Form and Object Garcia, Tristan; Ohm, Mark Allan; Cogburn, Jon
03/2014
eBook
What is a thing? What is an object? Tristan Garcia decisively overturns 100 years of Heideggerian orthodoxy about the supposedly derivative nature of objects to put forward a new theory of ontology ...that gives us deep insights into the world and our place in it.
Continuous liquid interface production of 3D objects Tumbleston, John R.; Shirvanyants, David; Ermoshkin, Nikita ...
Science (American Association for the Advancement of Science),
03/2015, Letnik:
347, Številka:
6228
Journal Article
Recenzirano
Odprti dostop
Additive manufacturing processes such as 3D printing use time-consuming, stepwise layer-by-layer approaches to object fabrication. We demonstrate the continuous generation of monolithic polymeric ...parts up to tens of centimeters in size with feature resolution below 100 micrometers. Continuous liquid interface production is achieved with an oxygen-permeable window below the ultraviolet image projection plane, which creates a "dead zone" (persistent liquid interface) where photopolymerization is inhibited between the window and the polymerizing part. We delineate critical control parameters and show that complex solid parts can be drawn out of the resin at rates of hundreds of millimeters per hour. These print speeds allow parts to be produced in minutes instead of hours.
In polymer chemistry, mechanical energy degrades polymeric chains. In contrast, in nature, mechanical energy is often used to create new polymers. This mechanically stimulated growth is a key ...component of the robustness of biological materials. A synthetic system in which mechanical force initiates polymerization will provide similar robustness in polymeric materials. Here we show a polymerization of acrylate monomers initiated and controlled by mechanical energy provided by ultrasonic agitation. The activator for an atom-transfer radical polymerization is generated using piezochemical reduction of a Cu(II) precursor complex, which thus converts a mechanical activation of piezoelectric particles to the synthesis of a new material. This polymerization reaction has some characteristics of controlled radical polymerization, such as narrow molecular-weight distribution and linear dependence of the polymeric chain length on the time of mechanical activation. This new method of controlled radical polymerization complements the existing methods to synthesize commercially useful well-defined polymers.
Zusammenfassung Die Studie untersucht den Zusammenhang in Bezug auf die Bewertung der Unbekanntheit von Objekten von Kindern und Studienteilnehmenden im Erwachsenenalter. Dazu wurden 23 Kinder im ...Alter von 3;0 bis 5;11 Jahren zu 16 Objekten der ,,Novel Object and Unusual Name (NOUN) Datenbank" (Horst, 2016) befragt. Das Konzept der Unbekanntheit wurde durch Fragen zu den Aspekten Benennfähigkeit und Einschätzung der Identität der Objekte operationalisiert. Die ermittelten kindlichen Scores der Bekanntheitsaspekte Vertrautheit und Benennfähigkeit wurden mit den in der NOUN-Datenbank vorliegenden Scores erwachsener Versuchspersonen auf Zusammenhänge hin analysiert. Hinsichtlich des Zusammenhangs der Vertrautheit-Scores waren die Ergebnisse abhängig vom Alter der Kinder uneinheitlich. Es zeigte sich nur für die Vierjährigen ein signifikanter und großer Zusammenhang zu den Einschätzungen der Erwachsenen, für die Drei- und Fünfjährigen wurde kein signifikanter Zusammenhang festgestellt. Bezüglich der Benennfähigkeit-Scores zeigte sich eine signifikante und hohe Korrelation in den Einschätzungswerten von erwachsenen und kindlichen Werten für alle kindlichen Altersgruppen (Dreijährige, Vierjährige, Fünfjährige). Der Aspekt der Identität stellte für die Kinder vor allem in seiner Operationalisierung eine deutliche Hürde dar.
Abstract The study examines the relationship between the evaluation of the novelty of objects by children and study participants in adulthood. For this purpose, 23 children aged 3;0 to 5;11 were asked about 16 objects from the "Novel Object and Unusual Name (NOUN) database" (Horst, 2016). The concept of novelty was operationalised through questions on the aspects of familiarity, naming ability and the identity of the objects. The child scores determined for the familiarity and naming ability aspects were analysed for correlations with the scores of adult test subjects available in the NOUN database. With regard to the correlation between the familiarity scores, the results were inconsistent depending on the age of the children. Only the four-year-olds showed a significant and large correlation with the assessments of the adults; no significant correlation was found for the three- and five-year-olds. With regard to the naming ability scores, there was a significant and high correlation in the assessment values of adult and child values for all child age groups (three-year-olds, four-year-olds, five-year-olds). The aspect of identity represented a clear hurdle for the children, particularly in its operationalisation.
Voxelated liquid crystal elastomers Ware, Taylor H.; McConney, Michael E.; Wie, Jeong Jae ...
