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1.
Proc Natl Acad Sci U S A ; 120(2): e2211416120, 2023 01 10.
Artículo en Inglés | MEDLINE | ID: mdl-36595665

RESUMEN

Soft systems that respond to external stimuli, such as heat, magnetic field, and light, find applications in a range of fields including soft robotics, energy harvesting, and biomedicine. However, most of the existing systems exhibit nondirectional, nastic movement as they can neither grow nor sense the direction of stimuli. In this regard, artificial systems are outperformed by organisms capable of directional growth in response to the sense of stimuli or tropic growth. Inspired by tropic growth schemes of plant cells and fungal hyphae, here we report an artificial multistimuli-responsive tropic tip-growing system based on nonsolvent-induced phase separation of polymer solution, where polymer precipitates as its solvent dissolves into surrounding nonsolvent. We provide a theoretical framework to predict the size and velocity of growing precipitates and demonstrate its capability of sensing the directions of gravity, mechanical contact, and light and adjusting its growing direction in response. Exploiting the embedded physical intelligence of sensing and responding to external stimuli, our soft material system achieves multiple tasks including printing 3D structures in a confined space, bypassing mechanical obstacles, and shielded transport of liquids within water.


Asunto(s)
Células Vegetales , Polímeros , Gravitación
2.
Proc Natl Acad Sci U S A ; 111(22): 8067-70, 2014 Jun 03.
Artículo en Inglés | MEDLINE | ID: mdl-24847065

RESUMEN

Fish respire through gills, which have evolved to extract aqueous oxygen. Fish gills consist of filaments with well-ordered lamellar structures, which play a role in maximizing oxygen diffusion. It is interesting that when we anatomically observe the gills of various fish species, gill interlamellar distances (d) vary little among them, despite large variations in body mass (Mb). Noting that the small channels formed by densely packed lamellae cause significant viscous resistance to water flow, we construct and test a model of oxygen transfer rate as a function of the lamellar dimensions and pumping pressure, which allows us to predict the optimal interlamellar distance that maximizes the oxygen transfer rate in the gill. Comparing our theory with biological data supports the hypothesis that fish gills have evolved to form the optimal interlamellar distances for maximizing oxygen transfer. This explains the weak scaling dependence of d on Mb: d ∼ Mb(1/6).


Asunto(s)
Evolución Biológica , Branquias/anatomía & histología , Branquias/irrigación sanguínea , Modelos Biológicos , Perciformes/anatomía & histología , Animales , Branquias/fisiología , Microfluídica , Oxígeno/metabolismo , Perciformes/fisiología , Respiración , Agua/metabolismo
3.
Nat Commun ; 10(1): 3564, 2019 08 08.
Artículo en Inglés | MEDLINE | ID: mdl-31395861

RESUMEN

In plants, plasmodesmata (PD) are nanopores that serve as channels for molecular cell-to-cell transport. Precise control of PD permeability is essential to regulate processes such as growth and tissue patterning, photoassimilate distribution and defense against pathogens. Callose deposition modulates PD transport but little is known of the rapid events that lead to PD closure in response to tissue damage or osmotic shock. We propose a mechanism of PD closure as a result of mechanosensing. Pressure forces acting on the dumbbell-shaped ER-desmotubule complex cause it to be displaced from its equilibrium position, thus closing the PD aperture. The filamentous protein tethers that link the plasma membrane to the ER-desmotubule complex play a key role in determining the selectivity of the PD pore. This model of PD control compares favorably with experimental data on the pressure-generated closure of PD.


