz forces or magnetic forces under an external magnetic field. Tailored designs guided by quantitative modeling and developed scaling laws allow formation of low-rigidity 3D architectures that deform significantly, reversibly, and rapidly by remotely controlled electromagnetic actuation. Reconfigurable mesostructures with multiple stable states can be also achieved, in which distinct 3D configurations are maintained after removal of the magnetic field. Demonstration of a functional device that combines the deep and shallow sensing for simultaneous measurements of thermal conductivities in bilayer films suggests the promising potential of the proposed strategy toward multimodal sensing of biomedical signals.

4.
Sci Adv ; 6(30): eabb7417, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32832676

RESUMO

Microelectronic devices with reconfigurable three-dimensional (3D) microarchitecture that can be repetitively switched among different geometrical and/or working states have promising applications in widespread areas. Traditional approaches usually rely on stimulated deformations of active materials under external electric/magnetic fields, which could potentially introduce parasitic side effects and lower device performances. Development of a rational strategy that allows access to high-performance 3D microdevices with multiple stable geometric configurations remains challenging. We introduce a mechanically guided scheme to build geometrically reconfigurable 3D mesostructures through a bottom-up design strategy based on a class of elementary reconfigurable structures with the simplest ribbon geometries. Quantitative mechanics modeling of the structural reconfigurability allows for the development of phase diagrams and design maps. Demonstrations of ~30 reconfigurable mesostructures with diverse geometric topologies and characteristic dimensions illustrate the versatile applicability. The multimode nature enables customized distinct beamforming and discrete beam scanning using a single antenna capable of on-demand reconfiguration.

5.
Adv Sci (Weinh) ; 7(13): 2000584, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32670768

RESUMO

Integrated sensor-actuators with exciting functionalities, such as action self-sensing, position self-sensing, posture self-sensing, or active sensing, are promising for applications in biomedical device, human-machine interaction, intelligent self-protection devices, and humanoid robots. Despite recent progress, it remains challenging to achieve a macroscopical integrated sensor-actuator in a material system with microstructures. To address this critical challenge, a 4D printing bioinspired microstructure strategy is reported to design a high-performance integrated sensor-actuator capable of simultaneous actuation and sensation. Decoupled thermal stimulation and strain sensation is achieved by combining nanocarbon black/polylactic acid composites with bioinspired gradient microgap structures. As a result, printed integrated sensor-actuators can actively touch objects triggered by thermal stimulation and self-sense the touching state through the resistance change. It is anticipated that the basic design principle underlying this behavior can be used to develop integrated sensor-actuators of various shapes and functionalities to meet desirable applications.

6.
Nat Commun ; 11(1): 1180, 2020 03 04.
Artigo em Inglês | MEDLINE | ID: mdl-32132524

RESUMO

Many biological tissues offer J-shaped stress-strain responses, since their microstructures exhibit a three-dimensional (3D) network construction of curvy filamentary structures that lead to a bending-to-stretching transition of the deformation mode under an external tension. The development of artificial 3D soft materials and device systems that can reproduce the nonlinear, anisotropic mechanical properties of biological tissues remains challenging. Here we report a class of soft 3D network materials that can offer defect-insensitive, nonlinear mechanical responses closely matched with those of biological tissues. This material system exploits a lattice configuration with different 3D topologies, where 3D helical microstructures that connect the lattice nodes serve as building blocks of the network. By tailoring geometries of helical microstructures or lattice topologies, a wide range of desired anisotropic J-shaped stress-strain curves can be achieved. Demonstrative applications of the developed conducting 3D network materials with bio-mimetic mechanical properties suggest potential uses in flexible bio-integrated devices.


Assuntos
Materiais Biomiméticos/química , Biomimética/métodos , Desenho Assistido por Computador , Anisotropia , Módulo de Elasticidade , Análise de Elementos Finitos , Teste de Materiais , Software , Estresse Mecânico
7.
Adv Mater ; 32(14): e1908424, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32100406

RESUMO

Deterministic transformations of 2D patterns of materials into well-controlled 3D mesostructures serve as the basis for manufacturing methods that can bypass limitations of conventional 3D micro/nanofabrication. Here, guided mechanical buckling processes provide access to a rich range of complex 3D mesostructures in high-performance materials, from inorganic and organic semiconductors, metals and dielectrics, to ceramics and even 2D materials (e.g., graphene, MoS2 ). Previous studies demonstrate that iterative computational procedures can define design parameters for certain targeted 3D configurations, but without the ability to address complex shapes. A technical need is in efficient, generalized inverse design algorithms that directly yield sets of optimized parameters. Here, such schemes are introduced, where the distributions of thicknesses across arrays of separated or interconnected ribbons provide scalable routes to 3D surfaces with a broad range of targeted shapes. Specifically, discretizing desired shapes into 2D ribbon components allows for analytic solutions to the inverse design of centrally symmetric and even general surfaces, in an approximate manner. Combined theoretical, numerical, and experimental studies of ≈20 different 3D structures with characteristic sizes (e.g., ribbon width) ranging from ≈200 µm to ≈2 cm and with geometries that resemble hemispheres, fire balloons, flowers, concave lenses, saddle surfaces, waterdrops, and rodents, illustrate the essential ideas.

