Drop-on-Demand Inkjet Printing of Liquid Crystals for Photonics Applications

Transcription

1 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

2 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

3 Experimental Set-up Custom Print head: Ink Heating Unit 1 Piezoelectric Transducer Nozzle Plate 3

4 Experimental Set-up 4

5 = Drop Formation 10% PVA 90V actuation wave 200μm nozzle diameter = 5

6 Drop Formation PVA 180V actuation wave 200μm nozzle diameter 6

7 Drop Formation PVA 90V actuation wave 200μm nozzle diameter 7

8 Experimental Set-up 75µm E7 Polarised Microscopy Images 100ms after deposition 8

9 Liquid Crystals A Conventional Liquid Crystal Cell: 9

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 10

11 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

12 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

13 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

14 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

15 Transmission (%) CLC Temperature Sensors 95 BL006 + R811 (70:30) Increasing Temperature Wavelength (nm)

16 CLC Temperature Sensors 25 C 28 C 30 C 35 C 40 C 45 C 50 C 55 C 60 C 65 C 16

17 Microlens Arrays Applications Applications: Light collection Laser Arrays Photovoltaics 3D photography and displays Machine Vision Pixel Detector 17

18 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

19 Forming LC Microlenses α ß 70µm Standard 1xSurface 55µm Hydrophobic Surface f f 75µm drop diameter Hydrophobic Surface D D 19

20 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

21 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

22 Printing LC Microlens Arrays 100µm µm µm 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

23 Microlens Arrays Thermal Tuning Parry. E, Bolis. S, Castrejón-Pita. A. A, Elston. S. J, Morris. M. M, Adv. Eng. Mat (2018) 23

24 Summary Homeotropic 24

25 Acknowledgements Oxford Serena Bolis Steve Elston Alfonso Castrejon-Pita Stephen Morris John Sandford O Neil Merck Eduardo Beltran Gracia Iain Gardiner 25

26 Summary Homeotropic 26