Science (American Association for the Advancement of Science),
02/2015, Letnik:
347, Številka:
6225
Journal Article
Recenzirano
Dynamic control of shape can bring multifunctionality to devices. Soft materials capable of programmable shape change require localized control of the magnitude and directionality of a mechanical ...response. We report the preparation of soft, ordered materials referred to as liquid crystal elastomers.The direction of molecular order, known as the director, is written within local volume elements (voxels) as small as 0.0005 cubic millimeters. Locally, the director controls the inherent mechanical response (55% strain) within the material. In monoliths with spatially patterned director, thermal or chemical stimuli transform flat sheets into three-dimensional objects through controlled bending and stretching. The programmable mechanical response of these materials could yield monolithic multifunctional devices or serve as reconfigurable substrates for flexible devices in aerospace, medicine, or consumer goods.
Additive manufacturing (AM) is the process of printing 3D objects in a layer‐by‐layer manner. Polymers and their composites are some of the most widely used materials in modern industries and are of ...great interest in the field of AM due to their vast potential for various applications, especially in the medical, aerospace, and automotive industries. Many studies have been conducted to develop new polymer materials for AM techniques, which include vat photopolymerization, material jetting, powder bed fusion, material extrusion, binder jetting, and sheet lamination. Although several reviews on the development of polymer materials for AM have been published, most of them only focus on a specific application, process, or type of material. Therefore, this article serves to provide a comprehensive review on the progress in polymer material development for AM techniques. It begins with an introduction to different AM techniques, followed by highlighting the progress of their development. Material requirements, notable advances in newly developed materials and their potential applications are discussed in detail and summarized. This review concludes by identifying the major challenges currently encountered in using AM for polymer materials and providing insights into the valuable opportunities it presents, in hopes of spurring further development in this field.
Additive manufacturing (AM) has emerged as a disruptive technology that is utilized to fabricate products with complex geometries to enable great design freedom. This article reviews the recent progress on polymer materials for various AM techniques. Material requirements, notable advances in new AM polymer materials, and their potential applications are discussed and major challenges and future research directions are identified.
Biological materials, such as bones, teeth and mollusc shells, are well known for their excellent strength, modulus and toughness
. Such properties are attributed to the elaborate layered ...microstructure of inorganic reinforcing nanofillers, especially two-dimensional nanosheets or nanoplatelets, within a ductile organic matrix
. Inspired by these biological structures, several assembly strategies-including layer-by-layer
, casting
, vacuum filtration
and use of magnetic fields
-have been used to develop layered nanocomposites. However, how to produce ultrastrong layered nanocomposites in a universal, viable and scalable manner remains an open issue. Here we present a strategy to produce nanocomposites with highly ordered layered structures using shear-flow-induced alignment of two-dimensional nanosheets at an immiscible hydrogel/oil interface. For example, nanocomposites based on nanosheets of graphene oxide and clay exhibit a tensile strength of up to 1,215 ± 80 megapascals and a Young's modulus of 198.8 ± 6.5 gigapascals, which are 9.0 and 2.8 times higher, respectively, than those of natural nacre (mother of pearl). When nanosheets of clay are used, the toughness of the resulting nanocomposite can reach 36.7 ± 3.0 megajoules per cubic metre, which is 20.4 times higher than that of natural nacre; meanwhile, the tensile strength is 1,195 ± 60 megapascals. Quantitative analysis indicates that the well aligned nanosheets form a critical interphase, and this results in the observed mechanical properties. We consider that our strategy, which could be readily extended to align a variety of two-dimensional nanofillers, could be applied to a wide range of structural composites and lead to the development of high-performance composites.
The most pressing challenges for light‐driven hydrogel actuators include reliance on UV light, slow response, poor mechanical properties, and limited functionalities. Now, a supramolecular design ...strategy is used to address these issues. Key is the use of a benzylimine‐functionalized anthracene group, which red‐shifts the absorption into the visible region and also stabilizes the supramolecular network through π–π interactions. Acid–ether hydrogen bonds are incorporated for energy dissipation under mechanical deformation and maintaining hydrophilicity of the network. This double‐crosslinked supramolecular hydrogel developed via a simple synthesis exhibits a unique combination of high strength, rapid self‐healing, and fast visible‐light‐driven shape morphing both in the wet and dry state. As all of the interactions are dynamic, the design enables the structures to be recycled and reprogrammed into different 3D objects.
A photoresponsive hydrogel was constructed by using a supramolecular design strategy. A red‐shifted anthracene group furnishes the system with fast photo‐actuation. Hydrogen bonding, π–π interactions, and anthracene photodimerization results in an actuator with high mechanical strength, fast self‐healing, and recyclability.
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