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Posts Tagged ‘dissolvable sensors’


Dissolvable sensor for determining temperature and pressure

Curator: Danut Dragoi, PhD

The Concept

The concept of dissolvable sensor in human body fluid and its experimentation was a successful task of electrical engineers at the University of Illinois at Urbana-Champaign. The device is intended to be implanted inside the head of human body in order to measure important parameters such as temperature and pressure.

Based on actual silicon technology, the device is built on a very thin silicon crystal, which is dissolvable in human body fluids after a given period and after  the measurements are done. The need for such device is required by a medical intervention, a surgery, or a special medication.

For measuring the temperature,the device uses the principle of variation of current / voltage of a silicon diode with temperature see link in here . To illustrate how the diode works as a thermometer, see the link in here  in which the curve voltage output versus temperature, variable T, is a decreasing linear function as a function of temperature.The other variable pressure P can be obtained from the base material, the thin silicon substrate, even if silicon is not a traditional piezoelectric material. Knowing that silicon can be a piezorezistive material, link in here,  a signal output can be obtained from an engineered part of the silicon chip that has the resistance as a function of pressure P.

Two Variable Sensor: Temperature and Pressure

The picture bellow, IMAGE CREDIT::JOHN A. ROGERS, UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN AND MDTMAG.COM,

T and P on Brain

is the actual device made by electrical engineers at the University of Illinois at Urbana-Champaign. The device shown in the picture, SOA in the field,  is based on silicon and is bioresorbable. The coil in the center is for transmission data purposes. The link in here  describes in more details the device.

According with Prof Rogers of University of Illinois at Urbana-Champaign, a new class of small, thin electronic sensors can monitor temperature and pressure within the skull – which are crucial health parameters after a brain injury or surgery – then melt away when they are no longer needed, eliminating the need for additional surgery to remove the monitors and reducing the risk of infection and hemorrhage. Similar sensors can be adapted for postoperative monitoring in other body systems as well.  John A. Rogers and Wilson Ray, a professor of neurological surgery at the Washington University School of Medicine in St. Louis,  published their work in the journal Nature.

Applications of the device

After a traumatic brain injury or brain surgery, it is crucial to monitor the patient for swelling and pressure on the brain. Current monitoring technology is bulky and invasive,and the wires restrict the patient’s movement and hamper physical therapy as they recover.

Because they require continuous, hard-wired access into the head, such implants also carry the risk of allergic reactions, infection and hemorrhage, and even could exacerbate the inflammation they are meant to monitor. Professor Rogers mentioned that the demonstration was done on animal models, with a measurement precision that’s just as good as that of conventional devices.

The sensors, smaller than a grain of rice, are built on extremely thin sheets of silicon – which are naturally biodegradable – that are configured to function normally for a few weeks, then dissolve away, completely and harmlessly, in the body’s own fluids.

Rogers’ group teamed with Illinois materials science and engineering professor Paul V. Braun to make the silicon platforms sensitive to clinically relevant pressure levels in the intracranial fluid surrounding the brain. They also added a tiny temperature sensor and connected it to a wireless transmitter roughly the size of a postage stamp, implanted under the skin but on top of the skull.

The Illinois group worked with clinical experts in traumatic brain injury at Washington University to implant the sensors in rats, testing for performance and bio-compatibility. They found that the temperature and pressure readings from the dissolvable sensors matched conventional monitoring devices for accuracy.

The researchers are moving toward human trials for this technology, as well as extending its functionality for other bio-medical applications.

Source

Nature(2016), Published online 18 January 2016, Bioresorbable silicon electronic sensors for the brain, Seung-Kyun Kang, Rory K. J. Murphy, Suk-Won Hwang, Seung Min Lee, Daniel V. Harburg, Neil A. Krueger, Jiho Shin, Paul Gamble, Huanyu Cheng, Sooyoun Yu, Zhuangjian Liu, Jordan G. McCall, Manu Stephen, Hanze Ying, Jeonghyun Kim, Gayoung Park, R. Chad Webb, Chi Hwan Lee, Sangjin Chung, Dae Seung Wie, Amit D. Gujar, Bharat Vemulapalli, Albert H. Kim, Kyung-Mi Lee, Jianjun Cheng, Younggang Huang, Sang Hoon Lee, Paul V. Braun, Wilson Z. Ray & John A. Rogers,

http://www.nature.com/nature/journal/v530/n7588/fig_tab/nature16492_SF1.html

http://www.pveducation.org/pvcdrom/pn-junction/diode-equation

Click to access ME189_Chapter%207.pdf

https://news.illinois.edu/blog/view/6367/312684

 

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