TY - JOUR
T1 - Enhanced Mixing of Microvascular Self-Healing Reagents Using Segmented Gas-Liquid Flow
AU - Dean, Leon M.
AU - Krull, Brett P.
AU - Li, Kevin R.
AU - Fedonina, Yelizaveta I.
AU - White, Scott R.
AU - Sottos, Nancy R.
N1 - Funding Information:
This research was supported by the Air Force Office of Scientific Research Center of Excellence for Self-Healing, Regeneration and Structural Remodeling (grant numbers FA9550-16-1-0017 and FA9550-15-1-0087). L.M.D. thanks the National Science Foundation for a Graduate Research Fellowship. The authors thank the following individuals for experimental assistance: Ryan Gergeley (healing experiments); Emmy Pruitt, Windy Santa Cruz (two-stage chemistry); Dianwen Zhang, Evan Lloyd (Raman spectroscopy); Greg Milner, Lee Booher (machining); and Jason Patrick (DCB specimen manufacturing). The authors also thank Alex Jerez Roman for graphics preparation and Andrew Lauer for videography, as well as Jeffrey Moore, Philippe Geubelle, and Aaron Esser-Kahn for helpful discussions.
Publisher Copyright:
© 2018 American Chemical Society.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2018/9/26
Y1 - 2018/9/26
N2 - Microvascular self-healing systems have previously been demonstrated to restore large-scale damage and achieve repeated healing of multiple damage events in polymers. However, the healing performance of these systems is often limited because the laminar nature of flow in microchannels results in poor mixing of two-part self-healing reagents. In this paper, we introduce segmented gas-liquid flow (SGLF) to enhance the mixing of reagents in microvascular self-healing systems. In SGLF, discrete liquid slugs containing self-healing reagents are separated by gas bubbles while flowing through a single microchannel. Recirculating streamlines within the liquid slugs can enhance the mixing of miscible liquids such as healing reagents. We investigate the effect of SGLF on mixing and healing for a two-stage chemistry used to restore large-scale damage in thermoset polymers. Additionally, we employ SGLF to deliver an epoxy-thiol chemistry, enabling the repeated recovery of fracture toughness in glass fiber-reinforced composites. In both systems, the mixing of healing agents delivered by SGLF is enhanced compared to alternative microvascular delivery strategies. For the two-stage chemistry, SGLF increases the maximum damage size that can be healed by 25% compared to laminar single-phase flow. Furthermore, there are concomitant increases in the extent of polymerization and the mechanical properties of the restored material, including a fivefold increase in the peak load sustained during a push-out test. For the epoxy-thiol chemistry, SGLF enables multiple healing cycles with healing efficiency above 100%. On the basis of these results, we envision that SGLF could improve performance for a variety of microvascular self-healing systems with different host materials, damage modes, and healing chemistries.
AB - Microvascular self-healing systems have previously been demonstrated to restore large-scale damage and achieve repeated healing of multiple damage events in polymers. However, the healing performance of these systems is often limited because the laminar nature of flow in microchannels results in poor mixing of two-part self-healing reagents. In this paper, we introduce segmented gas-liquid flow (SGLF) to enhance the mixing of reagents in microvascular self-healing systems. In SGLF, discrete liquid slugs containing self-healing reagents are separated by gas bubbles while flowing through a single microchannel. Recirculating streamlines within the liquid slugs can enhance the mixing of miscible liquids such as healing reagents. We investigate the effect of SGLF on mixing and healing for a two-stage chemistry used to restore large-scale damage in thermoset polymers. Additionally, we employ SGLF to deliver an epoxy-thiol chemistry, enabling the repeated recovery of fracture toughness in glass fiber-reinforced composites. In both systems, the mixing of healing agents delivered by SGLF is enhanced compared to alternative microvascular delivery strategies. For the two-stage chemistry, SGLF increases the maximum damage size that can be healed by 25% compared to laminar single-phase flow. Furthermore, there are concomitant increases in the extent of polymerization and the mechanical properties of the restored material, including a fivefold increase in the peak load sustained during a push-out test. For the epoxy-thiol chemistry, SGLF enables multiple healing cycles with healing efficiency above 100%. On the basis of these results, we envision that SGLF could improve performance for a variety of microvascular self-healing systems with different host materials, damage modes, and healing chemistries.
KW - composites
KW - microfluidic mixing
KW - microvascular self-healing
KW - multiphase flow
KW - self-healing polymers
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U2 - 10.1021/acsami.8b09966
DO - 10.1021/acsami.8b09966
M3 - Article
C2 - 30209942
AN - SCOPUS:85053635307
SN - 1944-8244
VL - 10
SP - 32659
EP - 32667
JO - ACS applied materials & interfaces
JF - ACS applied materials & interfaces
IS - 38
ER -