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International Journal of Bioprinting 3D printing and 3D-printed electronics in smart drug delivery devices

Figure 5. (a) Various 3D-printed porous structures: (i) grid, (ii) triangular, and (iii) hexagonal. (b and c) Temperature sensing performance of various
3D-printed temperature sensors with different porous structures. (d) Optical image of the 3D-printed temperature sensor. (e) Comparison between a com-
mercial temperature sensor and a 3D-printed temperature sensor. (f) Demonstration of strain-insensitive temperature sensor. (Reprinted with permission
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from . Copyright (2019) ACS Publications.)

Figure 6. Schematic showing various printed pH sensors, namely (a) conductometric PEDOT:PSS, (b) voltametric carbon-alizarin, and (c) potentiometric
graphene/PANI sensors. (Reprinted with permission from . Copyright (2021) Wiley, John, and Sons Inc.)
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Wang et al. demonstrated that stretchable temperature materials that have been used for 3D printing of pH
sensor can be fabricated using PDMS nanocomposite ink sensors include PEDOT:PSS, PANI, graphene, and CNT.
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with DIW technique (Figure 5) . They also showed that Naficy et al. fabricated a hydrogel-based pH sensor using a
the use of DIW technique to fabricate grid-like structure composite functional inks made of 5 wt.% of PEDOT:PSS
of the temperature sensor can help to decouple the effect and hydrophilic polyurethane and 3D printed the pH
of motions to enhance the accuracy of temperature sensors using material-extrusion printing method . They
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measurement. showed that the performance of printed pH sensors was
pH sensors are very useful for wound monitoring comparable to those prepared by conventional method. In
and management as it allows for in situ monitoring of another work, Jose et al. compared three types of printed
the wound condition and triggering of drug release as pH sensors, which are conductometric PEDOT:PSS,
early as possible. pH sensing can be achieved via different voltametric carbon-alizarin and potentiometric graphene/
sensing mechanisms such as conductometry, voltammetry, PANI sensors, and they found that the potentiometric
and potentiometry, just to name a few . In terms of PANI-based sensors outperformed the other two sensors
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3D-printed pH sensors, many different types of sensors in terms of linearity, repeatability, stability, and leaching
have been reported [57,67,69,73,78,84] . Typically, the pH-sensitive resistance (Figure 6) . Also, Goh and Agarwala et al.
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Volume 9 Issue 4 (2023) 154 https://doi.org/10.18063/ijb.725