Direct Color Observation of Light-Driven Molecular Conformation-Induced Stress

Although usually complex to handle, nanomechanical sensors are exceptional, label-free tools for monitoring molecular conformational changes, which makes them of paramount importance in understanding biomolecular interactions. Herein, a simple and inexpensive mechanical imaging approach based on low-stiffness cantilevers with structural coloration (mechanochromic cantilevers (MMC)) is demonstrated, able to monitor and quantify molecular conformational changes with similar sensitivity to the classical optical beam detection method of cantilever-based sensors (approximate to 4.6 x 10(-3) N m(-1)). This high sensitivity is achieved by using a white light and an RGB camera working in the reflection configuration. The sensor performance is demonstrated by monitoring the UV-light induced reversible conformational changes of azobenzene molecules coating. The trans-cis isomerization of the azobenzene molecules induces a deflection of the cantilevers modifying their diffracted color, which returns to the initial state by cis-trans relaxation. Interestingly, the mechanical imaging enables a simultaneous 2D mapping of the response thus enhancing the spatial resolution of the measurements. A tight correlation is found between the color output and the cantilever's deflection and curvature angle (sensitivities of 5 x 10(-3) Hue mu m(-1) and 1.5 x 10(-1) Hue (degrees)(-1)). These findings highlight the suitability of low-stiffness MMC as an enabling technology for monitoring molecular changes with unprecedented simplicity, high-throughput capability, and functionalities.

Automated summary

This study demonstrates a mechanical imaging approach based on low-stiffness cantilevers, which can monitor and quantify molecular conformational changes with high sensitivity and spatial resolution, suitable for monitoring molecular changes.