Printing of Biomaterials at defined Temperature

Different temperature control units are available for the pneumatic extruders of the BS printers. They fit to 10 Milliliter cartridges but 30 Milliliter cartridges can be used at room temperature.

Metal cartridge with steel or aluminum nozzle

Temperature control for 10 mL cartridges; Left: Peltier chiller; Right: Shell heater

A) Peltier chiller, range: 4°C to 80°C

B) Shell heater, range: RT to 100°C (190°C)

Disposable plastic cartridges with Luer lock adapter are fine for prints close to room temperature. Nozzle insulators are available for particular Aluminum needles.

Thermoplasts like PCL print better with a set comprising the proprietary GeSiM stainless steel cartridge (10 mL) and stainless steel nozzle, available at different size.

Aluminum nozzle with heat insulation shield

Metal nozzles for different applications

3D Structures from Melted Thermoplastics

Our advanced motor driven piston extruders extend the capability of the pneumatic basic set:

• High pressure (Virtually > 100 bar) prints viscoelastic and high-viscous materials, even with tiny nozzle diameters
• Constant piston moves ensure constant material flow, independent on the material level inside the cartridge

High-Temperature extruder for thermoplasts (Left); Pneumatic extruder (Right)

Gradient mixer for thermoplasts (Left); Piston extruder for hydrogels (Right)

The High-Temperature Piston Extruder prints thermoplastics like PLA (Polylactic acid) at temperatures up to 250°C. It comes with the stainless steel cartridge as well as stainless steel nozzle. A two zone heater compensates the temperature drop from the cartridge to the nozzle.

The Gradient Mixer (Available for BS4.2 only) combines the outlet of two HT-Extruders with a special mixing head. It allows varying mixing ratios of two thermoplasts during one print.

Printing of larger volumes (50 mL) is available by the piston extruder for hydrogels.

Tablets for Object Fixation

Well plate tray of BS3.1

The standard tray for BS printers accomodates two well plates (BS3.2 three well plates, BS4.2 six plates), e.g. cell culture plates. Trays for glass slides or other targets are available on request. The trays come with a snap-in fixation for quick replacement on the instrument main deck.

Temperature controlled well plate holders are available on request.

Low-Volume Sample Handling

Optionally BS printers can be equipped with a pipetting unit. Diverse pipetting needles applies small volumes (0.1 Nanolitre to a few Microlitres) of low-viscous liquids to previously printed scaffold struts. These liquids may contain drugs, cells or particular proteins.

There are two tools available:

• Passive needle for syringe supported displacement dispensing. The lowest dispense volume might be half a Microliter.
• Piezoelectric nozzles for free-flight microdrop dispensing. The lowest dispense volume is in the range of 0.1 Nanolitres:

Piezo Dispenser on a bioscaffold structure

Heater for 96well plates (BS2.1)

Piezoelectric GeSiM dispensers emit single drops in the range of 250 Pikolitre (Drop diameter about 50 Microns). Small amounts of proteins or cell suspensions can be applied to single or multiple layers of a bioscaffold structure during the printing process.

Twin-Tip-Pipettor with two piezoelectric Nanoliter Dispensers

• The innovative Twin-Tip-Pipettor operates two separate GeSiM piezoelectric nozzles on a swivel. For aspiration both nozzles dip into separate wells of a 96-well-plate. The droplets of both nozzles than hit together and mix up on the dispense target.
• The volume range between fifty Nanolitres and a few Microlitres is covered best by the solenoid dispense valve (Not for living cells.)

Contradictionary to the cartridge system the pipetting unit aspirates from 96 well plates. Only a few Microliters of each species are required. Heaters are available both for the sample plate and the piezo nozzle for producing microdrops of melted materials.

Piezoelectric Pipettor on BS3.1; Click here for full size BS3.1 video on YouTube

Customer experiments have shown the feasibility of printing cell suspensions (More…) as well as the application of VEGF to pneumatically extruded Calcium Phosphate strands (More…).

Artificial Tissue from Maccaroni Strands

Core/Shell Extruder with cartridges for two separate materials; Deactivating the core extruder allows hollow fibres (Left)

Layered stack of hollow fibres

CoreShell Extruder with Core (Orange) and Shell (Green) Material – Schematic View

Soft matrices like Hydrogels are cell friendly materials but hard to print into stable 3D structures. The combination with more stiff thermoplastic scaffolds may cause biocompatibility issues.The pneumatic C/S-extruder (Core/Shell extruder) for BS printers allow to combine two materials with different properties in a coaxial manner. The tool is equipped with a kind of double nozzle with different but corresponding inner and outer diameter, respectively. The print parameters can be set individually for both channels in order to match properties of the respective bioinks.

Core/Shell strand with cells inside after 7 days cultivation: Bright field image (left); Nuclei stained blue (right) (1)

A. R. Akkineni, T. Ahlfeld, A. Lode and M. Gelinsky: A versatile method for combining different biopolymers in a core/shell fashion by 3D plotting to achieve mechanically robust constructs, IOP Publishing Ltd., Oct 2016

(1)

Centre for Translational Bone, Joint and Soft Tissue Research
Technische Universität Dresden

Hardening of Scaffold Struts

There are lamp heads with different excitation wave lengths and different wave length available for the exposition of printed scaffold layers (Third party manufacturers). The lense head goes on one of the tool axes of BS3.1. One application is the hardening of UV curable materials.

THORLABS 4-fold LED head on BS3.1

For high power exposition we recommend the Omnicure 1500. Alternatively, LED-lamps from THORLABS are available with many different wave lengths but at limited power. The max. LED output power depends on the wavelength and is in the range of 50 mW to 210 mW.

Processing of External CAD Data

This extension just comprises software  – A dedicated input filter reads in STL files. An STL file describes triangulated surfaces in a three-dimensional Cartesian coordinate system. It is widely used for rapid prototyping, 3D printing and computer aided manufacturing.

3D models printed from STL files: Women breast model (left), bulbasaur (right)

The BioScaffolder 3.1 software allows to define inner “scaffold-” structures whereas the STL file brings in just surfaces. Like with the built-in scaffold generator, up to three different materials and different pore sizes can be assigned to the CAD model.

Phantasy insect printed from dough at room temperature

Melt Electrowriting (MEW)

The optional MEW module of BS3.1 combines pneumatic extrusion and high-voltage induced fibre deposition for particular thermoplastic materials. So far PCL 50,000 can be printed.

In contradiction to Melt Electrospinning (MES) Melt Electrospinning Writing deposits each fibre in a regular manner accordingly to the CAD model.

The Melt electrowriting module extends the standard configuration of the instrument by a special tray with embedded electrode, a high-voltage generator and security measures. The minimum strut width is in the range of 10…20 Micrometers. Left side picture shows the print setup with nozzle electrode, the right side shows the high-voltage generator.

Micro-Mesh from PCL 50,000l 100 layers. The strand distance is 500 Microns (Left side) and 200 Microns (Right side).