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6 comments

Smart Sutures Getting Hot

Posted August 29, 2012 4:30 PM by Chelsey H

The idea of a needle and thread being used to sew up a wound makes me queasy, but sutures are a very routine and simple method of treating open wounds from an injury, surgery, or small procedure. The method of closing a wound with a needle and thread is thousands of years old. Although little has changed in the process, there have been several iterations of the material used for the suture including gold, human hair, metal thread, silk, and catgut. At the beginning of the 21st Century, synthetically manufactured, absorbable materials were introduced and quickly became the most popular material option.

New Suture Technology

The next generation of suture material was recently introduced in an article in the nanotechnology magazine called Small. The smart suture materials are electronic sutures, which contain ultrathin silicon sensors integrated on polymer or silk strips. The material can be threaded through needles, laced through skin and knotted without degrading the device. The sensors can measure temperature in the surrounding tissue. A higher temperature would indicate infection causing the micro-heaters to deliver heat to the wound, which is known to aid healing. A professor of materials science and engineering at the University of Illinois at Urbana-Champaign is the inventor of the smart sutures. Professor John Rogers also imagines that the sutures could be laden with devices that provide electrical stimulation or release drugs in a programmed way to heal wounds.

How Smart Sutures Are Made

The smart sutures are made from silicon-based devices that flex and stretch. The silicon membranes and gold electrode wires are just a few hundred nanometers thick and are patterned in a serpentine shape. The researchers first use chemicals to slice off an ultrathin film of silicon from a silicon wafer. A rubber stamp is used to lift off and transfer the nanomembranes to polymer or silk strips. Then they deposit metal electrodes and wires on top and encapsulate the entire device in an epoxy coating. A similar technology is used to create inflatable catheters and medical tattoos.

The smart sutures have the ability to sense the temperature of the surrounding tissue. There are two types of temperature sensors on the sutures. One is a silicon diode that shifts its current output with temperature. The other sensor is a platinum nanomembrane resistor which changes its resistance with temperature. The microheaters are simply gold filaments that heat up when current passes through them. The addition of a drug release system could be accommodated by coating the electrical threads with drug-infused polymers, which would release the chemicals when triggered by heat or an electrical pulse.

The materials used to make the sutures are safe for the body. Researchers said the most difficult part of creating this device was making the silicon flexible. Since silicon is brittle, the nanomembranes had to be made as thin as possible. The silicon needed to be laid out in a winding pattern for elasticity and placed in-between the top layer of epoxy and bottom polymer surface of the suture. "When you bend the entire construct, the top surface is in tension and the bottom is in compression, but at midpoint the strains are very small," said Rogers.

The new suture device may aid in the proper healing of open wounds by ensuring flexibility of the skin and preventing infection in the tissue.

Resources

Smart Sutures That Detect Infections

1. Kim, D.-H., Wang, S., Keum, H., Ghaffari, R., Kim, Y.-S., Tao, H., Panilaitis, B., Li, M., Kang, Z., Omenetto, F., Huang, Y. and Rogers, J. A. (2012), Thin, Flexible Sensors and Actuators as 'Instrumented' Surgical Sutures for Targeted Wound Monitoring and Therapy. Small. doi: 10.1002/smll.201200933

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#1

Re: Smart Sutures Getting Hot

08/29/2012 10:47 PM

Well, then, don't watch Rambo in "First Blood"!

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#5
In reply to #1

Re: Smart Sutures Getting Hot

08/31/2012 9:49 AM

What about N-Butyl-2-Cyanoacrylate which features a plastic tube which when squeezed crushes a fine glass ampoule, and which is then further squeezed to create small drops of cyanoacrylate. This is applied to a wound with the doctor approximating the wound edges with one hand, whilst small drops of cyanoacrylate essentially 'glue' the wound together. The product passes through a micro-filter before appearing, and which filters out glass particles. The medium is inert and eventually sloughs off during healing.

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#6
In reply to #5

Re: Smart Sutures Getting Hot

10/05/2012 3:24 PM

Cyanoacrylate was orinally concieved as a medical replacement for sutures. Problem was that it tends to be too brittle. There are indeed adhesives used for suture replacement - my wife had a cut on her thumb glued together with a medical adhesive about three years ago. Nothing nearly so complicated as you describe, however - just a small tube similar to the .1 oz tubes of super glue you see in the stores.

The idea behind this story is not simply a replacement for sutures, but rather to add the capability of wound monitoring and additional treatment as needed to the suture, in order to make suture of wounds a more effective treatment.

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#2

Re: Smart Sutures Getting Hot

08/30/2012 1:17 AM

So if the wound is hot then the heater turns on. No thermal runaway?

Crackling anybody?

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#3
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Re: Smart Sutures Getting Hot

08/30/2012 4:41 PM

According to the blog, there are two sensors at work here. The one mentioned is a platinum nanomembrane resistor, which changes its resistance with temperature. The blog / source is scant on details from there, but I'd assume that this second sensor is in place to combat the thermal runaway.

Call me optimistic, but I like to hope that the people in charge of this are aware of the notion of "oh, it's warm, let's heat it up. Oh, it's still warm, let's heat it s'more." Also, being optimistic, I can say that at least the wound will be cauterized as it's being made by the sutures

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#4

Re: Smart Sutures Getting Hot

08/30/2012 6:46 PM

Sounds like a problem creation exercise to me.
I remember reading* about an old woodsman who got his belly ripped open by a grizzly.
He managed to get back to his cabin where he stitched up the wound. There was a big flap of fat hanging out so he cut it off, melted it down and used it to grease his boots!
We don't need no stinkin' smart sutures.
Del
*It was in 'Hunting with the bow and arrow'

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