Asunto(s)
Comunicación Celular/fisiología , Permeabilidad de la Membrana Celular/fisiología , Mecanotransducción Celular , Fenómenos Fisiológicos de las Plantas , Plasmodesmos/metabolismo , Transporte Biológico/fisiología , Retículo Endoplásmico/metabolismo , Glucanos/metabolismo , Nanoporos , Presión Osmótica/fisiología
4.
J R Soc Interface ; 16(161): 20190556, 2019 12.
Artículo en Inglés | MEDLINE | ID: mdl-31795862

RESUMEN

Shaping a plant root into an ideal structure for water capture is increasingly important for sustainable agriculture in the era of global climate change. Although the current genetic engineering of crops favours deep-reaching roots, here we show that nature has apparently adopted a different strategy of shaping roots. We construct a mathematical model for optimal root length distribution by considering that plants seek maximal water uptake at the metabolic expenses of root growth. Our theory finds a logarithmic decrease of root length density with depth to be most beneficial for efficient water uptake, which is supported by biological data as well as our experiments using root-mimicking network systems. Our study provides a tool to gauge the relative performance of root networks in transgenic plants engineered to endure a water deficit. Moreover, we lay a fundamental framework for mechanical understanding and design of water-absorptive growing networks, such as medical and industrial fluid transport systems and soft robots, which grow in porous media including soils and biotissues.


Asunto(s)
Modelos Biológicos , Raíces de Plantas/crecimiento & desarrollo , Suelo , Agua/metabolismo
5.
PLoS One ; 14(1): e0204191, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-30703086

RESUMEN

In the airway network of a human lung, the airway diameter gradually decreases through multiple branching. The diameter reduction ratio of the conducting airways that transport gases without gas exchange is 0.79, but this reduction ratio changes to 0.94 in acinar airways beyond transitional bronchioles. While the reduction in the conducting airways was previously rationalized on the basis of Murray's law, our understanding of the design principle behind the acinar airways has been far from clear. Here we elucidate that the change in gas transfer mode is responsible for the transition in the diameter reduction ratio. The oxygen transfer rate per unit surface area is maximized at the observed geometry of acinar airways, which suggests the minimum cost for the construction and maintenance of the acinar airways. The results revitalize and extend the framework of Murray's law over an entire human lung.


Asunto(s)
Bronquiolos/anatomía & histología , Modelos Biológicos , Oxígeno/metabolismo , Alveolos Pulmonares/anatomía & histología , Respiración , Células Acinares/fisiología , Bronquiolos/citología , Bronquiolos/fisiología , Humanos , Tamaño de los Órganos/fisiología , Alveolos Pulmonares/fisiología
6.
Sci Robot ; 3(14)2018 01 24.
Artículo en Inglés | MEDLINE | ID: mdl-33141700

RESUMEN

Microrobots that are light and agile yet require no artificial power input can be widely used in medical, military, and industrial applications. As an actuation system to drive such robots, here we report a biologically inspired bilayer structure that harnesses the environmental humidity energy, with ratchets to rectify the motion. We named this actuator-ratchet system the hygrobot. The actuator uses a hygroscopically responsive film consisting of aligned nanofibers produced by directional electrospinning, which quickly swells and shrinks in lengthwise direction in response to the change of humidity. The ratchets based on asymmetric friction coefficients rectify oscillatory bending motion in a directional locomotion. We mathematically analyzed the mechanical response of the hygrobot, which allowed not only prediction of its performance but also the optimal design to maximize the locomotion speed given geometric and environmental constraints. The hygrobot sterilized a trail across an agar plate without any artificial energy supply.

7.
Ultrasonics ; 50(8): 798-802, 2010 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-20462624

RESUMEN

Although ultrasonic technology has been successfully adopted for semiconductor cleaning, a recent trend of extreme miniaturization of patterns calls for a novel process that can remove contaminant particles without damaging nanoscale patterns. Unstable bubble oscillations have been hypothesized to cause such surface damages, and here we show direct visualization results that a high acoustic pressure induces bubble instability leading to pattern damages. As a remedy for the conventional ultrasonic cleaning scheme, we introduce a novel cleaning system using dual transducers, in which one transducer generates bubbles with a high acoustic pressure in an acoustically isolated sub-chamber and the other drives the oscillation of bubbles around the cleaning area at a low acoustic pressure. The system is shown to achieve a high cleaning efficiency for submicron-sized particles while significantly suppressing the disruptive bubble instability thereby reducing the detachment of firmly attached nanoparticles. Comparison of the adhesion force of the firmly attached nanoparticles and the yield strength of nanopatterns allows us to anticipate that this scheme is capable of reducing damages of nanopatterns on semiconductor wafers and photomasks.

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