Telescopes Based on Electrowetting Tunable Lenses

Rand Aqra(1) and Khattab AbualRob(2)
June 8th , 2020
TELESCOPES BASED ON ELECTRO-
WETTING TUNABLE LENSES
(1) Master of Physics Student and Teaching Assistant, Birzeit University, Palestine. Volunteering with PAS.
raqra@staff.birzeit.edu
(2) Master of Physics Student ,Birzeit University, Palestine. PAS Vice President. kaaburub@hotmail.com

Outline
Surface Tension
Surface Tension and
Droplet Shape
Wettability
Contact Angle
Surfaces
Electro-wetting
History
Concept
Experimental EW
Liquid Lenses and
Other Applications
The Telescope
Refractor Telescope
concept.
Lenses Setup
The Output Images
08/06/2020 Aqra and AbualRob
2

Surface Tension
• Surface tension dominates liquid droplets behaviour, especially on
horizontal surfaces and small droplets.
• In air: liquid droplet assumes a spherical shape.
• minimise its surface area → surface area → the total energy
3
Surface Tension and Droplet Shape:

Surface Tension
• Molecule environment is different when it is
buried inside a droplet, or being on or near the
surface of the droplet
• The density of the polar bonds to be less.
• This reduction in bonds causes an extra energy
associated with surface tension ( 𝛾).
• Typically expressed in units of J m−2 or N m−1.
• When droplets are placed on a surface, you
have to take into account the solid/liquid
tension interface.
4
Wettability:
Eid, K F, et al. 2018. European Journal of Physics
39 (2): 025804.

Surface Tension
• liquid- gas interface ( 𝛾 𝐿𝐺 ), liquid- solid
interface ( 𝛾𝑆𝐿 ), and solid-gas interface
(𝛾𝑆𝐺).
• these three are needed to determine the
equilibrium shape of the droplet.
• The shape of a liquid droplet on a solid
surface defines by the contact angle that
the droplet makes with the surface.
• Young’s law:
𝜃 = cos−1
𝛾𝑆𝐺 − 𝛾𝑆𝐿
𝛾 𝐿𝐺
5
Contact Angle:
Eid, K F, et al. 2018. European Journal of Physics
39 (2): 025804.

Surface Tension
• Hydrophobic surface → 𝜃 > 90°
• Hydrophilic surface → 𝜃 < 90°
6
Surfaces:

Electro-wetting
• Lipmann, 1857: applied voltage between the mercury and the
electrolyte could vary the capillary depression of mercury in contact
with electrolyte solutions.
• Brege, early of 1990s : electrowetting on dielectric (EWOD), separate
the liquid droplet from the metallic electrode using a thin dielectric
layer.
7
History:

Electro-wetting
• Electrowetting generally refers to the reduction of
the contact angle after applying an electric field.
• When the electric field is applied, the electrical
component in the surface energy must be
significant.
• the change in 𝜃 with EW is achieved with this
electric field.
• Described with the Lippmann- Young equation:
𝜃 = cos−1
𝛾𝑆𝐺 − 𝛾𝑆𝐿 +
𝐶𝑉2
2
𝛾 𝐿𝐺
8
Concept:
Mugele, F, and J Baret. 2005. Journal of Physics:
Condensed Matter 17 (28): R705–74.

Electro-wetting
9
Experimental EW :
Lin, J-W, et al. 2018. Inventions 3 (3): 46-55
Hou, J, et al. 2017. Polymers 9 (12): 217-29.

Electro-wetting
10
Experimental EW :
Kim J-H, et al. 2018. Journal of Materials Chemistry
C. 6:6808-15.
Zhou, R, et al. 2019. Results in Physics 12 (March):
1991–98.

Electro-wetting
• variable focal length → variable focus
• Telescopes
• Promising: In artificial eyes.
• Other applications:
• Lab-On- a Chip devices
• switches for fiber optics
• Transistors
11
Liquid Lenses and Other Applications:
https://www.edmundoptics.com/knowledge-center/application-
notes/imaging/liquid-lenses-in-imaging/
Ni, Q., and N. B. Crane. 2015. ‘Electrowetting Effect: Theory, Modeling, and Applications’. In Wiley Encyclopedia of Electrical and Electronics Engineering,
1–14. American Cancer Society.

Refractor Telescope concept:
08/06/2020 Aqra and AbualRob 12
𝑀 =
𝑓1
𝑓2

Images taken with the zoom lens when (a) zoomed out, (b) no zoom, and (c)
zoomed in, demonstrating 4× overall magnification.
Valley, Pouria, Mohammad Reza Dodge, Jim
Schwiegerling, Gholam Peyman, and N. Peyghambarian.
"Nonmechanical bifocal zoom telescope." Optics letters
35, no. 15 (2010): 2582-2584.

Lenses Setup:
(a) Lens structure and its components.
(PDMS: Polydimethylsiloxane)
Wang, Jin-Hui, Wei-Pu Tang, Lin-Yang Li, Liang Xiao, Xin Zhou, and
Qiong-Hua Wang. "Hybrid driving variable-focus optofluidic lens."
Optics Express 27, no. 24 (2019): 35203-35215.

(b) Initial state. (c) Only PDMS lens is driven by current.
(d) Only EW lens is driven by voltage. (e) Hybrid driving

The Output Images:
(a) Initial state, U1=0, I1=0. (b)1.3×, U2=60 V, I2=−0.75 mA. (c)2.1×,U3=65 V, I3=−0.85 mA.

Lenses Setup:
Schematic cross-sectional structure of the ultrathin zoom telescopic objective. (a) Cross-sectional of
the zoom objective. (b) Side view of the objective. (c) Zemax layout of the objective
Li, Lei, Di Wang, Chao Liu, and Qiong-Hua Wang. "Ultrathin zoom telescopic objective." Optics express 24, no. 16 (2016): 18674-
18684.

The Output Images:
Captured images. (a) Whole scene. (b) Total length of the two objectives. (c)
Captured by conventional objective with f = 48mm
18684.

(d) Captured by the proposed objective with f = 65mm. (e) Captured
by the proposed objective with f = 60 mm. (f) Captured by the
proposed objective with f = 53 mm. (g) Captured by the proposed
objective with f = 48 mm.
18684.

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