Organic Light‐Emitting Diode Sensing Platform: Challenges and Solutions

Abstract

electronics-based (bio)chemical sensing and biotechnology applications. [ 1 ] As examples, luminescent conjugated polymers have been used to gain insight into biology and pathology of protein aggregation diseases, [ 2 ] and for designing electrochemical switches and ion pumps for cell biology studies. [ 3 , 4 ] Organic thin fi lm transistors (OTFTs) were implemented to develop cost-effective and label-free DNA or protein sensor chips, [ 5 ] and organic light-emitting diodes (OLEDs) have been evaluated as excitation sources in photo luminescence (PL)-based sensing of analytes such as oxygen, ethanol, glucose, lactate, and cholesterol. [ 1 , 6-13 ] Other examples of the use of OLEDs (including polymer LEDs (PLEDs)) in sensing applications include an integrated PL-based oxygen and pH sensor, utilizing an OLED as the light source and an organic photodetector (PD); [ 13 -16 ] two polarizers were used for separating the PL and the OLED's electroluminescence (EL). [ 13 ] OLEDs were used also for fl uorescence detection of proteins [ 17 ] and PLEDs were used as an integrated excitation source for microfabricated capillary electrophoresis. [ 18 ] The use of PLEDs for monitoring biomolecules labeled with fl uorescent dyes by monitoring shifts in the PLED's EL [ 19 ] and a surface plasmon resonance sensor utilizing an OLED and a metallic sensing layer were also reported. [ 20 ] A nanotextured OLED-based chemical sensor for label-free detection of methanol and ethanol was demonstrated. [ 21 ] The detection was based on monitoring analyte-induced changes in the OLED turn-on voltage and EL intensity. In another example, a refractometer with an integrated OLED light source and dual organic PDs (OPDs) were used for sensitive analyte detection by monitoring the change in light fl ux from the OLED to the PD that resulted from changes in refractive index of the analyte solution relative to a reference solution. [ 16 ] Good detection sensitivities are often obtained using OTFTand OLED-based sensors, and the issue of the long-term stability that affects the organic devices is often less important in their sensing platforms, as the sensing probes are often shorter lived than the OLEDs. Moreover, as the cost of OTFTs and OLEDs is expected to drop, they are promising for use in disposable sensors. is used for directional PL scattering toward the photodetector, which leads to a ∼ 2.1-3.8 fold enhancement of the PL signal. This behavior is shown for oxygen sensing, which is the basis for sensing of bioanalytes such as glucose, lactate, ethanol, cholesterol, and uric acid.

Organic Photodetectors in Analytical Applications

“…The structure of PL-based sensors is similar to that of CL sensors [2,8,12], though the working principle is different. In PL-based sensors the analyte-dependent PL intensity I and/or decay time τ of the analyte-sensitive material are monitored.…”

“…Since optical sensors rely on the interaction between the sensing material and light from the excitation source, precise and sensitive detection of a signal originating from the sensing film is key in determining the device performance. Initially, OLEDs were integrated with a sensing film fabricated on the opposite side of a common substrate, but to achieve a sensitive and specific detection a photomultiplier tube (PMT) was commonly used [7,8]. Though optical sensors with a PMT have a very high signal to noise ratio (SNR) and fast response time [9,10], the PMT is highly magnetic-field sensitive and bulky, which prevents scaling down sensors with it and the sensor's use is limited to a magnetic-free environment.…”

Automated, Miniaturized, and Integrated Quality Control-on-Chip (QC-on-a-Chip) for Cell-Based Cancer Therapy Applications

“…Although a variety of excitation sources are available for fluorescent detection laser-induced fluorescence (LIF) is most easily adapted to the dimensions of microchips Gao et al, 2004;Lee and Wen, 2005). Since laser systems are often expensive and wavelength specific (exhibiting very narrow bandwidth), a range of alternative light sources, including organic light-emitting diodes (OLEDs) have been successfully integrated into microfluidic devices (Choudhury et al, 2004;Cai et al, 2008Cai et al, , 2010Shinar and Shinar, 2008;Liu et al, 2011;Sagmeister et al, 2013;Williams et al, 2014). Additionally, organic field-effect transistors (OFETs) ( Figure 3C) as read-out devices for various physical (Sekitani et al, 2009), chemical, and biological (Lin and Yan, 2012) sensing applications can be used in the non-invasive, label free analysis system (Someya et al, 2010;Yun et al, 2014).…”

Exploiting the Potential of OLED-Based Photo-Organic Sensors for Biotechnological Applications

“…Owing to the non-invasive nature, high sensitivity and easy implementation of optical monitoring systems such as lightemitting diodes (LEDs), lasers and photodiodes are widely used as monitoring devices in these small-scale systems. As discussed in other reviews, photo-organic electronics, in contrast to aforementioned conventional optical devices, allow the design of structurally integrated miniaturized sensor arrays that provide low-cost, portable and multianalyte detection systems [8][9][10]. The Figure 1 shows examples of suitable orientations of integrated photo-organic sensor systems.…”