Understanding Lamellae - How it Works
The ability certain geckos have to climb walls and other structures is accomplished by the special padding found on the pads of their feet. This padding, known as lamellae, in conjunction with an electrodynamic force, allows them this ability.
Hopefully after reading this, you will have a better understanding as to what lamellae is and how it functions.
What Is Lamellae
Lamellae is the plural form of the word lamella. Lamella, which is a thin plate-like structure, is technically the housing unit for the true means in which the gecko can adhere to surfaces.
The real magic in the geckos ability is hidden in microscopic hairs called setae. Positioned on the lamellae are millions of these setae. To understand how this is possible, image something so small that it is 100 millionth of a meter long. Unbelievably, it doesn't stop there. At the tip of each setae, there are even smaller hairs called spatulae. Each setae houses 1,000 of these spatulae. According to National Geographic, spatulae are only 200 billionths of a meter wide. These fine hairs allow the gecko the ability to make more surface contact than a leopard gecko would walking across the same surface. It's in this surface contact that the magic of dry adhesion transpires.
Surface density is mass divided by area / the quantity per unit of surface area .
The amount of spatulae that comes into contact with the surface, and its proximity to the surface, is dramatically increasing the surface density and make it sufficient for van der Waals forces to provide the adhesive strength applied when these geckos scamper up vertical surfaces.
Van der Waals forces
Johannes Diderik van der Waals is the Dutch scientist and thermodynamicist in which Van der Waals forces were named. His work on the equation of state for gases and liquids explains how molecules and atoms interact and bond with one another under various conditions.
In the simplest of terms, this process traps and bonds molecules on the surface of the structure being climbed and at the tips of the spatulae found at the end of the setae. The vast amount of spatulae present on the surface has increased the surface density. With the amount of intermolecular force being applied to each spatulae over such as small area, a dry bond takes place.
To truly understand the sheer number of contacts that are being made, you need to understand how many individual hairs are touching the surface simultaneously, each having their own molecular bond. The face of a dime is capable of housing over one million setae. Since each setae has one thousand spalulae at its tip, you would have one billion points of contact each holding an individual bond with the surface. It is in this surface density and the size/shape of the spalulaes that allow for this magnificent feat.
Leopard geckos do not possess lamellae which is why they can not climb vertical surfaces.
Articles Of Interest
Author: Richard Brooks
Lamellae Photo © Matt Reinbold