Drop-on-Demand Inkjet Printing of Liquid Crystals for Photonics Applications Ellis Parry, Steve Elston, Alfonson Castrejon-Pita, Serena Bolis and Stephen Morris PhD Student University of Oxford
Drop-on demand Printing of Liquid Crystals Advantages of Inkjet Printing: Control of droplet properties and positioning Low temperature and fast Compatible with a range of substrates and fluids Unique geometries (free-form) Lean, efficient and flexible manufacturing 2
Experimental Set-up Custom Print head: Ink Heating Unit 1 Piezoelectric Transducer Nozzle Plate 3
Experimental Set-up 4
= Drop Formation 10% PVA 90V actuation wave 200μm nozzle diameter = 5
Drop Formation PVA 180V actuation wave 200μm nozzle diameter 6
Drop Formation PVA 90V actuation wave 200μm nozzle diameter 7
Experimental Set-up 75µm E7 Polarised Microscopy Images 100ms after deposition 8
Liquid Crystals A Conventional Liquid Crystal Cell: 9
The Inkjet Printing of LCs 1. Reliable printing of fluid or ink 2. Formation of a defined droplet 3. Alignment of the LC Bare Glass 10
The Inkjet Printing of LCs 1. Reliable printing of fluid or ink 2. Formation of a defined droplet 3. Alignment of the LC Bare Glass Rubbed Polyamide Cell 11
Achieving LC Alignment Low molecular weight (10,000) PVA 80% Hydrolysed Wet layer 70µm deep (25µm when dry) E7 Nematic LC Dry PVA Bed Parry. E, Kim. D.J, Castrejón-Pita. A. A, Elston. S. J, Morris. M. M, Optical Materials (2018) 12
Achieving LC Alignment Low molecular weight (10,000) PVA 80% Hydrolysed Wet layer 70µm deep (25µm when dry) E7 Nematic LC Wet PVA Bed Parry. E, Kim. D.J, Castrejón-Pita. A. A, Elston. S. J, Morris. M. M, Optical Materials (2018) 13
Achieving LC Alignment Partially Dry Polymer Bed Experimental Details: 70-90% drying time Defined droplet boundary Passive radial planar alignment achieved Resultant Droplets: Spherical droplet boundary Uniformity of the LC director Passive radial planar alignment achieved Parry. E, Kim. D.J, Castrejón-Pita. A. A, Elston. S. J, Morris. M. M, Optical Materials (2018) 14
Transmission (%) CLC Temperature Sensors 95 BL006 + R811 (70:30) Increasing Temperature 0 350 Wavelength (nm) 800 15
CLC Temperature Sensors 25 C 28 C 30 C 35 C 40 C 45 C 50 C 55 C 60 C 65 C 16
Microlens Arrays Applications Applications: Light collection Laser Arrays Photovoltaics 3D photography and displays Machine Vision Pixel Detector 17
Printing a Microlens < 10ms the droplet forms a stable shape Drop profile is spherical Bo << 1 for L < 1mm f 10ms α 70µm R 75µm drop diameter 1.5ms -1 drop velocity 18
Forming LC Microlenses α ß 70µm Standard 1xSurface 55µm Hydrophobic Surface f f 75µm drop diameter Hydrophobic Surface D D 19
Printing a Microlens α α α 70µm 1 drop 150µm 200µm 10 drops 20 drops f f f 75µm drop diameter 10 drops 3500Hz D D D 20
Liquid Crystal Microlens Determination of focal Length Intensity cross section at focal plane Polarisation independent focussing Parry. E, Bolis. S, Castrejón-Pita. A. A, Elston. S. J, Morris. M. M, Adv. Eng. Mat (2018) 21
Printing LC Microlens Arrays 100µm 30 28 26 10 24 12 100µm 22 14 20 16 18 300µm 75µm drop diameter E7 LC Array Homeotropic E7 Array of different sized Lenses Parry. E, Bolis. S, Castrejón-Pita. A. A, Elston. S. J, Morris. M. M, Adv. Eng. Mat (2018) 22
Microlens Arrays Thermal Tuning 22 30 40 50 Parry. E, Bolis. S, Castrejón-Pita. A. A, Elston. S. J, Morris. M. M, Adv. Eng. Mat (2018) 23
Summary Homeotropic 24
Acknowledgements Oxford Serena Bolis Steve Elston Alfonso Castrejon-Pita Stephen Morris John Sandford O Neil Merck Eduardo Beltran Gracia Iain Gardiner 25
Summary Homeotropic 26