Table 5.

Characteristics of various molding processes for HMN manufacturing.

Mold type	Molding count	Method	Parameter (μm)	HMN Materials	Pros	Cons	Ref.
embossed mold	1st molding	Electroplating	Shape: pyramid	Nickel	Easy to check structures during electroplating	Difficult to separate after electroplating	[153]
			Heights: 140
			Hollow diameter: 50
		Casting	Shape: cone	Hyaluronic acid	Easy mold fabrication using methods like 3D printing and imprinting, easy demolding	Mold type depends on the material used	[109]
			Heights: 2000
			Hollow diameter: 50
	2nd molding	Electroplating	Shape: cone	Nickel	Easy to make first mold	Secondary molding must use if the first mold is hard	[108]
			Heights: 1100
			Hollow diameter: 20
Intaglio mold	1st molding	Electroplating	Shape: cone Heights: 250-500 Hollow diameter: 30-75	Nickel	Compatible with laser, imprinting and etching methods	Requires sputtering seed layer formation needed, mainly used with silicone-based materials due to separate	[88,100]
		Casting	Shapes: cone, pyramid, cylinder, syringe, triangular pyramid, triangular prism, triangular cross-section column	Polymethyl methacrylate (PMMA), Polyglycolic acid (PGA), Polycarbonate (PC), Negative PR (SU-8)	Reusable, enables uniform pattern formation, can form complex structures	Pattern distortion possible, risk of bubble formation, potential infiltration issues	[99,101,118,121,122,125,155,163,167,169,170]
			Heights: 50-1540
			Hollow diameter: 2-1054
	2nd molding	Electroplating	Shape: pyramid	Nickel	Easy to form the second mold from the first mold	Requires soft materials like silicon for easy separation	[168]
			Heights: 650
			Hollow diameter: 20-60
		Casting	Shapes: syringe, triangular pyramid	Polydimethylsiloxane, Polyimide (PI)	Suitable for manufacturing	Mold type depends on the material used	[86,114]
			Heights: 500-886
			Hollow diameter: 49-200