Table 1.

List of RFID tag antenna sensors for strain detection and characterization.

Sensing Principle (Antenna Type)	Sensing Variable	Feature	Pros.	Cons.	Refs.
Conductor loss resistance (stretchable dipole on fabric substrate)	Backscattered power at turn on threshold	Power variation	Strain level up to 50%;Sensitivity can be modified by conductive material; Read range: 1.5 m	Power is susceptible to wireless channel	[39]
Deformation of shape factor (meander line dipole)	Backscattered power	Power variation	Sensitivity: 16%; Read range: 0.6 m	Strain level up to 6% (poor-elastic conductor leads to small yield point)	[40]
Coupling (slotted circular patch)	Reflection coefficient (S11)	RFS	Omni-directional strain sensing	VNA is required; Not compatible with Gen2 regulation	[41]
Electrical length (fabric-based embroidered dipole)	Dual-interrogation-mode (read range/RCS)	RFS	Strain level up to 16%;Sensitivity: 0.66 parts per million (ppm)/με	Read range: 20 cm; Need calibration; Dedicated receiver	[107]
Elastic deformation (patch)	Turn on power	RFS	Read range: 2.1 m; Can be mounted on metallic surface	Sensitivity: 0.7907 ppm/με	[36]
LC resonator (PDMS substrate stamped with sliver nano ink)	Reflection coefficient (S11)	RFS	Strain level up to 7%; Chipless; Good mechanical	Sensitivity: 0.51 ppm/με; Read range: 20 cm; VNA is required; Dedicated receiver	[42]
Deformation of slot width (dipole on PDMS substrate with stretchable conducting Lycra fabric containing silver threads)	Turn on power	Power variation	Sensitivity: strains of up to 10% causing transmit power differences of about 4 dB; Read range: 1.6 m; Good repeatability	Power is susceptible to wireless channel	[43]
Elastic deformation (folded patch)	Turn on power	RFS	Can be mounted on metallic surface	Sensitivity: −0.7404 ppm/με; Read range: 30 cm	[46]
Elastic deformation (dual patches)	RCS	RFS	Sensitivity: −5.232 kHz/με	Not compatible with Gen2 regulation Dedicated receiver	[38]