To the Editor,
1.
Recalcati et al. 1 describe a welcome and pragmatic addition to the AFM toolkit: a single‐Peltier platform for imaging solid/water interfaces under freeze–thaw cycles, integrable with any tip‐scanning instrument. The emphasis on operational simplicity is valuable. We raise three points on measurement and validation.
First, the platform's central claim is interfacial temperature control, yet temperature is sensed where it is not most needed. The thermocouple is affixed to the Peltier junction by copper tape, 1 not at the HOPG/water interface, and the reported ±0.1°C therefore characterises junction stability rather than interfacial accuracy. The authors acknowledge that bulk‐to‐surface thermal gradients ‘could yield an overestimation of the actual nucleation temperature’, 1 but the abstract and results nonetheless present the 0°C to −2°C nucleation window as an interfacial quantity. Because supercooling magnitude is the key physical variable here, 2 an estimate of the gradient between sensor and interface or an independent interfacial calibration would substantiate the control the platform claims.
Second, each of the two settings rests on a single sample with qualitative image comparison. Conclusions of ‘robustness’, ‘no signs of degradation’, and, conversely, ‘general degradation in the quality of HOPG terraces’ 1 are drawn visually, without quantitative endpoints such as RMS roughness, step‐height distributions, or phase‐contrast statistics across replicates. For a proof‐of‐concept, the descriptive approach is reasonable, but reliability claims would be strengthened by minimal quantitative metrics and at least limited replication, given known sample‐to‐sample variability in exfoliated HOPG.
Third, the novel observation stability of circular wetting layers near freezing is supported by a single phase‐contrast frame (Figure 5) that the authors note is drift‐affected. 1 The further inference of ‘spatially heterogeneous tip–substrate interaction’ close to freezing is mechanistically appealing but under‐determined: AFM phase contrast convolves topography, adhesion, and viscoelastic response, so attributing the signal specifically to interfacial freezing would benefit from force–distance curves or quantitative nanomechanical mapping rather than phase imaging alone. 3 As presented, this remains a promising hypothesis rather than a demonstrated finding.
None of these points diminishes the platform's practical appeal or its potential across the material‐ and environmental‐science applications the authors envisage. We suggest only that interfacial temperature be calibrated or bounded independently of the junction sensor and that the wetting‐layer observation be framed as preliminary pending quantitative nanomechanical confirmation.
Yours sincerely,
AUTHOR CONTRIBUTIONS
All authors contributed to conception, drafting, critical revision and final approval.
CONFLICT OF INTEREST STATEMENT
The authors declare no conflicts of interest.
DATA AVAILABILITY STATEMENT
No new data; all data discussed are in the cited article.
REFERENCES
- 1. Recalcati, C. , Yivlialin, R. , Duò, L. , Guadagnini, A. , & Bussetti, G. (2026). A novel experimental platform to monitor solid/water interfaces under freeze–thaw cycles. Journal De Microscopie, 302(1), 92–99. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Chasnitsky, M. , Cohen, S. R. , Rudich, Y. , & Braslavsky, I. (2023). Atomic force microscopy imaging of ice crystal surfaces formed in aqueous solutions containing ice‐binding proteins. Journal of Crystal Growth, 601, 126961. [Google Scholar]
- 3. Fang, C.‐K. , Ko, H.‐C. , Yang, C.‐W. , Lu, Y.‐H. , & Hwang, I.‐S. (2016). Nucleation processes of nanobubbles at a solid/water interface. Scientific Reports, 6(1), 24651. [DOI] [PMC free article] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
No new data; all data discussed are in the cited article.