Fused deposition modeling (FDM), stereolithography (SLA) and Powder Bed Fusion (PBF) are the three common 3D printing (3DP) techniques. Some structured polymers or molds often formed using SLA and PBF techniques by researchers are much more expensive and a complicated post-processing. Here, we use FDM 3DP technique, which is simple, cheap and time-saving, to manufacture the polymer master mold for multi-use cycling casting polydimethylsiloxane (PDMS) with various structures such as waves and cones. The cast structured PDMS can be applied as a triboelectric layer for the Al-PDMS triboelectric nanogenerator (TENG) to harvest mechanical energy. The more effective contact area the structured PDMS has, the better electrical output performance is. The mechanical-to-electric conversion energy using the Al-PDMS TENG fabricated by the polymer FDM 3DP and casting is the potential sustainable energy for the self-powered device application in the future.
Keywords: Polymer; 3D Printing; Casting; Polydimethylsiloxane; Structure; Triboelectricity; TENG
3D printing technique has arisen as a multifaceted technology platform for computer-assisted design (CAD), and it’s a cost-effective additive manufacturing that has been developed since 1980s. It plays an indispensable role in various industrial fields, even in high-tech era nowadays, therefore 3D printing technique becomes one of the critical techniques for Industry 4.0 and digital fabrication [1-2]. The main feature of 3D printing technique is that it enables us to design complex three-dimensional geometries. There are three common 3D printing techniques, which are fused deposition modeling (FDM), stereolithography (SLA) and Powder Bed Fusion (PBF) [3-4]. Table 1 lists the comparison of 3D printing techniques with some of their relevant features. So far, 3D printing technique is used to various fields such as medical applications , sustainable energy , and so on. Here, we report on fabricating a PDMS film cast by polymer FDM 3D printed mold. We select the FDM technique because the fabrication is cheaper, simpler, and more time-saving. As the fact mentioned above, by using 3D printing technique, a macro-scale structured PDMS film is fabricated. Through applying the structured PDMS film to TENG, self-powered ability of the device has been tested. The structured PDMS for Al-PDMS TENG can light up LEDs in series and efficiently charge different capacitors, so that it is capable of providing sustainable electrical energy for practical applications in the future [7-8].
Table 2 lists the properties of polymer materials (Polylactic
acid(PLA), PolyMideTM(CoPA) and Copolyester plus (CPE+)) with
a focus on glass transition point, melting point, heat resistance,
surface quality and dimension accuracy. In this work, we select
PLA because of its good surface quality, which is important to be
a casting mold; and we also choose CoPA due to its high melting
point and heat resistance, which could cut down the curing time
and accelerate the process. Polymer materials all have their own
merit. According to the demand of various applications, each
polymer materials will be utilized effectively.
The schematic process flow and assembly of structured
PDMS film is shown in Figure 1. A computer-aided design tool
of Autodesk Inventor software is used to design the master mold
for casting to form structured PDMS. The PLA, CoPA (Ultimaker)
polymer molds are printed by 3D printer (Ultimaker 3, Ultimaker).
The PDMS solution is prepared by the well-mixed elastomer
(Sylgard 184, Dow corning) and curing agent (10:1 in weight). The
degassed solution was poured into the master mold. Then cure
the PDMS in the oven about 55-65oC depending on the material
of master molds for about 2h and cool down for peeling off the
structured PDMS. The structured-PDMS film and aluminum (Al)
are assembled into a TENG, and used as triboelectric layers,
respectively, and the other Al attached to the backside of PDMS
also as an electrode.
Through 3D printing technology, we can design the mold
with various creative structures, such as waves and cones, for
casting the PDMS film, as shown in Figure 2. A structured-TENG is
produced by combining with 3D printing and PDMS casting. The
output performance of structured-TENG (wave) is measured that
the maximum open-circuit voltage (Voc) and short circuit current
(Isc) is 21.8 V and 12.75 μA, respectively. The stable Voc has been
measured during the durable test for 10000 cycles, as shown in
Figure 3(a). We can examine that the device is reusable and has
great durability. The structured-TENG can also be applied to
charge different capacitors efficiently, which can light up 30 green
LEDs, as shown in Figure 3(b).
We demonstrate that using FDM 3D printing technology is
able to manufacture a reusable master mold, for casting PDMS
triboelectric layers with macro-scale structure quickly. Through
3D printing technology, complex and creative structures could
be designed and applied to TENGs. In terms of applications, it is
proved that the Al-PDMS structured-TENG can charge electronic
devices to achieve self-powered function through capacitor
charging tests. In the future, it can also extend its application to
self-powered pressure sensors and human-machine interfaces.
This work is partially sponsored by the Ministry of Science
and Technology (MOST), Taiwan, under contract No MOST108-
2221-E-006-187 and 110-2221-E-006-177. It was also supported
in part by SATU Joint Research Scheme (JRS) project, National
Cheng Kung University, Taiwan.
Darwish LR, El-Wakad MT, Farag MM (2021) Towards sustainable industry 4.0: A green real-time IIoT multitask scheduling architecture for distributed 3D printing services. Journal of Manufacturing Systems 61: 196-209.
Kafle A, Luis E, Silwal R, Pan HM, Shrestha PL, et al. (2021) 3D/4D Printing of polymers: Fused deposition modelling (FDM), selective laser sintering (SLS), and stereolithography (SLA). Polymers 13(18): 3101.