| 1. |
- Khorramdel, Behnam, et al.
(författare)
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Inkjet printing technology for increasing the I/O density of 3D TSV interposers
- 2017
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Ingår i: Microsystems & Nanoengineering. - : Nature Publishing Group. - 2055-7434. ; 3, s. 17002-
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Tidskriftsartikel (refereegranskat)abstract
- Interposers with through-silicon vias (TSVs) play a key role in the three-dimensional integration and packaging of integrated circuits and microelectromechanical systems. In the current practice of fabricating interposers, solder balls are placed next to the vias; however, this approach requires a large foot print for the input/output (I/O) connections. Therefore, in this study, we investigate the possibility of placing the solder balls directly on top of the vias, thereby enabling a smaller pitch between the solder balls and an increased density of the I/O connections. To reach this goal, inkjet printing (that is, piezo and super inkjet) was used to successfully fill and planarize hollow metal TSVs with a dielectric polymer. The under bump metallization (UBM) pads were also successfully printed with inkjet technology on top of the polymer-filled vias, using either Ag or Au inks. The reliability of the TSV interposers was investigated by a temperature cycling stress test (-40 °C to +125 °C). The stress test showed no impact on DC resistance of the TSVs; however, shrinkage and delamination of the polymer was observed, along with some micro-cracks in the UBM pads. For proof of concept, SnAgCu-based solder balls were jetted on the UBM pads.
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| 2. |
- Boda, Ulrika, 1990-
(författare)
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Screen Printed Stretchable Electronics
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wearable electronics that can be seamlessly integrated into clothing, onto skin, or inside the body, can enable a variety of novel applications within healthcare monitoring, biosensing, biomedical devices and the internet of things. Seamless integration requires matching of the mechanical properties of the electronics to clothing, skin, and tissues, i.e., the electronics need to be soft, flexible, and stretchable. One approach to achieve this is to make all or most components of a device stretchable in themselves by developing functional intrinsically stretchable composites. Such composites are typically based on a filler, which provides electronic or other functionality, and an elastomer matrix, which provides the mechanical properties of the composites. Manufacturing of intrinsically stretchable electronics is challenging and often involve time consuming and tedious fabrication procedures of low throughput, based on chemically harmful monomers and solvents. An alternative approach, printing of electronics, has experienced a boom in the past decade, recently even for stretchable applications. However, despite its appeal, stretchable printed electronic products have yet to reach the consumer market in larger numbers. Screen printing is a versatile printing method that is cost-effective, scalable, can be tailored to use harmless solvents with little waste, and can be made environmentally friendly by careful choice of materials. Furthermore, some applications of stretchable technology – such as implants and on-skin electronics – require conductors that are stable under humid, corrosive, or polluted conditions, which puts even more weight into choices of ink components.In paper I, we protected readily available conducting silver flakes through a thin coating with gold in a low-toxicity water-based process and demonstrated its use in inks for screen printed corrosion-resistant stretchable conductors. The novel silver-gold flake ink was used to fabricate a functional stretchable near-field communication device. Papers II and III both concern entirely screen printed and inherently stretchable devices, utilizing novel stretchable inks in combination with commercial inks to print vertical stacks. Two electrochemical devices – electrochromic displays and organic electrochemical transistors – were printed and tested under stretched conditions to push the limits of how screen printing can be used in applications for thin and stretchable wearable technology. The results show that the devices can retain electrical function even under practically high strains of 50 % (display) and 100 % (transistor). Finally, in paper IV, we investigate the operational principle of gold nanowire- based stretchable composites and find that interactions on the nano-and microscale differ between composites using the same filler but different elastomers. This study sheds light on the importance of the type of elastomer chosen for composites, as this heavily influences the composite’s electrical performance under strain.Altogether, the studies presented in this thesis provide knowledge, materials, and processes that in the long run can contribute to more effective devices within healthcare and other wearable electronics applications.
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| 3. |
- Feng, Yi, et al.
(författare)
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Electrical and humidity-sensing characterization of inkjet-printed multi-walled carbon nanotubes for smart packaging
- 2013
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Ingår i: IEEE SENSORS 2013 - Proceedings. - : IEEE. - 9781467346405 ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- Printing is considered a cost-effective way to fabricate electronics on unconventional substrates enabling, for example, smart packaging. Functionalized multi-walled carbon nanotubes (f-MWCNTs) having carboxylic groups on their surfaces possess great potential as flexible resistive humidity sensor. In this paper, we report on the inkjet printing and characterization of f-MWCNTs in terms of sheet resistance and humidity-sensitivity. Stable f-MWCNTs ink is formulated using aqueous ethylene glycol as solvent. Sheet resistance of printed f-MWCNTs films on polyimide foil reduces by increasing the number of printed layers as well as post-printing annealing temperature. Meanwhile, the raised annealing temperature degrades the films' humidity-sensitivity, which could be explained by the loss of the carboxylic groups. The electrical and sensing properties of f-MWCNTs also have a negative temperature coefficient regarding ambient temperature, which should be considered in practical application.
