title: Flexible Blade-Coated Multicolor Polymer Light-Emitting Diodes for Optoelectronic Sensors.
abstract: A method to print two materials of different functionality during the same printing step is presented. In printed electronics, devices are built layer by layer and conventionally only one type of material is deposited in one pass. Here, the challenges involving printing of two emissive materials to form polymer light-emitting diodes (PLEDs) that emit light of different wavelengths without any significant changes in the device characteristics are described. The surface-energy-patterning technique is utilized to print materials in regions of interest. This technique proves beneficial in reducing the amount of ink used during blade coating and improving the reproducibility of printed films. A variety of colors (green, red, and near-infrared) are demonstrated and characterized. This is the first known attempt to print multiple materials by blade coating. These devices are further used in conjunction with a commercially available photodiode to perform blood oxygenation measurements on the wrist, where common accessories are worn. Prior to actual application, the threshold conditions for each color are discussed, in order to acquire a stable and reproducible photoplethysmogram (PPG) signal. Finally, based on the conditions, PPG and oxygenation measurements are successfully performed on the wrist with green and red PLEDs.
authors.affiliation: Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA.
authors.forename: Donggeon
authors.initials: D
authors.lastname: Han
authors.affiliation: Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA.
authors.forename: Yasser
authors.initials: Y
authors.lastname: Khan
authors.affiliation: Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Ting
authors.affiliation: Cambridge Display Technology Limited, Godmanchester, Cambridgeshire, PE29 2XG, UK.
authors.forename: Simon M
authors.initials: SM
authors.lastname: King
authors.affiliation: Cambridge Display Technology Limited, Godmanchester, Cambridgeshire, PE29 2XG, UK.
authors.forename: Nir
authors.initials: N
authors.lastname: Yaacobi-Gross
authors.affiliation: Cambridge Display Technology Limited, Godmanchester, Cambridgeshire, PE29 2XG, UK.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Humphries
authors.affiliation: Cambridge Display Technology Limited, Godmanchester, Cambridgeshire, PE29 2XG, UK.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Newsome
authors.affiliation: Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA.
authors.forename: Ana C
authors.initials: AC
authors.lastname: Arias
keywords: blade coating; flexible electronics; organic light-emitting diodes (OLEDs); polymer light-emitting diodes (PLEDs); printed sensors; pulse oximetry; wearable sensors