Table 2.

Summary of representative 3D-printed conductive hydrogel-based sensors.

Hydrogels System and Component	Printing Techniques	Conductivity	Gauge Factor	Sensing Range	Application	Ref.
PPNGC hydrogel	N/A	2.1 S/m	0.78 (0–120% strain), 1.52 (120–600% strain)	0–600%	human motions	[111]
PANI hybrid hydrogel	DIW	N/A	2.2 (0–3% strain), 0.8 (40 ppm NH3), 7.3 (400 ppm NH3)	(1) stress sensing of 0–899.8 MPa, (2) strain sensing of 0–764.4%	human motions, NH3 detection, temperature detection	[108]
SMF/RSF/PAM composite hydrogel	DIW	0.056 S/m	0.9	0–200%	human motions	[112]
poly(ACMO)/pt hydrogel	DLP	1.6 S/cm	1.5 (0–10% strain), 7.2 (10–100% strain)	0–100%	human motions	[74]
polyaniline hybrid (PHH) hydrogels	DIW	0.04–0.21 S/m	∼1.77	0–820% (the resistive strain sensors)	human motions, human–machine interfaces, physiological signal detections	[32]
dorsal root ganglion (DRG) cell-encapsulated gelatin methacryloyl (GelMA) hydrogels	SLA	662.0~ 968.0 Ω/sq	N/A	N/A	healthcare applications, neural tissue regeneration	[85]
PPy/PEGDA hydrogel	DLP	2 MΩcm	N/A	N/A	biosensors, drug delivery, tissue engineering	[19]
PEGDA/AAm LiCl/nHAp hydrogels	projection microstereolithography (PμSL)	~0.1 S/cm	N/A	both large-scale and tiny human motions	human motions, conductor, neural interface
PAINT hydrogels	DIW	0.26~0.58 S/m	signal-to-noise ratio by 88%	N/A	healthcare applications	[2]
GNPs–CNTs (GC) hydrogels	multi-jet fusion (MJF)	1.48 × 10−2 S/m	20.1(0–5% strain), 2.3 (6–26% strain), 360.8 (26–70% strain)	0–70% strain, 10~90% humidity	strain/humidity sensors	[115]
PEGDA/MWCNT-based composite hydrogel	multimaterial mask image projection-based stereolithography	770 kΩ~17.25 MΩ	Rrel = 5.73 for 150 μm thickness to 2.17 for 450 μm thickness with 2 μL water	N/A	liquid sensing	[116]
PVA/agarose/ borax/liquid metal composite	three-dimensional printed molds	N/A	SNR = 4.05	N/A	multimodular sensor system biosignal detection	[33]
poly (N-isopropyl acrylamide)/polyaniline hydrogels	DIW	7.1 × 10−6 S/m	N/A	N/A	stimulus-response electronics, flexible electronics, artificial intelligence wearables	[124]
polyNCMA/LiTFSI gel	N/A	3.6 × 10−5 S/m at 30 °C, 2 × 10−3 S/m at 90 °C	8.4%/K	30~40 °C	temperature monitor	[117]
PEDOT:PSS/HPU gel	extrusion printing	N/A	N/A	pH 3~11	pH sensor	[123]
PEGDA–PANI electroconductive hydrogel	SLA	2.5 × 10−2 S/m		pH 2~7	smart biomedical sensors, pH sensor	[107]
(poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (PF127))/CNTs	N/A	0.16~0.20 S/m	N/A	N/A	wearable electronic devices, health monitoring	[38]
PANI-based biosensors	inkjet printing	N/A	(1) 7.4927 μA·mM−1·cm−2 of triglyceride, (2) 3.94 μA·mM−1·cm−2 of lactic acid, (3) 5.028 μA·mM−1·cm−2 of glucose	(1) 0.1–6 mM of triglyceride, (2) 0.5–1.7 mM of lactic acid, (3) 1–25 mM of glucose	biosensors for human health monitoring	[78]
GOx-loaded H/G4–PANI Hydrogel:	inkjet printing	N/A	N/A	H2O2 of (1–10) × 10−3 M	flexible bioelectronics	[130]

N/A indicates that this information is not applicable in the reference.