Degradation of all-inkjet-printed organic thin-film transistors with TIPS-pentacene under processes applied in textile manufacturing

Printed electronics represent an alternative solution for the manufacturing of low-temperature and large area flexible electronics. The use of inkjet printing is showing major advantages when compared to other established printing technologies such as, gravure, screen or offset printing, allowing the reduction of manufacturing costs due to its efficient material usage and the direct-writing approach without requirement of any masks. However, several technological restrictions for printed electronics can hinder its application potential, e.g. the device stability under atmospheric or even more stringent conditions. Here, we study the influence of specific mechanical, chemical, and temperature treatments usually appearing in manufacturing processes for textiles on the electrical performance of all-inkjet-printed organic thin-film transistors (OTFTs). Therefore, OTFTs where manufactured with silver electrodes, a UV curable dielectric, and 6,13-bis(triisopropylsilylethynyl) pentance (TIPS-pentacene) as the active semiconductor layer. All the layers were deposited using inkjet printing. After electrical characterization of the printed OTFTs, a simple encapsulation method was applied followed by the degradation study allowing a comparison of the electrical performance of treated and not treated OTFTs. Industrial calendering, dyeing, washing and stentering were selected as typical textile processes and treatment methods for the printed OTFTs. It is shown that the all-inkjet-printed OTFTs fabricated in this work are functional after their submission to the textiles processes but with degradation in the electrical performance, exhibiting higher degradation in the OTFTs with shorter channel lengths (L=10 μm).This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST C/FIS/UI607/2014 and the project PTDC/CTM-NAN/121038/2010. Enrico Sowade was financially supported by the European Commission within the Framework FP7-ICT (grant agreement number 287682, project acronym TDK4PE). The authors also thank for the support by the project Matepro – Optimizing Materials and Processes”, ref. NORTE-07-0124-FEDER-000037”, co-funded by the “Programa Operacional Regional do Norte” (ON.2 – O Novo Norte), under the “Quadro de Referência Estratégico Nacional” (QREN), through the “Fundo Europeu de Desenvolvimento Regional” (FEDER). Hélder Castro thanks for the support of the FCT under the grant SFRH/BDE/33350/2008

All-inkjet-printed thin-film transistors: manufacturing process reliability by root cause analysis

We report on the detailed electrical investigation of all-inkjet-printed thin-film transistor (TFT) arrays focusing on TFT failures and their origins. The TFT arrays were manufactured on flexible polymer substrates in ambient condition without the need for cleanroom environment or inert atmosphere and at a maximum temperature of 150 degrees C. Alternative manufacturing processes for electronic devices such as inkjet printing suffer from lower accuracy compared to traditional microelectronic manufacturing methods. Furthermore, usually printing methods do not allow the manufacturing of electronic devices with high yield (high number of functional devices). In general, the manufacturing yield is much lower compared to the established conventional manufacturing methods based on lithography. Thus, the focus of this contribution is set on a comprehensive analysis of defective TFTs printed by inkjet technology. Based on root cause analysis, we present the defects by developing failure categories and discuss the reasons for the defects. This procedure identifies failure origins and allows the optimization of the manufacturing resulting finally to a yield improvement

Drying-mediated patterns in colloid-polymer suspensions

Drying-mediated patterning of colloidal particles is a physical phenomenon that must be understood in inkjet printing technology to obtain crack-free uniform colloidal films. Here we experimentally study the drying-mediated patterns of a model colloid-polymer suspension and specifically observe how the deposit pattern appears after droplet evaporation by varying particle size and polymer concentration. We find that at a high polymer concentration, the ring-like pattern appears in suspensions with large colloids, contrary to suppression of ring formation in suspensions with small colloids thanks to colloidpolymer interactions. We attribute this unexpected reversal behavior to hydrodynamics and size dependence of colloid-polymer interactions. This finding would be very useful in developing control of drying-mediated self-assembly to produce crack-free uniform patterns from colloidal fluids.ope

Self-assembly of spherical colloidal photonic crystals inside inkjet-printed droplets

The manufacturing of three-dimensional colloidal structures on solid substrates is an important topic of applied research, aiming for photonic components especially in photovoltaic and sensor applications. Whereas conventional techniques such as wet self-assembly are based on engineering of the substrate surface energy, alternative strategies envisage the independence of the interfacial conditions. We report on inkjet printing of colloidal suspensions of monodisperse silica or polystyrene nanoparticles or both and their self-assembly to spherical colloidal photonic crystals. The formation process of the colloidal nanoparticles into stable spherical colloidal assemblies (SCAs) is achieved by a self-assembly process inside tiny droplets of a stochastic mist generated intentionally instead of a jet of individual single droplets using inkjet printing. The mist jetted, shrinking droplets serve as confined geometries for the solidification of the nanoparticles during the evaporation; thus the particles are packed into stable ball-shaped assemblies. We show how fine-tuning of the jetting parameters allows the reliable generation and deposition of three-dimensional (3D) spherical colloidal assemblies of nanoparticles variable in size and with a high packing order. Microreflectance spectroscopy proves that the degree of order in the SCA is such that photonic stop bands occur inherent for photonic crystals

A novel wearable electronic nose for healthcare based on flexible printed chemical sensor array

A novel wearable electronic nose for armpit odor analysis is proposed by using a low-cost chemical sensor array integrated in a ZigBee wireless communication system. We report the development of a carbon nanotubes (CNTs)/polymer sensor array based on inkjet printing technology. With this technique both composite-like layer and actual composite film of CNTs/polymer were prepared as sensing layers for the chemical sensor array. The sensor array can response to a variety of complex odors and is installed in a prototype of wearable e-nose for monitoring the axillary odor released from human body. The wearable e-nose allows the classification of different armpit odors and the amount of the volatiles released as a function of level of skin hygiene upon different activities

A Zigbee-based wireless wearable electronic nose using flexible printed sensor array

A wearable electronic nose (e-nose) has been developed by integrating a low cost chemical sensor array with a wireless communication for applications in healthcare. Its sensing unit was fabricated by a fully inkjet-printing technique, comprising eight different sensor elements manufactured by varying printing patterns and sensing materials. These sensors have shown response to a wide variety of complex odors. A wearable e-nose prototype using Zigbee wireless technology was designed as a compact armband for monitoring the axillary odor released from human body. Preliminary results based on principal component analysis (PCA) could classify different odors released from the human body upon various activities

Comparison of laser and intense pulsed light sintering (IPL) for inkjet-printed copper nanoparticle layers

In this contribution we discuss the sintering of an inkjet-printed copper nanoparticle ink based on electrical performance and microstructure analysis. Laser and intense pulsed light (IPL) sintering are employed in order to compare the different techniques and their feasibility for electronics manufacturing. Aconductivity of more than 20% of that of bulk copper material has been obtained with both sintering methods. Laser and IPL sintering techniques are considered to be complementary techniques and are highly suitable in different application fields