Los Angeles, CA--researchers at the University of California Los Angeles (UCLA) have redefined the concept of a microscope by demonstrating lens-free optical tomographic imaging on a chip, a technique capable of producing high-resolution 3D images of large volumes of microscopic objects.
The resulting device is small enough to fit in the palm of a hand but powerful enough to create 3D tomographic images of miniscule samples. The advance was featured this week in the early online edition of the journal Proceedings of the National Academy of Sciences.
An optical imaging system small enough to fit onto an opto-electronic chip provides a variety of benefits. Because of the automation involved in on-chip systems, scientific work could be sped up significantly, which might have a great impact in the fields of cell and developmental biology. In addition, the small size not only has great potential for miniaturizing systems but also leads to cost savings on equipment.
3D with no resolution loss
The researchers developed the new tomographic microscopy platform through the next evolution of a lens-free imaging technology the group created and has been improving for years. The system takes advantage of the fact that organic structures, such as cells, are partially transparent, so by illuminating a sample of cells, the shadows created reveal not only the cells' outlines but details about their subcellular structures as well. The platform's 3-D images are created by rotating the light source to illuminate the samples from multiple angles. Through a tomographic approach, the system is able to produce 3D images without sacrificing resolution.
"These details can be captured and analyzed if the shadow is directed onto a digital sensor array," said graduate student Serhan Isikman. "The end result of this process is an image taken without using a lens."
"This research clearly shows the potential of lens-free computational microscopy," said Aydogan Ozcan, senior author of the paper. "Wonderful progress has been made in recent years to miniaturize life-sciences tools with microfluidic and lab-on-a-chip technologies, but until now optical microscopy has not kept pace with the miniaturization trend."
Ozcan envisions this lens-free imaging system as one component in a lab-on-a-chip platform. It could potentially fit beneath a microfluidic chip; the two tools would operate in tandem, with the microfluidic chip depositing and subsequently removing a sample from the lens-free imager in an automated process.
"The field of view of lens-based microscopes is limited because the lens focuses on a narrow area of a sample," said postdoctoral researcher Waheb Bishara. "A lens-free microscope has both a much larger field of view and depth of field because the imaging is done by the digital sensor array and is not constrained by a lens."
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