Label in Fig. 2, Fig. 4	Item	Quantity	Cost per unit (USD)	Total cost (USD)	Supplier	Catalog number	Material type
T1	MQ3 (alcohol sensor)	4	3.16	12.64	Kinsten, https://kinsten.com.tw/	2D0075	Electronics
T2	DHT22 (temperature cum humidity sensor)	4	6.40	25.60		2D060	Electronics
T3	Flat rainbow ribbon cables (14 m)	1	9.50	9.50		WAD0018	Electronics
T4	20-AWG cable (14 m)	1	9.51	9.51		WAK0082	Electronics
T5	Onion Omega 2 + SBC	1	15.35	15.35	Onion Store, https://onion.io/store/	OM-O2P	Electronics
T6	Onion Omega expansion dock	1	15.00	15.00		OM-D-EXP	Electronics
T7	Onion Omega ADC expansion board	1	15.00	15.00		OM-E-ADC	Electronics
T8	Standard type A to micro B USB 2.0 cable	3	1.76	5.28	Centenary Materials, http://us.100y.com.tw/	107,551	Electronics
T9	Arduino Nano MCB	1	20.70	20.70		98,443	Electronics
T10	ADS_1115 ADC	1	4.43	4.43		136,511	Electronics
T11	LM2596S DC-DC converter	2	3.51	7.02		96,038	Electronics
T12	LED (460–465 nm)	1	0.88	0.88		96,662	Electronics
T13	Photoresistor (8–20 kΩ, 350–780 nm, highest sensitivity: 540 nm)	1	0.13	0.13		53,901	Electronics
T14	High thermal conductivity aluminum plate	1	0.07	0.07		91,069	Electronics
T15	Heatsink	1	1.25	1.25		138,583	Electronics
T16	Custom-made amplifier PCB (cf.[43])	1	13.28	13.28	Good Technology, Taichung, Taiwan	–	Electronics
T17	Optical fiber (Ø = 2 mm)	1	5.55	5.55	Shiner Fiber Optics, Hsinchu, Taiwan	TW-0200	Optics
T18	Optical fiber (Ø = 5 mm)	1	11.07	11.07		TW-0500	Optics
T19	3D printed probe	1	40.62	40.62	Brusat, Taichung, Taiwan	–	3D-printing (PEEK)
T20	Glass piece	2	5.27	10.54	NTHU workshop, Hsinchu, Taiwan	–	Optics
T21	M2 screw	3	0.07	0.21	Kinsten, https://kinsten.com.tw/	AWA002-008	Electronics
T22	Emission filter	1	27.73	27.73	Rosco, Stamford, CT, USA	100 0R26S 2024	Optics
T23	Lens	1	7.94	7.94	Koodyz Technology, Taipei County, Taiwan	–	Optics
T24, T25, T26, T27	light-proof holders and caps	4	–	–	–	–	3D-printing(ABS)
	Perfboard	2	0.35	0.70	Centenary Materials, http://us.100y.com.tw/	2826	Electronics
	Insulation tape	1	0.63	0.63		6640	Electronics
	Thermal grease	1	1.50	1.50		101,464	Polymer
	AC to DC wall adaptor (AC 110 V to DC 9 V)	1	7.08	7.08		104,583	Electronics
	AC to DC wall adaptor (AC 110 V to DC 5 V)	4	5.33	21.32		140,439	Electronics
	Dupont wires	36	0.05	1.80	Kinsten, https://kinsten.com.tw/	CBC001	Electronics
	Epoxy glue	1	1.40	1.40	Local hardware store, Hsinchu, Taiwan	CK-080	Polymer