DOI: 10.6078/d1zd6c
title: Data from: Role of multiple, adjustable toes in distributed control shown by sideways wall-running in geckos

description: Remarkable progress has been made characterising one of nature’s most
 integrated, hierarchical structures – the fibrillar adhesive system of
 geckos. Surprisingly, we lack an understanding of how multiple, soft toes
 coordinate to facilitate gecko’s acrobatic locomotion. Here, we tested the
 control function of multiple toes of sideways wall running geckos by
 varying substrate orientation, friction, and available area. Geckos
 realigned the toes of top feet toward the upward direction to resist
 gravity. Top front and hind feet functioned like the front feet during
 vertical climbing. The contact area was not compromised but redistributed
 by toes. Geckos aligned all toes upward to resist slipping when
 encountering low friction patches and increased the contribution of
 particular toes to compensate for adhesion loss when not all toes were
 available during the negotiation of intermittent slippery strips.
 Increasing substrate roughness by replacing the flat wall with discrete
 rods perpendicular to motion resulted in geckos bending and/or rotating
 toes to conform to and even grasp the rods, with a potential force more
 than five times body weight. Our findings revealed that geckos increase
 their effectiveness of manoeuvrability in demanding environments by taking
 advantage of the distributed control afforded by multiple, adjustable soft
 toes.
description: Data1.xlsx. The
 first file contains the frictional adhesion (i.e., shear force) and toes
 contact area at three moments in the stance phase of geckos climbing a
 wall upward.  We embedded several test units consisting of (frustrated
 total internal reflection) FTIR enhanced acrylic and force sensors in the
 wall. We collected the foot rection force and contact images at the same
 time (500Hz) through a DAQ module and highspeed camera.  We obtained the
 contact area of toes through the highspeed video images through image
 processing (Eason et al. 2015). We assumed toes as vectors with values of
 their contact area and directions of their own directions. Thus, we
 obtained the resultant contact area at feet (see the main text for the
 method). In this file, we show the frictional adhesion and resultant
 contact area for three moments in stance phase, (i) the moment when the
 force reached its half peak,(ii) the moment when the force reached its
 peak, (iii)the moment when the force reduced to its half peak.
 Data2.xlsx. The second
 file contains the contact area and orientation angles of all toes of
 geckos in upward climbing, sideways wall-running without slippery strips,
 and with slippery strips. We first ran geckos on a vertical, FTIR-enhanced
 acrylic sideways and recorded their toe contacts through highspeed camera.
 Then we ran the same individuals upward as control. We also added slippery
 strips (Teflon, width 5mm, and gaps 10mm) to the rear part of the acrylic
 and ran the same individuals sideways again.  We obtained the contact are
 and orientation angles of toes through images processing. The data in this
 file was selected at mid-stance. Data3.xlsx. The third file
 contains the relative force of geckos’ feet while being pulled along and
 across acrylic rods with diameters ranging from 6.4mm to 38mm. We
 connected the rods to force sensors and measured the shear force while
 dragging geckos feet along the rods and across the rods, respectively. We
 also pulled the geckos feet on a flat acrylic sheet before and after a
 test on the rod as its control. For each test, we divided the maximum
 shear force on the rod with the corresponding maximum shear force on the
 flat control surface to calculated the relative force.
description: There are many blanks in the second file. These are not missing data. The blanks indicate the toes that show no contact at the mid-stance of corresponding feet. This also indicates that some toes contribute to the whole feet adhesion occasionally. There is also some negative contact area in the dataset. This is not a n erroir, just because the direction of the resultant contact area calculated by defining toes as vectors is not in the positive direction we defined. These notes were also included in a ReadMe.txt.