8.
Adv Mater ; 32(15): e1902254, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31348578

RESUMO

Over the past decade, the area of stretchable inorganic electronics has evolved very rapidly, in part because the results have opened up a series of unprecedented applications with broad interest and potential for impact, especially in bio-integrated systems. Low modulus mechanics and the ability to accommodate extreme mechanical deformations, especially high levels of stretching, represent key defining characteristics. Most existing studies exploit structural material designs to achieve these properties, through the integration of hard inorganic electronic components configured into strategic 2D/3D geometries onto patterned soft substrates. The diverse structural geometries developed for stretchable inorganic electronics are summarized, covering the designs of functional devices and soft substrates, with a focus on fundamental principles, design approaches, and system demonstrations. Strategies that allow spatial integration of 3D stretchable device layouts are also highlighted. Finally, perspectives on the remaining challenges and open opportunities are provided.

9.
Natl Sci Rev ; 7(2): 342-354, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34692050

RESUMO

The manufacture of 3D mesostructures is receiving rapidly increasing attention, because of the fundamental significance and practical applications across wide-ranging areas. The recently developed approach of buckling-guided assembly allows deterministic formation of complex 3D mesostructures in a broad set of functional materials, with feature sizes spanning nanoscale to centimeter-scale. Previous studies mostly exploited mechanically controlled assembly platforms using elastomer substrates, which limits the capabilities to achieve on-demand local assembly, and to reshape assembled mesostructures into distinct 3D configurations. This work introduces a set of design concepts and assembly strategies to utilize dielectric elastomer actuators as powerful platforms for the electro-mechanically controlled 3D assembly. Capabilities of sequential, local loading with desired strain distributions allow access to precisely tailored 3D mesostructures that can be reshaped into distinct geometries, as demonstrated by experimental and theoretical studies of ∼30 examples. A reconfigurable inductive-capacitive radio-frequency circuit consisting of morphable 3D capacitors serves as an application example.

10.
ACS Appl Mater Interfaces ; 11(39): 36100-36109, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31502438

RESUMO

Development of stretchable devices with mechanical responses that mimic those of biological tissues/organs is of particular importance for the long-term biointegration, as the discomfort induced by the mechanical mismatch can be minimized. Recent works have established the bioinspired designs of soft network materials that can precisely reproduce the unconventional J-shaped stress-strain curves of human skin at different regions. Existing studies mostly focused on the design, fabrication, and modeling of perfect soft network materials. When utilized as the substrates of biointegrated electronics, the soft network designs, however, often need to incorporate deterministic holes, a type of imperfection, to accommodate hard, inorganic electronic components. Understanding of the effect of hole imperfections on the mechanical properties of soft network materials is thereby essential in practical applications. This paper presents a combined experimental and computational study of the stretchability and elastic modulus of imperfect soft network materials consisting of circular holes with a variety of diameters. Both the size and location of the circular-hole imperfections are shown to have profound influences on the stretchability. Based on these results, design guidelines of imperfection-insensitive network materials are introduced. For the imperfections that result in an evident reduction of stretchability, an effective reinforcement approach is presented by enlarging the width of horseshoe microstructures at strategic locations, which can enhance the stretchability considerably. A stretchable and imperfection-insensitive integrated device with a light-emitting diode embedded in the network material serves a demonstrative application.


Assuntos
Materiais Biomiméticos , Módulo de Elasticidade , Pele , Humanos , Dispositivos Eletrônicos Vestíveis
11.
ACS Appl Mater Interfaces ; 11(36): 33370-33379, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31408310

RESUMO

Flexible pressure sensors have attracted considerable attention because of their potential applications in healthcare monitoring and human-machine interactions. However, the complicated fabrication process and the cos of sensing materials limit their widespread applications in practice. Herein, a flexible pressure sensor with outstanding performances is presented through an extremely simple and cost-efficient fabrication process. The sensing materials of the sensor are based on low-cost carbon black (CB)@airlaid paper (AP) composites, which are just prepared by drop-casting CB solutions onto APs. Through simply stacking multiple CB@APs with an irregular surface and a fiber-network structure, the obtained pressure sensor demonstrates an ultrahigh sensitivity of 51.23 kPa-1 and an ultralow detection limit of 1 Pa. Additionally, the sensor exhibits fast response time, wide working range, good stability, as well as excellent flexibility and biocompatibility. All the comprehensive and superior performances endow the sensor with abilities to precisely detect weak air flow, wrist pulse, phonation, and wrist bending in real time. In addition, an array electronic skin integrated with multiple CB@AP sensors has been designed to identify spatial pressure distribution and pressure magnitude. Through a biomimetic structure inspired by blooming flowers, a sensor with the open-petal structure has been designed to recognize the wind direction. Therefore, our study, which demonstrates a flexible pressure sensor with low cost, simple preparation, and superior performances, will open up for the exploration of cost-efficient pressure sensors in wearable devices.


