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Mechanical Profiling of Biopolymer Condensates through Acoustic Trapping

Kichitaro Nakajima*

Tomas Sneideris and Nadia A. Erkamp

Lydia L. Good

Yuri Hideshima and Hirotsugu Ogi

Tuomas P. J. Knowles†

  • Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, England, United Kingdom

  • Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, England, United Kingdom and Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA

  • Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, England, United Kingdom and Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, England, United Kingdom

  • *Contact author: k.nakajima@prec.eng.osaka-u.ac.jp
  • †Contact author: tpjk2@cam.ac.uk
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PRX Life 4, 033015 – Published 17 August, 2026

DOI: https://doi.org/10.1103/kl9v-5ywv

Abstract

Characterizing the mechanical properties of single colloids is a central problem in soft matter physics. It also plays a key role in cell biology through biopolymer condensates, which function as membraneless compartments. Such systems can also malfunction, leading to the onset of a number of diseases, including many neurodegenerative diseases; the functional and pathological condensates are commonly differentiated by their mechanical signature. Comprehensive understanding of mechanical properties of biopolymer condensates has, however, remained challenging. In this study, we demonstrate that acoustic trapping can be used to probe the bulk modulus of biopolymer condensates in a contactless manner. We find that acoustic fields exert an acoustic radiation force on condensates, leading to their migration to a trapping point where acoustic potential energy is minimized. Furthermore, our results show that the positional fluctuation of a condensate undergoing Brownian motion in an acoustic potential well can be used as a probe for its bulk modulus. Using this framework, we infer changes in the bulk modulus of polyadenylic acid condensates in response to variations in ionic strength. Our results show that acoustic trapping opens up a path to characterize the bulk modulus of soft colloids in a noninvasive manner with applications in biology, materials science, and beyond.

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This article appears in the following collection:

Collection on Physics of Biomolecular Condensates

From the fundamentals of phase separation, dynamics and structure of condensates in biological settings, to advanced imaging methods, this special collection presented by PRX Life showcases exciting and timely work on the physics of biomolecular condensates.

This Invited Collection is coordinated by PRX Life Associate Editor Christoph Weber, in consultation with Jerelle Joseph, Simon Alberti, and Tanja Mittag. Every article published in this collection underwent a rigorous peer review process, adhering to the same high standards applied to all papers handled by the journal. The PRX Life editorial team managed the peer review and made all editorial decisions.

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PRX Life 4, 033015– Published 17 August, 2026
  • Received 28 October 2024
  • Accepted 29 June 2026
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