TY - JOUR
T1 - Liquid crystal elastomer strips as soft crawlers
Y1 - 2015
A1 - Antonio DeSimone
A1 - Paolo Gidoni
A1 - Giovanni Noselli
AB - In this paper, we speculate on a possible application of Liquid Crystal Elastomers to the field of soft robotics. In particular, we study a concept for limbless locomotion that is amenable to miniaturisation. For this purpose, we formulate and solve the evolution equations for a strip of nematic elastomer, subject to directional frictional interactions with a flat solid substrate, and cyclically actuated by a spatially uniform, time-periodic stimulus (e.g., temperature change). The presence of frictional forces that are sensitive to the direction of sliding transforms reciprocal, 'breathing-like' deformations into directed forward motion. We derive formulas quantifying this motion in the case of distributed friction, by solving a differential inclusion for the displacement field. The simpler case of concentrated frictional interactions at the two ends of the strip is also solved, in order to provide a benchmark to compare the continuously distributed case with a finite-dimensional benchmark. We also provide explicit formulas for the axial force along the crawler body.
PB - Elsevier
UR - http://urania.sissa.it/xmlui/handle/1963/34643
U1 - 34847
ER -
TY - JOUR
T1 - Crawling on directional surfaces
Y1 - 2014
A1 - Paolo Gidoni
A1 - Giovanni Noselli
A1 - Antonio DeSimone
AB - In this paper we study crawling locomotion based on directional frictional interactions, namely, frictional forces that are sensitive to the sign of the sliding velocity. Surface interactions of this type are common in biology, where they arise from the presence of inclined hairs or scales at the crawler/substrate interface, leading to low resistance when sliding ‘along the grain’, and high resistance when sliding ‘against the grain’. This asymmetry can be exploited for locomotion, in a way analogous to what is done in cross-country skiing (classic style, diagonal stride). We focus on a model system, namely, a continuous one-dimensional crawler and provide a detailed study of the motion resulting from several strategies of shape change. In particular, we provide explicit formulae for the displacements attainable with reciprocal extensions and contractions (breathing), or through the propagation of extension or contraction waves. We believe that our results will prove particularly helpful for the study of biological crawling motility and for the design of bio-mimetic crawling robots.
PB - Elsevier
UR - http://urania.sissa.it/xmlui/handle/1963/34450
U1 - 34593
U2 - Mathematics
ER -
TY - JOUR
T1 - Discrete one-dimensional crawlers on viscous substrates: achievable net displacements and their energy cost
Y1 - 2014
A1 - Giovanni Noselli
A1 - Amabile Tatone
A1 - Antonio DeSimone
KW - Cell migration
AB - We study model one-dimensional crawlers, namely, model mechanical systems that can achieve self-propulsion by controlled shape changes of their body (extension or contraction of portions of the body), thanks to frictional interactions with a rigid substrate. We evaluate the achievable net displacement and the related energetic cost for self-propulsion by discrete crawlers (i.e., whose body is made of a discrete number of contractile or extensile segments) moving on substrates with either a Newtonian (linear) or a Bingham-type (stick-slip) rheology. Our analysis is aimed at constructing the basic building blocks towards an integrative, multi-scale description of crawling cell motility.
PB - Elsevier
UR - http://urania.sissa.it/xmlui/handle/1963/34449
U1 - 34591
U2 - Mathematics
ER -
TY - JOUR
T1 - A robotic crawler exploiting directional frictional interactions: experiments, numerics, and derivation of a reduced model
JF - Proceedings of the Royal Society A 470, 20140333 (2014)
Y1 - 2014
A1 - Giovanni Noselli
A1 - Antonio DeSimone
AB - We present experimental and numerical results for a model crawler which is able to extract net positional changes from reciprocal shape changes, i.e. ‘breathing-like’ deformations, thanks to directional, frictional interactions with a textured solid substrate, mediated by flexible inclined feet. We also present a simple reduced model that captures the essential features of the kinematics and energetics of the gait, and compare its predictions with the results from experiments and from numerical simulations.
PB - Royal Society Publishing
U1 - 34594
U2 - Mathematics
ER -
TY - JOUR
T1 - Crawlers in viscous environments: linear vs nonlinear rheology
JF - International Journal of Non-Linear Mechanics 56, 142-147 (2013)
Y1 - 2013
A1 - Antonio DeSimone
A1 - Federica Guarnieri
A1 - Giovanni Noselli
A1 - Amabile Tatone
AB - We study model self-propelled crawlers which derive their propulsive capabilities from the tangential resistance to motion offered by the environment. Two types of relationships between tangential forces and slip velocities are considered: a linear, Newtonian one and a nonlinear one of Bingham-type. Different behaviors result from the two different rheologies. These differences and their implications in terms of motility performance are discussed. Our aim is to develop new tools and insight for future studies of cell motility by crawling.
PB - Elsevier
U1 - 34590
U2 - Mathematics
ER -