A Microfluidics Based Cell Culture Device with Controlled Temperature Gradient

Cell culture is an extensively used technique for studying the behavior and growth of cells in response to different conditions. Examining the effect of temperature variation on cells helps in understanding the characteristics of cancer cells and may help in developing therapeutic procedures. To study the effect of this variation, we propose to use a microenvironment with a programmable temperature gradient. Microfluidics based cell culture devices offer advantage of providing a controlled environment, effectively. The study focuses on creating a microfluidic cell culture device with a controlled temperature gradient. The device consists of two components– a microchannel (18mm×6mm) that holds the cell suspended in culture media and integrated multiple temperature sensors that detect the temperature in the microchannel. Soft lithography of Polydimethylsiloxane was used to fabricate the microchannel. The chromium temperature sensor, which is essentially a resistive pattern, was designed and fabricated using UV lithography technique. To measure the local temperature in a controlled gradient, integrated sensors are placed across the channel. These sensors give a measurement of the temperature inside the channel on the cold and hot regions. In order to provide this gradient, a custom built hotplate was devised which creates a difference of about 3˚ C across the width (6mm) of the channel. First, the designed sensors were calibrated and a linear relation between temperature and voltage was found. The device was evaluated by monitoring the temperature gradient across the channel for 6 hours. Cell compatibility of MCF-7 breast cancer cells was tested in the fabricated device with the set conditions and it can be used for in vitro experiments that last for hours

Aperture-scanning Fourier ptychography for 3D refocusing and super-resolution macroscopic imaging

We report an imaging scheme, termed aperture-scanning Fourier ptychography, for 3D refocusing and super-resolution macroscopic imaging. The reported scheme scans an aperture at the Fourier plane of an optical system and acquires the corresponding intensity images of the object. The acquired images are then synthesized in the frequency domain to recover a high-resolution complex sample wavefront; no phase information is needed in the recovery process. We demonstrate two applications of the reported scheme. In the first example, we use an aperture-scanning Fourier ptychography platform to recover the complex hologram of extended objects. The recovered hologram is then digitally propagated into different planes along the optical axis to examine the 3D structure of the object. We also demonstrate a reconstruction resolution better than the detector pixel limit (i.e., pixel super-resolution). In the second example, we develop a camera-scanning Fourier ptychography platform for super-resolution macroscopic imaging. By simply scanning the camera over different positions, we bypass the diffraction limit of the photographic lens and recover a super-resolution image of an object placed at the far field. This platform’s maximum achievable resolution is ultimately determined by the camera’s traveling range, not the aperture size of the lens. The FP scheme reported in this work may find applications in 3D object tracking, synthetic aperture imaging, remote sensing, and optical/electron/X-ray microscopy

Media 1: Aperture-scanning Fourier ptychography for 3D refocusing and super-resolution macroscopic imaging

Originally published in Optics Express on 02 June 2014 (oe-22-11-13586