Organic light-emitting diodes (OLEDs) offer unique properties such as large-area emission, compatibility with flexible substrates, tuning of emitted spectrum, and structuring into high-density arrays. This makes OLEDs attractive for biomedical applications like on-chip sensing or wearable health monitoring and, more recently, also to control the activity of neurons through a method called optogenetics. So far, most light sources used in optogenetics provide limited spatial resolution. In this contribution, we present micropatterned OLEDs that are capable of precisely controlling neuronal activity in Drosophila melanogaster (fruit fly) larvae. The OLEDs provide highly confined light stimuli to individual abdominal segments, which allows precise activation and inhibition of sensory input in larvae. Our work demonstrates the advantages of OLED technology for neuroscience and provides prospects for future integration of OLEDs in implants.
Optogenetics is a technique to modulate neuronal activity in response to light. Here, we present two different light sources that can provide high spatial resolution for precise optogenetic stimulation of Drosophila melanogaster (fruit fly) larvae: organic light-emitting diodes (OLEDs) and smartphone displays. Using micro-structured OLED arrays, we stimulated sensory neurons in individual abdominal segments of Drosophila larvae and thus controlled their crawling direction. Furthermore, we developed a smartphone app that allows spectral, spatial, and temporal control over the light emitted by the display and used this to deliver fine patterns of light to constrain larval movement.
Organic light-emitting diodes (OLEDs) possess many unique properties such as large-area emission, fabrication on flexible plastic films, adjustment of the emission spectrum and angular distribution by chemical and optical means, and structuring to high-density arrays with millions of pixels. While especially the latter contributed to commercialization of OLED displays in consumer electronics, the properties of OLEDs also make them highly attractive for biological applications. In this contribution, we present fluorescent blue OLEDs with electrically doped charge transport layers that reach more than 100,000 cd/m² at 5 V. We applied the light source in optogenetics to stimulate primary mouse hippocampal neurons and to evoke sensory response in Drosophila melanogaster larvae using micro-structured OLED pixels. Furthermore, by applying a distributed Bragg reflector, we narrowed the OLED spectrum down in order to enable imaging of neuronal activity using genetically encoded calcium indicators. Finally, we discuss our recent efforts on providing stable encapsulation of flexible OLEDs. These examples show how OLEDs may outperform traditional light sources applied in biophotonics by enabling conformable, bio-compatible, and bright illumination with unprecedented resolution.
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