Fig. 1. Electrowetting liquid lens.(a) Electrowetting liquid lens with conical electrodes; (b) initial focal length of the lens before microstructure adjustment; (c) initial focal length of the lens after microstructure adjustment

Fig. 2. Force on droplets under different arrangement of bumps.(a) Square microstructure; (b) cruciform microstructure; (c) concentric circular ring microstructures

Fig. 3. Theoretical wetting models. (a) Young's theoretical wetting model; (b) Wenzel's theoretical wetting model

Fig. 4. Effect of theoretical contact angle on focal length. (a) Focal length at large theoretical contact angle; (b) focal length at small theoretical contact angle

Fig. 5. Electrode surface microstructure.(a) Square microstructure; (b) concentric circular ring microstructures; (c) cruciform microstructure

Fig. 6. Geometric projections with their contained microstructural subunits. (a) Geometric projection of the contact surface of square microstructure; (b) geometric projection of the contact surface of cruciform microstructure; (c) geometric projection of the contact surface of concentric circular ring microstructures

Fig. 7. Principle of liquid surface curvature radius calculation

Fig. 8. Contact angle and shape measuring device

Fig. 9. Electrode surface microstructure

Fig. 10. Measurement of droplet contact angle

Fig. 11. SEM images of electrode surface microstructure.(a) SEM image of cruciform microstructure at magnification 35; (b) SEM image of concentric circular ring microstructures at magnification 35; (c) SEM image of square microstructure at magnification 35; (d) SEM image of cruciform microstructure at magnification 70; (e) SEM image of concentric circular ring microstructures at magnification 70; (f) SEM image of square microstructure at magnification 70; (g) SEM image of cruciform microstructure at magnification 200; (h) SEM image of concentric circular ring microstructures at magnification 200; (i) SEM image of square microstructure at magnification 200

Fig. 12. SEM images of the microstructure of the electrode surface at 45° tilt. (a) SEM image of cruciform microstructure at a magnification of 200 after 45° tilt; (b) SEM image of concentric circular ring microstructures at a magnification of 200 after 45° tilt; (c) SEM image of square microstructure at a magnification of 200 after 45° tilt; (d) SEM image of cruciform microstructure at a magnification of 500 after 45° tilt; (e) SEM image of concentric circular ring microstructures at a magnification of 500 after 45° tilt; (f) SEM image of square microstructure at a magnification of 500 after 45° tilt

Fig. 13. Microstructure SEM images at 45° electrode tilt.(a) Height of convex projection of cruciform microstructure; (b) height of convex projection of square microstructure; (c) height of convex projection of concentric circular ring microstructures

Fig. 14. Theoretical and measured curves for initial focal length of cruciform microstructure lenses. (a) Relationship curves of theoretical initial focal length and convex spacing; (b) relationship curves of measured initial focal length and convex spacing; (c) relationship curves of theoretical initial focal length and convex width; (d) relationship curves of measured initial focal length and convex width

Fig. 15. Theoretical and measured curves for initial focal length of square microstructure lenses. (a) Relationship curves of theoretical initial focal length and convex spacing; (b) relationship curves of measured initial focal length and convex spacing; (c) relationship curves of theoretical initial focal length and convex width; (d) relationship curves of measured initial focal length and convex width

Fig. 16. Theoretical and measured curves for initial focal length of concentric circular ring microstructure lenses. (a) Relationship curves of theoretical initial focal length and convex spacing; (b) relationship curves of measured initial focal length and convex spacing; (c) relationship curves of theoretical initial focal length and convex width; (d) relationship curves of measured initial focal length and convex width

Fig. 17. Fitting results of theoretical formulas for initial focal length of concentric circular ring microstructuresd lenses and measured data surface

Fig. 18. Droplet shapes on microstructured surfaces.(a) Droplet shape on cruciform microstructure surface with good hydrophobicity; (b) droplet shape on square microstructure surface with good hydrophobicity; (c) droplet shape on concentric circular ring microstructure surface with good hydrophobicity; (d) droplet shapes on cruciform microstructure surfaces with poor hydrophobicity; (e) droplet shape on square microstructure surface with poor hydrophobicity; (f) droplet shapes on concentric circular ring microstructure surfaces with poor hydrophobicity