Assuntos
Custos e Análise de Custo , Papel , Pressão , Fuligem/análise , Dispositivos Eletrônicos Vestíveis/economia , Maleabilidade
12.
Small ; 15(1): e1804055, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30515973

RESUMO

To address demands for increased data transmission rates, electrically small antennas (ESAs) that simultaneously offer large frequency bandwidths and small physical sizes are of growing interest. 3D layouts are particularly important in this context and among various 3D ESAs, systems that adopt hemispherical shapes are very promising, because they can occupy the entire Chu-sphere and offer outstanding electrical performance. Researchers have developed a few different approaches to fabricate high-quality hemispherical ESAs, but most have static layouts and fixed operating frequencies. Here, a mechanically guided 3D assembly approach is introduced for the design and fabrication of deformable hemispherical ESAs that can offer tunable, dynamic properties to adapt to changes in environmental conditions. The strategy exploits controlled compressive buckling of strategically patterned 2D precursor structures, as a low-cost and high-yield scheme that can exploit conventional, planar processing technologies and commercially available platforms. Combined numerical simulations and experimental measurements show outstanding performance characteristics in terms of the quality factor and radiation efficiency. Application of external tensile strains to elastomeric substrates for these systems allows them to be reshaped and reversibly tuned through a wide range of center frequencies. Mechanical testing under different loading conditions demonstrates the ability of these ESAs to accommodate large deformations.

13.
Nanoscale ; 10(32): 15178-15186, 2018 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-29892757

RESUMO

Biomimetic sensor technology is always superior to existing human technologies. The scorpion, especially the forest scorpion, has a unique ability to detect subtle vibrations, which is attributed to the microcrack-shaped slit sensillum on its legs. Here, the biological sensing mechanism of the typical scorpion (Heterometrus petersii) was intensively studied in order to newly design and significantly improve the flexible strain sensors. Benefiting from the easy-crack property of polystyrene (PS) and using the solvent-induced swelling as well as double template transferring method, regular and controllable microcrack arrays were successfully fabricated on top of polydimethylsiloxane (PDMS). Using this method, any physical damage to PDMS could be effectively avoided. More fortunately, this bio-inspired crack arrays fabricated in this work also had a radial-like pattern similar to the slit sensillum of the scorpion, which was another unexpected imitation. The gauge factor (GF) of the sensor was conservatively evaluated at 5888.89 upon 2% strain and the response time was 297 ms. Afterward, it was demonstrated that the bio-inspired regular microcrack arrays could also significantly enhance the performance of traditional strain sensors, especially in terms of the sensitivity and response time. The practical applications, such as the detection of human motions and surface folding, were also tested in this work, with the results showing significant potential applications in numerous fields. This work changes the traditional waste cracks on some damaged products into valuable things for ultrasensitive mechanical sensors. Moreover, with this manufacturing technique, we could easily realize the simple, low cost and large-scale fabrication of advanced bioinpired sensors.

14.
Nanoscale ; 9(3): 1166-1173, 2017 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-28009874

RESUMO

Functional electronics has promising applications, including highly advanced human-interactive devices and healthcare monitoring. Here, we present a unique printable micron-scale cracked strain sensor (PMSCSS), which is bioinspired by a spider's crack-shaped lyriform slit organ. The PMSCSS is fabricated by a facile process that utilizes screen-printing to coat carbon black (CB) ink onto a paper substrate. With a certain bending radius, a cracked morphology emerged on the solidified ink layer. The working principle of the PMSCSS is prominently attributed to the strain-dependent variation in resistance due to the reconnection-disconnection of the crack fracture surfaces. The device shows appealing performances, with superfast response times (∼0.625 ms) and high sensitivity (gauge factor = 647). The response time surpasses most recent reports, and the sensitivity is comparable. We demonstrate the application of the PMSCSSs as encoders, which have good linearity and negligible hysteresis. Also, the sensor can be manipulated as a vibration detector by monitoring human-motion disturbances. According to the sensory information, some details of movements can be deduced.


Assuntos
Actigrafia/instrumentação , Movimento , Vibração , Dispositivos Eletrônicos Vestíveis , Humanos , Movimento (Física)
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