Table 1.

Main advantages, disadvantages, resolution range and aspect ratio of microfabrication techniques used to develop microfluidic devices using polymer substrates. Adapted from [14].

Fabrication Technique	Advantages	Disadvantages	Resolution Range and Aspect Ratio
Hot embossing	Precise and rapid in the replication of microstructures. Mass production.	Restricted to thermoplastics. Time-consuming. Complex 3D structures are difficult to be fabricated.	Resolution between sub-100 nm and millimetre. Moderate aspect ratio (5:1) [32,33]
Injection molding	Mass production. Fine features. Low cycle time. Highly automated.	Restricted to thermoplastics. High cost mold. Nano-size precision is limited.	Resolution between sub-100 nm and millimetre. High aspect ratio (20:1) [34]
Laser photoablation	Rapid. Large format production.	Limited materials. Multiple treatment session. Difficulties for mass production. Micro-size precision is limited.	Resolution between micrometre and millimetre. High aspect ratio (30:1) [35,36]
X-ray lithography	High-resolution. Straight and smooth walls.	Complex and difficult master fabrication. Time consuming and high cost process.	Resolution between few nanometres and micrometres. Ultra-high aspect ratio (350:1) [37]
Soft-lithography	High-resolution and 3D geometries. Cost-effective. Excellent micro-size precision.	Pattern deformation and vulnerability to defects. Difficult to fabricate circular 3D geometries.	Resolution between 30 nm and 500 m. High aspect ratio (20:1) [18]
Xurography	Low-cost and rapid technique.	Complex 3D structures are difficult to be fabricated. Micro-size precision is limited.	Resolution between 150 m and millimetre. Moderate aspect ratio (8:1) [21,23,38,39]
Direct laser plotting	Low-cost and rapid technique. Free-mask technique. Good micro-size precision.	Complex 3D structures are difficult to be fabricated. Micro-size precision is limited. Reproducibility of the microdevices.	Resolution between 10–500 m. Moderate aspect ratio (7:1) [40,41]
Micromilling	Low-cost and rapid technique. Free-mask technique.	Complex 3D structures are difficult to be fabricated. Micro-size precision is limited. Reproducibility of the microdevices. Roughness.	Resolution between 30 m and millimetre. Moderate aspect ratio (8:1) [26,42]
Desktop fused deposition modeling (FDM), 3D-printing	Low-cost and rapid technique to fabricate prototypes.	Micro-size precision is limited. High roughness and complex to perform flow visualizations. Not suitable for mass production.	Resolution between 100 m and millimetre. Moderate aspect ratio (10:1) [43,44,45]
Nanofabrication	High-resolution of 2D and 3D geometries. Excellent nano-size precision. Highly repeatable, periodical structures.	High cost. Multiple process steps. Limited for microfluidic applications.	Resolution between 1–800 nm. Ultra-high aspect ratio (100:1) [17,46]