Control Temperature (silver ant)

 

Silver ant hair

2.png

fig (1,a) silver ants nest ,fig (1,b) and fig(1,c) hair arrangement on ant body

  • In the Sahara, Cataglyphis bombycinathe silver ant is the most heat-tolerant creatures known
  • Feed on corpses of insects and other arthropods that have died to the thermally harsh desert conditions, which they themselves are able to withstand more successfully
  • They can forage in the Saharan Desert in the full midday sun when surface temperatures reach up to 70°C (158°F), and they must keep their body temperature below their critical thermal maximum of 53.6°C (128.48°F) most of the time [1]

 

What is its secret ?

  • Saharan silver ants, where covered with dense array of uniquely shaped triangular hairs with two thermo-regulatory effects.[2]
  • Hair characteristic for (Cataglyphis bombycina), enables the ants to maintain lower body temperatures by:
  1. 3.png

    fig (2) showing electromagnetic spectrum hair blocks

    Reflecting a large portion of the solar radiation in the visible and near infrared(NIR) range of the spectrum,

  2. Radiating heat to the surrounding environment by enhancing the emissivity in the mid-infrared (MIR)

 

 

 

4.png

Hair shape

  • By using the electron  microscope (fig 3,4)  to examine the hairs we find that it had
  1.  triangular shape and end in a sharp point:
    5.png

    fig (3) hairs under electron microscope

    • The two upper sides of the triangular shape are corrugated (have grooves)increasing the surface area facing skywards.
    • the base is flat enhancing reflection.
  2. hairs shows that they all adopt the same orientation, with their flat side parallel to each other and to the surface.

 

 

9.png

fig(4) showing cross-section in single hair

 

 Hair Mechanisms

8.png

  • 10.png

    in visible and near-infrared  light spectrum

    total internal reflection of incident light, corrugated sheets act as anti glare.

 

  • med – infrared  light spectrum11.png

    hair arrangement act as a Protective anti reflection layer

     

 

Factors affecting system

  1. Cross section [2]

    555.jpg

    fig (5) comparison between   triangular and circular hairs

triangular hairs are much better at higher angles of incidence ( 40 -60 ) as the presence of bottom facet ( flat surface ) enhances reflection  further.

 

 

 

 

 

 

 

  1. Angle of incidence123.png

Maximum reflectivity of angles range from 30- 75 degrees

At angles approaching 90°, reflectivity drops off when total internal reflection at one of the top facets starts to direct more of the radiation toward the ant’s body

233.jpg

fig (6) relation of gap size and reflectivity  for a periodic array of triangular hairs

 

 

3.Gap size [2]

Reactivity in the visible and near infrared  (NIR) increases as the gap opens up.

 

 

4. Arrangement

hair arrangement play  a crucial role in the efficiency of the system (as all hairs act as a group  (prisms) units reflecting electromagnetic waves  to block the heating )

7.jpg

Ant hair group under the microscope

6.jpg

hair arrangement appear as group of prisms

Possible technique ( digital model )

  • Swarming intelligence : as a way to organize the  hair arrangement  to acquire optimum sun light

Picture4.png   Picture5.png

 

Project mind map ( final conclusion)Picture6.png                                                                                                              

References :

[1] http://phys.org/news/2015-06-saharan-silver-ants-electromagnetic-extremely.html

[2]  Keeping cool: Enhanced optical reflection and heat dissipation in silver ants

(Norman Nan Shi,1 Cheng-Chia Tsai,1 Fernando Camino,2 Gary D.Bernard,3 Nanfang Yu,1* Rüdiger Wehner4* ) Department of Applied Physics and Applied Mathematics, Columbia University, New York, USA

 

 

 

 

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