ML² Multi Layer Micro Lab

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Oswald Shelton
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1 Deliverable 9.2 ML² Multi Layer Micro Lab Report on high volume pilot production 1. Introduction Mastering, mould making and roll-to-roll embossing of optical layers (IPT) Roll-to-roll production of microfluidic layers for Demo 3 (VTT) Inkjet printing of electronics and bio-substances (DUR) Detailed investigation of suitable industrial inkjet printheads Single pass inkjet printing system mechanics and implementation Ink Supply and drying system... 20

1. Introduction The primary goal of the 9.2 deliverable of the MultiLayer-MultiLab (ML 2 ) project is to report the high-volume production chain of the functional layers for selected demonstrators.

Figure 1: Schematic picture of the microfluidic layer of Demonstrator 3 The sample inlet collects a sufficient volume of urine.

The antibodies of the test and the control line are located in the detection layer that works as a lid for the channel. The absorption pad maintains the capillary flow in the microfluidic channel. 2.

2 1. Introduction The primary goal of the 9.2 deliverable of the MultiLayer-MultiLab (ML 2 ) project is to report the high-volume production chain of the functional layers for selected demonstrators. Roll-to-roll (R2R) fabrication has been realized for the microfluidic layers of Demonstrator 3 and for optical, electronic and bio-functionalized layers of Demonstrators 1 and 2. Figure 1: Schematic picture of the microfluidic layer of Demonstrator 3 The sample inlet collects a sufficient volume of urine. The sample together with the conjugate flows into the microfluidic channel towards the test line and the control line. The antibodies of the test and the control line are located in the detection layer that works as a lid for the channel. The absorption pad maintains the capillary flow in the microfluidic channel. 2. Mastering, mould making and roll-to-roll embossing of optical layers (IPT) Autofluorescence detection and other optical detection methods require optical layers on chip. Optical structures can be manufactured by laser structuring or embossing. Optical layers like diffusor layers, non-glaring layers, brightness enhancement films, asymmetric light turning films consist of repetitive structures with low geometric complexity. V-groove, pyramides, sinusoidal waves are some examples of such structures. Microfluidic geometries are mastered by UV lithography processes and replicated by electroplating to achieve the required nickel sleeve (comp. D6.2 Machning data for the production of the optical layers of the demonstrators ). Figure 2: Ultraprecision drum turning machine (left) and diamond tool chipping a copper plated drum

In contrast to this, the regular geometries for light guiding or beam shaping are cut into a plated drum by diamond turning process

In particular brass drums or drums plated with nickel or copper have been investigated regarding quality of mastered structures,

To compare results, micro-pyramids were chosen as target structures cut into the different materials on a width of 300 mm.

Brass Phosphorous Nickel Copper Figure 3: Comparison of pyramid films regarding drum material Figure 3 shows embossing results with

3 In contrast to this, the regular geometries for light guiding or beam shaping are cut into a plated drum by diamond turning process (comp. Figure 2). Various structures and drum materials have been tested. In particular brass drums or drums plated with nickel or copper have been investigated regarding quality of mastered structures, defects and wear behaviour. To compare results, micro-pyramids were chosen as target structures cut into the different materials on a width of 300 mm. Significant differences could be found in the quality of the mastering process. Brass Phosphorous Nickel Copper Figure 3: Comparison of pyramid films regarding drum material Figure 3 shows embossing results with different drums. The film material produced with brass drums has a sufficient quality for the continuous surface in general. At microscale the surface shows crystalline structures from the brass material and regular defects. First assumption was that the defects are air bubbles enclosed in the lacquer. Figure 4: Confocal microscopy image of pyramid structures

But confocal microscopy (Figure 4) showed that the expected pits in the lacquer are heights. Those are caused by irregular breakouts of the brass crystals during chipping process.

First structures cut show good quality even at microscale. But the wear of diamond tool after a few centimetres of machining is that high that unacceptable burr formation occur (comp.

4 But confocal microscopy (Figure 4) showed that the expected pits in the lacquer are heights. Those are caused by irregular breakouts of the brass crystals during chipping process. The effect is strongly depending on the material properties and can t be compensated by process optimisation. The phosphorous nickel drums did not show this phenomenon. First structures cut show good quality even at microscale. But the wear of diamond tool after a few centimetres of machining is that high that unacceptable burr formation occur (comp. Figure 3 middle, small image). The electroplated copper surface admits a high quality mastering result. The replicated structures are of good quality as well and have an acceptable low surface roughness. The major drawback of the copper material is the limited corrosion resistance. Similar effects can be found with the brass and nickel materials as well. The electroplating process can be optimised and tuned to enlarge the corrosion resistance and the cutting quality. For optical layers the copper plated drums are used. The results are acceptable. Examples of production can be seen in Figure 5. Beam shaping effects Figure 5: Embossing results Embossing and cut film

3. Roll-to-roll production of microfluidic layers for Demo 3 (VTT) Roll-to-roll process was developed for fabrication of microfluidic layers for Demonstrator 3.

