Raman thermometry indicates aggregation-induced localized hotspots in optical tweezers
*Correspondence to:
Dezhao Huang, School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, Hubei, China; Institute for GONEO New Energy, Wuhan University, Wuhan 430072, Hubei, China.
E-mail: dhuang2@whu.edu.cn
Yanan Yue, Department of Mechanical and Manufacturing Engineering, Miami University, Oxford, Ohio 45056, USA. E-mail: yueyanan@hotmail.com
Yanan Yue, Department of Mechanical and Manufacturing Engineering, Miami University, Oxford, Ohio 45056, USA. E-mail: yueyanan@hotmail.com
Thermo-X. 2027;3:202629. 10.70401/tx.2026.0037
Received: June 15, 2026Accepted: October 12, 2026Published: October 12, 2026
This manuscript is made available in its unedited form to allow early access to the
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Abstract
Gold nanoparticles (Au NPs) provide useful but difficult-to-measure heating in optical tweezers used for colloidal transport, assembly, optofluidics, and bubble-mediated manipulation. Here, we combine 60 nm Au NPs with 5 μm polystyrene (PS) microspheres in a dual-laser Raman optical-tweezers platform. Au NPs serve as heat sources and PS microspheres report the microscale temperature through their Raman spectra. The PS band near 1,000 cm-1 has a calibrated temperature coefficient of -0.0054 cm-1·K-1. For Au stock-dispersion fractions of 0, 0.3, and 1 vol.%, the temperature-power coefficients are 53.5 ± 10.9, 110.4 ± 23.8, and 170.3 ± 18.2 K·W-1, respectively. At 1 vol.% Au suspension, extrapolation of the pre-bubble temperature-power relation to 0.341 W gives a PS-reported temperature of approximately 351 K, below the normal boiling point of water. Electromagnetic simulations show that normalized per-particle absorption increases from 1.00 for an isolated Au nanoparticle to 15.35 for a seven-particle cluster, supporting aggregation-induced nanoscale heating as a mechanism for bubble formation. The PS reporter thus gives the microscale thermal response, and the nanoscale hotspots associated with bubble formation are inferred, not measured directly.
Keywords
optical tweezers, Raman thermometry, gold nanoparticles, photothermal control, bubble onset
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© The Author(s) 2027. This is an Open Access article licensed under a Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, sharing, adaptation, distribution and reproduction in any medium or format, for any purpose, even commercially, 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.
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Zhang H, Zhang N, Huang X, Pang Y, Wu S, Huang D, et al. Raman thermometry indicates aggregation-induced localized hotspots in optical tweezers. Thermo-X. 2027;3:202629. https://doi.org/10.70401/tx.2026.0037
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Zhang H, Zhang N, Huang X, Pang Y, Wu S, Huang D, et al. Raman thermometry indicates aggregation-induced localized hotspots in optical tweezers. Thermo-X. 2027;3:202629. https://doi.org/10.70401/tx.2026.0037
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