Tampere University of Technology

Multi-material bio-printing facilities

CitationVirtanen, J., & Tuukkanen, S. (2017). Multi-material bio-printing facilities. Paper presented at Nanoscience Days2017, Jyväskylä, Finland.

Year2017

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Dispenser printing provides a method to produce 2D and 3D patterns from

basically any liquid phase material. Dispensing considered here is a form of

extrusion of material through a narrow diameter needle. An advantage of

dispensing technique over conventional printing techniques is the

avoidance of complicated ink formulation, which generally requires

hazardous organic solvents that may be harmful to biological objects.

Dispensing also allows materials with rather different properties such as

different viscosity to be printed in the same process. Combining the

dispensing printing of liquid phase materials and 3D printing of solid

materials, complex structures with new functional properties can be

fabricated, which is very challenging if not impossible using conventional

manufacturing techniques.

Juhani Virtanen, Sampo Tuukkanen*

BioMediTech Institute and Faculty of Biomedical Sciences and Engineering, Tampere University of Technology (TUT), Finland. *sampo.tuukkanen@tut.fi

1. Virtanen J., Janka M., Tuukkanen S., ”Fabrication and characterization of nanocellulose aerogel structures”, EMBEC & NBC

2017 Conference. IFMBE Proceedings 65, 1029 (2017).

2. J. Virtanen, J. Keskinen, A. Pammo, E. Sarlin, and S. Tuukkanen, ”Pyrolysed cellulose nanofibrils and dandelion pappus in

supercapacitor application”, Cellulose 24(8), 3387 (2017).

3. Satu Rajala, Tuomo Siponkoski, Essi Sarlin, Marja Mettänen, Maija Vuoriluoto, Arno Pammo, Jari Juuti, Orlando J. Rojas, Sami

Franssila and Sampo Tuukkanen, “Cellulose nanofibril film as a piezoelectric sensor material”, ACS Appl. Mater. Interfaces

8(24) (2016) 15607.

4. Rahul Mangayil, Arno Pammo, Essi Sarlin, Satu Rajala, Jin Luo, Ville Santala, Matti Karp, Sampo Tuukkanen, “Bacterial

NanoCellulose Films as Low cost, Flexible Piezoelectric Material”, ACS Applied Materials & Interfaces 9(22), 19048 (2017).

Fig. 1 shows a dispenser robot (EFD Nordson) capable for printing liquid phase

materials, e.g. hydrogel or nanocellulose dispersions. The robot is controlled by

a PC software and the actual liquid volume with dispensing controllers (three

dispenser seen in Fig. 1). The working area of this dispensing robot is

400x400x200 mm with a repeating accuracy of 10 µm. The needle diameter

can be varied between 50 µm and 2000 µm. Figs. 2 and 3 show the dispenser-

printed tracks of cellulose nanofibril (CNF) gel (Fig. 4).

Aerogels can be prepared by freeze-casting or freeze-drying process. Freeze-

casting is a method where aquaeous dispersion is deposited and solidified by

simultaneous freezing the water molecules (freezing-stage in Fig. 5). The

solidified water crystals the retain the shape of the casting even though the

solid material concentration is vey low (~1 wt-%). After the structure is

solidified by freezing water is removed with a freeze-drying process. If done

properly the water removal won’t affect the solid components and an aerogels

structure is remains (Fig. 6). Dispenser printed aerogel (Fig. 7) which has been

freeze dried can be seen. Nanocellulose aerogels [1] are potential lightweight

materials for example in biomedical or membrane applications.

Nanocellulose is an interesting material for electronic applications, such

as supercapacitors [2] and piezoelectric sensors [3, 4] because of high

surface area, entangled networks of cellulose nanofibrils (CNF) and

permanent dipole moment of cellulose nanocrystals (CNC).

Figure shows a multi-material Fused Deposition Modeling (FDM)

printer. This particular Prusa i3 Mk2 printer is capable of printing 4

different filament materials in a single print without operator

interaction. Therefore it can be used to combine functional properties

such as flexibility, electrical conductivity or visibility to the structure.

The FDM prints can also be combined with the dispenser robot prints

to enable even more complicated material combinations.

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500 nm

500 nm

100 µm

100 µm 100 µm

100 µm

Cellulose nanocrystal (CNC) aerogel

Cellulose nanofibril (CNF) aerogel

SEM µCT HIM

The prepared aerogels from cellulose nanofibrils (CNF) and cellulose

nanocrystals (CNC) (Fig. 6) were imaged with three microscopic

techniques, scanning electron microscopy (SEM, Figs. 11, 12), X-ray

micro–computed tomography (µCT, Figs. 13,14) and He-ion microscopy

(HIM, Figs. 15,16). SEM shows well the aerogel surface features, such

as well distinguishable CNC particles, whereas µCT and HIM gives more

information about 3D-structure of the aerogels. CNF aerogel appears as

lamellar planes, whereas CNC aerogel forms a needle-like mesh.

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10 mm