5 3. Roll-to-roll production of microfluidic layers for Demo 3 (VTT) Roll-to-roll process was developed for fabrication of microfluidic layers for Demonstrator 3. Methods used were roll-to-roll laser cutting, die cutting, lamination and assembly. Manufacturing includes the following steps: Lamination of the tapes (R2R Pilot line) Screen printing the hydrophobic stops/areas to the cover layer (R2R Pilot line) (Optional step) Diecut (R2R Pilot line) Lamination of the cover layer (R2R Pilot line) Splitting the roll (R2R Rewinder) Laser cutting the suction pads (R2R laser) Laser cutting the inlets+outlets (R2R laser) Assembling the suction pads (R2R Hybrid Assembly line) Dispensing (R2R Hybrid Assembly line /Laboratory). Dispensing of reagents was only demonstrated in sheet process. Laminating the bottom layer (R2R Pilot line/r2r Hybrid Assembly line /Laboratory) Figure 6: Microfluidic layers of Demo 3 The process flow and different process steps/instruments for roll-to-roll fabrication of microfluidic layers of Demo 3 are shown below:

manufacturing of Demo 3 Figure 8: Channel layer after diecutting process Diecut and lamination process with VTT s R2R

6 Tape lamination Diecut Roll slitting Lamination Laser cut of the inlets&outlets R2R Pilot line Rewinder R2R Laser R2R Hybrid line Laser cut of the suction pads Suction pad assembly Dispensing Lamination Figure 7: Process flow for manufacturing of Demo 3 Figure 8: Channel layer after diecutting process Diecut and lamination process with VTT s R2R Pilot line. On the left side of the image is the diecut unit, where microfluidic channels are cut on the tape, the waste from the cut is removed

together with the liner right after the diecut nip. On the right side of the image is the lamination unit, where the tape and the cover layer are bonded together with pressure.

7 together with the liner right after the diecut nip. On the right side of the image is the lamination unit, where the tape and the cover layer are bonded together with pressure. Figure 9: Diecut layer with printed coils The cover layer with coils (= screen printed dummy coils) is aligned and laminated together with the tape channels. Dummy coils were screen printed with black ink on PET for demonstrating the alignment process and tools in the roll-to-roll process.

8 Figure 10: Splitting of web material The roll containing tape channels laminated with a cover layer is split longitudinally in half to form two rolls with Alphareel rewinder. Figure 11: Laser cutting of holes R2R laser is used for cutting the inlet and outlet holes on microfluidic layer..

Figure 13: Assembly of suction pads Assembly of the suction pads in VTT s R2R hybrid

9 Figure 12: Cutting of suction pads R2R laser is used also for cutting the suction pads which are then assembled on microfluidic layer by using the R2R hybrid assembly line. Figure 13: Assembly of suction pads Assembly of the suction pads in VTT s R2R hybrid line. The suction pads are mounted into the microfluidic channel and secured with UV-curable glue.

10 Figure 14: Product before final cut-out Microfluidic channels and (screen printed dummy) coils on roll.

4. Inkjet printing of electronics and bio-substances (DUR) Thanks to its versatility inkjet printing has gained a lot of interest as a cost efficient replacement for established analogous printing

