Endowing a plain fluidic chip with micro-optics: a holographic microscope slide

Lab-on-a-Chip (LoC) devices are extremely promising in that they enable diagnostic functions at the point-of-care. Within this scope, an important goal is to design imaging schemes that can be used out of the laboratory. In this paper, we introduce and test a pocket holographic slide that allows digital holography microscopy to be performed without an interferometer setup. Instead, a commercial off-the-shelf plastic chip is engineered and functionalized with this aim. The microfluidic chip is endowed with micro-optics, that is, a diffraction grating and polymeric lenses, to build an interferometer directly on the chip, avoiding the need for a reference arm and external bulky optical components. Thanks to the single-beam scheme, the system is completely integrated and robust against vibrations, sharing the useful features of any common path interferometer. Hence, it becomes possible to bring holographic functionalities out of the lab, moving complexity from the external optical apparatus to the chip itself. Label-free imaging and quantitative phase contrast mapping of live samples are demonstrated, along with flexible refocusing capabilities. Thus, a liquid volume can be analyzed in one single shot with no need for mechanical scanning systems. Digital holography microscopy: on-chip microscopy system A microfluidic chip featuring a built-in interferometer promises to greatly faciliate digital holography microscopy. Lab-on-the chip devices will enable biomedical devices to be taken to the point of care. Vittorio Bianco and co-workers from the Institute of Applied Sciences and Intelligent Systems in Italy have added a diffraction grating and printed polymer lenses to a microfluidic chip to enable it to function as an interferometer. Using the chip, they performed digital holography microscopy of various biological specimens, including nematodes and diatoms. The single-beam setup is simple and requires only a CCD image sensor. Furthermore, it is portable, providing a lab-on-a-chip imaging system that is simple to use and cheap to mass produce, making it potentially suitable for point-of-care diagnostics. The researchers will investigate using a light-emitting diode rather than a laser as the light source.