Polymeric Additive Manufacturing

3D Printable Functional Materials & Composites

 

The use of 3D printing or Additive Manufacturing (AM) for scientific and industrial applications is rapidly increasing and, simultaneously, is growing the interest toward printable smart materials.

This technology allows for an easy transfer from the idea to the fabrication of a part or assembly by localized (layer-by-layer) addition of material. The consumer 3D printers market has grown with an impressive rate in the last decade and today there are printers able to work with resolutions from tens of nanometers to one millimeter and employing different printing materials.

From the point of view of the AM technology, two main challenges are emerging: the first is to improve the printing resolution by exploiting mechanical, chemical or physical tools without affecting the yield and the printing time; the second is to develop a class of smart functional materials suitable for specific customized applications. Inter alia, the combination of nanomaterials and polymers offers new possibilities for printing objects that are characterized by peculiar thermal, electrical, mechanical and optical properties. Among the available 3D printing technologies (Inkjet, Fused Deposition Modeling (FDM), Digital Light Processing (DLP), Selective Laser Sintering (SLS), …), one of the most established, versatile and cost efficient is StereoLithography (SL), which exploits a photosensitive resin and a UV laser to print complex shapes with a good resolution as compared to others.

The continuous expansion of the interest towards functional materials for SL has prompted us to develop new types of filled resins using nano- or composite materials. In particular, conductive resins are obtained by (i) adding carbon nanotubes (CNTs) or multi wall carbon nanotubes (MWCNTs) to acrylic photocurable formulations, (ii) by in-situ synthesis of silver nanoparticles (AgNPs) and by (iii) new custom formulations of conductive resins where Poly(ethylene glycol) diacrylate (PEGDA) is the bulk material and Irgacure 819 the crosslinking agent.

 

Contact information

Valentina Bertana
Tel. +39 011 911 4899
valentina.bertana@polito.it

Giorgio Scordo
Tel. +39 011 911 4899
giorgio.scordo@polito.it

Ignazio Roppolo
Tel. +39 011 090 7393
ignazio.roppolo@polito.it

Annalisa Chiappone
Tel. +39 011 090 7393
annalisa.chiappone@polito.it

 

 

3D Printed Microfluidics

 

Since the introduction of Lab-On-Chip devices in the early 1990s, silicon and glass have been the dominant substrate materials for their fabrication. This was primarily driven by the fact that fabrication methods were well established and surface properties and functionalization methods were well characterized and developed. However, the cost of producing systems in silicon or glass was driving commercial producers to seek other materials like polymers that involve reduced costs and simplified manufacturing procedures (applicable to mass replication technologies). The introduction of polymer technology allows to overcome the disadvantages linked to the rigid silicon processing.

In this perspective, 3D printing promises to be an effective alternative to micromachining as it allows to print not only a single-layer microfluidic device with the desired geometry, but a multi-layered more complex microfluidic chip, eventually embedding external electrical/mechanical components.

We are currently working on this topic, implementing processes to build micro- and nano-fluidic structures with high-resolution additive manufacturing techniques. By Micro StereoLithography (SL) we fabricate microfluidics and Lab-On-a-Chip with the advantages to easily pass from the design to the device avoiding the implementation of high cost processes or micromachining technology. Novel printing strategies are on the way to integrate SL fabrication with two-photon polymerization (2PP) to build features with a spatial resolution down to 120 nm. 2PP is combined with faster techniques so that most of the device is obtained by a lower resolution and more efficient approach (SL), while the 3D micro-/nano- feature is printed by 2PP, thus shortening process times. The adopted novel printing strategy allows for maximizing the printing resolution with respect to printing velocity.

Ancillaries activities in this field are aiming to (i) exploit the flexibility of Additive Manufacturing with respect to the traditional rigid approach of silicon and polymer planar micromachining and (ii) to introduce functional and/or biocompatible materials in the 3D printing of microfluidic devices.

Contact information

Valentina Bertana
Tel. +39 011 911 4899
valentina.bertana@polito.it

 

 

3D Printing Technologies & Applications

 

The aim of this research activity is to develop a multi-scale (micro, sub-micro and nano) and multi-function system for the micro and nano rapid prototyping of devices based on polymeric materials, in order to guarantee an efficient integration of the nano structures aligned with the micro-manufactured parts or external components. Machining on a micro and nano scale will be based on a mixture of different Rapid Prototyping technologies, mainly focused on polymers. This mixture will rely on additive manufacturing processes (micro-stereolithography (SL), two-photon polymerization (2PP), fused deposition modeling (FDM), …), subtractive processes (laser ablation) and complementary technologies (laser welding, pick&place, laser induced graphene (LIG)).

The idea of ​​the project is to merge these cutting-edge processes into a single platform with the fundamental advantage of integrating multiple operations, and directly align the nano/sub-micro structures with the micro one, an upgrade that is missing in the current high-tech Rapid Prototyping technical scenario.