11 4. Inkjet printing of electronics and bio-substances (DUR) Thanks to its versatility inkjet printing has gained a lot of interest as a cost efficient replacement for established analogous printing and production techniques in different industries. Moreover in the last two decades it has been shown that it is possible to develop functional inkjet processable fluids which after film formation and post treatment lead to the needed functionalities for a lot of different applications, for example numerous sub processes in the microelectronics industry. However the conversion from conventional analogous techniques towards inkjet and especially the industrial implementation very often is challenging due to the complexity of inkjet technology. The basic concept of droplet generation is given by the natural instability of a liquid jet which is a complex surface tension driven process. In high throughput industrial single pass printing systems millions of microscale droplets are generated every second. The precise control of droplet generation and the overall process for accurate placement of each droplet on the substrate is of major importance. The mentioned overall process can be represented by the so called magic triangle of inkjet which is shown in Figure 15. Figure 15: Magic triangle of inkjet consisting of printhead, ink and substrate The magic triangle is defined by the main components of an inkjet process which are printhead, ink and substrate and the interaction between them. For each application the right main components have to be chosen and the precise adjustment of their interaction is crucial for a reliable high quality printing process. Within the ML 2 project and the underlying idea of roll to roll production of multilayer microlabs different sub processes where inkjet printing could be an efficient production technique can be identified. These sub processes are: Printing of conducting paths onto thin plastic films (PET, PMMA, OPP etc.) for heterogeneous implementation together with pick and place. Therefore nano particulate silver and copper dispersions should be used. Precise deposition of bio-chemical reagents such as for example antibodies

Deposition of adhesives to prevent blocking of micro fluidic structures during lamination Printing of microlenses for use with planar light guide structures As already mentioned each layer of the

12 Deposition of adhesives to prevent blocking of micro fluidic structures during lamination Printing of microlenses for use with planar light guide structures As already mentioned each layer of the multilayer devices should be treated in a roll to roll process. In order to have a complete inline production process with an implemented inkjet printing system a single pass printing process is needed which should be able to handle flexible (thin foils with a thickness down to 50µm) as well as rigid media (laminated stack of multiple layers). The production line and therefore the inkjet printing system should be able to handle media widths up to 600mm although in a first step the printing width will be limited to 300mm (just 300mm equipped with printheads). The targeted overall line speed is 10m/min which is limited by production processes such as embossing. The single pass inkjet printing system will be able to reach line speeds up to 60m/min and will contain three bars with printheads to be able to handle three different fluids. The above mentioned possible applications of inkjet printing within the ML 2 project have different requirements in terms of jetting, integration of the fluidic system and post treatment of the printed films. The single pass inkjet printing system has been designed to meet these requirements by a detailed evaluation of core components which will be described in the following chapters Detailed investigation of suitable industrial inkjet printheads As already described above the printheads are one of the core components of an inkjet printing system and the careful selection of the right printhead and the exact fine tuning of the interaction between printhead and fluid is of major importance to achieve a reliable high quality printing process. Functional fluids, which should be printed within the ML 2 project, are often prone to sedimentation, gelation and/or drying processes caused by volatile solvents and this has an impact on reliability of the printing process. Single pass printing does not allow cyclic maintenance such as spitting and/or purging and therefore printheads with recirculation at nozzleplate level are needed where continuous fluid recirculation within the printheads prevent loss of reliability. A lot of different types of industrial piezo drop on demand inkjet printheads from different manufacturers are available but just two manufacturers offer printheads with continuous fluid recirculation at nozzleplate level which are Fujifilm Dimatix and Xaar. Thanks to their silicon MEMS technology the Fujifilm Dimatix printheads are robust and moreover very precise products which are tailored towards accurate and reliable single pass printing processes. Therefore we decided to evaluate two different piezo drop on demand inkjet printheads based on silicon MEMS technology from Fujifilm Dimatix. Table 1: Comparison of two different Fujifilm Dimatix piezo drop on demand inkjet printheads based on silicon MEMS technology with integrated fluid recirculation on nozzle plate level Fujifilm Dimatix SAMBA G5L Silicon MEMS technology 2048 Nozzles, 32 rows 1200dpi native resolution Native Drop Size 5pl

Fujifilm Dimatix QSRJM 256/10 Silicon MEMS technology 256 Nozzles, single row 100dpi native resolution Native drop size 10pl Looking at the two dimensional printhead design space spanned by the ink

Figure 16 also indicates the location of the possible ML 2 applications.

13 Fujifilm Dimatix QSRJM 256/10 Silicon MEMS technology 256 Nozzles, single row 100dpi native resolution Native drop size 10pl Looking at the two dimensional printhead design space spanned by the ink viscosity range for reliable jetting and the native drop size of the printhead these two drop ejectors cover different areas as can be seen in Figure 16. Figure 16 also indicates the location of the possible ML 2 applications. Figure 16: Depiction of the printhead design space spanned by ink viscosity and native drop size and indicated positions of possible applications within ML 2 ; Yellow area covered by QSRJM 256/10 and orange area covered by SAMBA It can clearly be seen in Figure 16 that the areas covered by the two printheads within the printhead design space have a good overlap with respective two ML 2 applications. Droplet generation with a piezo drop on demand inkjet printhead is a multistage process where multiple energy conversions from electrical energy to the point of kinetic energy of the microscale droplet take place. A detailed understanding of the physics behind these processes

especially the acoustic phenomena within the microfluidic channels of each droplet ejector are of major importance for gaining reliability.

