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Replication of surface micro-features using variothermal injection molding: Application to micro-fluidics

P. G. Wlodarski, J. F. T. Pittman, John Pittman, Patrick Wlodarski

Polymer Engineering & Science

Swansea University Authors: John Pittman, Patrick Wlodarski

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DOI (Published version): 10.1002/pen.24772

Abstract

We study injection molding of mesoscale items with µm-scale surface features, namely micro-fluidic channels, relating replication quality to process conditions. Using variothermal molding, the variables are the pre-heat temperature of the cavity insert surface before melt injection and the mold cool...

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Published in: Polymer Engineering & Science
ISSN: 0032-3888
Published: 2017
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URI: https://cronfa.swan.ac.uk/Record/cronfa37783
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first_indexed 2018-01-02T14:08:08Z
last_indexed 2018-02-09T05:31:33Z
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spelling 2018-01-03T10:43:41.2574639 v2 37783 2018-01-02 Replication of surface micro-features using variothermal injection molding: Application to micro-fluidics 9e89bf430b648088d29a705d182849b4 John Pittman John Pittman true false c1e636a42ca06d7d65a69317220d85ae Patrick Wlodarski Patrick Wlodarski true false 2018-01-02 AERO We study injection molding of mesoscale items with µm-scale surface features, namely micro-fluidic channels, relating replication quality to process conditions. Using variothermal molding, the variables are the pre-heat temperature of the cavity insert surface before melt injection and the mold cooling start time. Surface temperatures and in-cavity melt pressures are continuously measured. Rounded upper corners of the micro-channels are used as an index of replication quality. For polymethylmethacrylate the thickness of a layer with solid-like properties (below 124°C) is calculated and used with pressures to interpret results. It is shown how improved replication correlates with low layer thickness at the end of the compression phase when pressures are at a maximum, and the necessity of properly timed cooling to lock in replication before melt pressures fall. Results show how the inter-relationship of layer thickness and melt pressure is controlled by pre-heat temperature and cooling switch-on time. Delayed cooling can result in poorer replication, due to a retraction effect of the plastic. Too early cooling also reduces replication of parallel-to-flow features downstream of transverse features, and of the replication of transverse features on their downstream side. Good replication of 100 and 70 µm channels requires lower pre-heat than 400 µm ones. Journal Article Polymer Engineering & Science 0032-3888 31 12 2017 2017-12-31 10.1002/pen.24772 COLLEGE NANME Aerospace Engineering COLLEGE CODE AERO Swansea University 2018-01-03T10:43:41.2574639 2018-01-02T11:43:15.3480655 Faculty of Science and Engineering School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Aerospace Engineering P. G. Wlodarski 1 J. F. T. Pittman 2 John Pittman 3 Patrick Wlodarski 4 0037783-03012018104257.pdf Wlodarski2017.pdf 2018-01-03T10:42:57.3730000 Output 4678596 application/pdf Accepted Manuscript true 2018-12-04T00:00:00.0000000 false eng
title Replication of surface micro-features using variothermal injection molding: Application to micro-fluidics
spellingShingle Replication of surface micro-features using variothermal injection molding: Application to micro-fluidics
John Pittman
Patrick Wlodarski
title_short Replication of surface micro-features using variothermal injection molding: Application to micro-fluidics
title_full Replication of surface micro-features using variothermal injection molding: Application to micro-fluidics
title_fullStr Replication of surface micro-features using variothermal injection molding: Application to micro-fluidics
title_full_unstemmed Replication of surface micro-features using variothermal injection molding: Application to micro-fluidics
title_sort Replication of surface micro-features using variothermal injection molding: Application to micro-fluidics
author_id_str_mv 9e89bf430b648088d29a705d182849b4
c1e636a42ca06d7d65a69317220d85ae
author_id_fullname_str_mv 9e89bf430b648088d29a705d182849b4_***_John Pittman
c1e636a42ca06d7d65a69317220d85ae_***_Patrick Wlodarski
author John Pittman
Patrick Wlodarski
author2 P. G. Wlodarski
J. F. T. Pittman
John Pittman
Patrick Wlodarski
format Journal article
container_title Polymer Engineering & Science
publishDate 2017
institution Swansea University
issn 0032-3888
doi_str_mv 10.1002/pen.24772
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Aerospace Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Aerospace Engineering
document_store_str 1
active_str 0
description We study injection molding of mesoscale items with µm-scale surface features, namely micro-fluidic channels, relating replication quality to process conditions. Using variothermal molding, the variables are the pre-heat temperature of the cavity insert surface before melt injection and the mold cooling start time. Surface temperatures and in-cavity melt pressures are continuously measured. Rounded upper corners of the micro-channels are used as an index of replication quality. For polymethylmethacrylate the thickness of a layer with solid-like properties (below 124°C) is calculated and used with pressures to interpret results. It is shown how improved replication correlates with low layer thickness at the end of the compression phase when pressures are at a maximum, and the necessity of properly timed cooling to lock in replication before melt pressures fall. Results show how the inter-relationship of layer thickness and melt pressure is controlled by pre-heat temperature and cooling switch-on time. Delayed cooling can result in poorer replication, due to a retraction effect of the plastic. Too early cooling also reduces replication of parallel-to-flow features downstream of transverse features, and of the replication of transverse features on their downstream side. Good replication of 100 and 70 µm channels requires lower pre-heat than 400 µm ones.
published_date 2017-12-31T03:47:38Z
_version_ 1763752289190805504
score 11.012678

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