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Xu, et al.
pressure from damaging the cells. In the FDM process, which will not pollute the printed samples. The additive
polymer pellets were loaded into a stainless steel syringe manufacturing platform of 3D printing is usually a flat
and then melted, and the compressed gas acted directly plate, but cell printing is a special printing environment
on the molten material (Figure 4J and K). This design that needs to prevent bacterial contamination, and its
does not need to consider the resistance of the piston to commonly used carrier vessels include Petri dishes and
high temperatures, and the bubbles in the material will well plates. Among them, the diameters of commonly
be eliminated. Compared with the mechanical piston used Petri dishes are 35 mm, 60 mm, and 90 mm, and
driven by a motor, the printing method has significant the diameters of commonly used orifice plates are 6-well
advantages in eliminating bubbles. plates, 12-well plates, 24-well plates, 96-well plates, and
so on. To allow users to accurately use the abovementioned
(C) Mechanical screw-based nozzle various types of Petri dishes and well plates when using

During the screw extrusion process, the material chamber the printer, this research developed a multifunctional
will not change in volume, and the material can be additive manufacturing platform that uses the groove
continuously fed for a long time, which is suitable for structure to locate different Petri dishes and well plates
printing biological materials with high viscosity and (secured with elastic claw structure) (Figure 3G).
easy precipitation. The temperature of the material in the 2.2.4. Accurate positioning and temperature control
screw can be controlled by wrapping a heating resistor on device
the periphery of the screw (Figure 4M).
Using an infrared laser sensor and mechanical position
(D) Concentricity maintaining structure designed for sensor composite software system, the system allows the
coaxial printing nozzle (the outlet position of the extruded material on the
nozzle) tip position of all nozzles to be corrected in 3D
The key to the success of the inner and outer nesting space. We designed and manufactured rapid temperature
structure of the coaxial extrusion cell printing nozzle change controls. Semiconductor refrigeration and
is to ensure that the relative positions of the inner and resistance heating are used to provide temperature control
outer needles are not eccentric. Therefore, a triangular for the nozzles and the print bed Figure 5. Each nozzle
claw structure was designed to ensure its coaxiality. Due was equipped with a temperature control device. There
to different bioink materials, the success of printing in are two specifications, one of which has a temperature
the coaxial nozzle also depends on the height difference control range of 10 – 70°C (with heating and cooling
between the inner and outer needles. The height difference functions, which can quickly adjust the temperature,
between the inner and outer needles was designed in ~10°C/min) used for low-viscosity materials, and the other
an adjustable way to facilitate printing with different has a temperature control range of RT-270°C (heating
materials. Another problem often encountered in actual up fast (>20°C/min) cooling down slowly (~6°C/min))
use of coaxial printing is the problem of nozzle clogging. was designed for the FDM process. For the (10 – 70°C)
The difference between this research and other research temperature control devices, the heating unit used a
designs is that we designed the coaxiality guaranteed ceramic heater, and the cooling unit used semiconductor
structure on the outer sprinkler. The inner diameter of the refrigeration with an air-cooled device. For the (RT-
outer nozzle is designed to be larger and easy to clean 270°C) temperature control devices, the heating unit
and can be used non-disposably. The inner diameter of used a resistance wire with a spiral sleeve shape, and a
the inner nozzle is very thin and not easy to clean, so we powerful air-cooled heat dissipation system was designed
use a disposable standard syringe steel needle, which can to dissipate heat in the non-heated area, which could
reduce the difficulty of cleaning the nozzle and reduce the reduce the impact of the high-temperature environment
cost of use. In the subsequent printing test experiments, on the nozzle motor and other electronic components.
the inner diameter of the final needle used was 0.33 mm, The print bed equipped with a temperature control device
and the inner diameter of the outer needle was 1.1 mm. (range of 10 – 60°C), which has heating (used a ceramic
heater) and cooling (used semiconductor refrigeration)
2.2.3. Multifunctional additive manufacturing platform functions, makes the heating and cooling process very
The additive manufacturing platform designed in this fast. The temperature control error is 0.1℃ ([10 – 70 ℃]
research realizes two-way temperature control with and [10 – 60°C]) and 1℃ ([RT-270℃]).
both cooling and heating functions and adopts the
temperature control system of the forming platform, in 2.2.5. Integrated hardware control system
which the heating sheet and the semiconductor cooling During the research and development process, we
sheet are compounded. The heat dissipation system of the chose the Arduino Mega 2560 chip as the mother
additive manufacturing platform is set directly below it, board, which has strong development and expansion

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