14 especially the acoustic phenomena within the microfluidic channels of each droplet ejector are of major importance for gaining reliability. For that reason the idealised jetting performance of both printheads under lab conditions was investigated. Therefor a JetXpert drop visualisation system was used which is shown in Figure 17. Figure 17: Image of a drop visualisation system from ImageXpert ( At first the hydrodynamic behaviour of the fluid recirculation inside the printheads was evaluated. Especially the hydraulic resistance of the printhead was of interest. Additionally to experiments a simple mathematical model was developed and the output was compared to measurement results. Figure 18 shows an example of the measured and calculated fluid flow rate versus pressure difference between inlet and outlet port for one of the two printheads. Flow rate calculated Flow rate measured flow rate (ml/min) pressure difference (mbar) Figure 18: Measured and calculated fluid flow rate versus pressure conditions at the inlet and outlet port of the printhead

15 Measurement and calculation were in good agreement for both printheads. This can also be seen in Figure 18. For piezo drop on demand printheads droplet generation results from applying an electrical signal to a piezo actuator which changes its shape as a response to the electrical signal. This change in the outer dimensions of the piezo actuator induces a pressure wave inside a microfluidic channel. Due to the complex geometry of the microfluidic channels inside the printhead, which is a composite of different materials, the induced pressure wave is multiple reflected and results in complex acoustic phenomena. When measuring drop velocity at different frequencies the channel acoustic can clearly be seen. Figure 19: Sequence of drop visualisation system images at printing frequencies from 1kHz to 30kHz The temporal evolution of the applied voltage in most cases mimics trapezoid shape with pulse widths of microseconds and the exact timing within a single trapezoid pulse and moreover a sequence of pulses is crucial. For both printheads channel acoustic was investigated in detail and the shape of applied voltage was optimised for reliable jetting. For single pass printing the ability for easy integration of the printheads into print modules and furthermore into print bars is very important. When aligning printheads into print modules the jetting performance of the printheads in the stitching area has to be controlled and strategies to avoid and/or hide defects like wood grain pattern and missing jets have to be developed. Therefore different module designs and alignment strategies were evaluated and printing tests on a roll to roll lab system were performed.

Figure 20: Image of multiple Fujifilm Dimatix QSRJM 256/10 printheads aligned in a print module with integrated fluidic and electrical interface These experiments gave promising results for both

16 Figure 20: Image of multiple Fujifilm Dimatix QSRJM 256/10 printheads aligned in a print module with integrated fluidic and electrical interface These experiments gave promising results for both printheads although the limits of the QSRJM 256/10 printhead technology in terms of integration into the single pass inkjet system could be seen. Two different industrial piezo drop on demand inkjet printheads from Fujifilm Dimatix were evaluated which are SAMBA and QSRJM 256/10. Both are robust industrial products with integrated ink recirculation at nozzle plate level based on silicon MEMS technology. Main focus of the investigation was to get a detailed understanding of the strengths and weaknesses of both printheads in terms of fluid recirculation, jetting performance and integration into the single pass inkjet system. After detailed analysis of all available data and also including commercial aspects we came to the conclusion that the SAMBA technology fits best for the requirements within the ML 2 project. The main reason is that it s a very compact high resolution printhead which is easily scalable to any print width. The native resolution of 1200dpi allows easy compensation for missing or deviated jets. Moreover from commercial point of view it s the most cost effective solution which fulfils the requirements within the project Single pass inkjet printing system mechanics and implementation As described in first section the magic triangle of inkjet printing is defined by three main components. One of these are the printheads and the process which led to the decision which industrial piezo drop on demand printhead fits best for the requirements of the ML 2 project is described in chapter 0. Nevertheless in a real industrial printing process more is needed than just precise adjustment of printing parameters on stationary printheads. Because of printhead maintenance and height adjustment due to variable thickness of the substrates the printheads have to be moved in two dimensions. Another main component of the magic triangle is the media and media handling system. The movement of the substrate underneath the printheads is done by a vacuum conveyor belt system which is able to handle flexible and rigid media. Figure 21 and Figure 22 show a CAD drawing and a photographic image of the ML 2 single pass inkjet printing system.

