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Ultra-robust, flexible organic sensors for application in lactic acid sensing and selective biosensing

Periodic Reporting for period 1 - Robust OTFT sensors (Ultra-robust, flexible organic sensors for application in lactic acid sensing and selective biosensing)

Reporting period: 2017-07-01 to 2018-06-30

The overall objective of this project is the development of novel, highly-stable sensors architectures based on semiconducting polymers that are cheaper and more capable than their inorganic counterpart. The goal is to make true use of organic semiconductor’s unique properties as a soft and stretchable material for the application in reliable biosensors for wearable health monitoring and personalized medical applications.

- One example is the development of sweat sensors for constant monitoring of patients' cortisol concentration which is indicative of their psychological health and varies greatly between patients and throughout the day. Cortisol is linked to psychological illnesses such as depression and a constant monitoring can allow for a targeted and personalized treatment with targeted drug delivery. So far this constant monitoring is not possible since tests can only be done in a laboratory.

- Another example is the use of biosensors for the screening for DNA/RNA for a fast detection and screening of cancer. An array of biosensors could greatly simplify the tests making it more viable and easier to test a larger number of patients at a higher frequency

The objective of this project is the development of a sensors architecture that can be produced cheaply and can be modified for targeted sensing of the above-mentioned analytes (cortisol, RNA etc.). Here the main goal is to develop a platform that exhibits long time stability such that it can record and monitor small signals induced by the binding of a bio-molecule reliably over the course of days. For some applications such as cortisol sensing it is furthermore desirable to have the sensor in close contact witht he human skin (i.e. for skin patches that can monitor the concentration of an analyte over the course of hours or even days) and therefore it is desirable to make the architecture flexible and if possible, stretchable.
During the outgoing phase of the Fellowship, a new sensors architecture was designed that has the potential to address the above-mentioned objectives. The project work led to the discovery of a intrinsically and fully stretchable polymer semiconductor that can operate without a loss of performance even when exposed to strains >50%. This is a significant finding and has implications beyond the original project scope. The results are novel and have significant impact in the community and beyond such that they are currently prepared for publication in a high impact journal. The new polymer class described above could be used in a newly developed sensor architecture that is based on a transistor design with a polar, ionic elastomer dielectric which is highly stable in analyte solutions (such as water, biological buffer solutions). The polar dielectric forms an electric double layer making it highly sensitive while simultaneously encapsulating the device against the analyte solution. By specific functionalization, the design can be made highly selective to specific analytes such as proteins, RNA, DNA, PH etc. with long term stability enabling health monitoring applications. The long-term stability of the architecture has been demonstrated and its functionality as a sensor has been shown with the proof of concept protein BSA. Currently further optimization as well as the application for real-world applications in health monitoring and personalized medicine are being explored in collaboration with Stanford University.
Over the coming year, the sensors design developed during the outgoing phase of the fellowship will be further optimized and refined. The sensors design will also be integrated on a flexible substrate to demonstrate its applicability for wearable health applications. In addition, specific surface functionalization will be used to test the architecture’s obtainable sensitivity to Cortisol and RNA. For the publication of these results, a high impact publication is planned. Currently also, potential patenting approaches are being investigated. The final design is then expected to be integrated into the wider research efforts on personalized medicine and potentially be used in field trials at Stanford University. The current state of the art does not allow for such applications.

The new architecture developed within the framework of this Marie-Curie Fellowship offers a powerful tool for the selective sensing of analytes. This is one of the key challenges in the research field of biosensing and a big step towards higher reliability. Here, the use of an elastomer ionic dielectric overcomes these selectivity issues while simultaneously allowing for a maximum signal amplification. The new platform additionally offers long-term stability needed for real-world applications beyond the research laboratory environment as well as flexibility and stretchability needed for wearable skin patches and health monitors. Integrated within the bigger framework of wearable and personalized health applications, the sensor design can tap into research done on surface modification and functionalization for improving the selectivity to relevant analytes for real world health applications. In this respect the newly established collaboration between Stanford University and the University of Cambridge profs to be extremely helpful. The research is therefore expected to have a broader impact in the development of real-world personalized medical applications such as the monitoring of psychological health or the quick and cheap screening for cancer biomarkers and currently work is under way to test these potential applications.
Novel biosensor architecture and response to sensing BSA protein