**3.3 Microembossing**

Microembossing, also known as microtransfer molding or hot-embossing, is the process by which the configuration of microfluidic channels is transferred onto


**201**

*mHealth-Based Microfluidic Lab-on-a-Chip for International Health Security*

laboratories for the production of disposable LoCs [31].

the thermoplastic material. The polymer material is pressed with a heated barrel so that the material becomes soft and molted. By applying pressure and heat onto the polymer sheet, the shape is then transferred from metal press to the sheet. To transfer microscale patterns inexpensively, the hot-embossing method can be used. Such a method is affordable, assessable, and available even to resource-constrained

In injection molding fabrication protocol, the injection of molten thermoplastic involves under high pressure into a heated closed master mold, followed by cooling until the thermoplastic solidifies, and subsequent demolding the replica from the master mold. For industrial scale manufacturing of macroscopic objects in thermoplastics that has been adopted for micromanufacturing, injection molding is a

PDMS (polydimethylsiloxane) is a straightforward, adaptable, and low-cost polymer that can be used to fabricate LoC by the softlithography. Research laboratories commonly use PDMS for LoC prototyping, which is one of the least resource demanding fabricating methods. PDMS is also broadly utilized on the grounds that it is simple and shabby to create PDMS LoCs [36]. Moreover, LoC made of PDMS takes preferred standpoint of the simple mix of shudder miniaturized scale valves for quick stream switch and penetrability of air for cell-and-tissue-culture-LoCs [37]. Commonly utilized for LoCs prototyping, PDMS demonstrates extreme impediments for modern generation. The properties of PDMS are surprisingly close to that could be obtained from glass and plastic. The cross-linking of many of these polymer chains makes a structure that is flexible and reversibly deformable. **Table 4** summarizes the physical properties of PDMS, and **Table 5** compares polymer and glass as substrate for chemical and biomedical applications [36]. Many of properties demonstrate that the PDMS is very desirable for fabricating

Irrespective of the opportunity that it is a little bit more uncertain and expensive to actualize than PDMS, thermoplastics are great contender for the manufacture of LoCs. Thermoplastic polymers are generally utilized by specialists to manufacture LoCs. Polymethyl methacrylate (PMMA), given its transparency, can be used as the positive tone photoresist in X-ray lithography and e-beam lithography processes [38]. Cyclic-olefin Copolymer (CoC) polymer is a popular fabrication material for various applications, including lenses and medical devices. CoC can also be used for the 3D printing of microfluidic LoC devices. PolyCarbonate (PC), which is more inert to chemical solvent than PDMS therefore, can be useful for some LoC applications where PDMS are not suitable for the required LoC applications. However, fabricating LoCs using PC requires investment intensive high-pressure embossing micromachining tools. Poly vinyl alcohol (PVA) is used for fabricating sophisticated LoCs with three-dimensional polymer microstructures. PVA can be dissolved in water but not in solvents, so they can be used as sacrificial materials. One more type of polymer not directly used for fabricating LoCs but still useful for biomedical application is Parylene. Parylene allows the transmission of waves in the visible spectrum, and it is not porous and can be coated onto electronics to prevent it from

*DOI: http://dx.doi.org/10.5772/intechopen.90283*

**3.4 Injection molding**

well-established technique [32].

**3.5 PDMS Lab-on-a-Chip**

microfluidic LoCs.

**3.6 Thermoplastic-polymers Lab-on-a-Chip**

#### **Table 3.**

*Comparison between photolithography and softlithography [21–24, 29, 30, 33–35].*

the thermoplastic material. The polymer material is pressed with a heated barrel so that the material becomes soft and molted. By applying pressure and heat onto the polymer sheet, the shape is then transferred from metal press to the sheet. To transfer microscale patterns inexpensively, the hot-embossing method can be used. Such a method is affordable, assessable, and available even to resource-constrained laboratories for the production of disposable LoCs [31].
