Abstract
Highly sensitive force measurements of a single microscopic particle with femto-Newton sensitivity have remained elusive owing to the existence of fundamental thermal noise. Now, researchers have proposed an optically controlled hydrodynamic manipulation method, which can measure the weak force of a single microscopic particle with femto-Newton sensitivity.
Micromanipulation techniques have experienced impressive progress for manipulating and trapping microscopic objectives. Common micromanipulation techniques include optical, magnetic, electrokinetic, acoustic, thermophoretic, and hydrodynamic tweezers1,2,3. Different technologies have their own advantages and disadvantages. The optical and magnetic tweezers have high requirements on material properties4. In contrast, the electrokinetic and hydrodynamic tweezers can manipulate the particle without restrictions on the material properties. However, most of these techniques have a relatively low spatial resolution. Optical tweezers may not be suitable for long-time trapping of objects owing to the photo-induced damage or heating4. Compound manipulation is the most effective way to alleviate these limitations, such as magneto-optical, opto-thermophoretic, and opto-hydrodynamic5,6,7. Based on the optical and hydrodynamic manipulations, the optically controlled hydrodynamic manipulations have been proposed to trap and observe microscopy objects6,7. This method does not expose the object to the high-intensity optical field, while also lifting material constraints.
How to improve the sensitivity of measurement techniques is a major concern for many experimental scientists. In the past few decades, a variety of methods for weak force measurements have been proposed, including micro-electro-mechanical force sensors, fiber-optic force sensors, nanocantilevers, and atomic force microscopy8,9,10. These weak force measurement methods exhibited an unambiguous range of ~0.6 mN and an ultra-small detection limit down to ~0.1 pN2. These force measurement methods face a common problem: the fundamental thermal noise related to the motional degree of freedom11. Therefore, it is difficult to achieve the detection of the weak force of a single microscopic particle at femto-Newton level.
A recent research paper in eLight12, entitled “Highly sensitive force measurements in an optically generated, harmonic hydrodynamic trap”, by Iliya D. Stoev from Max Planck Institute of Molecular Cell Biology and Genetics, provides an optically controlled trapping method enabled by light-induced hydrodynamic thermoviscous flows in a thin microchannel. By splitting the scanning line of an infrared laser into two counter-directed paths on the same axis, they transition from a flow dipole to a quadrupole-like flow-field making use of opposite collinear thermoviscous flow fields. Specifically, a stagnation point is formed between the two counter-directed laser scan paths in a region without direct laser exposure (Fig. 1b). By using a feedback control system (Fig. 1a), they effectively create a quasi-1D-trapping situation. As shown in Fig. 1c, these four particles are always to be displaced along the compressional axis only. Furthermore, they investigate the relationship between the velocity and distance of a 3 μm trapped polystyrene particle. Interestingly, they observe an exponential approach to the stagnation point, suggesting a linear force-displacement relationship (Fig. 1d). They also measure the properties of the trap, showing a femto-Newton range force measurement with sensitivity close to the thermal limit. In addition, this optofluidic trap is highly tunable, including the laser power, the scan path length, or the counterflow. Their force measurements eliminate the material constraints and also remove the need for laser-particle contact. This optofluidic trap is an appealing alternative or complement to optical tweezers for probing the active microrheology of weak viscoelastic networks. These results obtained by this manuscript open the exciting possibilities of ultrasensitive force measurements of individual nanoparticles. The optically controlled hydrodynamic manipulation with ultrasensitive will certainly be widely used in the life sciences and engineering.
Although optical micro/nanomanipulations are advancing rapidly in the past few decades, there are still some grand challenges that deserve more attention and effort to address. First, we still need to identify effective approaches to realize strong manipulation under moderate light or even without direct contact with light exposure. Different degrees of freedom and mechanisms, other than just intensity gradient, are to be studied. Second, extraordinary multipoles of high-index dielectric particles provide unprecedented optical force and torques. This should be an interesting topic in biological and quantum sensing. Third, it is still largely elusive how to achieve multifunctional manipulation of arbitrary single or massive tiny bioparticles (e.g., viruses) in a solution.
References
Florin, E. L. et al. Photonic force microscope based on optical tweezers and two-photon excitation for biological applications. J. Struct. Biol. 119, 202–211 (1997).
Neuman, K. C. & Nagy, A. Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy. Nat. Methods 5, 491–505 (2008).
Lutz, B. R., Chen, J. & Schwartz, D. T. Hydrodynamic tweezers: 1. Noncontact trapping of single cells using steady streaming microeddies. Anal. Chem. 78, 5429–5435 (2006).
Kumar, D. et al. Automation and flow control for particle manipulation. Curr. Opin. Chem. Eng. 29, 1–8 (2020).
Liu, S., Lin, L. & Sun, H. B. Opto-thermophoretic manipulation. Acs Nano 15, 5925–5943 (2021).
Shi, Y. et al. Sculpting nanoparticle dynamics for single-bacteria-level screening and direct binding-efficiency measurement. Nat. Commun. 9, 815 (2018).
Shi, Y. et al. Nanometer-precision linear sorting with synchronized optofluidic dual barriers. Sci. Adv. 4, eaao0773 (2018).
Šiškins, M. et al. Sensitive capacitive pressure sensors based on graphene membrane arrays. Microsyst. Nanoeng. 6, 102 (2020).
Zou, M. et al. Fiber-tip polymer clamped-beam probe for high-sensitivity nanoforce measurements. Light. Sci. Appl. 10, 171 (2021).
Sarioglu, A. F. & Solgaard, O. Modeling, design, and analysis of interferometric cantilevers for timeresolved force measurements in tapping-mode atomic force microscopy. J. Appl. Phys. 109, 064316 (2011).
Mueller, F., Heugel, S. & Wang, L. J. Subkelvin cooling of a gram-sized oscillator. Appl. Phys. Lett. 92, 044101 (2008).
Iliya, D. S. Highly sensitive force measurements in an optically generated, harmonic hydrodynamic trap. eLight 1, 7, https://doi.org/10.1186/s43593-021-00007-7 (2021).
Erben, E. et al. Feedback-based positioning and diffusion suppression of particles via optical control of thermoviscous flows. Opt. Express 29, 30272–30283 (2021).
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Zhang, X., Gu, B. & Qiu, CW. Force measurement goes to femto-Newton sensitivity of single microscopic particle. Light Sci Appl 10, 243 (2021). https://doi.org/10.1038/s41377-021-00684-6
Published:
DOI: https://doi.org/10.1038/s41377-021-00684-6
This article is cited by
-
ISO-FLUCS: symmetrization of optofluidic manipulations in quasi-isothermal micro-environments
eLight (2023)
-
Progress in percolative composites with negative permittivity for applications in electromagnetic interference shielding and capacitors
Advanced Composites and Hybrid Materials (2023)