On the Activity of Materials

Fratzl, Peter; Schäffner, Wolfgang

doi:10.1515/9783110562064-002

Cited by 5 publications

(5 citation statements)

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“…After the idea of nano- and micromachines that carry out medical tasks inside a patient’s body has been a dream for several decades, the progress in nanotechnology at the end of the last century made the fabrication of motile nano- and microparticles (so-called active particles) possible. − During the last two decades, a large number of artificial motile nano- and microparticles that utilize various mechanisms for propulsion have been developed, ,− and fascinating future applications of these particles have been envisaged in fields like medicine, − where they could be used for targeted drug delivery, − materials science, − where they could be used to form active crystals − and other new types of matter, and environmental care. ,− …”

Section: Introductionmentioning

confidence: 99%

Acoustic Propulsion of Nano- and Microcones: Dependence on the Viscosity of the Surrounding Fluid

Voß

Wittkowski

2022

Langmuir

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This article investigates how the acoustic propulsion of cone-shaped colloidal particles that are exposed to a traveling ultrasound wave depends on the viscosity of the fluid surrounding the particles. Using acoustofluidic computer simulations, we found that the propulsion of such nano-and microcones decreases strongly and even changes sign for increasing shear viscosity. In contrast, we found only a weak dependence of the propulsion on the bulk viscosity. The obtained results are in line with the findings of previous theoretical and experimental studies.

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Section: Introductionmentioning

confidence: 99%

Acoustic Propulsion of Nano- and Microcones: Dependence on the Viscosity of the Surrounding Fluid

Voß

Wittkowski

2022

Langmuir

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“…All these trends require new materials to be implemented. [ 64 ] A biologically inspired robotic material should be able to sense, actuate, self‐control and interact with the environment, but without the need of bulky electronics and complex computing. [ 25 ] This vision requires future robotic materials to be increasingly “life‐like” and one of the most important principles behind “life‐like” materials is that they should function out of equilibrium, allowing to realize synthetic material systems that are dynamic, autonomous, interactive and communicative.…”

Section: Discussionmentioning

confidence: 99%

Light‐Fueled Nonreciprocal Self‐Oscillators for Fluidic Transportation and Coupling

et al. 2023

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based soft robotics. [9,10] These robots often capture intriguing design principles from nature, being able to locomote, [11][12][13][14] exhibit functions such as grasping, [15] object recognition, [16] and cilia-like motion. [17][18][19][20][21] Conventionally, the robotic movements are determined by on-purpose field operations. [22][23][24] Thus they require sophisticated design, programming, and control of the field source to achieve on-demand robotic movements.Another nature-inspired principle arises from driving the responsive materials out of equilibrium, allowing us to realize synthetic material systems that are dynamic, autonomous, interactive and communicative. [25] In the context of responsive-material-based soft robots, this principle can yield a radical change in the correlation between the stimulus and the response. First, the stimulus field is no more considered as a control-type operation but instead, it serves as a constant energy source to sustain the material motion without human influence. [26][27][28] Second, the specific form of movement relies on the interaction between the active structure and its surrounding environment, providing the material with the ability to autonomously respond to environmental changes. [29] To follow the above bioinspiration scheme, the key is to attain a self-oscillating material construct that mechanically vibrates under a constant stimulus field. [28][29][30] Self-sustained motions have been studied in non-equilibrium material systems driven by, for example, light, [31] heat, [32] and chemical reactions. [33] The mechanisms include self-shadowing, [34] mechanical zeroelastic-energy mode, [35] Belousov-Zhabotinsky reaction, [36] self-regulation between photoisomerization efficiency (change of cis life-time), phase transitions of the molecular assembly (crystallinity), [37][38][39] etc. Based on those mechanisms, dissipative robotic systems displaying self-sustained walking, swimming, object transportation and electric power generation, have been demonstrated. [40][41][42][43][44] However, the use of self-oscillating materials in microfluidics is rarely reported, [42,45] due to the fact that most self-oscillating structures are not able to generate sufficient motions in fluids and more importantly, the typical reciprocal oscillation does not produce effective fluid-structure interaction (pumping), which highly relies on nonreciprocal strokes. Reports demonstrating a photo-deforming strips with coupled twisting and bending motions as well as travellingwave deformation in air or solutions unveil the possibility of Light-fueled self-oscillators based on soft actuating materials have triggered novel designs for small-scale robotic constructs that self-sustain their motion at non-equilibrium states and possess bioinspired autonomy and adaptive functions. However, the motions of most self-oscillators are reciprocal, which hinders their use in sophisticated biomimetic functions such as fluidic transportation. Here, an optically powered soft material strip that can perfor...

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“…[ 53 ] To adapt to the environment and self‐regulate their action in response to it, living entities have exploited efficient approaches to address this process by functioning around instabilities that are maintained in a controllable manner. [ 54 ] Taking the well‐known Venus flytrap as an example, the fast closure of the trap results from the snap‐buckling instability, where a small perturbation can trigger the onset of the instability and push the system transiently from one unstable state toward the other one. [ 55 ] Counterintuitively, the leaf is not operating in its global energy minimum state but in an intermediate unstable state, which enables the occurrence of rapid closure.…”

Section: Discussionmentioning

confidence: 99%

A Scalable, Incoherent‐Light‐Powered, Omnidirectional Self‐Oscillator

Nemati

Deng

et al. 2023

Advanced Intelligent Systems

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Light‐fueled self‐oscillators based on stimuli‐responsive soft materials have been explored toward the realization of a myriad of nonequilibrium robotic functions, such as adaptation, autonomous locomotion, and energy conversion. However, the high energy density and unidirectionality of the light field, together with the unscalable design of the existing demonstrations, hinder their further implementation. Herein, a light‐responsive lampshade‐like smart material assembly as a new self‐oscillator model that is unfettered by the abovementioned challenges, is introduced. Liquid crystal elastomer with low phase transition temperature is used as the photomechanical component to provide twisting movement under low‐intensity incoherent light field. A spiral lampshade frame ensures an equal amount of light being shadowed as negative feedback to sustain the oscillation upon constant light field from omnidirectional excitation (0°–360° azimuth and 20°–90° zenith). Different‐sized oscillators with 6, 15, and 50 mm in diameter are fabricated to prove the possibility of scaling up and down the concept. The results provide a viewpoint on the fast‐growing topic of self‐oscillation in soft matter and new implications for self‐sustained soft robots.

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On the Activity of Materials

Cited by 5 publications

References 0 publications

Acoustic Propulsion of Nano- and Microcones: Dependence on the Viscosity of the Surrounding Fluid

Acoustic Propulsion of Nano- and Microcones: Dependence on the Viscosity of the Surrounding Fluid

Light‐Fueled Nonreciprocal Self‐Oscillators for Fluidic Transportation and Coupling

A Scalable, Incoherent‐Light‐Powered, Omnidirectional Self‐Oscillator

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