The aim of the initial project (SFA) was the realization of high performance and flexible field effect transistors based on ultrathin free-standing films that involve a spontaneous phase separation between the polymer dielectric and the organic semiconductor. This approach is applied to reduce the number of production steps of flexible organic/inorganic based transistors. In the frame of the research project (dedicated to organic electronic), basic knowledge about deposition process of organic materials has been investigated. In cooperation with dr. Jasper Michels (Max Planck Institute for Polymer Research) theoretical model, concerning prediction of the surface morphology of organic semiconductor has been developed. It has to be pointed out, that the surface morphology and microstructure is one of the crucial point, which determine future application of organic field-effect transistors. Biosensing is one of the possible usage of organic transistors; however, it is still highly limited by the interaction between organic semiconductor and biomolecules. As it was already pointed out in our last work, the mechanism of the controlled molecules deposition (crystallization, nanostructured organization) at the air/liquid/solid interface could be implemented for inorganic or biomolecules for a specific future application. The ability to create electronic devices that enable the monitoring of cell-cell communication has important implications for many disciplines such as cellular biology, material science, and molecular electronics. Current systems typically use thin coatings of polycations like poly(L-lysine) (PLL) to facilitate the attachment and growth of neuronal cells on the final device. While this polymer is widely available, it does not allow for easy chemical modifications and consequently it is difficult to introduce bioactive signals into these systems. On the other hand, supramolecular polymers from self-assembling peptides have gained significant interest in recent years, as they mimic the fibrous structure natural extracellular matrix proteins, while using much smaller building blocks. They provide ideal substrates for different types of cells both in 2D and 3D environments. Due to the assembly of small peptide building blocks, different functionalities such as bioactive epitopes can be easily incorporated into the nanofibers, thus enabling to study cellular responses to different types of signals that cannot be achieved with simple PLL coatings. However, the homogeneity and controlled surface morphology is a main disadvantage in their application as cell-cell communication device. This hypothesis assuming the use of a zone-casting for homogenous biomolecules deposition has been confirmed by the preliminary results obtained in the frame of cooperation between prof. Tanja Weil group and dr. Marszalek group. Figure 1 presents the comparison of the drop-cast and zone-cast CKFKFQF peptide thin films. A clear difference in a surface morphology (variation in packing density and homogeneity) between currently used deposition method (drop casting) and the proposed zone-casting can be observed. Additionally the strong influence of the zone-cast deposition parameters like: concentration, covering speed has been noticed.

Figure 1. The sequence of CKFKFQF peptide (a), drop-cast CKFKFQF peptide (b), zone-cast CKFKFQF peptide layer (c), fluorescence microscopy images of zone-cast layer, images were done after exposure to a proteostat solution (d).

        Here, we finally plan to prepare bioactive coatings on electronic chips using the zone-casting that provide an adjustable substrate for studying neuronal cells. The submitted proposal is a kind of proof-of-concept of using zone-casting method previously used for organic semiconductor deposition to controlled deposition of biological materials. We would like to combine the knowledge of three groups, namely the expertise of the prof. T. Weil (C. Synatschke) – the preparation of self-assembled peptide nanomaterials suitable as neuronal substrates, dr. Marszalek – the expertise to produce precise and homogeneous coatings of organic molecules on a diverse range of substrates using the zone-casting and prof. P. W.M. Blom (D. Koutsouras) in fabricating electronic devices.