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Data for: Pendulum-based measurements reveal impact dynamics at the scale of a trap-jaw ant

Citation

Jorge, Justin; Bergbreiter, Sarah; Patek, Sheila (2021), Data for: Pendulum-based measurements reveal impact dynamics at the scale of a trap-jaw ant , Dryad, Dataset, https://doi.org/10.5061/dryad.b2rbnzsbm

Abstract

Small organisms can produce powerful, sub-millisecond impacts by moving tiny structures at high accelerations. We developed and validated a pendulum device to measure the impact energetics of microgram-sized trap-jaw ant mandibles accelerated against targets at 105 m s-2. Trap-jaw ants (Odontomachus brunneus; 19 individuals; 212 strikes) were suspended on one pendulum and struck swappable targets that were either attached to an opposing pendulum or fixed in place. Mean post-impact kinetic energy (energy from strike converted to pendulum motion) was higher with a stiff target (21.0-21.5 µJ) than a compliant target (6.4-6.5 µJ). Target mobility had relatively little influence. Mean contact duration of strikes against stiff targets was shorter (3.9-4.5 ms) than against compliant targets (6.2-7.9 ms). Shorter contact duration was correlated with higher post-impact kinetic energy. These findings contextualize and provide an energetic explanation for the diverse, natural uses of trap-jaw ant strikes such as impaling prey, launching away threats, and performing mandible-powered jumps. The strong effect of target material on energetic exchange suggests material interactions as an avenue for tuning performance of small, high acceleration impacts. Our device offers a foundation for novel research into the ecomechanics and evolution of tiny biological impacts and their application in synthetic systems.

Usage Notes

Tracks: tracks.zip

These are the outputs from the automated digitizing routine. Each file has the A#**#.csv naming scheme where the A# stands for the ant number, the ** specifies the target type (C = Compliant, S = Stiff, FC = Fixed Compliant, FS = Fixed Stiff), and the last # represents the strike number. In each file, the column titles are as follows:

pt1_cam1_X: The x coordinates for the ant pendulum immediately after impact
pt1_cam1_Y: The y coordinates for the ant pendulum immediately after impact
pt2_cam2_X: The x coordinates for the target pendulum immediately after impact (note that this column does not exist for the fixed targets as the target does not move after impact)
pt2_cam2_Y: The y coordinates for the target pendulum immediately after impact (note that this column does not exist for the fixed targets as the target does not move after impact)

Verification impactor dataset: mICP_Impactor_Dataset.csv

This contains the dataset of impacts with the verification impactor as the energy source. Information included is as follows:

group: Specifies the target type where C = Compliant, S = Stiff, FC = Fixed Compliant, and FS = Fixed Steel   
strike: Strike number - specifies the order of the observation in the amount of strikes performed by the ant for this target type  
initial: The amount of energy delivered by the swinging impactor pendulum measured in Joules. Calculated by finding the velocity of the impactor right before impact with the target 
tke: The kinetic energy of the target's pendulum after the impact measured in Joules
ike: The kinetic energy of the impactor's pendulum after the impact measured in Joules  
pike: Post-impact kinetic energy calculated by adding the kinetic energy of the target's pendulum after impact and the kinetic energy of the impactor's pendulum after impact (tke + ike). Measured in Joules.  

Live trap-jaw ant dataset: mICP_Brunneus_Dataset.csv 

This contains the dataset of impacts with live trap-jaw ants as the energy source. Information included is as follows:

ant: Specifies which ant is performing the strike     
group: Specifies the target type where C = Compliant, S = Stiff, FC = Fixed Compliant, and FS = Fixed Steel  
strike: Specifies the order of the observation in the amount of strikes performed by the ant for this target type  
seq: Specifies the order of the observation in the total amount of strikes performed by the ant across all target types  
duration: The amount of time in seconds during which the mandibles were in contact with the target   
ake: The kinetic energy of the ant's pendulum after the impact measured in Joules   
tke: The kinetic energy of the target's pendulum after the impact measured in Joules  
pike: Post-impact kinetic energy calculated by adding the kinetic energy of the target's pendulum after impact and the kinetic energy of the ant's pendulum after impact (ake + tke). Measured in Joules.   
ratio: The ratio of ake to tke. Note that for impacts against fixed targets, the target remains stationary after the impact and therefore the tke is NA  
dist: The distance (in millimeters) between the ant and the target before the strike  

Annotated Rcode: mICP_DataAnalysis_R_Code.Rmd

This Rcode was used to analyze the verification impactor dataset and the live trap-jaw ant dataset.

CAD files: mICP_CAD.zip 

The folder contains the necessary CAD files (in .stl format) to 3D print the pendulum housings for the mICP as well as the axel insert described in the publication.

Funding

U.S. Army Research Laboratory and U.S. Army Research Office, Award: W911NF-15-1-0358

United States Army Educational Outreach Program, Award: W911SR-15-2-0001

U.S. Army Research Laboratory and U.S. Army Research Office, Award: W911NF-15-1-0358

United States Army Educational Outreach Program, Award: W911SR-15-2-0001