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Extra flat, flexible and disposable endoscope for lateral imaging

We present an innovative disposable endoscope based on extra flat flexible polymer slabs used as multimode waveguides. The waveguides are compatible with low-cost roll-to-roll production technologies and can be easily customized by patterning, coating and printing techniques according to the specifications of the target application. In order to couple the light (i.e. the illumination beam and the imaging beam) in and out of the waveguide, diffractive subwavelength gratings are used. These nano-scale optical structures enable an efficient and controlled light trapping by total internal reflection, thus minimizing the distortion effects generated by the rough edges. Nano-patterning is obtained using established techniques (i.e. hot embossing and/or UV casting) that are compatible with industrial roll-to-roll production lines or plastic injection molding. Unique features of these innovative endoscopes are i) the achievable very thin form that can be reduced to thicknesses below 200 μm, ii) the ability to record lateral images with respect to the endoscope direction, iii) the ability to image samples (e.g. tissues, tiny objects) in direct contact with the polymer slab, with a minimum imaging distance equal to zero, and iv) the access to high volume fabrication techniques that can enable the production of low-cost disposable endoscopes. A possible device implementation is demonstrated and tested, which consists of a flat line-scanning endoscope enabling the acquisition of 1D images in monochromatic illumination and the reconstruction of 2D images by scanning. Images taken with such a disposable endoscope are discussed and the related technological constraints such as manufacturing tolerances, image distortion, scattered light and signal to noise ratio are further described. Finally, advantages and disadvantages with respect to other endoscopic techniques will be discussed, thus demonstrating the potential of this innovative approach for endoscopic applications in very confined volumes.