Materials as Machines McCracken, Joselle M.; Donovan, Brian R.; White, Timothy J.
Advanced materials (Weinheim),
05/2020, Volume:
32, Issue:
20
Journal Article
Peer reviewed
Machines are systems that harness input power to extend or advance function. Fundamentally, machines are based on the integration of materials with mechanisms to accomplish tasks—such as generating ...motion or lifting an object. An emerging research paradigm is the design, synthesis, and integration of responsive materials within or as machines. Herein, a particular focus is the integration of responsive materials to enable robotic (machine) functions such as gripping, lifting, or motility (walking, crawling, swimming, and flying). Key functional considerations of responsive materials in machine implementations are response time, cyclability (frequency and ruggedness), sizing, payload capacity, amenability to mechanical programming, performance in extreme environments, and autonomy. This review summarizes the material transformation mechanisms, mechanical design, and robotic integration of responsive materials including shape memory alloys (SMAs), piezoelectrics, dielectric elastomer actuators (DEAs), ionic electroactive polymers (IEAPs), pneumatics and hydraulics systems, shape memory polymers (SMPs), hydrogels, and liquid crystalline elastomers (LCEs) and networks (LCNs). Structural and geometrical fabrication of these materials as wires, coils, films, tubes, cones, unimorphs, bimorphs, and printed elements enables differentiated mechanical responses and consistently enables and extends functional use.
Advances in the development and integration of responsive materials are comprehensively surveyed with a particular emphasis on robotics, spanning shape‐memory alloys, piezoelectrics, electroactive polymers, shape‐memory polymers, hydrogels, and liquid crystalline polymer networks and elastomers.
This field experiment manipulated the racial framing of a reading on human genetic disease to explore whether racial terminology in the biology curriculum affects how adolescents explain and respond ...to the racial achievement gap in American education. Carried out in a public high school in the San Francisco Bay Area, students recruited for the study (N = 86) were randomly assigned to read either a racially framed or a nonracially framed textbook passage on genetic diseases as part of a unit on Mendelian genetics. Afterwards, they responded to two instruments measuring belief in the biological/genetic basis of race and one measure that recorded their explanations of the racial achievement gap and their willingness to volunteer their free time to fix it. Results demonstrated that students in the racially framed condition exhibited significantly greater agreement in the genetic basis of racial difference than students in the nonracially framed condition. A content analysis of students' explanations of the achievement gap also demonstrated that a significantly greater proportion of students gave genetic explanations of the achievement gap in the racially framed condition compared to the other condition. Furthermore, students' prior beliefs about race interacted with the reading treatments to affect students' willingness to fix the racial achievement gap.
Liquid crystalline elastomers (LCE) are stimuli‐responsive materials with a distinguished mechanical response. LCE have been subject to numerous recent functional examinations in robotics, health ...sciences, and optics. The liquid crystallinity of the elastomeric polymer networks of LCE are largely derived from liquid crystalline monomer precursors. Recent reports have utilized commercially available liquid crystalline diacrylate monomers in chain extension reactions to prepare LCE. These reactions have been largely based on monomeric precursors originally to enhance the and thermal stability of optical films. Here, it is demonstrated that preparing LCE via a liquid crystalline diacrylate with reduced mesogen–mesogen interaction enhances and sharpens the thermotropic actuation of these materials. Robust composition‐response correlations are demonstrated in LCE prepared by three common synthetic methods. The enhanced thermotropic response of LCE prepared from this precursor increases the thermomechanical efficiency by sixfold. Accordingly, this work addresses important limitations in utilizing the thermal response of LCE in robotics, health care, and consumer goods.
Numerous reports document liquid crystalline elastomers (LCE) based on commercially available liquid crystalline monomers containing three phenyl rings that demonstrate exceptional stimuli‐induced mechanical response in functional applications in robotics, health care, aerospace, and consumer goods. Here, a LCE monomer with reduced intermolecular coupling is incorporated to lower actuation onset temperature and enhance the thermomechanical efficiency of LCE sixfold.