17 Figure 21: CAD Image of the ML 2 single pass inkjet printing system without casing, printheads and ink management system Figure 22: Photographic image of the single pass inkjet printing system

Figure 23: CAD drawing of the carriage and the support which holds the carriage Figure 24: Photographic image of the carriage and the support The z movement of the carriage is done by a stepper motor

18 The printheads will be mounted on a carriage which can be moved in two dimensions. Figure 23 and Figure 24 show a CAD drawing of the carriage and the support which holds the carriage and a photographic image thereof respectively. Figure 23: CAD drawing of the carriage and the support which holds the carriage Figure 24: Photographic image of the carriage and the support The z movement of the carriage is done by a stepper motor with integrated encoder with a maximum travelling distance of 180mm. The support contains a rail system which allows the x movement of the carriage for maintenance. In that direction it is driven by a linear motor which allows precise adjustment of the position. All axes including the vacuum conveyor belt are controlled by a Beckhoff automation system and accessible via touch panel. One of the main components of the single pass inkjet printer is the media handling system. As already mentioned the single pass inkjet printing system has to be able to handle rigid and flexible media. Therefore a high precision vacuum conveyor belt system was designed which fulfils the requirements of the ML 2 project. Due to the fact that the media handling system has a big impact on possible printing accuracy it has to be very well engineered and strategies to optimise velocity uniformity and minimise drift of the belt have to be developed.

Figure 25 shows a CAD drawing (left) and a photographic image of the conveyor belt system.

The overall system is designed in a way that also a stainless steel belt could be used.

Figure 26 shows a CAD drawing of the belt with punched suction holes.

19 Figure 25 shows a CAD drawing (left) and a photographic image of the conveyor belt system. Figure 25: CAD drawing (left) and photographic image of the conveyor belt system The belt of the current system is made of a polyester mesh with polyurethane topcoat and has a width of 800mm. The overall system is designed in a way that also a stainless steel belt could be used. A slightly decreased pressure in a vacuum chamber underneath the belt, which has punched holes with a diameter of 2mm, fixes the substrate at the required position. Figure 26 shows a CAD drawing of the belt with punched suction holes. Suction Figure 26: CAD drawing of the belt with suction holes Extensive tests with 50µm PMMA sheets were performed to ensure that the distortion of the thin substrates through the cross sectional area of the punched holes does not have a negative influence on the printed image. These tests clearly showed that this is not the case. The conveyor belt system is driven by a servo asynchronous motor (nominal torque 6,7Nm) with coupled planetary gear which allows a maximum linear belt speed of 60m/min. Measurements of velocity uniformity clearly showed that at a linear speed of 1m/s the maximum variation is 1mm/s. For precise control of the belt position on the rollers and for preventing a belt movement in cross process direction an active belt control system is implemented. It consists of a tensioning roller

It can be shown that the maximum belt movement in cross process direction is less than 100µm over one passage (which corresponds to 8,5m) at a speed of 60m/min. 4.3.

20 which forces a tension gradient to the belt and this leads to a controlled movement in cross process direction. The actual position of the belt on the rollers is measured by a laser micrometer which is triggered by a light barrier to be able to always measure at the same position. It can be shown that the maximum belt movement in cross process direction is less than 100µm over one passage (which corresponds to 8,5m) at a speed of 60m/min Ink Supply and drying system The choice of a suitable ink supply and recirculation system is essential for a stable operation of the printer. The main requirements in the current machine were a high enough flow rate to drive 8 Samba printheads per colour, compatibility with the used inks as well as a minimized volume in order to keep the amount of fluid needed to fill the system as low as possible due to the high pricing of most functional inks. The optimum flow rate for a Samba head is approximately 35ml/min, thus meaning that the recirculation system must provide at least a flow rate of 280ml/min. Since material compatibility must be achieved with various fluids, very robust gasket materials should be implemented. These requirements were fulfilled by the CIMS2 ink supply system from the British company Megnajet (Figure 27), which can reach flow rates up to 400ml/min. After compatibility testing standard FKM gaskets were replaced by highly inert FFKM as well as EPDM. The tank volume of the system is only 50ml, which allows to drive the whole ink supply with an ink volume of approximately 300ml. The flow rate of the ink supply is set by the differential pressure between infeed and return lines, while the meniscus pressure at the nozzleplate is adjusted by changing the return pressure relative to ambient conditions. In order to avoid bubble formation during printing as well as printhead contamination, additional filtration and degassing devices were installed between the main unit and the printheads (Figure 27). For efficient degassing, a vacuum with a pressure of -900mbar relative to ambient was applied to the modules. Figure 27: Left: Main unit of the ink supply system. Right: Inline filter and degassing unit. During testing it turned out that the system was not running stable enough due to the quite long tubing between the ink tanks and printheads. In order to resolve this issue, Megnajet provided

additional sensor units to be mounted on the printhead carriage (Figure 28), thus reducing the distance between pressure sensors and printheads from 5m to less than 1m.