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| 4. |
- Mäntysalo, Matti, et al.
(författare)
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System integration of smart packages using printed electronics
- 2012
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Ingår i: Electronic Components and Technology Conference (ECTC), 2012 IEEE 62nd. - : IEEE. - 9781467319669 ; , s. 997-1002
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Konferensbidrag (refereegranskat)abstract
- The last decade has shown enormous interest in additive and printed electronics manufacturing technologies, especially in intelligent packaging. Scientists and engineers all over the world are developing printed organic circuits. Despite their effort, the performance and yield of all-printed devices cannot replace silicon-based devices in smart package applications. Therefore, we have developed a hybrid interconnection platform to seamlessly integrate printed electronics with silicon-based electronics, close the gap between the two technologies, and to anticipate adaption of printed electronic technologies. We studied the suitability of a printed interconnection platform by fabricating a printed sensor-box that contains printed nano-Ag-interconnections on low-temperature plastic, a printable humidity sensor based on functionalized MWCNTs, a printed battery, conventional SMDs, and a silicon-based MCU.
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| 5. |
- Reinhold, Ingo, 1981-
(författare)
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Industrial Digital Fabrication Using Inkjet Technology
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 6. |
- Su, Yingchun, et al.
(författare)
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Monolithic Fabrication of Metal‐Free On‐Paper Self‐Charging Power Systems
- 2024
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028.
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Tidskriftsartikel (refereegranskat)abstract
- Self-charging power systems (SCPSs) are envisioned as promising solutions for emerging electronics to mitigate the increasing global concern about battery waste. However, present SCPSs suffer from large form factors, unscalable fabrication, and material complexity. Herein, a type of highly stable, eco-friendly conductive inks based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are developed for direct ink writing of multiple components in the SCPSs, including electrodes for miniaturized spacer-free triboelectric nanogenerators (TENGs) and microsupercapacitors (MSCs), and interconnects. The principle of “one ink, multiple functions” enables to almost fully print the entire SCPSs on the same paper substrate in a monolithic manner without post-integration. The monolithic fabrication significantly improves the upscaling capability for manufacturing and reduces the form factor of the entire SCPSs (a small footprint area of ≈2 cm × 3 cm and thickness of ≈1 mm). After pressing/releasing the TENGs for ≈79000 cycles, the 3-cell series-connected MSC array can be charged to 1.6 V while the 6-cell array to 3.0 V. On-paper SCPSs are promising to serve as lightweight, thin, sustainable, and low-cost power supplies.
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| 7. |
- Xie, Li, et al.
(författare)
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Electrical performance and reliability evaluation of inkjet-printed Ag interconnections on paper substrates
- 2012
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Ingår i: Materials letters (General ed.). - : Elsevier BV. - 0167-577X .- 1873-4979. ; 88, s. 68-72
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Tidskriftsartikel (refereegranskat)abstract
- Printing technology, especially inkjet printing, enables mass manufacturing of electronics on various substrate materials. Paper is one potential carrier for printed electronics to realize low-cost, flexible, recyclable smart packages. However, concerns exist regarding commonly used photo paper substrate, in terms of price and reliability against environmental variation. In this work, for the first time, ordinary low-cost and high-moisture-resistance package paper is investigated as an alternative to be the substrate of printed electronics. The surface morphology and electrical performance of inkjet printed interconnections on six different paper substrates from two categories (inkjet paper and package paper) are examined and compared. The printed interconnections on inkjet papers show smaller sheet resistance and better repeatability than those on package papers. However, low-cost package paper stands higher temperature and exhibits better reliability during 85°C/85 RH aging test. Package paper is suitable for smart package applications that have relaxed requirements of conductivity and high requests of moisture resistance.
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| 8. |
- Xie, Li, et al.
