​​​K. H. (Koko) LAM Research group

K. H. (Koko) Lam - The Hong Kong Polytechnic University © All rights reserved.

Devices for micro particle manipulation have been developed for many biophysical applications including quantifying mechanical properties of various cells and molecules. Optical tweezers were developed in 1970s, using the gradient of radiation force to trap the objects toward the focus of the laser beam. It has become an extremely useful tool in biophysics. With using the focused laser beam, optical tweezers have an absolute advantage in resolution, which are able to produce forces at pico–newton level to manipulate particles or molecules of a size from tens of nanometers to tens of micrometers accurately. However, they are commonly limited to optical purified samples. With highly focused laser beam, the targeted biological samples would easily be damaged by inducing local heat. Besides, the force is usually too small to manipulate larger cells or particles. 

Compared to the optical tweezers, the setup of acoustic devices is much simpler at a lower cost than the optical devices. The most important advantage is that the biological samples are less likely to be damaged by the acoustic energy. Thus, an acoustic microbeam is an alternative non–invasive way to offer the capability of particle manipulation in biomedical applications.

This goal cannot be met without the development of highly sensitive ultrahigh frequency ultrasonic transducers since the beam width is inversely proportional to the transducer frequency. The alternative way is to develop with a steep intensity gradient of the microbeam (low f–number, f#). Our demonstrations show the acoustic microbeam is able to manipulate the particles or cells in micron scale as well as the organisms in millimeter scale. Besides, red blood cell deformation was demonstrated successfully to be deformed by using the acoustic microbeam, which is the first time to report the utilization of acoustic microbeam on biophysical applications of cell. 

Hwang, J.Y., Lee, N.S., Lee, C., Lam, K.H., et al. Biotechnology and Bioengineering, Vol.110(10), pp.2697–2705 (2013) 

Lam, K.H.*, et al. Biotechnology and Bioengineering, Vol.110(3), pp.881–886 (2013) 

Li, Y., Lee, C., Lam, K.H., et al. Applied Physics Letters, Vol.102, 084102 (2013)

Lam, K.H., et al. 2012 IEEE International Ultrasonics Symposium, pp.1994–1997 (2012)

Hwang, J.Y., Lee, N.S., Lee, C., Lam, K.H., et al. 2012 IEEE International Ultrasonics Symposium, pp.596–599 (2012)

Example of 1–µm microsphere manipulation using a 200–MHz f#1.6 LiNbO3 press–focused microbeam device.

Example of Zebrafish egg (~1.6 mm diameter) manipulation using a 60–MHz f#0.6 LiNbO3 press–focused microbeam device.

Example of mechanical deformation of a RBC using a single microsphere manipulated by a 200–MHz f#1.6 LiNbO3 press–focused microbeam device.