In order to maintain ink circulation even in the case no printhead is attached or the heads being clogged, a small bypass is included in the manifolds.

21 additional sensor units to be mounted on the printhead carriage (Figure 28), thus reducing the distance between pressure sensors and printheads from 5m to less than 1m. From these remote units the tubing leads to 2 manifolds where 4 printheads each could be attached (Figure 28). In order to maintain ink circulation even in the case no printhead is attached or the heads being clogged, a small bypass is included in the manifolds. Before filling the actual ink, each ink supply was flushed with the respective carrier vehicle in order to clean the systems from residual manufacturing contaminations as well as to provide better wetting. Figure 28: Left: Remote sensor unit. Right: Head attachments and ink delivery ports. Before printing tests could be performed, the inks were evaluated on a drop visualisation system (Figure 17), which included the creation and tuning of suitable electrical pulse shapes (waveforms) to optimize drop formation, volume and velocity as well as stability tests. After loading the ink in the printer, nozzle testpattern (Figure 29) were printed in order to adjust the printhead positions relative to each other and check for missing nozzles.

Figure 29: Nozzle testpattern. Here one of the biggest advantages of the Samba printhead comes into effect: the high native resolution of 1200dpi.

gap created by a missing jet is covered by the neighbouring nozzles, which is the case on most substrates. Figure 30: Test images printed with silver ink.

22 Figure 29: Nozzle testpattern. Here one of the biggest advantages of the Samba printhead comes into effect: the high native resolution of 1200dpi. Even if individual nozzles are missing, the visual appearance as well as the conductivity of printed images are not affected (Figure 30), as long as the gap created by a missing jet is covered by the neighbouring nozzles, which is the case on most substrates. Figure 30: Test images printed with silver ink. In order to increase the conductivity of printed structures, either the resolution or the size of the drops has to be increased to achieve higher layer thickness. While the first is difficult to achieve due to the nozzle arrangement of the printhead, the drop size can easily be adjusted by changing the voltage of the applied pulse or by using multipulsing, which utilizes the resonances in the printhead to generate one large drop out of several pulses. An example for such a

waveform, which allows the creation of drops between 3 and 9pl, is shown in Figure 31. Thus the jetting performance can be adjusted to various applications, inks and substrates.

Since a Novacentrix Pulse Forge Device will be implemented in the pilot line, full sintering of conductive inks is not required within the inkjet printer, but only a pre-drying step to fix the ink

23 waveform, which allows the creation of drops between 3 and 9pl, is shown in Figure 31. Thus the jetting performance can be adjusted to various applications, inks and substrates. Figure 31: Multipulse waveform for the creation of larger drops. Since a Novacentrix Pulse Forge Device will be implemented in the pilot line, full sintering of conductive inks is not required within the inkjet printer, but only a pre-drying step to fix the ink drops on the substrate (pinning) had to be implemented. Near Infrared (NIR) turned out to be the most suitable solution, since the emission spectrum is shifted towards shorter wavelengths compared to standard infrared systems, thus causing less absorption by thin film substrates and subsequently less substrate deformation. The used system from Adphos is located on the conveyor belt after the printing carriage and has a width of 550mm (Figure 32). Thus the less homogeneous areas at the edge of the emitters are not used and more uniform drying can be achieved. The dryer is equipped with 3 emitters of 5kW electrical power each, yielding a maximum power of 15kW or approximately 22W/m². In order to avoid overheating of the conveyor belt at low printing velocities, only 2 of 3 emitters were used in most tests, which is sufficient for pre-drying in many cases. In order to get rid of evaporated solvents, the drying module is equipped with an exhaust system. In case the conveyor belt stops, the NIR module switches off automatically to avoid substrate or belt overheating. Figure 32: Adphos NIR drying system with attached fan and exhaust pipe.

selecting and driving inkjet print heads presented by Clive Ayling, Meteor Inkjet Ltd

selecting and driving inkjet print heads presented by Clive Ayling, Meteor Inkjet Ltd Marriage selecting and driving inkjet print heads Inkjet Technologies Focus on Commercial Printheads inkjet print head