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article imageEssential Science: Medical technology that can dissolve away

By Tim Sandle     May 2, 2016 in Science
Tiny electronic sensors and devices are being developed as medical devices. These can be implanted in the body and then dissolve away without a trace. This avoids the risks involved with removing them.
Medical devices cover a broad spectrum of technology. The term refers to any type of instrument, apparatus, appliance or computer software used for medical diagnostic or therapeutic purposes. Examples include equipment used to diagnose diseases; devices designed to alleviate an injury; devices designed to modify or replace part of the human anatomy (such as a hip replacement); or something designed to control conception.
The global market in medical device is huge, being valued at over $200 billion. The technologies range (depending on definition) across tongue depressors, thermometers, disposable gloves, computers, implants, and prostheses. The devices are covered by various parts of national and international regulation.
Implantable pacemaker
Implantable pacemaker
Steven Fruitsmaak (CC BY 3.0)
Medical devices implanted into the human body carry risks. Risks include the material used, such as whether a plastic is compatible with the human body. A few years ago there was a scandal involving an unsuitable material being used to manufacture breast implants. The silicone breast implants were manufactured by a French company called Poly Implant Prothèse. An investigation found the company to have been illegally manufacturing and selling breast implants made from cheaper industrial-grade silicone for many years.
Other risks with medical device implants concern the process of implanting the devices, in terms of the sterility of the implant and the surgical procedure. Another area, which is the main topic of this article, concerns the removal of the devices. The removal process can present a medical challenge.
One goal with medical device research is to create miniature electronic sensors and devices that can be implanted in the body, via a surgical procedure, and which then dissolve away without a trace. No such devices currently exist at the commercial level. However, the concept is edging closer to reality.
In a recent study, materials scientists have examined a range of biodegradable materials to be used as the basis of such devices. The materials include DNA, proteins and metals. The materials need to be of a type that does not react with the human body in an adverse way; which are capable to dissolving once the devices have performed their required function; and which are compatible with electronics.
The optimal material, the study has found, is a material constructed from egg proteins, magnesium and tungsten. Egg white is a substance called albumen, and it is made up of the proteins albumin, mucoproteins, and globulins. Albumins are a family of globular proteins; a mucoprotein is a glycoprotein composed primarily of mucopolysaccharides; and globulins are a family of globular proteins that have higher molecular weights than albumins.
With the metals, magnesium is a shiny gray solid; a material it is soft and lightweight. Tungsten is a rare, hard metal also known as wolfram. Tungsten is used to make electrodes, incandescent light bulb filaments, X-ray tubes.
These three materials can, according to the research, form the basis of a scientific field called transient electronics (meaning devices that last for a short period of time.) As well as being dissolvable, a secondary aim is to have the devices ‘environmentally friendly’, generating residues that do not add to the raft of other polluting materials associated with healthcare facilities.
To achieve the material, scientists centrifuged diluted egg albumin onto a silicon wafer. This created an ultra-thin film. To this, electrodes were added, formed from the magnesium and tungsten. The device was performance checked, and the electrical functionality was good.
For the electrical part, a special component called a memristor (derived from "memory resistor") has been developed. This represents a new type of resistor that regulates the flow of electric current. Memristors are basically a fourth class of electrical circuit, joining the resistor, the capacitor, and the inductor, that exhibit their unique properties primarily at the nanoscale. More about these devices is shown in the video below.
The newly developed device can also "remember" charges. In terms of the dissolvability, the electrodes and albumin decomposed within 10 hours and the electronic chip disappeared within three days.
The study has been led by Chinese scientists Jikui Luo, and Xiaozhi Wang. The review of materials has been published in the journal Applied Materials & Interfaces. The paper is titled “In Vitro and in Vivo Evaluation of Silicate-coated Polyetheretherketone Fabricated by Electron Beam Evaporation.”
This article is one of Digital Journal's regular Essential Science columns. Each week we explore a topical and important scientific issue. Last week we examined the current research into natural antimicrobial compounds. The week before we explored the link between gum disease and heart problems.
More about essential science, Medical devices, Medical Technology, Technology, dissolvable
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