And now for something completely different:
Acoustic waves have been used to move and position biological specimens along the x, y and z axes, but for the first time researchers have used them to gently and safely rotate samples, a crucial capability in single-cell analysis, drug discovery and organism studies.
To achieve this, researchers from Penn State University trapped microbubbles within predefined sidewall microcavities inside a microchannel. They describe the acoustofluidic rotational manipulation (ARM) method that traps bubbles in a series of small cavities inside a microfluidic device. Acoustic transducers similar to ultrasound imaging transducers create an acoustic wave in the fluid, causing the bubbles to vibrate. The vibrating bubbles create microvortexes in the flowing liquid that can be tuned to cause the sample to rotate in any direction and at any desired speed.
Currently, confocal microscopes are required in many biological, biochemical and biomedical studies, but many labs do not have access to a confocal microscope, which costs more than $200,000. Our ARM method is a very inexpensive platform. And it is compatible with all the optical characterization tools. You can literally use a cell phone to do three-dimensional imaging.
To demonstrate the device's capabilities, the researchers rotated the famous model organism Caenorhabditis elegans, that is about a millimeter in length. They also acoustically rotated and imaged a HeLa cancer cell, also for the first time. Existing methods of manipulating small objects either depend on the optical, magnetic or electrical properties of the specimen, and/or damage the specimen due to laser heating. The ARM method, on the other hand, uses a gentle acoustic wave generated by a similar power as ultrasound imaging and at a lower frequency. The device is also compact and simple to use.