ABSTRACT
Even though human racial difference has been a longstanding topic of the school biology curriculum, there is little evidence that contemporary biology textbooks challenge stereotypical ...racial beliefs that are based in biological thinking. Rather, the modern biology curriculum may be a place where such beliefs about race are perpetuated unwittingly. Drawing upon a theoretical framework of racial conceptualization based in psychological essentialism, this paper argues that biology textbook curricula ought to directly challenge problematic and unscientific racial beliefs to increase understanding of human genetic variation and decrease racial beliefs associated with prejudice.
Recently, it has been argued that improving students' genomics literacy could prevent students from developing erroneous beliefs about social identity, such as the belief that racial groups differ ...cognitively and behaviorally because of their genes; a belief called genetic essentialism. To date, however, little research has explored if or how a conceptual understanding of genomics protects against the development of genetic essentialism. Using a randomized control trial (RCT) (N = 721, 9th–12th graders), we explore if students with more genomics literacy are more able to conceptually change their genetic essentialist beliefs after engaging in a learning experience designed to refute essentialist thinking. The results of the RCT demonstrated that students with higher genomics literacy (relative to those with lower genomics literacy) exhibited greater reductions in the perception of racial differences and greater reductions in belief in genetic essentialism after learning how patterns of human genetic variation refute genetic essentialism. These results suggest that genetics education can protect students from developing a belief in genetic essentialism when it provides them with opportunities to learn multifactorial genetics and population thinking in conjunction with how these concepts refute essentialist thinking.
The stereotype of the "gold digger" has had a fascinating trajectory in twentieth-century America, from tales of greedy flapper-era chorus girls to tabloid coverage of Anna Nicole Smith and her ...octogenarian tycoon husband. The term entered American vernacular in the 1910s as women began to assert greater power over courtship, marriage, and finances, threatening men's control of legal and economic structures. Over the course of the century, the gold digger stereotype reappeared as women pressed for further control over love, sex, and money while laws failed to keep pace with such realignments. The gold digger can be seen in silent films, vaudeville jokes, hip hop lyrics, and reality television. Whether feared, admired, or desired, the figure of the gold digger appears almost everywhere gender, sexuality, class, and race collide. This fascinating interdisciplinary work reveals the assumptions and disputes around women's sexual agency in American life, shedding new light on the cultural and legal forces underpinning romantic, sexual, and marital relationships.
During the early twentieth century, individuals and organizations from across the political spectrum launched a sustained effort to eradicate forced prostitution, commonly known as "white slavery." ...White Slave Crusades is the first comparative study to focus on how these anti-vice campaigns also resulted in the creation of a racial hierarchy in the United States. _x000B_Focusing on the intersection of race, gender, and sex in the antiprostitution campaigns, Brian Donovan analyzes the reactions of native-born whites to new immigrant groups in Chicago, to African Americans in New York City, and to Chinese immigrants in San Francisco. Donovan shows how reformers employed white slavery narratives of sexual danger to clarify the boundaries of racial categories, allowing native-born whites to speak of a collective "us" as opposed to a "them." These stories about forced prostitution provided an emotionally powerful justification for segregation, as well as other forms of racial and sexual boundary maintenance in urban America.
Genetic concepts are regularly used in arguments about racial inequality. This review summarizes research about the relationship between genetics education and a particular form of racial prejudice ...known as genetic essentialism. Genetic essentialism is a cognitive form of prejudice that is used to rationalize inequality. Studies suggest that belief in genetic essentialism among genetics students can be increased or decreased based on what students learn about human genetics and why they learn it. Research suggests that genetics education does little to prevent the development of genetic essentialism, and it may even exacerbate belief in it. However, some forms of genetics education can avert this problem. In particular, if instructors teach genetics to help students understand the flaws in genetic essentialist arguments, then it is possible to reduce belief in genetic essentialism among biology students. This review outlines our knowledge about how to accomplish this goal and the research that needs to be done to end genetic essentialism through genetics education.
This review suggests that genetics education could increase or decrease prejudiced beliefs about race depending on what it teaches students about genetics and why it teaches them genetics. To reduce racial prejudice in society, genetics educators need to teach students how the science of genomics refutes naive beliefs about race.
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