Liquid polymeric materials for optical nano-bio sensing

Abstract

Detecting, counting, and sizing nanoparticles is a key problem in biomedical, environmental, and materials synthesis fields. Here we demonstrate a cost-effective and high-performance approach that uses wide-field microscopy enabled by the combination of inline lensfree holography, pixel super-resolution, and vapor-condensed nano-scale lenses (nanolenses). These nanolenses are composed of liquid polyethylene glycol (PEG) that self-assembles in situ around particles of interest. A nanolens around each particle generates a more substantial phase shift than the native object alone, making it more easily detectible in the imaging system. This latest generation of lensfree holographic microscope incorporates more precise temperature control and utilizes a hermetically sealed chamber allowing for a controlled, repeatable environment for simultaneous hologram measurements and nanolens formation. To further enhance the sensitivity of our system, we have compared the performance of two different pixel super-resolution algorithms: shiftand- add and gradient descent. It was found that the gradient descent approach provides the highest resolution. Detection and localization results for 1 μm, 400 nm, and 100 nm particles are presented.