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Quantitative Assessment of Inkjet Reliability under Industrial Conditions: Measuring All Drops during Extended High‐Duty Printing
KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electronics and Embedded systems, Electronic and embedded systems. XaarJet ltd.. (Division of Electronics)
Xaar plc.
2018 (English)In: Handbook of Industrial Inkjet Printing / [ed] Werner Zapka, Weinheim: Wiley-VCH Verlagsgesellschaft, 2018, p. 445-458Chapter in book (Refereed)
Abstract [en]

Reliability is one of the key challenges in inkjet technology. Nozzles perform unreliably for a number of reasons, such as drying, clogging through air‐ and inkborne contaminants, ingestion of air, or nozzle plate flooding. To extract quantitative information about the number of missing droplets from the acquired images, suitable algorithms need to be applied. To identify the presence of the droplet, a value derived from the characteristics of the area of interest needs to be compared with the threshold value. The Line Scan approach for the measurement of reliability offers a convenient way to assess reliability of a printhead in a laboratory environment providing quantitative and statistical data about location, duration, and time of misfire events. With the knowledge of the printhead frequency and the hypothetical print resolution applied in the printing experiments, the length of such tic marks as a number of subsequent missing droplets can be calculated.

Place, publisher, year, edition, pages
Weinheim: Wiley-VCH Verlagsgesellschaft, 2018. p. 445-458
National Category
Fluid Mechanics and Acoustics Signal Processing Media Engineering
Identifiers
URN: urn:nbn:se:kth:diva-263707DOI: 10.1002/9783527687169.ch24Scopus ID: 2-s2.0-85052003312ISBN: 9783527338320 (print)ISBN: 9783527687169 (electronic)OAI: oai:DiVA.org:kth-263707DiVA, id: diva2:1368965
Note

QC 20191111

Available from: 2019-11-09 Created: 2019-11-09 Last updated: 2019-11-11Bibliographically approved
In thesis
1. Industrial Digital Fabrication Using Inkjet Technology
Open this publication in new window or tab >>Industrial Digital Fabrication Using Inkjet Technology
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of acoustic waves initiated by the deformation of a microchannel is one method for generating monodisperse, micrometer-sized droplets from small orifices and is employed in piezo-electric inkjet printheads. These printheads are used in both graphical printing and digital fabrication, where functionalities, such as optical, biological, electrical or mechanical, are being produced locally. The processes leading to detrimental artifacts such as satellite droplets or nozzle outages, however, are not fully understood and require profound experimentation. This thesis presents both novel techniques to study jetting for optimal droplet formation and reliability, as well as the post-processing techniques required for solution-based production of a conductive feature on low-cost polymeric substrates.

A multi-exposure imaging system using laser light pulses shorter than 50 ns and a MEMS micro-mirror enabled the imaging of the droplet formation at ten instances on the droplet's  travel towards the substrate. The technique allows for the study of droplet formation, satellite droplet break-up and secondary tail formation allowing for better control and understanding of the process.

Reliability measurement using a linescan camera was introduced to record every droplet ejected from the width of a printhead. The variations in droplet velocity and misalignment of the printhead required the use of a constant background illumination to reliably capture the droplets. The resulting low-contrast images were post-processed using statistical analysis of the graylevel distributions of both, the droplet and background pixels, and were subsequently used in a histogram matching algorithm to enable reliable identification of the threshold value required for unhindered detection of missing droplets based on the printed image. Using temporal oversampling the technique was shown to qualitatively describe droplet velocity variations introduced by the actuation of the printhead.  

The conversion of inkjet-printed metallic nanoparticle inks to conductive structures was investigated with a focus on the applicability to industrial processes. Intense pulsed light (IPL) processing achieved comparable results to convective oven sintering in less than ten seconds. The dynamics of IPL sintering were found to be strongly dependent on the spectral composition of the light resonating in the processing chamber. By implementing a passive filtering concept, thermal runaway was prevented and the line conformation was optimized irrespective of the underlying substrate. Alternatively, pulse-shaping, to tailor the energy flux into the deposit and incorporate drying in the IPL process, was found to generate conductive copper features without pre-drying.

The findings were applied to applications comprising small droplet generation for nanoimprint lithography, the fabrication of conductors for blind via connections to buried LED dies as well as the hybrid generation of hyperbolic ion-trap electrodes for  mass spectrometry applications. The addition of the non-contact and high accuracy of the inkjet process enabled suitable performance that lies beyond that of conventional processes.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 92
Series
TRITA-EECS-AVL ; 2019:82
Keywords
inkjet printing, droplet formation, digital fabrication, sintering, nanoparticles, printed electronics
National Category
Media and Communication Technology Other Electrical Engineering, Electronic Engineering, Information Engineering Fluid Mechanics and Acoustics
Research subject
Industrial Information and Control Systems; Media Technology; Information and Communication Technology
Identifiers
urn:nbn:se:kth:diva-263711 (URN)978-91-7873-366-8 (ISBN)
Public defence
2019-12-09, Ka-Sal B (Peter Weissglas), Kistagången 16, Kista, 10:00 (English)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework Programme, CP-TP 228686EU, FP7, Seventh Framework Programme, CP-TP 285045Vinnova, 2013-01473
Available from: 2019-11-11 Created: 2019-11-10 Last updated: 2019-11-11Bibliographically approved

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