Gecko Adhesion in Space and Time: A Phylogenetic Perspective on the Scansorial Success Story

Abstract An evolutionary perspective on gecko adhesion was previously hampered by a lack of an explicit phylogeny for the group and of robust comparative methods to study trait evolution, an underappreciation for the taxonomic and structural diversity of geckos, and a dearth of fossil evidence bearing directly on the origin of the scansorial apparatus. With a multigene dataset as the basis for a comprehensive gekkotan phylogeny, model-based methods have recently been employed to estimate the number of unique derivations of the adhesive system and its role in lineage diversification. Evidence points to a single basal origin of the spinulate oberhautchen layer of the epidermis, which is a necessary precursor for the subsequent elaboration of a functional adhesive mechanism in geckos. However, multiple gains and losses are implicated for the elaborated setae that are necessary for adhesion via van der Waals forces. The well-supported phylogeny of gekkotans has demonstrated that convergence and parallelism in digital design are even more prevalent than previously believed. It also permits the reexamination of previously collected morphological data in an explicitly evolutionary context. Both time-calibrated trees and recently discovered amber fossils that preserve gecko toepads suggest that a fully-functional adhesive apparatus was not only present, but also represented by diverse architectures, by the mid-Cretaceous. Further characterization and phylogenetically-informed analyses of the other components of the adhesive system (muscles, tendons, blood sinuses, etc.) will permit a more comprehensive reconstruction of the evolutionary pathway(s) by which geckos have achieved their structural and taxonomic diversity. A phylogenetic perspective can meaningfully inform functional and performance studies of gecko adhesion and locomotion and can contribute to advances in bioinspired materials.

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3D Printable Resources for Engaging STEM Students in Laboratory Learning Activities and Outreach Programs: Inexpensive and User-Friendly Instrument Kits for Educators

MRS Advances ◽

10.1557/adv.2018.441 ◽

2018 ◽

Vol 3 (49) ◽

pp. 2937-2942 ◽

Cited By ~ 1

Author(s):

Lon A. Porter

Keyword(s):

3D Printing ◽

Mathematics Learning ◽

Digital Design ◽

Outreach Programs ◽

Stem Students ◽

3D Printed ◽

Design Software ◽

And Performance ◽

And Mathematics ◽

User Friendly

ABSTRACTContinued advances in digital design software and 3D printing methods enable innovative approaches in the development of new educational tools for laboratory-based STEM (science, technology, engineering and mathematics) learning. The decreasing cost of 3D printing equipment and greater access provided by university fabrication centers afford unique opportunities for educators to transcend the limitations of conventional modes of student engagement with analytical instrumentation. This work shares successful efforts at Wabash College to integrate user-friendly and inexpensive 3D printed instruments kits into introductory STEM coursework. The laboratory kits and activities described provide new tools for engaging students in the exploration of instrument design and performance. These experiences provide effective ways to assist active-learners in discovering the technology and fundamental principles of analysis and deliberately confront the “black box” perception of instrumentation.

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Stick or Slip: Adhesive Performance of Geckos and Gecko-Inspired Synthetics in Wet Environments

Integrative and Comparative Biology ◽

10.1093/icb/icz008 ◽

2019 ◽

Vol 59 (1) ◽

pp. 214-226 ◽

Cited By ~ 8

Author(s):

Alyssa Y Stark ◽

Christopher T Mitchell

Keyword(s):

Adhesive System ◽

Natural System ◽

Contact Structures ◽

Principal Mechanism ◽

Synthetic Adhesives ◽

Decision Making Behavior ◽

The Tropics ◽

Gecko Adhesion ◽

Adhesive Performance

Abstract The gecko adhesive system has inspired hundreds of synthetic mimics principally focused on replicating the strong, reversible, and versatile properties of the natural system. For geckos native to the tropics, versatility includes the need to remain attached to substrates that become wet from high humidity and frequent rain. Paradoxically, van der Waals forces, the principal mechanism responsible for gecko adhesion, reduce to zero when two contacting surfaces separate even slightly by entrapped water layers. A series of laboratory studies show that instead of slipping, geckos maintain and even improve their adhesive performance in many wet conditions (i.e., on wet hydrophobic substrates, on humid substrates held at low temperatures). The mechanism for this is not fully clarified, and likely ranges in scale from the chemical and material properties of the gecko’s contact structures called setae (e.g., setae soften and change surface confirmation when exposed to water), to their locomotor biomechanics and decision-making behavior when encountering water on a substrate in their natural environment (e.g., some geckos tend to run faster and stop more frequently on misted substrates than dry). Current work has also focused on applying results from the natural system to gecko-inspired synthetic adhesives, improving their performance in wet conditions. Gecko-inspired synthetic adhesives have also provided a unique opportunity to test hypotheses about the natural system in semi-natural conditions replicated in the laboratory. Despite many detailed studies focused on the role of water and humidity on gecko and gecko-inspired synthetic adhesion, there remains several outstanding questions: (1) what, if any, role does capillary or capillary-like adhesion play on overall adhesive performance of geckos and gecko-inspired synthetics, (2) how do chemical and material changes at the surface and in the bulk of gecko setae and synthetic fibrils change when exposed to water, and what does this mean for adhesive performance, and (3) how much water do geckos encounter in their native environment, and what is their corresponding behavioral response? This review will detail what we know about gecko adhesion in wet environments, and outline the necessary next steps in biological and synthetic system investigations.

