Microvalve Jetting of Biomaterials

Acoustic Inkjet Printing (AIP) is suitable for jetting a small drop when compared with other available methods because the drop size depends not on the nozzle area but on the frequency of acoustic beam that enables ejection from free liquid surface.For inkjet printing, drop modulation is the major technology being effective to realize both high image quality and high print speed. In the previous reports regarding AIP, multiple droplets were fired at the same location on paper for gray scale of image.1 This method could enhance image quality at the sacrifice of print speed.Here we propose a method of drop size modulation in AIP to achieve both high image quality and high print speed. It has been proved that the drop size is modulated by a second harmonic on fresnel lens without changing the liquid level and other dimensions. This report also shows that calculations and experiments ascertained drop modulation by the second harmonic.

SEIKO EPSON Corporation has successfully developed the original ink jet printing technology MACH. MACH has overcome all defects of the conventional piezo ink jet technology and realized high printing quality and high printing speed. In this paper, history, principle, features of MACH and other effective means for high printing quality and high printing speed are described.

This contribution focusses on three printing techniques: inkjet printing, flexographic printing and gravure printing for the manufacture of ITO structures based on nanoparticular ITO inks. The quality and stability of nanoparticular inks depends mainly on the dispersing step and is reflected by the achieved particle size distribution. The particle size distribution of the ITO inks has a distinct influence on the optical and electrical properties of the deposited ITO structures. The optimization of nanoparticular ITO inks concerning rheological behavior, wetting behavior and resulting material performance is presented. Inkjet printing was used as a low speed method to manufacture structures in the range of 30 μm. It is shown how coffee-staining, a frequently arising problem in inkjet printing, can be prevented by different strategies. Nanoparticular ITO structures with layer thicknesses clearly below 1 μm were printed. Gravure and flexography printing are well-established industrial printing processes with printing speeds above 100 m/min. These high-speed printing processes were used to print structures on PET film and glass substrates. Different solvents, e.g., water and ethanol, solvent compositions and binder types were varied to optimize the resulting ITO structures. The printed structures in the range of 10 to 2000 μm with thicknesses down to 1 μm were evaluated concerning surface topography and electrical conductivity. The high inter-grain porosity and the used organic additives limit the electrical conductivity of nanoparticulate ITO structures. To further improve their electrical conductivity laser post-treatment of printed ITO structures was performed.

Design and direct fabrication of high-performance thermosets and composites via 3D printing are highly desirable in engineering applications. Most 3D printed thermosetting polymers to date suffer from poor mechanical properties and low printing speed. Here, a novel ink for high-speed 3D printing of high-performance epoxy thermosets via a two-stage curing approach is presented. The ink containing photocurable resin and thermally curable epoxy resin is used for the digital light processing (DLP) 3D printing. After printing, the part is thermally cured at elevated temperature to yield an interpenetrating polymer network epoxy composite, whose mechanical properties are comparable to engineering epoxy. The printing speed is accelerated by the continuous liquid interface production assisted DLP 3D printing method, achieving a printing speed as high as 216 mm h-1 . It is also demonstrated that 3D printing structural electronics can be achieved by combining the 3D printed epoxy composites with infilled silver ink in the hollow channels. The new 3D printing method via two-stage curing combines the attributes of outstanding printing speed, high resolution, low volume shrinkage, and excellent mechanical properties, and provides a new avenue to fabricate 3D thermosetting composites with excellent mechanical properties and high efficiency toward high-performance and functional applications.

Ultrafast electrohydrodynamic 3D printing with in situ jet speed monitoring

The field of additive manufacturing has expanded from single material-based 3D printing to multimaterial printed complex smart structures with intrinsic sensing capability. However, current multimaterial 3D printers allow printing of one material at a time, with limited ability of mixing multiple materials. Herein, we present the new 3D printer which eliminates the above shortcoming by merging the Fused Filament Fabrication and Direct Ink Write in one compact system. The developed printer expands the range of materials that can be printed and allows mixing and printing of multi-part materials with cost effective parts and increases the printing window of complex materials such as two-part rubbers. The experiments performed using various materials show the developed 3D printer having good control even at high printing speeds (up to 20 mm/s). The performance of the printer was evaluated extensively by varying different parameters such as nozzle diameter, pressure and printing speed. Finally, the capability of developed printer is demonstrated by autonomous printing of various 3D smart structures.

The Fused Filament Fabrication technique was used to build PLA scaffolds for bone tissue replacement. Scaffolds with 100% interconnectivity were fabricated using different printing parameters and geometry design. Two temperature values and two extrusion speeds were combined with two different layer thicknesses. The influence of these parameters upon produced scaffold morphology and compressive mechanical properties was assessed. Afterwards, two different geometries were fabricated considering only the best performing parameters, to assess the influence of the main and lateral pores dimension on scaffolds mechanical properties. Specimen morphology was analysed by scanning electron microscopy, to assess the geometrical quality of the produced parts. It was verified that the higher tested temperatures combined with the lower printing speeds increased the overall mechanical strength of produced scaffolds. Low temperatures and high printing speeds were found to limit the amount of material possible to be extruded due to viscosity issues, and introduced scaffold defects. Creating staggered scaffolds with offsets between layers, decreased the resulting scaffold mechanical performance.

