Study on the Optimum Cutting Parameters of an Aluminum Mold for Effective Bonding Strength of a PDMS Microfluidic Device
Abstract
:1. Introduction
2. Materials and Methods
2.1. Experiment Design and Fabrication of Aluminium Master Mold
2.2. Experimental Setup
2.3. Fabrication of PDMS Microfluidic Device
2.4. Bonding Strength Measurements
3. Results and Discussion
3.1. Experimental Design with Experimental Responses
3.2. Regression Equations
3.3. Adequacy of the Model
3.4. 3D Plots for Surface Roughness
3.5. Verification Test
3.6. Optimization of the Cutting Parameters
4. Effect of Tool Diameter on Microstructures
5. Bonding Strength Measurement
6. Conclusions
- (1)
- The feed rate has the greatest influence on the surface roughness followed by the spindle speed for both tools: 200 µm and 400 µm. Depth of cut has the least effect in the case of smaller tool size and almost no effect was observed for the larger tool size.
- (2)
- From the roughness measurement, the samples with tool T1 had lower roughness compared to tool T2.
- (3)
- With RSM factor analysis, the optimal cutting parameters were found to be as follows: 20,000 rpm spindle speed, 50 mm/min feed rate, depth of cut 5 µm with tool size 200 µm or less. These parameters are the best choice to achieve a smooth micro-milled surface and fine resolution structure using a conventional CNC machine.
- (4)
- For the given cutting combinations, a minimum surface roughness of 0.169 µm is achieved; this provides efficient PDMS bonding strength of greater than 300 kPa.
- (5)
- It is also observed that a much narrower gap between the structures can be produced by using the smallest tool diameter with a fine resolution microstructure at a reduced time; this is on par with the photo lithography-based microstructure without the requirement of a clean room.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Notation | Factor/Level | Tool Diameter (T1) 200 µm | Tool Diameter (T2) 400 µm | ||||
---|---|---|---|---|---|---|---|
−1 | 0 | 1 | −1 | 0 | 1 | ||
A | Spindle speed (rpm) | 10,000 | 15,000 | 20,000 | 10,000 | 15,000 | 20,000 |
B | Feed rate (mm/min) | 50 | 100 | 150 | 50 | 100 | 150 |
C | Depth of cut (µm) | 5 | 10 | 15 | 5 | 10 | 15 |
Run No. | Spindle Speed (rpm) | Feed Rate (mm/min) | Depth of Cut (µm) | Surface Roughness for T1 (µm) | Surface Roughness for T2 (µm) |
---|---|---|---|---|---|
1 | 15,000 | 100 | 10 | 0.270 | 0.371 |
2 | 15,000 | 100 | 10 | 0.203 | 0.369 |
3 | 20,000 | 150 | 5 | 0.225 | 0.340 |
4 | 20,000 | 50 | 5 | 0.169 | 0.388 |
5 | 15,000 | 100 | 5 | 0.231 | 0.319 |
6 | 15,000 | 100 | 10 | 0.253 | 0.371 |
7 | 15,000 | 150 | 10 | 0.221 | 0.320 |
8 | 20,000 | 50 | 15 | 0.251 | 0.359 |
9 | 15000 | 100 | 15 | 0.199 | 0.370 |
10 | 10,000 | 150 | 5 | 0.233 | 0.333 |
11 | 20,000 | 150 | 15 | 0.241 | 0.309 |
12 | 15,000 | 100 | 10 | 0.232 | 0.364 |
13 | 10,000 | 150 | 15 | 0.182 | 0.368 |
14 | 15,000 | 100 | 10 | 0.274 | 0.389 |
15 | 20,000 | 100 | 10 | 0.230 | 0.355 |
16 | 10,000 | 50 | 5 | 0.229 | 0.350 |
17 | 15,000 | 100 | 10 | 0.233 | 0.320 |
18 | 10,000 | 50 | 15 | 0.210 | 0.367 |
19 | 15,000 | 50 | 10 | 0.226 | 0.341 |
20 | 10,000 | 100 | 10 | 0.241 | 0.351 |
Source | Sum of Squares | Degree of Freedom | Mean Square | F-Value | p-Value (Prob > F) |
---|---|---|---|---|---|
Model | 0.013 | 9 | 1.425 × 10−3 | 195.90 | <0.0001 |
A | 4.580 × 10−3 | 1 | 4.580 × 10−3 | 629.54 | <0.0001 |
B | 7.508 × 10−3 | 1 | 7.508 × 10−3 | 1032.04 | <0.0001 |
C | 4.489 × 10−4 | 1 | 4.489 × 10−4 | 61.71 | <0.0001 |
A2 | 5.020 × 10−5 | 1 | 5.020 × 10−5 | 6.90 | 0.0253 |
B2 | 7.645 × 10−5 | 1 | 7.645 × 10−5 | 10.51 | 0.0088 |
