MMEAW: Modelling the MEchanics of Animal Whiskers

MMEAW is a multidisciplinary project, lying at the interface between structural engineering, robotics and comparative animal physiology. It aims to extend our understanding and knowledge of how whiskers are adapted to their function and apply that understanding to applications in engineering. MMEAW builds on previous research in this field, for example the EPSRC funded Whiskerbot project (EPSRC ref: GR/S19639/01).
The aims of MMEAW are as follows:
1) Understanding how animals exploit a range of whisker morphological parameters such as taper, curvature, twist, stiffness, anisotropy and weight, to their advantage.
2) Determining critical values of taper, twist, curvature and relationships between them e.g., ratio of weight to length (curliness), which lead to qualitative change in vibrissae mechanics. Thereby identify criteria for optimal performance.
3) Establishing a rational scheme for classifying vibrissae.
MMEAW involves two key activities. First, by taking measurements of the shape and form of animal whiskers, it will build a data base of detailed information on whisker morphologies. Working with museums, we shall gather data on a range of species - from small rodents, to large mammals and to birds. The information we are interested in includes details of the length, curvature, taper, weight, tortuosity (i.e., out of plane curvature), and cross sectional properties, such as shape, diameter and stiffness. We also want to know details of how and where each whisker connects to the animal's face, including the angle and orientation of the whisker. All that information will be stored in a data base. Since no such data base exists anywhere, it will be made available to museums internationally, where it can be aggrandized. The process of gathering data on vibrissae will last one year.
The second major activity involves the formulation of mathematical models, using the data gathered on vibrissae shape and form, and applying mechanics principles to analyse what happens to a whisker when its tip is disturbed e.g., when it brushes against different surfaces, is pressed in by a force, passes through a liquid (otters and seals) and undergoes the 'whisking motions' observed in some species (rats). MMEAW will use advanced modelling methods, based on the Cosserat Theory of rods, i.e., a rigorous mathematical theory of long slender structures. That approach will enable MMEAW to model the effects of different curvatures, tapers, tortuosity etc., within a unified and rational scheme, one that provides detailed information on the loads transmitted from the tip of the whisker to the base. The modelling and analysis will be complemented by field work (observations of animals) carried out by a member of the team with extensive specialist experience. Indeed, MMEAW involves the collaboration of a multidisciplinary team with strong track records in elastic rod theory, engineering and animal comparative physiology.
By formulating a well posed mathematical problem, MMEAW will be able to identify optimal conditions for vibrissae and extend the analysis to embrace extreme loadings and deflections, thereby offering a global perspective on how different vibrissae morphologies affect performance. That information can be used by robotics engineers and structural engineers to implement optimal designs for flexible robotic arms and antennae, indeed it carries across to any engineer developing technology that involves long slender flexible structures; whether a robot arm, a building structure (beam, column, strut), a cable buoy system, a space tether, or a medical stent.

The MMEAW project will discover new things about the variety of animal whiskers. It will examine the varieties of cross sections, of curvatures and tapering and how animals exploit those to their advantage, whether that be burrowing, foraging, hunting in water, or processing information on shape, form and texture. Whilst that may be of interest to comparative physiologists and evolutionists, MMEAW is primarily motivated by engineering considerations, and connects with a long UK tradition of developing bio-inspired technology.

Indeed MMEAW has potential for impacting on the design and development of any technological device that can be described as long, slender, elastic and load bearing. That device may be a flexible robotic arm used for exploring areas where vision is restricted and/or where surface texture is important. For structural engineers, it can apply to any long slender structural load bearing component used in buildings; for example, beams, struts and columns. For marine engineers, it may be a cable buoy system deployed in deep oceans, where cable tangling is a problem. In the textiles industry, it relates to the bending and twisting of yarn. For engineers developing medical technology, it applies to devices such as flexible guide wires used for interventional radiology procedures.

Note, in general, engineers seeking to improve the performance of technology based on rod-like structures, tend to model them as naturally straight and with uniform circular cross sections. Whilst that is the simplest model, such rods are rarely encountered in nature. Engineers will benefit from MMEAW's research because they will learn how combinations of initial curvature, taper and twist impact on the performance of a long slender rod under a range of loading conditions. Furthermore, MMEAW will extend its analysis to specify optimal combinations of taper, curvature, length, weight etc., for particular loading sequences. MMEAW will develop user-friendly simulation software that will allow engineers to study how variations and combinations of those parameters affect the performance of a 'whisker-like' device.

There are other potential beneficiaries of MMEAW - animals themselves! In recent years, engineers have developed early warning systems for manatees, a threatened species (whose whole body is covered with whiskers). That technology was developed on the basis of research that led to understanding of how manatees use their whiskers to detect on-coming boats in the water. Indeed, knowledge and understanding of how mammals use their whiskers to gather information about their surroundings will assist in planning human activities such that they do not adversely impact on threatened species.