**3. Scaling up production of microfluidic chips**

In general, to achieve batch production of polymer microfluidic chips, a highquality mold insert is indispensable for precision replication of micro structure using microinjection molding. In this case, developing a reliable tooling technology for mold insert fabrication is important. Besides, after microinjection molding of polymeric chips, the bonding process for sealing microchannels of chips determines the final functionality of microfluidic chips. Therefore, each process step is significantly important.

**37**

**3.1 Tooling technology**

**Figure 4.**

*publishing, LTD.*

machinable materials.

There are a variety of manufacturing technologies available to fabricate micro mold inserts, such as ultraprecision micro milling, micro-electrical discharge machining (*μ*EDM), electrochemical machining (ECM), silicon wet etching, deep reactive ion etching, laser machining, and LIGA-based processes (LIGA, UV-LIGA). **Table 1** shows a comparison among the mold insert manufacturing technologies according to the achievable feature size, surface roughness, aspect ratio, and

*3D printed polymer microfluidic chip: (a)schematic of SLA process; (b) printing platform configuration; (c) channel washing; (d) application of hydrogel; (e) remaining hydrogel remove; (f) cross-section of the 3D chip; (g) 500 μm raised structures intersecting at a 45° and 45° [32]. Copyright (2016) with permission from IOP* 

*Prototyping and Production of Polymeric Microfluidic Chip*

*DOI: http://dx.doi.org/10.5772/intechopen.96355*

*Prototyping and Production of Polymeric Microfluidic Chip DOI: http://dx.doi.org/10.5772/intechopen.96355*

*Advances in Microfluidics and Nanofluids*

*Direct-write laser machining for microfluidic chip [31].*

For laser micro machining, when the laser beam is moving above the workpiece space, the heated spots will gather to form various patterns. Through the reflection in the light path and the focusing effect of the focusing lens, the laser is finally focused on the workpiece, where the temperature of the focal point increases rapidly. After the polymer material melts and decomposes, scratches will be left on the surface of the polymer, where the microchannels are formed [24]. The scanning speed is programmed and controlled by a computer. **Figure 3** shows the specific process methods of laser micro machining and machined glass microfluidic chip.

3D-printing is different from traditional manufacturing techniques. It achieves the fabrication of materials utilizing additive manufacturing (AM). Under computeraided control, it can construct the 3D structure layer by layer. The most common 3D printing technologies used in the manufacture of microfluidic devices are stereolithography (SL), multi-jet modeling (MJM), and fused deposition modeling (FDM). SL utilizes selective light exposure to photopolymerize precursor to construct object layer by layer [27]. For MJM, it works by using an inkjet head to spray curable liquid photopolymers into a tray, and photopolymerization will happen on each layer when exposed quickly to UV light. FDM uses a motor-driven nozzle head to print heated thermoplastic material in three dimensions. **Figure 4** demonstrates the 3d-printing devices and printed polymer microfluidic chips. A thin resin layer as printed material is solidified via laser beam for the fabrication of 3D-chip that features the channel layer and bottom layer of 500 μm and intersects at 45° and 20°. The printing resolution is 50 μm in line width. After the printing process, the chip needs to be washed using isopropanol (IPA) and deionized (DI) water in the micropump platform.

In general, to achieve batch production of polymer microfluidic chips, a highquality mold insert is indispensable for precision replication of micro structure using microinjection molding. In this case, developing a reliable tooling technology for mold insert fabrication is important. Besides, after microinjection molding of polymeric chips, the bonding process for sealing microchannels of chips determines the final functionality of microfluidic chips. Therefore, each process step is

**3. Scaling up production of microfluidic chips**

**36**

significantly important.

**2.3 3D-printing**

**Figure 3.**

#### **Figure 4.**

*3D printed polymer microfluidic chip: (a)schematic of SLA process; (b) printing platform configuration; (c) channel washing; (d) application of hydrogel; (e) remaining hydrogel remove; (f) cross-section of the 3D chip; (g) 500 μm raised structures intersecting at a 45° and 45° [32]. Copyright (2016) with permission from IOP publishing, LTD.*
