M. Makrygianni

Applications of laser printing for organic electronics

The development of organic electronic requires a non contact digital printing process. The European funded e-LIFT project investigated the possibility of using the Laser Induced Forward Transfer (LIFT) technique to address this field of applications. This process has been optimized for the deposition of functional organic and inorganic materials in liquid and solid phase, and a set of polymer dynamic release layer (DRL) has been developed to allow a safe transfer of a large range of thin films. Then, some specific applications related to the development of heterogeneous integration in organic electronics have been addressed. We demonstrated the ability of LIFT process to print thin film of organic semiconductor and to realize Organic Thin Film Transistors (OTFT) with mobilities as high as 4 10-2 cm2.V-1.s-1 and Ion/Ioff ratio of 2.8 105. Polymer Light Emitting Diodes (PLED) have been laser printed by transferring in a single step process a stack of thin films, leading to the fabrication of red, blue green PLEDs with luminance ranging from 145 cd.m-2 to 540 cd.m-2. Then, chemical sensors and biosensors have been fabricated by printing polymers and proteins on Surface Acoustic Wave (SAW) devices. The ability of LIFT to transfer several sensing elements on a same device with high resolution allows improving the selectivity of these sensors and biosensors. Gas sensors based on the deposition of semiconducting oxide (SnO2) and biosensors for the detection of herbicides relying on the printing of proteins have also been realized and their performances overcome those of commercial devices. At last, we successfully laser-printed thermoelectric materials and realized microgenerators for energy harvesting applications.

Direct Laser Printing for Organic Electronics

This article reviews the latest developments as well as the background and the evolution of direct laser printing of various materials for organic electronics applications. Current technological trends require the precise deposition of highly resolved features, which preserve their structural and electronic properties upon transfer, while increasing the number of components that can be integrated in a single device. Direct laser printing techniques meet these requirements and examples of selected applications, including chemical sensors and biosensors, organic thin-film transistors, organic light-emitting diodes, and power generating devices, are presented highlighting the potential incorporation of lasers into the direct printing of entire devices and components. In particular, the successful laser printing of polymers, metals, semiconducting inks, and viable biological materials such as DNA, proteins, and enzymes with high spatial resolution offers unique advantages compared to traditional inkjet and thin-film techniques. Moreover, the mechanisms of liquid- and solid-phase laser printing are investigated through time-resolved studies, while postprinting processes such as laser sintering, a process used for the formation of conductive features on laser-printed metallic nanoparticle patterns, are also discussed in this article. Keywords: devices; direct laser printing; laser-induced forward transfer technique (LIFT); MAPLE-DWOLEDs; organic electronics; OTFTs; sensors

High-speed imaging and evolution dynamics of laser induced deposition of conductive inks (Conference Presentation)

During the last decade there is an ever-increasing interest for the study of laser processes dynamics and specifically of the Laser Induced Forward Transfer (LIFT) technique, since the evolution of the phenomena under investigation may provide real time metrology in terms of jet velocity, adjacent jet interaction and impact pressure. The study of such effects leads to a more thorough understanding of the deposition process, hence to an improved printing outcome and in these frames, this work presents a study on the dynamics of LIFT for conductive nanoparticles inks using high-speed imaging approaches. Moreover, in this study, we investigated the printing regimes and the printing quality during the transfer of copper (Cu) nanoink, which is a metallic nanoink usually employed in interconnect formation as well as the printing of silver nanowires, which provide transparency and may be used in applications where transparent electrodes are needed as in photovoltaics, batteries, etc. Furthermore, we demonstrate the fabrication of an all laser printed resistive chemical sensor device that combines Ag nanoparticles ink and graphene oxide, for the detection of humidity fabricated on a flexible polyimide substrate. The sensor device architecture was able to host multiple pairs of electrodes, where Ag nanoink or nanopaste were laser printed, to form the electrodes as well as the electrical interconnections between the operating device and the printed circuit board. Performance evaluation was conducted upon flow of different concentrations of humidity vapors to the sensor, and good response (500 ppm limit of detection) with reproducible operation was observed.