This PDF file contains the front matter associated with SPIE Proceedings Volume 8479 including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

This work demonstrates a novel surface scanning method for the quantitative determination of the local pyroelectric coefficient in ferroelectric thin films. Such films find application in flexible and large-area printed ferroelectric sensors for gesture-controlled non-touch human-machine interface devices.

The method is called Pyroelectric Scanning Probe Microscopy (PyroSPM)^[1] and allows generating a map of the pyroelectric response with very high spatial resolution. In domains of previously aligned dipole moments small heat fluctuations are achieved by laser diode excitation from the bottom side thus inducing changes in the surface potential due to the pyroelectric effect. Simultaneously, the surface potential variations are detected by scanning surface potential microscopy thus forming the base for the pyroelectric coefficient map. The potential of the method is demonstrated on the basis of ferroelectric semi-crystalline copolymer thin films yielding local maxima of the pyroelectric coefficients around 40µC/m²K. Another promising feature of PyroSPM is the ability to visualize “screened” polarization thus enabling in-depth profiling of polarization distributions and domain formation and to study the composition dependence and the time and frequency behavior of ferroelectric nano-domains.

In this paper, we report on a novel device that addresses the needs for an efficient, field deployable and disposable system in the field of bio-chemical sensors using organic semiconductors. The Fraunhofer Institute has enabled a complete roll-to-roll manufactured polymer-opto-chemical-electronic module on a foil substrate, wherein an electroluminescent light source has been hetero-integrated together with an organic TFT, working as a photo detector. A chemically sensitive, colour changing film is sandwiched in between the two elements to form an optical detection system for volatile analytes such as amines. The setup, henceforth referred to as the “PolyOpto” module, comprises of a dye coated layer that can detect specific chemical reactions by colour change inserted in between the EL light source and the OTFT photo-detector. A hole is laser cut through the system to allow the sensor layer to come in contact with the gases, which then through a chemical reaction, changes colour and initiates a different response in the output of the organic transistor. Hence, this allows for a disposable chemo-analytical system that can be used in various application fields. As compared to conventional systems, the advantage here lies in the direct integration of the different functionalities without any advanced assembly steps, simultaneous use of coatings for both components (transparent electrode and wiring layer) and roll-to-roll compatibility, thus rendering a disposable system. We believe that it aptly demonstrates the capabilities of polytronics in functional integration for low-cost bio-sensor manufacturing.

The recent advances on a monolithically integrated sensor platform based on ring-shaped organic photo detectors are presented. Various sensing chemistries based on luminescence for the detection of a number of parameters such as oxygen, carbon dioxide, humidity and pH in gaseous and/or liquid phase were investigated and optimized to the requirements of the sensor platform. Aiming on practical application, the need and methods to reference luminescence signals are evaluated including two wavelength rationing and lifetime measurements. Finally, we will discuss potential applications of the platform and present a micro-fluidic chip containing an array of integrated sensor spots and organic photodiodes.

We report on the influence of photolithographic processing of source/drain electrodes on the device performance of regioregular poly(3-hexylthiophene)-based bottom-gate bottom-contact organic field-effect transistors (OFETs). The presented results demonstrate that it is not only the processing conditions of the organic semiconductor influencing relevant device parameters, but it is also the preceding process steps including the structuring of electrodes via lift-off which significantly determine the OFET performance. In particular, the effects of photoresist residuals within the active channel region and the influence of the application of various lift-off chemicals were thoroughly investigated by contact angle measurements, atomic force microscopy and electrical characterization of OFET-based devices. By modifying the dielectric/semiconductor and/or electrode/semiconductor interfaces, the applied chemicals are shown to affect the device performance in terms of switch-on voltage, subthreshold swing and on/off-current ratio. The present study emphasizes the necessity for the optimization of the manufacturing process in order to obtain reproducible high-performing OFETs and OFET-based sensors.

Organic solution-gated field-effect transistors (SGFETs) can be operated at low voltages in aqueous environments, paving the way to the use of organic semiconductors in bio-sensing applications. However, it has been shown that these devices exhibit only a rather weak sensitivity to standard electrolyte parameters such as pH and ionic strength. In order to increase the sensitivity and to add specificity towards a given analyte, the covalent attachment of functional groups and enzymes to the device surface would be desirable. In this contribution we demonstrate that enzyme modified organic SGFETs can be used for the in-situ detection of penicillin in the low μM regime. In a first step, silane molecules with amine terminal groups are grafted to α-sexithiophene-based thin film transistors. Surface characterization techniques like X-ray photoemission confirm the modification of the surface with these functional groups, which are stable in standard aqueous electrolytes. We show that the presence of surface-bound amphoteric groups (e.g. amino or carboxylic moieties) increases the pH-sensitivity of the organic SGFETs. In addition, these groups serve as anchoring sites for the attachment of the enzyme penicillinase. The resulting enzyme-FETs are used for the detection of penicillin, enabling the study of the influence of the buffer strength and the pH of the electrolyte on the enzyme kinetics. The functionalization of the organic FETs shown here can be extended to a large variety of enzymes, allowing the specific detection of different chemical and biochemical analytes.