TABLE 1.

Properties of MNs for transdermal sampling.

MN type	MN material	Manufacturing method	Sampling mechanism	Sampling amount/efficiency	Reference
Solid	Glass	Glass pulling	Pressure-driven convection	1–10 µl ISF	Wang et al. (2005)
	Polycarbonate	—	Capillary action	—	Sato et al. (2011)
	Stainless steel	Laser cutting	Capillary action	>2 µl of ISF in 1 min	Kolluru et al. (2019)
	Stainless steel	Micromachining	Capillary action	2.9 μl of ISF in 30 s	Kim et al. (2021)
Hollow	Stainless steel	Laser cutting	Inherent pumping mechanism	Up to 20 and 60 μl from humans and rats, respectively	Miller et al. (2018)
	Silicon	Micromachining	Capillary action	—	Mukerjee et al. (2004)
	Glycidyl methacrylate, trimethylolpropane trimethacrylate, and triethylene glycol dimethacrylate	Micromolding	Capillary action	Extracted simulated ISF within 5 s	Nicholas et al. (2018)
Porous	Cellulose acetate	Phase inversion	Capillary action	1.33 mg ISF in 10 min	Liu et al. (2020)
	PSF, PDA, and PEG	Phase inversion	Capillary action	1.41 mg ISF in 10 min	Liu P. et al. (2021)
	PDMS	Mold casting and salt leaching	Pressure-driven convection	0.019 µl/min (80 min after insertion: 0.080 µl/min)	Takeuchi et al. (2022)
Swelling	Acrylate-based hydrogels	Micromolding	Diffusion	6 µl of ISF in 10 min	Laszlo et al. (2021)
	MeHA	Micromolding	Diffusion	1.4 mg ISF in 1 min	Chang et al. (2017)
	MeHA	Micromolding	Diffusion	3.82 µl of ISF in 3 min	Zheng et al. (2020)
	GelMA	Micromolding	Diffusion	1.9 mg after 5 min	Zhu et al. (2020)
	PVA/CS	Micromolding	Diffusion	—	He R. et al. (2020)

PDMS, dimethylpolysiloxane; PSF, polysulfone; PDA, polydopamine; PEG, poly(ethylene glycol); MEMS, microelectro-mechanical system; MeHA, methacrylated hyaluronic acid; GelMA, gelatin methacryloy; PVA, polyvinyl alcohol; CS, chitosan.