@article {45, title = {Continuum theory of swelling material surfaces with applications to thermo-responsive gel membranes and surface mass transport}, journal = {Journal of the Mechanics and Physics of Solids}, volume = {89}, year = {2016}, pages = {96-109}, abstract = {

Soft membranes are commonly employed in shape-morphing applications, where the material is programmed to achieve a target shape upon activation by an external trigger, and as coating layers that alter the surface characteristics of bulk materials, such as the properties of spreading and absorption of liquids. In particular, polymer gel membranes experience swelling or shrinking when their solvent content change, and the non-homogeneous swelling field may be exploited to control their shape. Here, we develop a theory of swelling material surfaces to model polymer gel membranes and demonstrate its features by numerically studying applications in the contexts of biomedicine, micro-motility, and coating technology. We also specialize the theory to thermo-responsive gels, which are made of polymers that change their affinity with a solvent when temperature varies.

}, keywords = {drug delivery, material surface, membrane, micro-motility, polymer gel, spreading, swelling}, doi = {10.1016/j.jmps.2016.02.001}, author = {Alessandro Lucantonio and Luciano Teresi and Antonio DeSimone} } @article {36, title = {Crawling on directional surfaces}, journal = {International Journal of Non-Linear Mechanics}, volume = {61}, year = {2014}, pages = {65-73}, abstract = {

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 {\textquoteleft}along the grain{\textquoteright}, and high resistance when sliding {\textquoteleft}against the grain{\textquoteright}. 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.

}, keywords = {bio-mimetic micro-robots, cell migration, crawling motility, directional surfaces, self-propulsion}, doi = {10.1016/j.ijnonlinmec.2014.01.012}, author = {Paolo Gidoni and Giovanni Noselli and Antonio DeSimone} } @article {30, title = {Crawlers in viscous environments: linear vs. nonlinear rheologies}, journal = {International Journal of Non-Linear Mechanics}, volume = {56}, year = {2013}, pages = {142-147}, abstract = {

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 force and slip velocity 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.

}, keywords = {cell migration, cell motility, crawling motility, motility on a solid substrate, self-propulsion, soft biomimetic robots}, doi = {10.1016/j.ijnonlinmec.2013.02.007}, author = {Antonio DeSimone and Federica Guarnieri and Giovanni Noselli and Amabile Tatone} } @article {28, title = {Crawling motility through the analysis of model locomotors: two case studies}, journal = {The European Physical Journal E}, volume = {35}, year = {2012}, pages = {1-8}, abstract = {

We study model locomotors on a substrate, which derive their propulsive capabilities from the tangential (viscous or frictional) resistance offered by the substrate. Our aim is to develop new tools and insight for future studies of cellular motility by crawling and of collective bacterial motion. The purely viscous case (worm) is relevant for cellular motility by crawling of individual cells. We re-examine some recent results on snail locomotion in order to assess the role of finely regulated adhesion mechanisms in crawling motility. Our main conclusion is that such regulation, although well documented in several biological systems, is not indispensable to accomplish locomotion driven by internal deformations, provided that the crawler may execute sufficiently large body deformations. Thus, there is no snail theorem. Namely, the crawling analog of the scallop theorem of low Reynolds number hydrodynamics does not hold for snail-like crawlers. The frictional case is obtained by assuming that the viscous coefficient governing tangential resistance forces, which act parallel and in the direction opposite to the velocity of the point to which they are applied, depends on the normal force acting at that point. We combine these surface interactions with inertial effects in order to investigate the mechanisms governing the motility of a bristle-robot. This model locomotor is easily manufactured and has been proposed as an effective tool to replicate and study collective bacterial motility.

}, keywords = {crawling motility}, doi = {10.1140/epje/i2012-12085-x}, author = {Antonio DeSimone and Amabile Tatone} }