SAMBA™ inkjet printheads offer a high nozzle packing density of 1200 nozzles per inch, flexibility to print with multiple drop sizes, and wide ink latitude making them attractive candidates for a variety of inkjet printing applications. In this paper, we offer insight into how these features can be utilized to enable imaging models that provide high image resolution and print speed as well as increased robustness to missing jets, a key element required in single pass printing. We show that SAMBA printheads can be designed to operate in multiple imaging modes and we use simulation and experimental data to analyze their performance. We evaluate multiple imaging models enabled by SAMBA 1200 printheads and compare them for their image quality capability, image artifacts caused by transient jets, and productivity potential for single pass printing. We show that Samba 1200 imaging models combined with over-addressing and grayscale printing offer superior image quality and improved robustness to streaks without compromising on productivity.

Polyhedral oligomeric silsesquioxane (POSS) is a unique molecule that is composed of an inorganic silica core with eight organic functional arms, which can be used as a nucleus for covalent bonding to create star-shaped block copolymers with improved mechanical and biological properties. In this work, highly porous star-shaped POSS-polycaprolactone-polyurethane (POSS-PCL-PU) films were synthesized as scaffold biomaterials for tissue engineering. These films have an interesting morphology consisting of rough spherulites with filamentous structures spreading out from their centers; the unique nanotopography was shown to be suitable for cell growth. In vitro degradation was monitored for 52 weeks in terms of the weight loss and morphology changes of the films. The degradation profile exhibited a slow initial weight loss of <1% during the first 24 weeks, followed by a rapid weight loss of ~18% in the following 28 weeks. The films demonstrated excellent biocompatibility and cell-substrate affinity, with a high cell viability of >95% and rapid cell proliferation. The high porosity, unique surface nanotopography and excellent biocompatibility of the star-shaped POSS-PCL-PU film make it a great candidate as a tissue engineering scaffold biomaterial. Researchers in Singapore have prepared highly porous films that are very promising as scaffold biomaterials for tissue engineering. They synthesized the films by using star-shaped polyhedral oligomeric silsesquioxane as the starting inorganic core and incorporating polycaprolactone (PCL) and polyurethane (PU). The researchers, who are from the Institute of Materials Research and Engineering and the National University of Singapore, demonstrate that the inorganic-organic nanocomposite films satisfy all the key criteria for a biodegradable scaffold biomaterial — they have an excellent biocompatibility, a high porosity and a controlled and slow degradability. In addition, the scientists show that the material's unique nanotopography, which is produced by filamentous structures branching out from the centres of rough spherulites, promotes cell growth. The combination of organic and inorganic functionalities makes these films superior to conventional PCL-PU films. Highly porous star-shaped polyhedral oligomeric silsesquioxane (POSS) hybrid films were synthesized using POSS as the starting core followed by polycaprolactone (PCL) extension and polyurethane (PU) cross-linking. The unique three-dimensional nanotopography of these films is conducive for cell growth. The combination of favorable factors such as high porosity, reactive surface topography, excellent biocompatibility and biphasic degradation makes the star-shaped POSS-PCL-PU film a great candidate as a tissue engineering scaffold biomaterial.

Invisible Ag mesh transparent electrodes (TEs), with a width of 7 μm, were prepared on a curved glass surface by electrohydrodynamic (EHD) jet printing. With a 100 μm pitch, the EHD jet printed the Ag mesh on the convex glass which had a sheet resistance of 1.49 Ω/□. The printing speed was 30 cm s−1 using Ag ink, which had a 10 000 cPs viscosity and a 70 wt% Ag nanoparticle concentration. We further showed the performance of a 3-D transparent heater using the Ag mesh transparent electrode. The EHD jet printed an invisible Ag grid transparent electrode with good electrical and optical properties with promising applications on printed optoelectronic devices.

A waveform design method for high-speed inkjet printing based on self-sensing measurement

Influence of 3D printing parameters on surface roughness and stainability of a denture base resin: An in vitro study.

Magnetic printing is quite similar to electrostatic printing. The basic steps consist of recording a magnetic latent image, development of the recording with a magnetic ink and finally transferring the ink to a sheet of paper. Since papers on magnetic printing were first published in 1951, each step of this process has become highly developed. Impactless magnetic printers have been displayed at several conferences during the past few years. This review of the work on magnetic printers shows that printing speeds and print quality equal to electrostatic and ink jet printers can be achieved.

High-resolution direct printing of molten-metal using electrohydrodynamic jet plotting

11 - Polysaccharide-based 3D bioprinter inks for tissue engineering