This Behind the Scenes article was provided to LiveScience in partnership with the National Science Foundation.
Acoustic tweezers are capable of precisely manipulating cellular-scale objects that are essential to many areas of fundamental biomedical research. The device, developed in the bioengineering lab of Tony Jun Huang at Penn State University, uses ultrasound to capture and control miniscule items like the one-millimeter long roundworm known as Caenorhabditis elegans (C. elegans), a remarkable little creature.
A multicellular organism whose genome has been sequenced, scientists consider C. elegans an ideal model for studying diseases and development in higher animals, including humans. Because C. elegans is transparent, scientists find it easy to observe its life cycle as it grows from an embryo into adulthood.
This miniaturized ultrasound tool should make the study of C. elegans even simpler. The set of acoustic tweezers is the first technology capable of trapping and manipulating C. elegans without touching it.
In some respects, acoustic tweezers are comparable to optical tweezers — the gold standard of manipulation devices — which use lasers to trap and move nano and microscale objects. Acoustic tweezers, however, are simpler, cheaper and considerably less bulky. And because their power density is as much as 10,000,000 times lower than optical tweezers’, they are less likely to damage biological objects.
Acoustic tweezers use ultrasound — the same noninvasive technology doctors use to capture images of a fetus in the womb. They are based on a material that produces mechanical motion when an electrical current is applied.
Here is how they work.
Vibrations pass through transducers attached to a piezoelectric substrate — a solid material capable of producing an electric charge. The transducers convert the vibrations into a special kind of sound wave that creates pressure fields in the liquid medium that holds the specimen. Simple electronics in the instrument can tune the sound waves to precisely and noninvasively hold and move a specimen.
Eighteen months of research went into developing the exact ultrasonic frequencies required to capture C. elegans, Huang says. The scientists described their recent work in an online edition of the Proceedings of the National Academy of Sciences (PNAS).
The authors of the PNAS paper included biochemists in the lab of Stephen Benkovic, a National Medal of Science recipient in Penn State’s chemistry department.
Benkovic would like to use the acoustic tweezers to study how living cells respond to chemicals and pressures that mimic processes taking place within the body. Benkovic would depend on biochemical markers within cells to reveal the effects of the testing in real-time.
Other applications include blood cell and cancer cell sorting, study of cell-to-cell or cell-to-environment interactions and observations of the behavior of entire organisms such as C. elegans.
The ultimate goal may be to see this inexpensive and compact tool available in every doctor’s office for blood and cancer cell sorting and diagnosis.
Contributing to the PNAS paper, “On-chip Manipulation of Single Microparticles, Cells, and Organisms Using Surface Acoustic Waves,” were Xiaoyun Ding, Sz-Chin Steven Lin, Brian Kirby, Hongjun Yue, Sixing Li, Jinjie Shi, Stephen J. Benkovic, and Tony Jun Huang.
The National Science Foundation and the National Institutes of Health provided funding for the research.
To see a short video clip of cell manipulation, visit Penn State’s Materials Research Institute’s webpage.
Editor's Note: This research was supported by the National Science Foundation (NSF), the federal agency charged with funding basic research and education across all fields of science and engineering. See the Behind the Scenes Archive.