Table 1.

Characteristics and operating principles of common sensors for volatile organic compounds (VOCs) detection. Microfabricated devices are compared to commercial units already in the market.

Transduction Mechanism	Sensor Type	Dimensions	Active Layer	Sensitivity Range	LOD	Operating Conditions	Response Time	Manufacturing Techniques	Reference
Traditional devices commercially available
Optical	NDIR	L: 5–8.2 cm W: 3–5 cm H: 1.2–2 cm	–	0–5.000 ppm	2–20 ppm	4.5–20 VDC	20–120 s	–	[46]
Optical	PID (MiniPID 2)	Ø 20 mm C.V: 15 µL	–	0–40 ppm	1 ppb	10.6 eV lamp 3–3.6 VDC	8 s	–	[204]
Acoustic	SAW	L: 4.0 mm W: 1.0 mm H: 0.5 mm	6–30 nm (CNTs)	10–180 ppm	1–10 ppm	Room temp. fr = 433.92 MHz noise: 3 kHz	2–4 min	–	[205]
Conductometric	Chemiresistor (MiCS-2714)	D: 5 mm × 7 mm H: 2.25 mm	MOS	0.1–10 ppm	50 ppb	High temp. (220 °C/50 mW)	12 s	–	[206]
Potentiometric	MOSFET (Z-900)	4.75 cm × 2.5 cm × 1.5 cm	MOS	0–50 ppm	0.1 ppm	High temp. 9 V battery power	<30 s	–	[207]
Microfabricated devices
Optical	µPID	2.4 mm × 2.4 mm C.V: 1.3 µL	–	0–1 ppb	2–8 ppt	10.6 eV lamp 5–6 VDC	0.1 s	–	[48]
Gravimetric	SAW	20 mm × 20 mm	53.91 nm (CuO)	0–50 ppm	500 ppb	Room temp. fr = 198.98 MHz noise: <300 Hz	10–90 s	Sol–gel	[66]
Gravimetric	CMUT	4 mm × 1.5 mm Øe: 5.3 µm	50 nm (Polymer)	10–100 ppb	51 ppt	Room temp. fr = 47.7 MHz noise: <2 Hz	<120 s	Direct wafer-bonding + local oxidation	[74]
Amperometric	RTILs	Øe: 1 mm VRTILs: 2–8 µL	150 nm (Pt-TFEs)	0.1–2 ppm	20–110 ppb	Room temp. LSV (100 mV·s−1)	–	Electrodeposition	[90]
Conductometric	MOS-chemiresistor	13.4 mm × 7 mm (Ag-Pd IDEs)	Nanobricks (In2O3)	0.1–1 ppm	<100 ppb	Low temp. (50 °C)	114 s	Electrochemical anodization	[125]
Potentiometric	Polymer-FET	Au-elec. (30 nm; 20 µm × 1 mm)	20 nm (OSC-film)	1–25 ppm	1 ppb	Room temp. RH (45–70%)	5 s	Dip coating	[99]
Potentiometric	Bioelectronic-FET	–	12–15 nm (ORs + CNTs)	10 ppt–1 ppb	10 ppt	Room temp.	Real time (<5 s)	Photolithography	[180]