C2 | 1.364 × 10−5 | 1 | 1.364 × 10−5 | 1.88 | 0.2008 |
AB | 5.000 × 10−7 | 1 | 5.000 × 10−7 | 0.069 | 0.7985 |
AC | 2.450 × 10−5 | 1 | 2.450 × 10−5 | 3.37 | 0.0964 |
BC | 2.000 × 10−6 | 1 | 2.000 × 10−6 | 0.27 | 0.6115 |
Residual | 7.275 × 10−5 | 10 | 7.275 × 10−6 | - | - |
Lack of Fit | 5.941 × 10−5 | 5 | 1.188 × 10−5 | 4.46 | 0.0634 |
Pure Error | 1.333 × 10−5 | 5 | 2.667 × 10−6 | - | - |
Source | Sum of Squares | Degree of Freedom | Mean Square | F-Value | p-Value (Prob > F) |
---|---|---|---|---|---|
Model | 8.135 × 10−3 | 9 | 9.039 × 10−4 | 8.54 | 0.0012 |
A | 1.440 × 10−3 | 1 | 1.440 × 10−3 | 13.60 | 0.0042 |
B | 5.808 × 10−3 | 1 | 5.808 × 10−3 | 54.86 | <0.0001 |
C | 4.840 × 10−5 | 1 | 4.840 × 10−5 | 0.46 | 0.5143 |
A2 | 1.642 × 10−6 | 1 | 1.642 × 10−6 | 0.016 | 0.9034 |
B2 | 4.845 × 10−4 | 1 | 4.845 × 10−4 | 4.58 | 0.0581 |
C2 | 1.364 × 10−5 | 1 | 1.364 × 10−5 | 0.13 | 0.7271 |
AB | 4.500 × 10−6 | 1 | 4.500 × 10−6 | 0.043 | 0.8408 |
AC | 2.000 × 10−6 | 1 | 2.000 × 10−6 | 0.019 | 0.8934 |
BC | 5.000 × 10−5 | 1 | 5.000 × 10−5 | 0.47 | 0.5076 |
Residual | 1.059 × 10−3 | 10 | 1.059 × 10−4 | - | - |
Lack of Fit | 7.479 × 10−4 | 5 | 1.496 × 10−4 | 2.41 | 0.1787 |
Pure Error | 3.108 × 10−4 | 5 | 6.217 × 10−5 | - | - |
Test No. | Spindle Speed (rpm) | Feed Rate (mm/min) | Depth of Cut (µm) | Tool | Predicted Value of Ra (µm) | Experimental Value of Ra (µm) |
---|---|---|---|---|---|---|
1 | 20,000 | 100 | 10 | T1 | 0.230 | 0.219 |
2 | 10,000 | 50 | 15 | T1 | 0.210 | 0.211 |
3 | 15,000 | 100 | 10 | T1 | 0.270 | 0.254 |
4 | 20,000 | 150 | 05 | T1 | 0.215 | 0.216 |
5 | 20,000 | 50 | 15 | T1 | 0.250 | 0.242 |
Response/Cutting Parameters | Goal | Lowest Value | Highest Value |
---|---|---|---|
Surface roughness (µm) | Minimum | - | - |
Spindle speed (rpm) | In the range | 10,000 | 20,000 |
Feed rate (mm/min) | In the range | 50 | 150 |
Depth of cut (µm) | In the range | 5 | 15 |
Serial No. | Spindle Speed (rpm) | Feed Rate (mm/min) | Depth of Cut (µm) | Surface Roughness (µm) T1 | Desirability |
---|---|---|---|---|---|
1 | 19,889.42 | 50.01 | 5.10 | 0.168983 | 1.000 |
2 | 19,999.97 | 51.21 | 5.00 | 0.169089 | 0.999 |
3 | 19,837.82 | 50.06 | 5.00 | 0.169169 | 0.998 |
4 | 20,000.00 | 50.00 | 5.74 | 0.169201 | 0.998 |
5 | 19,763.74 | 50.01 | 5.00 | 0.169552 | 0.993 |
Surface Roughness (µm) | Bonding Strength (kPa) | ||||
---|---|---|---|---|---|
Oxygen Plasma Treatment | UV-Ozone Treatment | PDMS Adhesive and Partially Cured PDMS | |||
PDMS–Glass | PDMS–PDMS | PDMS–Glass | PDMS–PDMS | PDMS–PDMS and PDMS–Glass | |
0.17 | 270 ± 20 | 180 ± 20 | 314 ± 20 | 95 ± 20 | >500 kPa |
0.27 | 263 ± 20 | 168 ± 20 | 301 ± 20 | 92 ± 20 | >500 kPa |
0.32 | 228 ± 20 | 147 ± 20 | 288 ± 20 | 92 ± 20 | >500 kPa |
0.4 | 185 ± 20 | 105 ± 30 | 270 ± 20 | 87 ± 20 | >500 kPa |
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Yousuff, C.M.; Danish, M.; Ho, E.T.W.; Kamal Basha, I.H.; Hamid, N.H.B. Study on the Optimum Cutting Parameters of an Aluminum Mold for Effective Bonding Strength of a PDMS Microfluidic Device. Micromachines 2017, 8, 258. https://doi.org/10.3390/mi8080258
Yousuff CM, Danish M, Ho ETW, Kamal Basha IH, Hamid NHB. Study on the Optimum Cutting Parameters of an Aluminum Mold for Effective Bonding Strength of a PDMS Microfluidic Device. Micromachines. 2017; 8(8):258. https://doi.org/10.3390/mi8080258
Chicago/Turabian StyleYousuff, Caffiyar Mohamed, Mohd. Danish, Eric Tatt Wei Ho, Ismail Hussain Kamal Basha, and Nor Hisham B. Hamid. 2017. "Study on the Optimum Cutting Parameters of an Aluminum Mold for Effective Bonding Strength of a PDMS Microfluidic Device" Micromachines 8, no. 8: 258. https://doi.org/10.3390/mi8080258