Plastic Lab-on-a-Chip Curbs Clots

A plastic lab-on-a-chip system is being developed for fast and easy testing of thrombosis, or blood clots.

An EU project that involves ten research institutes and high tech firms in eight European countries, called DVT-IMP, is developing the system that they say will be inexpensive to produce because of the plastic components.

"This example shows clearly the possibilities for polytronics. In a networked world, oriented towards people, inexpensive, multifunctional systems are needed - for example in assisted living. In order to build up the infrastructure necessary for this, electronic systems have to be produced in large quantities, in a cost-effective manner on large substrates. And with polymer electronics, this would be perfectly possible," said Karlheinz Bock, professor and head of the "Polytronic Systems" division at Fraunhofer IZM, where the core of the device was built and tested.

Plastic chips monitor body functions. (Image: Fraunhofer IZM)

Polytronics is a key technology that combines functional materials and electronics. A major advantage is the simple and inexpensive production: the polymer materials can be dissolved and then, like electronic ink, be recaptured through a printing process, structured on flexible sheets. "In this manner, we can construct small, handy and easy-to-use systems that for the most part make life easier for the sick and elderly," explained Bock.

The analytical device is a small, high-precision manufactured single-use cartridge that acts as a tool for the biochemical analysis of a drop of blood. It consists of a polycarbonate plate measuring 3 mm by 22 mm by 70 mm, and unites two critical components in one device. The most important component is a foil of 150 micrometers thickness on which a filigree network with conductor lines and gold sensors for blood analysis is attached, as well as a 120 micrometer deep fluid channel for conducting blood to the analysis elements. Inside the sensor chamber, the antibodies are integrated on electrodes that allow it to analyze the concentration of blood clotting markers. If the number is elevated, then the risk of a thrombus is forming.

For those who are prone to thrombosis, this device could be an important companion. They will no longer have to wait days for lab results on possible clot forming in their blood. Just like glucose tests, a drop of the patient's blood suffices on the single-use cartridge the physician places then in a little hand-held scanner. Within minutes, the results appear on the display - and, if necessary, immediately apply the according measures. The EU project on the feasibility of the system runs until the middle of this year.

The sensor wristband, also engineered at IZM, is suited for the long-term monitoring of various important body functions of older patients - but also of athletes. It is like a plastic wristwatch. Instead of a clock dial, the sensor wristband is equipped with an illuminated "electroluminescent display" that indicates for example the actual body temperature at any time of the day. It also detects skin moisture, which may be a sign for the dehydration of the patient or athlete. For a person with a pacemaker the patient wristband may also signal potential danger, indicating the strength of electric or electromagnetic fields in close proximity. A number of other applications are conceivable: if needed, the most diverse array of sensors can be integrated into the polytronic platform.

From a technical perspective, the sensory wristband is a combination of polymer and conventional electronics. Lighting elements, sensors and polymer resistances printed on the foils are connected into one system with integrated circuits made of silicon. A three micrometer-thin resonance circuit with an etched coil - a kind of minute antenna - records the electric smog. An interdigital capacitor attached to a foil and only 30 micrometers thick detects skin moisture.

Comb-shaped, narrowly interlaced meanders made of copper bands of a mere 0.5 micrometer thickness, measure the body temperature.

"The sensor wristband demonstrates the potential that lies within the flexible electronics mounted on foils," said Bock.

The tiny sensors and the optical functions are applied to the foils through a combination of technical printing and lithographic processes. The sensor wristband, just like the diagnostic device for deep vein thrombosis, can be manufactured cost-effectively both as individual sheets as well as by roll-to-roll production in larger batches.

For more information, visit: www.izm-m.fraunhofer.de or www.diagnosingdvt.com