We report the first disposable fluorescent biosensor based on algae, with an organic light emitting diode and an organic photodetector (OPD) miniaturized into a microfluidic chip. A DPVBi OLED was used as the excitation source, while a blend of PTB3/PCBM was used for the organic photodetector. The fluorescence biosensor is integrated in a microfluidic chip made from polymeric materials such as (poly)dimethylsiloxane (PDMS), which is transparent, biocompatible and can easily be processed by conventional lithography. The complete detector is designed to detect Chlamydomonas reinhardtii green algae fluorescence in the microfluidic chamber. Algal chlorophyll fluorescence is a physiological parameter routinely used to measure the photochemical efficiency of PSII. This measurement is a reliable and non-invasive method to determine the toxicity of pollutants like herbicides and metals.

“Label-free” biomolecule sensors for detection of inflammatory cardiovascular biomarker associated with vulnerable coronary vascular plaque were designed and fabricated using micro and nano-textured polystyrene structures that functioned as sensing elements coupled with electronic measurement equipment. We demonstrated that scaling down the surface texturing from the micro to the nanoscale enhances the amplitude of the measured signal strength. We believe that the nanoscale fiber morphology provides size matched spaces for trapping and immobilizing the protein biomolecules resulting in enhanced detection and signal strength. We selected polystyrene as the model system and demonstrated the detection of human serum C-reactive protein (hs-CRP). We employed these findings in designing a platform “lab-on-a-chip” protein sensor. Comparative studies were performed on two different polystyrene textured surfaces: a polystyrene microsphere mat, and an electrospun polystyrene nanofiber matrix.

We studied the electrical and optical responses of organic light-emitting devices (OLEDs) with green and red phosphorescent dyes doped in a polymer matrix to compressive stresses. The green OLED converted stresses as low as 6.8 kPa into measurable and reversible changes in both current density and electroluminescence (EL) intensity. The current showed a nearly linear characteristic response with sensitivity up to 205 μA kPa-1, whereas the EL intensity decreased by over three orders of magnitude at 107 kPa. In contrast, stress-induced modulations in current and light intensity were noticeable in the red OLED only above 160 kPa. The discrepancy has been attributed to different rates of stress-enhanced back exciton energy transfer between guest and host molecules, which quenches the EL of the green OLED, but has a much smaller impact on the performance of the red OLED. It is expected that similar green phosphorescent OLEDs built on large curved surfaces may directly image stress distributions and sense touch on a par with a human finger.

In this work we investigate polymer photodiodes based on a blend system consisting of poly(3-hexylthiophene-2,5-diyl) (P3HT) and the fullerene derivative (6,6)-phenyl C-butyric acid methyl ester (PCBM). An optimized low source impedance architecture allows measurements in the GHz range with minimum distortion, while at the same time allowing to probe the favourable sandwich device structure. We have studied the underlying device physics and investigated the influence of parameters such as active layer thickness and bias voltage on the transient photocurrent response. Using a numerical simulation software combining a self-consistent drift-diffusion model in conjunction with an optical model based on the transfer matrix method we model the transient photocurrent of polymer photodiodes. Transient photocurrent measurements utilizing this low impedance device architecture excited by 1.6 ns short laser pulses show very good correlation between simulated and measured results. Furthermore we have developed an encapsulation technique to integrate high-speed organic photodiodes onto standard printed circuit boards (PCBs) to avoid the degradation of the devices by humidity or oxygen.