A near-field scanner

For moving molecules has been built and demonstrated by a multinational research team. The scanner offers a potentially fast way to make high-resolution images of molecules such as DNA. Traditional scanning-probe microscopes can produce molecular-resolution images, but at the cost of slow scanning speeds. The new device, shown here, is stationary; molecules travel past an array of posts intended to stretch them, then proceed through a microscopic fluid channel (5 microns wide by 1 micron deep) across a trio of 100-nm-wide slits illuminated with near-field laser light. The laser causes the molecules to fluoresce, and that fluorescence yields a far-field image. To ensure high-quality images, the microscope accepts data only from those molecules that cross the three slits at roughly equal time intervals. The researchers obtained 200-nm-resolution imaging data in just 100 milliseconds for a DNA molecule with 200‥000 base pairs (corresponding to about 74 microns in stretched form). Resolution...