Paper Number
PO27 

Session
Poster Session

Title
Design and fabrication of an optimized “6-arm cross-slot” device

Presentation Date and Time
October 12, 2022 (Wednesday) 6:30

Track / Room
Poster Session / Riverwalk A

Authors (Click on name to view author profile)

  1. Haward, Simon J. (Okinawa Institute of Science and Technology)
  2. Pimenta, Francisco (Faculdade de Engenharia da Universidade do Porto)
  3. Varchanis, Stylianos (Okinawa Institute of Science and Technology)
  4. Carlson, Daniel W. (Okinawa Institute of Science and Technology)
  5. Toda-Peters, Kazumi (Okinawa Institute of Science and Technology)
  6. Alves, Manuel A. (Faculdade de Engenharia da Universidade do Porto)
  7. Shen, Amy Q. (Okinawa Institute of Science and Technology)

Author and Affiliation Lines (in printed abstract book)
Simon J. Haward1, Francisco Pimenta2, Stylianos Varchanis1, Daniel W. Carlson1, Kazumi Toda-Peters1, Manuel A. Alves2 and Amy Q. Shen1
1Okinawa Institute of Science and Technology, Okinawa, Japan; 2Faculdade de Engenharia da Universidade do Porto, Porto 4200-465, Portugal

Speaker / Presenter 
Haward, Simon J.

Keywords
experimental methods; computational methods; polymer solutions; rheometry techniques

Text of Abstract
We present a numerical optimization of a “6-arm cross-slot” device, revealing the three-dimensional shape of a fluidic channel designed to impose close approximations to ideal uniaxial (or biaxial) stagnation point extensional flow under the constraints of having four inlets and two outlets (or two inlets and four outlets) and Newtonian creeping flow conditions. Numerical simulations with the Oldroyd-B and Phan-Thien and Tanner models at various Weissenberg numbers confirm that the flow fields for viscoelastic and shear thinning fluids in the geometry are minimally altered from the optimal case. Fabrication of the geometry at the microscale is achieved with high precision by selective laser-induced etching of a fused-silica substrate. Employing a viscous Newtonian fluid with a refractive index matched to that of the optically transparent microfluidic device, we conduct microtomographic-particle image velocimetry in order to resolve the flow field in a substantial volume about the stagnation point. The flow velocimetry (at Reynolds number ~ 0.02) confirms the accurate imposition of the desired and predicted flows, with pure extensional flow at an essentially uniform deformation rate being applied over a wide region about the stagnation point. We envisage the new geometry being used for the uniaxial and biaxial extensional rheometry of mobile complex fluids.