0
Research Papers

Effect of Micro-Injection Molding Processing Conditions on the Replication and Consistency of a Dense Network of High Aspect Ratio Microstructures

[+] Author and Article Information
John W. Rodgers

Mechanical Engineering and Mechanics,
Lehigh University,
Bethlehem, PA 18015
e-mail: johnwilliamrodgers@gmail.com

Meghan E. Casey

Bioengineering,
Lehigh University,
Bethlehem, PA 18015

Sabrina S. Jedlicka

Materials Science and Engineering,
Bioengineering,
Lehigh University,
Bethlehem, PA 18015

John P. Coulter

Mechanical Engineering and Mechanics,
Lehigh University,
Bethlehem, PA 18015

1Corresponding author.

Contributed by the Manufacturing Engineering of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received April 29, 2013; final manuscript received January 15, 2014; published online February 20, 2014. Assoc. Editor: Ashutosh Sharma.

J. Micro Nano-Manuf 2(1), 011006 (Feb 20, 2014) (8 pages) Paper No: JMNM-13-1023; doi: 10.1115/1.4026606 History: Received April 29, 2013; Revised January 15, 2014

When molding macroscale polymer parts with a high density of microfeatures (>1 × 106/cm2), a concern that presents itself is the ability to achieve uniform replication across the entire domain. In the given study, micro-injection molding was used to manufacture microfeatured polymer substrates containing over 10 × 106 microfeatures per cm2. Polystyrene (PS) plates containing microtopography were molded using different processing parameters to study the effect of flow rate and mold temperature on replication quality and uniformity. Flow rate was found to significantly affect replication at mold temperatures above the glass transition temperature (Tg) of PS while having no significant effect on filling at mold temperatures below Tg. Moreover, replication was dependent on distance from the main cavity entrance, with increased flow rate facilitating higher replication differentials and higher replication near the gate. Simulation of the molding process was used to corroborate experimental trials. A deeper understanding of polymer fluid behavior associated with micro-injection molding is vital to reliably manufacture parts containing consistent microtopography (Note: Values are expressed in average ± standard error).

Copyright © 2014 by ASME
Your Session has timed out. Please sign back in to continue.

References

Lee, N., and Han, J., 2008, “Injection Molding of Nanopillars for Perpendicular Patterned Magnetic Media With Nanostamp,” Jpn. J. Appl. Phys., 47(3), pp. 1803–1805. [CrossRef]
Attia, U. M., Marson, S., and AlcockJ. R., 2009, “Micro-Injection Moulding of Polymer Microfluidic Devices,” Microfluid. Nanofluid., 7(1), pp. 1–28. [CrossRef]
Cha, K. J., Na, M.-H., and Kim, D. S., 2013, “Injection Molded Nano Petri Dishes: A New Platform for Studying Cell-Nanoengineered Surface Interaction,” International Conference on MicroManufacturing, Victoria, BC, pp. 305–308.
Heckele, M., 2004, “Review on Micro Molding of Thermoplastic Polymers,” J. Micromech. Microeng., 14, pp. R1–R14. [CrossRef]
Kang, S., 2012, Micro/Nano Replication, John Wiley and Sons, Inc., Hoboken, NJ, Chap. 4.
Sha, B., 2007, “Investigation of Micro-Injection Moulding: Factors Affecting the Replication Quality,” J. Mater. Process. Technol., 183, pp. 284–296. [CrossRef]
Srirojpinyo, C., 2004, “Processing Parameters Affecting Nanoinjection Molding,” Nanotechnology Conference, NSTI-Nanotech, pp. 464–467.
Larsen, N. B., and Matschuk, M., 2013, “Injection Molding of High Aspect Ratio Sub-100 nm Nanostructures." J. Micromech. Microeng., 23, p. 025003. [CrossRef]
Barry, C. M. F., 2010, “Tooling for Injection Molded Micro and Nanoscale Features,” Nano Summit Lowell, MA.
Chandekar, A., Alabran, M., Sengupta, S. K., Lee, J. S., Mead, J. L., Barry, C. M. F., Whitten, J. E., Somu, S., and Busnaina, A. A., 2008, “Fabrication of Stamps for Microcontact Printing by Injection Molding,” Microelectron. Eng., 85, pp. 187–194. [CrossRef]
Werkmeister, J., Gosalvez, M. A., Willoughby, P., Slocum, A. H., and Sato, K., 2006, “Anisotropic Etching of Silicon as a Tool for Creating Injection Molding Tooling Surfaces,” J. Microelectromech. Syst., 15, pp. 1671–1680. [CrossRef]
Bruck, R., Hainberger, R., Heer, R., Kataeva, N., Köck, A., Krapf-Günther, M., Kaiblinger, K., Pipelka, F., and Bilenberg, B., 2010, “Direct Replication of Nanostructures From Silicon Wafers in Polymethylpentene by Injection Molding,” Proc. SPIE, 7788, 77880A. [CrossRef]
Huang, C. K., 2007, “Polymeric Nanofeatures of 100 nm Using Injection Moulding for Replication,” J. Micromech. Microeng., 17, pp. 1518–1526. [CrossRef]
Zhang, N., 2012, “Replication of Micro/Nano-Scale Features by Micro Injection Molding With a Bulk Metallic Glass Insert,” J. Micromech. Microeng., 22, p. 065019. [CrossRef]
Yoon, S. H., 2005, “Evaluation of Novel Tooling for Nanoscale Injection Molding,” SPIE International Symposia, Smart Structures & Materials/NDE, San Diego, CA, pp. 107–116.
Chen, S.-C., Jong, W.-R., Chang, Y.-J., Chang, J.-A., and Cin, J.-C., 2006, “Rapid Mold Temperature Variation for Assisting the Micro Injection of High Aspect Ratio Micro-Feature Parts Using Induction Heating Technology,” J. Micromech. Microeng., 16, pp. 1783–1791. [CrossRef]
Liou, A.-C., and Chen, R.-H., 2006, “Injection Molding of Polymer Micro- and Sub-Micron Structures With High-Aspect Ratios,” Int. J. Adv. Manuf. Technol., 28, pp. 1097–1103. [CrossRef]
Zhang, N., Chu, J. S., Byrne, C. J., Browne, D. J., and Gilchrist, M. D., 2012, “Replication of Micro/Nano-Scale Features by Micro Injection Molding With a Bulk Metallic Glass Mold Insert,” J. Micromech. Microeng., 22, p. 065019. [CrossRef]
Despa, M. S., Kelly, K. W., and Collier, J. R., 1998, “Injection Molding Using High Aspect Ratio Microstructures Mold Inserts Produced by LIGA Technique,” Proc. SPIE, 3512, pp. 286–294. [CrossRef]
Park, S. H., Lee, W. I., Moon, S. N., Yoo, Y.-E., and Cho, Y. H., 2011, “Injection Molding Micro Patterns With High Aspect Ratio Using a Polymeric Flexible Stamper,” eXPRESS Polym. Lett., 5(11), pp. 950–958. [CrossRef]
Chang, C., Wang, Y.-F., Kanamori, Y., Shih, J. J., Kawai, Y., Lee, C.-K., WuK.-C. and Esashi, M., 2005, “Etching Submicrometer Trenches by Using Etching Submicrometer Trenches by Using the Bosch process and its Application to the Fabrication of Antireflection Structures,” J. Micromech. Microeng., 15(3), pp. 580–585. [CrossRef]
Product Information: Styron 666D, 2011, Americas Styrenics.
Giboz, J., Copponnex, T., and Mélé, P., 2007, “Microinjection Molding of Thermoplastic Polymers: A Review,” J. Micromech. Microeng., 17, pp. R96–R109. [CrossRef]
Yao, D., 2002, “Simulation of the Filling Process in Micro Channels for Polymeric Materials,” J. Micromech. Microeng., 12, pp. 604–610. [CrossRef]
Kim, S. H., 2013, “Robust Fabrication and Evaluation of Nanopattern Insert Molded Parts,” Eur. Polym. J., 49, pp. 1437–1445. [CrossRef]
Lin, H.-Y., 2010, “Experimental and Analytical Study on Filling of Nano Structures in Micro Injection Molding,” Int. Commun. Heat Mass Transfer, 37, pp. 1477–1486. [CrossRef]
Yoo, Y.-E., Kim, T.-H., Je, T.-J., Choi, D.-S., Kim, C.-W., and Kim, S.-K., 2011, “Injection Molding of Micro Patterned PMMA Plate,” Trans. Nonferrous Met. Soc. China, 21, pp. s148–s152. [CrossRef]
Guo, Y., Liu, G., Xiong, Y., and Tian, Y., 2007, “Study of the Demolding Process—Implications for Thermal Stress, Adhesion and Friction Control,” J. Micromech. Microeng., 17, pp. 9–19. [CrossRef]

