3D Printed e-Tongue

Abstract

Nowadays, one of the biggest issues addressed to electronic sensor fabrication is the build-up of efficient electrodes as an alternative way to the expensive, complex and multistage processes required by traditional techniques. Printed electronics arises as an interesting alternative to fulfill this task due to the simplicity and speed to stamp electrodes on various surfaces. Within this context, the Fused Deposition Modeling 3D printing is an emerging, cost-effective and alternative technology to fabricate complex structures that potentiates several fields with more creative ideas and new materials for a rapid prototyping of devices. We show here the fabrication of interdigitated electrodes using a standard home-made CoreXY 3D printer using transparent and graphene-based PLA filaments. Macro 3D printed electrodes were easily assembled within 6 min with outstanding reproducibility. The electrodes were also functionalized with different nanostructured thin films via dip-coating Layer-by-Layer technique to develop a 3D printed e-tongue setup. As a proof of concept, the printed e-tongue was applied to soil analysis. A control soil sample was enriched with several macro-nutrients to the plants (N, P, K, S, Mg, and Ca) and the discrimination was done by electrical impedance spectroscopy of water solution of the soil samples. The data was analyzed by Principal Component Analysis and the 3D printed sensor distinguished clearly all enriched samples despite the complexity of the soil chemical composition. The 3D printed e-tongue successfully used in soil analysis encourages further investments in developing new sensory tools for precision agriculture and other fields exploiting the simplicity and flexibility offered by the 3D printing techniques.

Multilayered Nanostructures Integrated with Emerging Technologies

“…Recently, a homemade dualextruder FDM printer was used to fabricate macro planar IDEs and sensor body in e-tongue applications. Each sensing unit was printed within 8 minutes having good reproducibility in the fabrication process of conventional e-tongue devices [24].…”

“…Traditional soil chemical investigation is an expensive and time-consuming process, thus motivating the development of alternative approaches in precision agriculture [69][70][71]. Recently, we have used an e-tongue system based on impedance spectroscopy to recognize different soil samples enriched with macronutrients [24,72]. Initially, it was used a traditional PDMS microchannel sealed onto gold IDEs fabricated on glass substrates by photolithography (Figure 7a).…”

“…A cluster between control and P soil samples using the 3D-printed electrodes was observed (Figure 8b), which does not occur with the conventional device (Figure 8a) fabricated with gold IDEs and PDMS microchannels. However, considering the contribution of the third main Principal Component (PC3), all the samples could also be easily separated with the 3D-printed device [24].…”

3D-Printed Graphene Electrodes Applied in an Impedimetric Electronic Tongue for Soil Analysis

“…Interdigitated electrodes (IDEs) were fabricated with a conductive filament and the fused deposition modeling (FDM) method using a homemade two nozzle CoreXY FDM 3D printer built based on the RepRap open hardware, as previously reported [30]. The conductive filament was a commercial polylactic acid (PLA)-based thermoplastic doped with graphene fibers purchased from BlackMagic 3D (Graphene Supermarket, Ronkonkoma, NY, USA).…”

“…The e-tongue system presented here was composed of one bare electrode and three IDEs covered with PDDA/CuTsPc, PDDA/MMt-K, and PDDA/PEDOT:PSS LbL films, similar to [26,30]. Electrical measurements were performed using 25 mV of amplitude in the frequency range 1-10 6 Hz using a Solartron 1260A impedance/gain-phase analyzer coupled to a 1296A dielectric interface.…”