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Printing Technologies and Systems
Published in Jerry C. Whitaker, Microelectronics, 2018
This technology involves the transfer of dye from a coated donor ribbon to a receiver sheet via sublimation and diffusion, separately or in combination. The amount of dye transferred is proportional to the amount of heat energy supplied; therefore, this is a continuous tone technology. It has found application as an alternative to silver halide photography, graphics, and prepress proofing. As with all thermal printers the energy is transferred via a transient heating process. This is governed by a diffusion equation and depending on the length of the heating pulse will produce either large temperature gradients over very short distances or lesser gradients extending well outside the perimeter of the resistor. Much of the design, therefore, focuses on the thicknesses of the various layers through which the heat is to be conducted. In the case of thermal dye sublimation transfer a soft-edged dot results, which is suitable for images but not for text. Shorter heating pulses will lead to sharper dots.
Desktop Publishing
Published in Paul W. Ross, The Handbook of Software for Engineers and Scientists, 2018
Thermal printers require a chemically treated, heat-sensitive paper. Instead of pins to form the letters, small heater elements cause the paper to darken. This printer technology is most commonly found in low-cost facsimile machines. The paper is fairly costly, difficult to handle, and does not produce a permanent image.
3D bio-printing technology for body tissues and organs regeneration
Published in Journal of Medical Engineering & Technology, 2018
Esmaeil Biazar, Masoumeh Najafi S., Saeed Heidari K., Meysam Yazdankhah, Ataollah Rafiei, Dariush Biazar
Bio-injector printing is a non-contact technique in which droplets of cells or biological materials are controlled by thermoelectric bubbles, piezoelectric activators or pressure pulses. In this technology, droplets of ink are placed on a piece of paper with a narrow hole; bio-ink made from cells and biological materials is used to print live drops into cells using a non-contact nozzle. Inkjet printers are divided into three categories: thermal actuator, piezoelectric activator and electrostatic actuator. In the thermal printers, the presence of a heater next to the ink chamber causes ink to warm up and to bubble, and the bubble expansion acts as a driving force to move the ink into the nozzle to be released. The local heat creates a bubble in the bulk ink chamber and a small drop drops out. The temperature in thermal printers can be very high, but for a very short time (about 2 μs), so in general the temperature increase is only up to a maximum of 4–10 °C and usually has no significant effect on cell viability. Piezoelectric 3D printers contain a piezoelectric crystal that, in response to the applied voltage, causes rapid deformation and introduces pressure into the ink container to release the ink out of the nozzle. An Epson-based electrostatic stimulating printer operates by creating an electric field by two electrodes around the ink placement chamber. By connecting the flow with two electrodes, a pressure is applied to the chamber, which causes the ink to be released. Compared with the thermal inkjet printing, this method does not warm the cells, so the mild cell surface of the cells and the survival of the dye adjournment layer (1–1000 diameter/s) can be electromechanically controlled. Due to the distribution mechanisms and the non-contact nature of the inkjet printer, materials with low viscosity (<10 cp) are preferably used, while high-viscosity materials cannot be effectively applied by the inkjet printer. As a result, the printed structure often has poor mechanical properties. Inkjet bio-printing not only facilitates the distribution of primary cells or stem cells of the desired density but also preserves the survival of cells and their function after printing. Advantages of inkjet printers are low cost and ease of accessibility, bio-printing capabilities in micron dimensions, precise control of very low amounts of biology and medication, the ability to arrange several cell types and biological components, extracellular matrix, medications, etc., the ability to supply tissue in a high speed, the use of computer-aided design and manufacturing systems, the ability to use in rapid prototyping, printing on cell screens, 3D scaffolds, gels and liquids. The disadvantages include precision non-conductivity and control of the size of droplets, thermal and mechanical stress applied to cells and biological materials Frequent nozzle blockage and unsafe cell encapsulation. Additionally, specific vibrating frequencies and force levels used in piezoelectric biomechanical printing may disrupt cell membranes and cause cell death [22].