The multi-scale (micro, sub-micro and nano) and multi-function system will guarantee the enabling technology able to connect the nano-structures with the micro manufactured parts, usually worked separately and rarely interacting efficiently to provide technical results scalable to an industrial level.

This platform will use versatile laser-based technologies to allow different machining on the same piece. Laser technologies can be used as extremely versatile tools for laser ablation processing of microfluidic circuits and for mechanical microstructures, to join different substrates by laser welding, to “write” conductive paths by LIG and for layer-by-layer fabrication of micro and sub-micro 3D printed scaffolds by UV-induced polymerization. These are well-known and consolidated technologies if considered separately, but the creation of a single platform that integrates all these processes is not currently available. We trust that the integration of several concurrent polymeric rapid prototyping technologies will be one of the main driving forces in this field in the near future.

From the point of view of 3D printing applications, most of our current applications are in the field of electronics, microsensors customized packaging and for microfluidic masters fabrication, nevertheless many other technical fields may take advantage from a rapid prototyping approach. As an example, a short description of our last “smart”, sometimes unconventional, applications is reported in the following:

  • A dummy eyeball prototype (DEP) was designed and fabricated for the test of new ophthalmic tamponades. The term “temporary tamponades" indicates a group of substances that are injected into the vitreous chamber in order to replace the corpus vitreum and to promote the adhesion of the retina. They are often described by the term, fully equivalent, of "vitreous substitutes". The vitreous substitutes may be temporary (buffering gases like SF6) or permanent (silicone oil). The dummy eyeball spheroidal hollow structure was designed through a 3D CAD software and was sized in order to respect the average dimensions of a human ocular bulb. The prototype was fabricated layer-by-layer by 3D ink-jet printing. The DEP was then integrated with 3 absolute pressure sensors, mounted on strategic spots on the outer surface of the DEP and connected to a customized electronic read out circuit. Pressure data were collected by an Analog to Digital Converter (ADC) and displayed with a LabVIEW Graphic User Interface (GUI).

  • A three-layer dielectric structure was fabricated as innovative unit-cell element for Transmitarray (TA) Antennas with enhanced bandwidth. It consists of a central layer, with a varying size square hole, used to compensate the phase of the incident field and located between two other identical layers with linearly tapered square holes, acting as matching circuits. Starting from a numerical model, a 3D-printed dielectric Transmitarray with a size of 15.6λ0x15.6λ0 has been manufactured and experimentally characterized. The measured prototype showed excellent performances, achieving a 1-dB gain bandwidth of 21.5%: these results prove the enhanced features of the introduced unit-cell and demonstrate the TA feasibility by Additive Manufacturing techniques.

  • A suspended microfilter obtained by two-photon polymerization (2PP) has been successfully integrated in a 3D printed microfluidic structure. In particular microchannels were fabricated by a standard Stereolithography (SLA) printer equipped with 405 nm laser using a low cost commercial 3D printing resin, while the suspended microfilter was obtained using a 2PP Micro-3-Dimensional Structuring System (M3D) and a drop of Femtobond D resin. Finally, a characterization of the filter was carried out with a simple particle track experiment to verify the functionality of the filtering mechanism. Fluorescence microparticles of two different diameters were dispersed in solution and then inserted in the inlet while the fluorescence signal was collected in the outlet tube. A correct filtering efficiency was evaluated by the fluorescence signal ratio between in and out.

  • Using a customized SLA equipment, a novel process was developed to print microfluidic channels enclosed between two PMMA layers in a sandwich-like structure. For microfluidic walls, two distinct commercial resins with different properties were used. Once thermal and pressure resistance of the obtained microfluidic device were assessed, DNA was amplified by Polymerase Chain Reaction (PCR) inside the microfluidic chambers. Test results indicated favourable mechanical and thermal resistance, as well as chemical compatibility with the assay reagents. Such observations suggest that this novel approach can be applied to 3D printing of customized microfluidics with embedded features.

  • We had an unusual and weird experience in the field of forensic and archeological reconstruction of human skulls and faces. Through a 3D inkjet printing technique, we contributed to the reconstruction of the skull of Agnolo Poliziano (1454-1494) an Italian poet of the Florentine Renaissance. The skull, reproduced for identification purpose, was then processed by an expert form scientific police through traditional face reconstruction forensic techniques.