Figures

Grahic Jump Location
Fig. 1

Supported (a) versus Unsupported and (b) high aspect ratio microfeature

Grahic Jump Location
Fig. 2

Schematic of silicon wafer surface prior to etching (a) and dimensions of photoresist windows on silicon substrate with the dimensions of the tooling inset (b)

Grahic Jump Location
Fig. 3

Micromold aluminum insert assembly exploded (a) and assembled (b). TC = thermocouple.

Grahic Jump Location
Fig. 4

Full mold assembly schematic with aluminum insert fixed to moving mold half

Grahic Jump Location
Fig. 5

Schematic of molded part (a), locations of measured regions (b), actual molded part (c), and meshed model containing three higher mesh density locations (d)

Grahic Jump Location
Fig. 6

Microfeatured silicon mold insert micrograph (a) and evidence of slight microchannel widening (inset; indicated with arrow). Bar indicates 2 μm.

Grahic Jump Location
Fig. 7

Trial 1 micrographs of topography near gate of Tmold = 65.6 °C (a) versus Tmold = 76.7 °C at identical flow rate of 7.54 cm3/s

Grahic Jump Location
Fig. 8

Cross-WLF plot of viscosity versus shear rate (a) and viscosity versus melt temperature for different melt temperatures (b) of 666D

Grahic Jump Location
Fig. 9

Trial 1 micrographs of topography near gate showing the effect of flow rate on replication at Tmold = 76.7 °C. Substrates were molded with Qinj = 2.51 cm3/s (a), 5.03 cm3/s (b), and 7.54 cm3/s (c).

Grahic Jump Location
Fig. 10

Trial 2 micrographs of 9 regions of PS molded with flow rate of 2.01 cm3/s

Grahic Jump Location
Fig. 11

Trial 2 micrographs of 9 regions of PS molded with flow rate of 4.02 cm3/s

Grahic Jump Location
Fig. 12

Trial 2 micrographs of 9 regions of PS molded with flow rate of 6.03 cm3/s

Grahic Jump Location
Fig. 13

Pillar heights along the part for different flow rates at a mold temperature of 104.4 °C

Grahic Jump Location
Fig. 14

Velocity streamlines showing outward flow near tip and slight backward flow after initial filling

Grahic Jump Location
Fig. 15

Micrograph of pillars with slightly stretched scallop marks closer to base of pillar

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In