(författare)
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Heterogeneous integration of bio-sensing system-on-chip and printed electronics
- 2012
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Ingår i: IEEE Journal on Emerging and Selected Topics in Circuits and Systems. - 2156-3357 .- 2156-3365. ; 2:4, s. 672-682
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a heterogeneous integration platform for bio-sensing applications, which seamlessly integrates low-power silicon-based circuits with cost-effective printed electronics. A prototype of wearable Bio-Sensing Node is fabricated to investigate the suitability of this integration approach. A customized mixed-signal system-on-chip (SoC) with the size of 1.5× 3.0 mm2 is utilized to amplify, digitize, buffer, and transmit the sensed bio-signals. Inkjet printing technology is employed to print nano-particle silver ink on a flexible substrate to fabricate chip-on-flex, electrodes as well as interconnections. This additive and digital fabrication technology enables fast prototype of the customized electrode pattern. Its high accuracy and fine resolution features allow the direct integration of the bare die (the pad size of 65 μ m and pitch size of 90 μ m) on the flexible substrate, which significantly miniaturizes the wearable system. The optimal size and layout of printed electrodes are investigated through the in vivo test for electrocardiogram recording applications. The total size of the implemented Bio-Sensing Node is 4.5× 2.5 cm2, which is comparable with a commercial electrode. This inkjet printed heterogeneous integration approach offers a promising solution for the next-generation cost-effective personalized wearable healthcare monitoring devices.
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| 9. |
- Yang, Geng, et al.
(författare)
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Bio-Patch Design and Implementation Based on a Low-Power System-on-Chip and Paper-Based Inkjet Printing Technology
- 2012
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Ingår i: IEEE transactions on information technology in biomedicine. - 1089-7771 .- 1558-0032. ; 16:6, s. 1043-1050
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the prototype implementation of a Bio-Patch using fully integrated low-power System-on-Chip (SoC) sensor and paper-based inkjet printing technology. The SoC sensor is featured with programmable gain and bandwidth to accommodate a variety of bio-signals. It is fabricated in a 0.18-µm standard CMOS technology, with a total power consumption of 20 µW from a 1.2 V supply. Both the electrodes and interconnections are implemented by printing conductive nano-particle inks on a flexible photo paper substrate using inkjet printing technology. A Bio-Patch prototype is developed by integrating the SoC sensor, a soft battery, printed electrodes and interconnections on a photo paper substrate. The Bio-Patch can work alone or operate along with other patches to establish a wired network for synchronous multiple-channel bio-signals recording. The measurement results show that electrocardiogram and electromyogram are successfully measured in in-vivo tests using the implemented Bio-Patch prototype.
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| 10. |
- Zhao, Jie
(författare)
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Solution-Processable Conductive Graphene-Based Materials for Flexible Electronics
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis work explores electrical conductors based on few-layer graphene flakes as an enabler for low-cost, mechanically flexible, and high-conductivity conductors in large area flexible and printed electronic devices. The flakes are deposited from aqueous solutions and processed at low temperature.Graphene is selected for its excellent properties in mechanical, optical, electronic, and electrical aspects. However, thin films of pristine few-layer graphene flakes deposited from dispersions normally exhibit inferior electrical conductivity. One cause responsible for this problem is the loose stacking and random orientation of graphene flakes in a graphene deposition. We have solved this problem by implementing a simple post-deposition treatment leading to dramatically densified and planarized thin films. Significantly increased electrical conductivity by ~20 times is obtained. The 1-pyrenebutyric acid tetrabutylammonium salt as an exfoliation enhancer and dispersant in water yields ~110 S/m in conductivity when the graphene based thin films are processed at 90 °C. In order to achieve higher conductivity, a room-temperature method for site-selective copper electroless deposition has been developed. This method is of particular interest for the self-aligned copper deposition to the predefined graphene films. The resultant two-layer graphene/copper structure is characterized by an overall conductivity of ~7.9 × 105 S/m, an increase by ~7000 times from the template graphene films. Several electronic circuits based on the graphene/copper bilayer interconnect have been subsequently fabricated on plastic foils as proof-of-concept demonstrators. Alternatively, highly conductive composites featuring graphene flakes coated with silver nanoparticles with electrical conductivity beyond 106 S/m can be readily obtained at 100 oC. Moreover, a highly conductive reduced-graphene-oxide/copper hybrid hydrogel has been achieved by mixing aqueous graphene oxide solution and copper-containing Fehling's solution. The corresponding aerogel of high porosity exhibits an apparent electrical conductivity of ~430 S/m and delivers a specific capacity of ~453 mAh g−1 at current density of 1 A/g. The experimental results presented in this thesis show that the solution-phase, low-temperature fabrication of highly conductive graphene-based materials holds promises for flexible electronics and energy storage applications.
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