Samsung, Sony and Google have filed patents for smart contact lenses that take still pictures and video, or record and display information. The camera trigger is a light sensor that detects eyelid movement. In some versions, an embedded antenna sends images wirelessly to a smartphone for processing. The Samsung lens seems designed primarily as an augmented reality tool. In contrast, the Google products target the medical sector. One includes sensors to read blood sugar levels in tears, while another is designed to correct presbyopia. However, certain experts doubt the former type is possible, and the project may be stalled. Sony claims its lens can differentiate between deliberate and involuntary blinking. The former activates video recording. In addition, eye movement would power the device via piezoelectric sensors. Challenges common to all such efforts include miniaturization of components, dramatic reductions in power consumption and biocompatibility of materials.