Fig. 6

Fabrication of various ECM hydrogel-based nanobiomaterial ink for in vitro tissue-integrated monitoring platforms using different 3D printing techniques. a Schematic diagram of the fabrication process of the 3D intestinal microvillus-mimetic electrochemical cell sensor. Reprinted with permission from [277]. b, c Diagram illustrating the bioprinter setup for the one-step fabrication of a bioelectronics platform and the resulting freestanding and flexible sensor: b comprehensive 3D bioprinting process and c images of the bioelectronic platforms printed (i) on glass, (ii) in freestanding form, and (iii) the heating coil; (iv) the printed electrical circuits are flexible enough to be conformally wrapped around a cylinder into a conformal shape and (v) stable even when immersed in a wet environment, while (vi) the heating coils printed on GelMA are also flexible. Reprinted with permission from [278]. d–g Novel approach for the fabrication of an oxygen-sensitive sensor using 3D printing and functionalized ink: d schematic diagram illustrating the printing process for the oxygen sensor using O₂-sensitive luminescent indicator-incorporated ink, e images of a 3D-printed optical oxygen sensor at various oxygen concentrations, f calibration curve obtained from e, and g a Stern–Volmer (fluorescence quenching) plot illustrating the calibration curve. Reprinted with permission from [279]