Table 3.

Performance comparison of recently published microwave chemical sensors utilizing various manufacturing technologies.

Reference	Technology	Manufacturing	Weight (g)	fr (GHz)	Δfmax (MHz)	S (%)
This work	3D SRR	3D-printing	22.8	2.56	205	8
[12]	3D SRR	Milling machine	140.1	2.53	60	2.37
[24] †	SIW *	Photolithography	N/A	5.81	470	8
[26] †	Dual mode resonator	LTCC **	N/A	3	300	10
[27] †	Planar SRR	Photolithography	N/A	0.87	100	11.49

SIW represents * substrate-integrated waveguide. LTCC ** represents low-temperature co-fired ceramics. N/A represents not available. ^† They are consisted of planar structures and metallic patterns are fabricated on conventional circuit board.