A Sligo researcher is developing a computer model that mimics how skin wrinkles, writes Dr Claire O'Connell.
Not many jobs involve repeatedly pinching the arms of your work colleagues, but for a researcher at the Institute of Technology (IT) Sligo it is part of a valid scientific experiment.
Mechanical engineer Cormac Flynn is building a computer model of "virtual" skin that he hopes will help scientists better understand how skin reacts to cutting and wrinkling. Pinching real skin allows Flynn to compare the virtual system with a live situation.
His computer-based skin model will soon be used in a wider project that aims to devise a scale for measuring sharpness. "You can measure length and temperature with Celsius and metres, but there's no actual measurement for sharpness," says Flynn, who is a PhD candidate with Dr Brendan McCormack in IT Sligo's school of engineering.
Modelling how scalpels and bone chisels interact with the virtual skin will help researchers to look at what parameters influence sharpness and devise a scale of measurement, he explains.
When he started to develop the virtual skin, Flynn researched existing computer-based models and found some of them lacking. "Skin is quite a complex material. It varies from person to person, and also the skin on the sole of your foot is a lot different to the skin on your arm," he says.
"It is also multi-layered. The epidermis is the outside and then the dermal layer is underneath that and then you get the fat layers underneath that. A lot of the existing models just lump it in as a homogenous material."
Flynn developed his own multi-layered model using finite element software that analyses the forces and displacements in a structure by dividing it up into linked parts.
"If you have a computer drawing of a structure you can break it up into simpler components and look at how parameters affect them. It can be used in anything from car engines to buildings to bridges and biomedical applications like this one," he says.
He based his own model on an existing programme used to simulate elastic polymers and extended it to include some properties of skin. To get data for the virtual model he looked at existing information about rabbit skin, including experiments that measured the forces generated over time as the isolated skin was stretched.
"If you have a piece of skin in your hand and you stretch it one way the response will be a lot different than if you stretch it in another direction," he explains.
Then he decided to use the multi-layer skin model to look at the mechanics of wrinkling. "If you imagine pinching your arm, wrinkles develop between your thumb and forefinger, and I am looking at the wavelength and height of the wrinkles," says Flynn.
He is also investigating wrinkles that form around scars. "When a scar heals it contracts and can deform the skin around it," he says. "Depending on where that happens it can be quite painful or restrict the movement of joints."
The virtual model will make it easier for researchers to test a number of conditions on the computer, but Flynn points out that the work needs to be validated by experiments on actual skin too.
"You can vary parameters a lot easier, but a computer model doesn't stand up by itself, you do have to compare it with real life," he says.
This is why his colleagues are letting him pinch their arms. "We have built a simple device where you stick two tabs onto the skin and you can move them towards each other at a fixed displacement so it wrinkles in a controlled, repeatable manner," explains Flynn, who says that so far the data from the live subjects and the computer agree well.
He hopes the virtual skin model will be ready within a year to form the test bed for the cutting project, which will be carried out with researchers in University College Dublin, Trinity College Dublin and Waterford Institute of Technology. He also sees wider applications for the skin model in cosmetics and in reconstructive surgery, where it could help map in advance where incisions should go to minimise scarring.