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Study on the Design and Analysis of Spindle System of NС Machine Tools Based on Digital Design

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.522.668 ◽

2012 ◽

Vol 522 ◽

pp. 668-672

Author(s):

Hui Juan Sun ◽

Guo Fu Yin ◽

Liang Mi ◽

Yang Yin

Keyword(s):

Performance Analysis ◽

Resource Sharing ◽

Machine Tools ◽

Optimization Design ◽

Structure Design ◽

Digital Design ◽

Element Analysis ◽

Development Platform ◽

Nc Machine ◽

And Performance

Aiming at these problems of complicated analysis, high repeated rate and resource sharing in the process of the NC machine tools design and performance analysis, a development platform is built to integrate the structure design, performance analysis, optimization of spindle and resource sharing. The platform includes digital design, 3D entity modeling and virtual assembly, finite element analysis and optimization, and dynamic simulation module. Each module can normally operate and exchange data by means of coordinating the interface between modules. The experiment shows that the developed system could effectively improve the efficiency of design and analysis of spindle, and could provide reference for the optimization design and the actual production manufacturing.

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Protists and Phanerozoic Evolution in the Oceans

Notes for a Short Course: Studies in Geology ◽

10.1017/s0271164800001561 ◽

1987 ◽

Vol 18 ◽

pp. 248-264 ◽

Cited By ~ 1

Author(s):

Andrew H. Knoll

Keyword(s):

Temporal Pattern ◽

Taxonomic Diversity ◽

Evolutionary Change ◽

Morphological Data ◽

Biological Interactions ◽

Mass Extinctions ◽

Oceanic Circulation ◽

The Past ◽

Circulation Patterns ◽

History Of

In an essay published in 1977, S.J. Gould argued that three major questions have dominated paleontological thinking for more than a century. Does the history of life have direction? What is the motor of evolutionary change? And, what is the tempo of change? Certainly, these “eternal metaphors” have figured prominently in the research of invertebrate paleontologists during the past decade. Temporal pattern has been sought in changing morphologies within lineages, the changing structure and composition of communities, trends in taxonomic diversity, and even the occurrence of mass extinctions. Drifting continents, changing climates and oceanic circulation patterns, biological interactions, and extraterrestrial influences have all been championed as significant determinants of evolutionary change. The punctuation/gradualism debate has generated an impressive body of stratigraphic and morphological data, if not an unambiguous resolution of the issue.

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Ultra-Low-Power Digital Design with Body Biasing for Low Area and Performance-Efficient Operation

Journal of Low Power Electronics ◽

10.1166/jolpe.2010.1101 ◽

2010 ◽

Vol 6 (4) ◽

pp. 521-532 ◽

Cited By ~ 9

Author(s):

Maurice Meijer ◽

José Pineda De Gyvez ◽

Ajay Kapoor

Keyword(s):

Low Power ◽

Digital Design ◽

Efficient Operation ◽

Ultra Low Power ◽

Low Area ◽

Body Biasing ◽

And Performance

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The Ecomechanics of Gecko Adhesion: Natural Surface Topography, Evolution, and Biomimetics

Integrative and Comparative Biology ◽

10.1093/icb/icz013 ◽

2019 ◽

Vol 59 (1) ◽

pp. 148-167 ◽

Cited By ~ 5

Author(s):

Timothy E Higham ◽

Anthony P Russell ◽

Peter H Niewiarowski ◽

Amber Wright ◽

Thomas Speck

Keyword(s):

