Minimally invasive medical devices can greatly benefit from Narrow Band Imaging (NBI) diagnostic capabilities, as different wavelengths allow penetration of distinct layers of the gastrointestinal tract mucosa, improving diagnostic accuracy and targeting different pathologies. An important performance parameter is the light intensity at a given power consumption of the medical device. A method to increase the illumination intensity in the NBI diagnostic technique was developed and applied to minimally invasive medical devices (e.g., endoscopic capsules), without increasing the size and power consumption of such instruments. Endoscopic capsules are generally equipped with light-emitting diodes (LEDs) operating in the RGB (red, green, and blue) visible light spectrum. A polydimethylsiloxane (PDMS) µ-lens was designed for a maximum light intensity at the target area of interest when placed on top of the LEDs. The PDMS µ-lens was fabricated using a low-cost hanging droplet method. Experiments reveal an increased illumination intensity by a factor of 1.21 for both the blue and green LEDs and 1.18 for the red LED. These promising results can increase the resolution of NBI in endoscopic capsules, which can contribute to early gastric lesions diagnosis.

Minimally invasive medical devices are widely investigated, because of their advantages for in-situ medical examination in real time with highly reduced risk and patient discomfort, as compared to more traditional approaches. Optical biopsy is a prominent example of this trend and provides essential diagnostic information on tissue histopathology in the gastro-intestinal tract. Micro-electro mechanical system technology is demonstrated in this paper to be highly suitable for fabrication of an optical biopsy microsystem, where overall system dimensions and power consumption are key enabling factors. The biopsy microsystem presented is 11.2 mm in diameter and 18.6 mm in length and contains an imaging system with a dedicated image magnification optical microsystem (IMOM) and light emitting diodes (LEDs). Polydimethylsiloxane microlenses have been fabricated using the “hanging droplet” approach and integrated in the IMOM subsystem for achieving an image magnification by a factor 4 and a 30% improvement in optical irradiance from the LED illumination.