Saturday, March 31, 2012

Pictures of the Month - Turbines and Beams

I don't know what it is about late March. Spring has sprung, flowers are blooming, grass growing green...and researchers are releasing killer images and wild papers at breakneck speed. This week, two images really caught my eye - a heart turbine, and a molecular beam generator. 

Artificial dual-turbine heart | Credit: New Scientist / Jeremiah Zagar
First up, a still from the short film Heart Stop Beating, shown courtesy of New Scientist TV. You're not imagining things - that's a dual-turbine pump, in a man's chest cavity! What's more, the man in question, Craig Lewis, lived for 5 weeks with this device in his chest, apparently no worse for wear, and died of an unrelated condition. 

In a Popular Science article from last month, one of the doctors behind the tech, Billy Cohn, described the materials used to construct the heart turbine:
"The materials needed to be blood-friendly. The structure needed to be resilient to deformation. It had to be formable in a limited space. We needed to be able to sew it, but the needle holes couldn’t let blood leak. And we had to be able to customize it in the OR by cutting it. I bought some ordinary Dacron from the fabric store and RTV silicone from Home Depot to impregnate the outside. I did all this in my garage."
Here's my question: What other materials could we construct replacement hearts out of? Perusing the stent literature, it seems like medical device makers try two different tactics: either a non-allergenic metal alloy, like nitinol (Ni-Ti) or cobalt chromium; or a biodegradable polymer, like a polyamide or poly-lactic acid (PLA). I'm hoping one of my materials-leaning readers could help me work through this in the comments.

Bumper Sticker: "My other car is a Molecular Beam Generator"
Credit: G. Meijer, Chem. Rev.
Next, in keeping with the "unbelievable machines" motif, here's the abstract picture for a recent Chem. Rev. on molecular beam generation. I'll admit, I'm not a physical chemist, but I would offer to learn if I got to play with a device like this! 

Molecular beams are formed, in the words of Prof. Gerard Meijer (Fritz Haber Institute | Max Planck), through a "controlled leak" from a pressurized cavity into a vacuum. Electromagnetic fields can be used to "shape" the beam, which chemists direct at targets, or smash into another beam to simulate basic binding events. My second question: What else could we do with these beams? Brief explorations into physics texts mention roles in quantum dots and nanocrystals, but I'd like to learn more. Readers?

1 comment:

  1. Medical device development in the garage - I guess this is DIYBio taken to a logical endpoint. Heh.

    What I know about molecular beam epitaxy is probably better summed up at that Wikipedia article. I suppose molecular beams could also be used for chemical lithography applications, in lieu of electron beams or your preferred interval of the EM spectrum. I'm pretty sure it's been done, just can't quite remember where. I do recall that there are analytical chemistry applications of molecular beams, typically in analysis of environmental samples. The sample is pyrolyzed, a molecular beam is formed from the gas-phase species, and then subjected to mass spectrometry.