Sand Dunes ◽

Science Research ◽

Adhesive System ◽

Microhabitat Use ◽

Natural Habitats ◽

Complex Interactions ◽

Wide Range ◽

Hierarchical Nature ◽

Gecko Adhesion ◽

Adhesive Performance

Abstract The study of gecko adhesion is necessarily interdisciplinary due to the hierarchical nature of the adhesive system and the complexity of interactions between the animals and their habitats. In nature, geckos move on a wide range of surfaces including soft sand dunes, trees, and rocks, but much of the research over the past two decades has focused on their adhesive performance on artificial surfaces. Exploring the complex interactions between geckos and their natural habitats will reveal aspects of the adhesive system that can be applied to biomimetic research, such as the factors that facilitate movement on dirty and rough surfaces with varying microtopography. Additionally, contrasting suites of constraints and topographies are found on rocks and plants, likely driving differences in locomotion and morphology. Our overarching goals are to bring to light several aspects of ecology that are important for gecko–habitat interactions, and to propose a framework for how they can inspire material scientists and functional ecologists. We also present new data on surface roughness and topography of a variety of surfaces, and adhesive performance of Phelsuma geckos on surfaces of varying roughness. We address the following key questions: (1) why and how should ecology be incorporated into the study of gecko adhesion? (2) What topographical features of rocks and plants likely drive adhesive performance? (3) How can ecological studies inform material science research? Recent advances in surface replication techniques that eliminate confounding factors among surface types facilitate the ability to address some of these questions. We pinpoint gaps in our understanding and identify key initiatives that should be adopted as we move forward. Most importantly, fine details of locomotor microhabitat use of both diurnal and nocturnal geckos are needed.

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Superhydrophobicity of the gecko toe pad: biological optimization versus laboratory maximization

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2016.0184 ◽

2016 ◽

Vol 374 (2073) ◽

pp. 20160184 ◽

Cited By ~ 7

Author(s):

Alyssa Y. Stark ◽

Shairani Subarajan ◽

Dharamdeep Jain ◽

Peter H. Niewiarowski ◽

Ali Dhinojwala

Keyword(s):

Adhesive System ◽

System Level ◽

Structured Surfaces ◽

Natural Systems ◽

Surface Lipids ◽

Gecko Adhesion ◽

Biological Optimization ◽

Direct Investigation ◽

Better Than

While many gecko-inspired hierarchically structured surfaces perform as well as or better than the natural adhesive system, these designs often fail to function across a variety of contexts. For example, the gecko can adhere to rough, wet and dirty surfaces; however, most synthetic mimics cannot maintain function when faced with a similar situation. The solution to this problem lies in a more thorough investigation of the natural system. Here, we review the adhesive system of the gecko toe pad, as well as the far less-well-studied anti-adhesive system that results from the chemistry and structure of the toe pad (superhydrophobicity). This paradoxical relationship serves as motivation to study functional optimization at the system level. As an example, we experimentally investigate the role of surface lipids in adhesion and anti-adhesion, and find a clear performance trade-off related to shear adhesion in air on a hydrophilic surface. This represents the first direct investigation of the role of surface lipids in gecko adhesion and anti-adhesion, and supports the argument that a system-level approach is necessary to elucidate optimization in biological systems. Without such an approach, bioinspired designs will be limited in functionality and context, especially compared to the natural systems they mimic. This article is part of the themed issue ‘Bioinspired hierarchically structured surfaces for green science’.

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A morphospace of planktonic marine diatoms. II. Sampling standardization and spatial disparity partitioning

Paleobiology ◽

10.1017/pab.2014.5 ◽

2015 ◽

Vol 41 (1) ◽

pp. 68-88 ◽

Cited By ~ 3

Author(s):

Benjamin Kotrc ◽

Andrew H. Knoll

Keyword(s):

Quantitative Methods ◽

Sampling Bias ◽

Taxonomic Diversity ◽

Morphological Characters ◽

Morphological Data ◽

Small Magnitude ◽

Morphological Disparity ◽

Level Data ◽

Ordination Method ◽

Average Dispersion

AbstractMorphospace occupation through time provides a view of diversification distinct from the more familiar taxonomic tabulations. However, this view is subject to the same geological biases long recognized in studies of taxonomic diversification, where techniques for correcting secular bias in sampling have become standard practice. In this study, we apply sampling standardization techniques to a morphospace investigation to test whether observed stratigraphic trends in morphospace occupation are artifacts of trends in sampling. When sampling bias is corrected by randomized subsampling, all disparity metrics show stationary patterns, or at most directional changes of small magnitude. Metrics describing the average dispersion of taxa in morphospace are less subject to sampling bias than those describing the total extent of morphospace occupied. We also investigate a measure of disparity that is insensitive to sampling intensity, introducing a geographic component of morphological disparity. By analogy to α and β components of taxonomic diversity, we suggest the notions of α and β disparity, and find that α disparity remains roughly constant through time. Our analysis also allows us to present the first taxonomic diversity curve of diatoms under shareholder quorum subsampling (SQS), showing similar results to previously published subsampling methods: a roughly twofold rise over the Cenozoic, with peak diversity around the Eocene/Oligocene boundary. Tests for methodological bias from choices in ordination method and data culling during morphospace construction indicate that our results are relatively insensitive to both factors: Cenozoic occupation of planktonic diatom morphospace is largely unchanging. We find a similarly stationary pattern when we directly analyze the morphological data, seeing no change in the prevalence of taxa with different sets of morphological characters. More broadly, our results make clear that a complete view of morphological disparity must consider sampling biases, which can be addressed with wellestablished, quantitative methods in morphospaces populated using occurrence-level data.

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