Fig. 1. (a, b) Photograph of the multi^3D system. (c) Schematic of a fabrication example^{9, 14}

Fig. 2. (a) Process flow of the multi^3D system. (b) Fabricated parts^{9, 14}

Fig. 3. Fabrication procedure of fully encapsulated capacitive sensor with 3D printing. (a) Polycarbonate (PC) substrate with recesses designed for all electronic components. (b) Components arranged in in the PC substrate. (c) Electrical components with corresponding embedded wiring. (d) Completed capacitive sensor with fully embedded wiring, diodes, LEDs, resistors, and a microcontroller²¹

Fig. 4. (a) Printed wireless pressure and temperature sensor within a shoe's insole. (b) Pressure and temperature data obtained through wireless communication from the printed insole²²

Fig. 5. Fabrication process of 3D "smart cap" with an embedded inductor–a wireless passive sensor¹². (a) 3D fabrication process with embedded and electrically conductive structures. (b) 3D microelectronics components, including parallel-plate capacitors, solenoid-type inductors, and meandering-shape resistors. (c) A 3D LC tank, which is formed by combining a solenoid-type inductor and a parallel-plate capacitor. (d) A wireless passive sensor demonstration of a "smart cap", containing the 3D-printed LC-resonant circuit. (e) A smart cap with a half-gallon milk package, and the cross-sectional schematic diagram. (f) Sensing principle with the equivalent circuit diagram

Fig. 6. (a) Schematic of the hybrid SL/DP system. (b~d) Fabricated 3D 555 timer circuits packaged within SL substrates²⁴

Fig. 7. The hybrid 3D printing process and fabricated 3D structural electronics¹⁰. (a) Bottom insulating structure. (b) "U" shape wire. (c) Top insulating layer. (d) Wires on top surface. (e) PμSL of the bottom insulating structure. (f) DWC of the "U" shape wire. (g) PμSL of the top insulating structure. (h) DWC of wires on the top surface. (i) Fabricated 3D structural electronics with embedded wires

Fig. 8. Examples of printed 3D structural electronics¹⁸. (a) A gaming die which includes a microcontroller and accelerometer. (b, c) A magnetometer system with microprocessor and orthogonal Hall Effect sensors

Fig. 9. Schematic illustration of the embedded 3D printing (e-3DP) process and printed stretchable electronics¹¹. (a) Schematic illustration of the e-3DP process. (b) Photograph of a glove with embedded strain sensors produced by e-3DP. (c) Photograph of a three-layer strain and pressure sensor in the stretched state

Fig. 10. Fabricated stretchable tactile sensor using integrated PSL and DP processes²⁷. (a) An example (partial sphere) of 3D structure built in the PSL system. (b) Printed sensing elements using the DP process on the insulating layers built in the PSL system. (c) Final sensor with two sensing layers. (d) Deformed sensor

Fig. 11. 3D printed electronics using Aerosol Jet printing from Optomec^28-30. (a) 3D MID demonstrator. (b) 3D MID with integrated sensor. (c) Printed conformal electronics (curve). (d) Printed conformal electronics (dome). (e) Printed conformal electronics (dome). (f) Sub-mm length scale, custom made 3D metal-dielectric

Fig. 12. Leg prosthesis part produced by FDM and Aerosol Jet printing³¹

Fig. 13. Voxel8 and some printed products³². (a, b) Photograph of Voxel8 3D printer. (c) Printed unmanned aerial vehicle. (d) Printed antenna (dome). (e) Printed wearable device