Cost-effective and efficient - biosensors on a roll

These days, biosensors have become an essential part of medical technology. However, manufacturing them is still very expensive. The interdisciplinary joint project M-era.Net BIOGRAPHY wants to change this with a process that is suitable for mass production.


Photo: Rolls on a printing machine

Using a roll-to-roll printing machine, biosensors from graphene could be made via mass production (symbol picture); © reflex_safak

The research team's goal is to apply graphene electrodes with biofunctional coatings on large-area polymer foils. This is designed to enable the printing of foils that can be used to produce biosensors on an industrial scale.

Biosensors make it possible to simply and reliably test drugs or quickly detect cell growth in changed environmental conditions. These sensors are based on electrodes to which proteins have been applied to. They change depending on the measuring task and release signals to these electrodes. Due to its catalytic activity, conductivity, biocompatibility and transparency, the modified carbon graphene is considered to be the ideal electrode material for many biosensors. Even though it was first presented in 2004, there has not been a method until 2014 that facilitates a high-quality production of larger quantities of graphene. To industrially produce graphene-based biosensors, processes for the reliable and automated production of electrode structures and their coating are required.

We already know coating techniques from the cell culture technology area that are biocompatible. Here, the culture dishes are inoculated with a variety of proteins. Popular procedures include spin coating where the liquid protein is distributed from the center onto the substrate area, and microcontact printing where micrometer-scaled protein structures are printed onto the substrate. Each method has its own set of disadvantages: a lot of liquid protein gets wasted during spin coating while microcontact printing is currently too expensive and elaborate for large-scale applications.
Graphic: Graphene

Does the "wonder material" graphene live up to its promise - also for printable sensors? © ogwen

Classic printing technology for graphene-based sensors of the future

The EU-funded joint project M-era.Net BIOGRAPHY between researchers and manufacturers from Great Britain and Germany relies on a new type of printing process for substrate coating. Researchers at the Fraunhofer Institute for Biomedical Engineering IBMT use a conductive graphene-containing ink by its research partner Haydale. The collaboration with the British company is essential since they have the necessary expertise in the development of novel graphene ink. With their help, a conductive protein-based ink was developed which - as is also the case with the other used materials - is biocompatible.

A micro engraving system was prepared for the required printing cylinder, in which a specially focused ultrashort pulse laser and novel surface coatings were being used. To produce the sensors, this printing cylinder is integrated into a roll-to-roll printing machine that was jointly developed with the German Saueressig Company. The basic principle of the printing machine is the same process that is used in newspaper printing. First the substrate is rolled up onto this roll-to-roll machine and transported to the other roll during the printing process. This process makes it possible to print large quantities of substrates in a very quick, stable and cost-efficient manner. The maximum sheet width is currently 30 centimeters and the smallest printable structures range between 10 and 20 micrometers.

Large quantities can be produced for automated applications

This production line is designed to make it possible to print complete microstructured biosensors in a reliable and automated manner in the future. With the help of these newly developed inks and printing processes, cost-efficient disposable sensors for direct virus detection by online monitoring the virus-induced cytopathic effect (CPE) via impedance spectroscopy will be produced for instance. One potential area of application is the automated validation of vaccines by monitoring the inhibition of the CPE in the presence of neutralizing antibodies.

The test system has already been in use for several months and is available to develop customer-specific printing processes. The project itself is scheduled to run until the end of 2017.

The progress made during the first year is already remarkable and shows –among other things- the type of potential the much-lauded wonder material graphene also provides.
Photo: Mareike Scholze; Copyright: B. Frommann

© B. Frommann

The article was written by Mareike Scholze and translated from German by Elena O'Meara.