Contact information

Luciano Scaltrito
Tel. +39 011 090 7337
luciano.scaltrito@polito.it

Valentina Bertana
Tel. +39 011 911 4899
valentina.bertana@polito.it

Matteo Cocuzza
Tel. +39 011 090 7392
matteo.cocuzza@infm.polito.it

 

 

Publications

 

  1. "An hyper-realistic method for facial approximation: the case of italian humanist Angelo Poliziano", Milani C., Capussotto V., Guaschino M., Mombello D., Cocuzza M., Pirri C.F., Panattoni G.L., Lambiase S., Gruppioni G., Journal of Biological and Clinical Anthropology, 72(2), 2015, pp. 235-244, DOI: http://dx.doi.org/10.1127/anthranz/2015/0493
  2. "Oxygen Inhibition Lithography for the Fabrication of Multi-Polymeric Structures", A. Vitale, M. Quaglio, A. Chiodoni, K. Bejtka, M. Cocuzza, C.F. Pirri and R. Bongiovanni, Advanced Materials, 2015, Vol.27(31), pp. 4560-4565, doi:10.1002/adma.201501737
  3. "In situ thermal generation of silver nanoparticles in 3D printed polymeric structures", Fantino, E., Chiappone, A., Calignano, F., Fontana, M., Pirri, F., Roppolo, I., 2016 Materials, 9 (7), art. no. 589
  4. "3D Printed PEG-Based Hybrid Nanocomposites Obtained by Sol-Gel Technique", Chiappone, A., Fantino, E., Roppolo, I., Lorusso, M., Manfredi, D., Fino, P., Pirri, C.F., Calignano, F., 2016, ACS Applied Materials and Interfaces, 8 (8), pp. 5627-5633
  5. "3D Printing of Conductive Complex Structures with in Situ Generation of Silver Nanoparticles", Fantino, E., Chiappone, A., Roppolo, I., Manfredi, D., Bongiovanni, R., Pirri, C.F., Calignano, F., 2016, Advanced Materials, 28 (19), pp. 3712-3717
  6. "Behaviour of the Intraocular Pressure during Manual and Vented Gas Forced Infusion in a Simulated Pars Plana Vitrectomy", M. Dal Vecchio, A. M. Fea, R. Spinetta, S.L. Marasso, M. Cocuzza, L. Scaltrito, G. Canavese, International Journal of Applied Engineering Research, 2017, Vol. 12(17), pp. 6751-6757, ISSN 0973-4562
  7. "Polymeric 3D Printed Functional Microcantilevers for Biosensing Applications", Stassi, S., Fantino, E., Calmo, R., Chiappone, A., Gillono, M., Scaiola, D., Pirri, C.F., Ricciardi, C., Chiadò, A., Roppolo, I., 2017, ACS Applied Materials and Interfaces, 9 (22), pp. 19193-19201
  8. "Study of graphene oxide-based 3D printable composites: Effect of the in situ reduction", Chiappone, A., Roppolo, I., Naretto, E., Fantino, E., Calignano, F., Sangermano, M., Pirri, F., 2017, Composites Part B: Engineering, 124, pp. 9-15
  9. "Development of 3D printable formulations containing CNT with enhanced electrical properties", Gonzalez, G., Chiappone, A., Roppolo, I., Fantino, E., Bertana, V., Perrucci, F., Scaltrito, L., Pirri, F., Sangermano, M., 2017, Polymer (United Kingdom), 109, pp. 246-253
  10. "3D-printed microfluidics on thin Poly(methyl methacrylate) substrates for genetic applications", V. Bertana, C. Potrich, G. Scordo, L. Scaltrito, S. Ferrero, A. Lamberti, F. Perrucci, C.F. Pirri, C. Pederzolli, M. Cocuzza, S.L. Marasso, Journal of Vacuum Science and Technology B, 36(1), Jan/Feb 2018, 01A106-1/7, DOI: 10.1116/1.5003203
  11. "Optimization of a suspended Two Photon Polymerized microfluidic filtration system", F. Perrucci, V. Bertana, S.L. Marasso, G. Scordo, S. Ferrero, C.F. Pirri, M. Cocuzza, A. El-Tamer, U. Hinze, B.N. Chichkov, G. Canavese, L. Scaltrito, Microelectronic Engineering, 2018, 195, pp. 95-100, DOI: 10.1016/j.mee.2018.04.001
  12. "3D Printing/Interfacial Polymerization Coupling for the Fabrication of Conductive Hydrogel",Fantino, E., Roppolo, I., Zhang, D., Xiao, J., Chiappone, A., Castellino, M., Guo, Q., Pirri, C.F., Yang, J., 2018, Macromolecular Materials and Engineering, 303 (4), art. no. 1700356
  13. "All-in-One Cellulose Nanocrystals for 3D Printing of Nanocomposite Hydrogels", Wang, J., Chiappone, A., Roppolo, I., Shao, F., Fantino, E., Lorusso, M., Rentsch, D., Dietliker, K., Pirri, C.F., Grützmacher, H., 2018, Angewandte Chemie - International Edition, 57 (9), pp. 2353-2356
  14. "PLA conductive filament for 3D printed smart sensing applications", S.L. Marasso, M. Cocuzza, V. Bertana, F. Perrucci, A. Tommasi, S. Ferrero, L. Scaltrito, C.F. Pirri, Rapid Prototyping Journal, DOI: 10.1108/RPJ-09-2016-0150, in Press
  15. "Experimental evaluation of mechanical properties repeatability of SLA polymers for labs-on-chip and bio-MEMS", De Pasquale, G., Bertana, V., Scaltrito, L., 2018, Microsystem Technologies, pp. 1-11. in Press