Hydrogel microlens

SEM image of hydrogel microlens array taken at grazing angle with respect to substrate. The microgels formed an ordered array of planoconvex shapes. Source Kim, M.J. Serpe, and L.A. Lyon. 2004. Journal of the American Chemical Society, 126(31), 9512-9513. With permission.)... 

Multiple islands arranged on hemisphere. Each island houses a tunable liquid microlens formed by a curved water-to-oU interface pinned at the edge of a polymer aperture by surface tension. The change in the curvature of the interface is caused by stimulus-responsive hydrogel actuators. (Source Adapted from Zhu, D., Zeng, X., Li, C. and Jiang, H. 2011. Journal of Microelectromechanical Systems, 20(2), 389-395. With permission.)... 

Zeng et al. extended the hydrogel-driven liquid microlens technology and presented a liquid variable focus microlens tuned by light-responsive hydrogels [30]. Figure 6.30 shows the schematics and optical images of a tunable... 

Focal length of pH-responsive liquid microlens using AA hydrogel as function of pH. (Source Dong, L., A.K. Agarwal, D.J. Beebe et al. 2006. Nature, 442(7102), 551-554. With permission.)... 

Formation of microlens at interface between oil and aqueous solution. Interface is pinned stably at a hydrophobic-hydrophilic boundary along circular aperture. Volumetric changes of hydrogel microposts cause flexible aperture slip to bend in the z direction. The pinned water-oil interface is pressed downward or upward, thus tuning the focal length. (Source Dong, L. and H. Jiang. 2006. Applied Physics Letters, 89(21), 211120. With permission.)... 

Microlens Array Actuated through Thermoresponsive Hydrogels... 

The hydrogel-driven tunable liquid microlenses can be extended to microlens arrays in which microlenses can be individually and independently... 

L. Dong, A. K. Agarwal, D. J. Beebe, and H. Jiang, "Variable-focus liquid microlenses and microlens arrays actuated by thermoresponsive hydrogels," Advanced Materials, vol. 19, pp. 401-405, Feb 2007. 

X. Zeng and H. Jiang, Tunable liquid microlens actuated by infrared light-responsive hydrogel," Applied Physics Letters, vol. 93, p. 151101, Oct 2008. 

Bio-responsive hydrogel lenses can be prepared from functional modified polymer gels. Antigen-antibody binding to a microlens was achieved biotin functionalization. The optical system responds in an analogue manner to input concentrations and could enable die construction of label-free optical biosensors (Kim et al. 2007). 

Responsive polymers, especially hydrogels, combine both sensor and actuator characteristics. Nevertheless, to date there are only a few devices on the market, because response time can be slow, the materials are weak, and greater precision needs to be developed. Intriguing applications are being explored including the creation of artificial muscle using chemomecha-nical transducers and their use in thin films where response time is not so critical. Other applications include the use of micro- and nanogels and particles in applications such as photonic crystals, microlens systems, dmg delivery vehicles, and microfluidic valves. 

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