Understanding biologicalisation of the snake-skin inspired textures through additive manufacturing for mechanical traction

Abstract

This biologicalisation aimed research explores the convergence of bio-inspired design and additive manufacturing for mechanical traction. Snake-skin inspired anisotropic textures having different hierarchical designs were manufactured using a laser powder-bed fusion (L-PBF) process. Laser microscopy was performed to characterize the texture while tribological measurements were performed to understand the role of texture on frictional properties for guided traction. The results showed oscillating and anisotropic frictional response dictated by the relative orientation of micro-texture with respect to the motion. The learning from this research can facilitate additive manufacturing of anti-slippery designs suitable for applications such as mechanical fixtures and components.

Introduction

Managing friction is a common challenge associated with many production processes and machine components where two or more surfaces come in direct contact. On one hand, machining operations such as cutting, grinding and metalworking rely on the use of proper lubrication at the tool-workpiece interface to reduce friction and energy losses. On the other hand, several manufacturing processes and engineering components rely on utilizing controlled friction between the interfaces to manipulate traction for efficient operation. The development of anti-slippery components having anisotropic frictional properties is required to enhance the precision and accuracy of traction at mating interfaces. This research explores the use of additive manufacturing as a production tool to achieve anisotropic frictional properties through bio-inspired textures.

Nature serves as an inspiration for ‘biologicalisation’ to develop advanced products through bio-inspired designs, materials and manufacturing processes [1], [2], [3]. Biologicalisation is defined as “the use and integration of biological and bio-inspired principles, materials, functions, structures and resources for intelligent and sustainable manufacturing technologies and systems with the aim of achieving their full potential [1].” In particular, physical and chemical texture on the skins of biological species control their interaction with the environment and result in the desired functional response(s) [3]. These functional responses include anti-reflectivity, dry adhesion, antifouling properties, controlled wettability, and friction management [2,3]. Snakes are one such example of species that exhibit functional surface on their ventral skin [4]. The ventral skin is in continuous contact with the ground and exhibits hierarchical texture design that is responsible for friction management during locomotion [5], [6], [7]. It was identified that the key texture design components of the snake-skin are the size, distribution and directionality (orientation) of features along with hierarchical arrangement [3]. During locomotion, the directional texture on snake-skin results in anisotropic frictional properties so that the backward movement is inhibited because of the higher friction while allowing easy forward movement [8,9]. Thus, snakes serve as a bio-inspiration to manufacture directional textures with anisotropic frictional properties suitable for applications described above.

Authors have previously published preliminary results exploring the feasibility of using a laser powder-bed fusion (L-PBF) process to write snake-skin inspired design [10]. For testing the feasibility of the technical approach, the design was created based on the dimensions of the ventral scales measured on the shed skin of a ball python snake.

The study in reference [10] raised multiple fundamental manufacturing science and engineering issues including the mechanics of the L-PBF process for delivering the snake-skin texture, the role of hierarchical texture in delivering precision of mechanical traction, scalability of the manufacturing process for various dimensions, and more. These issues form the foundation of the work presented in this manuscript. The presented research focuses on studying the parametric dependence on the fundamental understanding of the texture mechanism for manufacturability and functionality. Through the design of tribological experiments, the frictional response of three sets of hierarchical designs (with different dimensions) was studied for traction and the details are discussed in the following sections.