**3. Case study**

#### **3.1 Design of microfluidic**

Since this study uses a micro milling a microfluidic design with a rectangular geometry will be used. From **Figure 3**, the designed depth is 50 um, 200 um wide, and the circle on the inlet and outlet has a diameter of 0.6 um. **Figure 3** shows microfluidics with 2 layer PMMA to be fabricated. From **Figure 3**, the top layer has 4 holes with a diameter of 0.8 mm, the design of the hole is based on the need to place a tube with an outer diameter of 0.7 mm. While the design for the bottom layer of microfluidics, there is a circular inlet and outlet with a diameter of 0.6 mm which is smaller than the outer diameter of the tube, to allow the tube to be above the microfluidic layer and the entire fluid can enter the micro flow.

The tool used in this research is a 0.2 mm diameter tool made of carbide material, has 2 flutes and Aluminum coated. While the workpiece that will be used in this research is Poly (methyl methacrylate) or referred to as acrylic which has a thickness of 2 mm.

**85**

**Table 3.**

**Table 2.**

*Machining parameter (Taguchi method).*

*Experiment number (Taguchi method).*

*Micro Milling Process for the Rapid Prototyping of Microfluidic Devices*

The Taguchi method as shown in **Table 2** is used taking into account 3 main parameters, namely, spindle speed, cutting depth, and feed rate to obtain the lowest surface roughness. The Taguchi method which uses 3 parameters along with 3 stages is used as **Table 2**. Spindle speeds consisting of 4000 rpm, 5000 rpm, and 6000 rpm, and spindle speeds lower than 10,000 rpm are used because PMMA material will burn when high speeds are used, as high speeds can increase the temperature on the tool can cause micro flow size the result is greater than desired. The cutting depths used for each cut are 0.01 μm, 0.025 μm, and 0.05. This is to ensure that the discarded chip is smaller than the tip of the tool. While the feed rate used is 10 mm/min, 15 mm/min, and 20 mm/min. Due to the high feed rate it can cause the tool to break. The total number of experiments produced is 9 experiments as shown in **Table 3**, each surface roughness average will be recorded, based on the smallerer the better method, and the smallest surface roughness average parameter will be taken. Then the optimal parameters will be repeated 10 times to ensure that

After analyzing the experimental data from **Table 4**, the lowest surface roughness can be obtained by using a spindle speed of 4000 rpm, a feed rate of 10 mm/ min and a depth cut of 0.01 mm. However, based on **Table 4**, it can be seen that while the spindle speed is 6000 rpm, cutting depth and feed rate do not have a significant impact on surface roughness, where the average surface roughness is recorded around 100 nm to 200 nm, at the same time, increasing cutting depth and feed rate, increasing average surface roughness resulting. Moreover, it can be observed that all the resulting surface roughness is less than 450 nm. Next, to validate the experiment, 10 microcontrollers were built on PMMA with spindle speed parameters of 4000 rpm, feed rate of 10 mm/min and depth depth of 0.01.

**Factors Level 1 Level 2 Aras 3** Spindle speed (rpm) 4000 5000 6000 Depth of cut (μm) 0.01 0.025 0.05 Feed rate (mm/min) 10 15 20

**Experiment number Spindle speed (rpm) Depth of cut (mm) Feed rate (mm/min)**

 4000 0.010 10 4000 0.025 15 4000 0.050 20 5000 0.010 15 5000 0.025 20 5000 0.050 10 6000 0.010 20 6000 0.250 10 6000 0.050 15

**3.2 Fabrication of microfluidic using micromilling**

the parameters produce consistent and stable results.

*DOI: http://dx.doi.org/10.5772/intechopen.96723*

**Figure 3.** *Top and bottom layer of microfluidic.*
