Temperature responsive 4D liquid crystal microactuators fabricated by direct laser writing by two-photon polymerization

Over the past decade, progress in direct laser writing by two-photon polymerization (DLW-TPP) of stimuli-responsive materials has made considerable inroads into the realization of microactuators. With the focus on performing complex tasks such as walking, grasping, or delivering drugs, these actuators require a controlled preprogrammed actuation. Liquid crystalline microactuators enable such programmed movement when the mesogenic alignment can be successfully controlled. To date, this has necessitated low crosslink density networks, which are not readily conducive to the fabrication of 3D geometries. Herein, a liquid crystalline photoresist is reported, which results in a highly crosslinked network, that permits fabrication of 4D microactuators having a highly crosslinked network in which the molecular alignment is determined by the alignment layers in the cell construct. In addition to controllable deformation of the microactuators, they also display a characteristic and unique polarization color that can be used for both identification and reporting in real time, enabling their integration into sensing and anti-anticounterfeiting microdevices

Dermatophylosis in Santa Inês sheep from Distrito Federal

Relataram-se quatro casos de dermatofilose em ovinos da raça Santa Inês, no período de um ano. Microscopicamente observaram-se filamentos na forma de "trilho de bonde" e zoósporos nos quatro casos. A tentativa do isolamento do microrganismo foi realizada por meio do método de Haalstra e em apenas um caso obteve-se sucesso, observando-se colônias de aparência lisa, formato circular, cor amarelada e hemolítica em ágar sangue. O exame direto com coloração de Gram mostrou-se um método bastante eficiente na confirmação da presença do microrganismo afetando a epiderme em razão da morfologia típica do agente.Four cases of dermatophylosis were reported in Santa Inês sheep in a study period of one year. Microscopically, septate filaments and coccoid forms zoospores were observed. Attempts to isolate the microorganisms were accomplished using Haastra's method and it was successful in only one case. Dermatophilus congolensis samples have grown on blood agar, colonies where hemolytic, small, round and pigmentation vary from yellow to orange. The gram staining method was efficient to confirm the presence of the microorganism affecting the epidermis due to typical morphology of the agent

Bioinspired light-driven soft robots based on liquid crystal polymers

Nature is a constant source of inspiration for materials scientists, fueling the dream of mimicking life-like motion and tasks in untethered, man-made devices. Liquid crystalline polymers (LCPs) programmed to undergo three-dimensional shape changes in response to light are promising materials for fulfilling this dream. The successful development of autonomous, highly controlled light-driven soft robots calls for an understanding of light-driven actuation, advancements in material function and performance, and progress in engineering principles for transforming actuation into life-like motions, from simple bending to walking, for example. This tutorial review includes an introduction to liquid crystal (LC)-based materials and highlights developments in light-responsive LC polymers, shape programmability and sustained motions to finally achieve bioinspired untethered soft robots able to perform locomotion and tasks

Intoxicação crônica por cobre em ovinos: conduta para o diagnóstico conclusivo

Descreveram-se os sinais clínicos e achados anatomopatológicos da intoxicação crônica por cobre em um ovino da raça Texxel e definiu-se a conduta diagnóstica correta para confirmação da enfermidade. Um ovino foi encaminhado ao setor de patologia com histórico de apatia, hemoglobinúria e morte em dois a três dias. No exame necroscópico, observaram-se icterícia e edema subcutâneo, fígado aumentado de volume e amarelado e rins escuros. No exame histológico, observaram-se necrose zonal aleatória e acentuada no fígado, necrose epitelial tubular, gotas hialinas e cilindros marrom-alaranjados em túbulos coletores dos rins. O histórico alimentar, a sensibilidade de espécie/raça, o quadro clínico, as alterações macroscópicas e microscópicas sugeriram o quadro de intoxicação crônica por cobre. A confirmação diagnóstica somente foi possível após a marcação de pigmentos de cobre pela técnica histoquímica de Ulzmann e pela quantificação de cobre em matéria seca de fígado e rins, cujos valores foram mais altos que o normal

Brush-paintable, temperature and light responsive triple shape-memory photonic coatings based on micrometer-sized cholesteric liquid crystal polymer particles

In this work, light and temperature responsive, brush-painted photonic coatings exhibiting three different colored and surface topographical states are reported. The different states arise from the use of cholesteric liquid-crystalline micrometer-sized polymer particles as shape-memory photonic pigments that are dispersed in a shape-memory binder. The first temporal state is induced by compressing the photonic particles at high temperature, resulting in blueshift of the structural color. The second temporal state is obtained by embossing a diffractive grating on the surface at an intermediate temperature leading to a relief topography and a rainbow optical effect. Both optical and surface topographical changes coexist and are stable at room temperature until they are reverted independently either by heating or locally by light illumination. Multicolored paints that reflect selectively left-handed or right-handed polarized light are developed to create arbitrary polarization-dependent multicolor and topographical brush-painted patterns. These temperature and light responsive triple shape-memory photonic paints have potential applications as battery-free optical sensors, responsive decoration, and smart adhesives

Liquid crystal networks on thermoplastics : reprogrammable photo-responsive actuators

Arbitrary shape (re)programming is appealing for fabricating, untethered shape‐morphing photo actuators with intricate configurations and features. We present re‐programmable light responsive thermoplastic actuators with arbitrary initial shapes through spray‐coating of polyethylene terephthalate (PET) with an azobenzene‐doped light responsive liquid crystal network (LCN). The initial geometry of the actuator is controlled by thermally shaping and fixing the thermoplastic PET, allowing arbitrary shapes, including origami‐like folds and left and right handed helicity within a single sample. The thermally fixed geometries can be reversibly actuated through light exposure, with fast, reversible area‐specific actuation, such as winding, unwinding and unfolding. By shape re‐programming, the same sample can be re‐designed and light actuated again. The strategy presented here demonstrates easy fabrication of mechanically robust, recyclable, photo‐responsive actuators with highly tuneable geometries and actuation modes

Light-Driven Continual Oscillatory Rocking of a Polymer Film

Achieving oscillatory motion in polymers without requiring on/off switching of stimuli is a current challenge. Hereby, a free-standing liquid crystal polymer (LCP) is demonstrated to undergo a sustained oscillatory motion when triggered by light, moving back and forth, resembling the motion of a rocking-chair. Two polymer films having different azobenzene photo-switches have been studied, revealing photoswitch requirements as well as illumination conditions necessary to sustain oscillations. The motion presented here shows how feedback loops involving light-triggered actuation, self-shadowing and a shifting center of gravity can be utilized to achieve self-sustained motion in free-standing polymers