Molecular recognition using nanomechanical photothermal spectroscopy

尽管具有诸如小尺寸、高灵敏度、基于阵列的检测和低功耗等优点，诸如微悬臂梁的微型传感器仍然作为实验室工具。这主要是由于检测中缺乏选择性和重现性，特别是在检测小分子时。选择性挑战一直是间接传感平台的反复出现的问题，例如基于分子吸附引起的质量、电学、光学和机械性质变化的那些。由于化学/生物界面缺乏均匀性而产生繁殖问题，而化学/生物界面是选择性吸附靶分子的基础。 这些问题可以通过将悬臂梁的物理灵敏度与正交的、基于物理的信号生成（例如，中红外光谱）相结合来克服。吸附在双材料悬臂梁上的分子的振动模式的共振激发产生可以被检测为悬臂梁的弯曲的小的温度变化。这种技术是无标记的，也是无受体的，只依赖于分子的物理性质。因此，该技术结合了悬臂梁的极高灵敏度和分子识别的分子振动的极高选择性。通过同时从共振频率变化监测吸附质量，克服了再现性挑战。该技术具有使用纳米悬臂研究单个分子的潜力。除了作为化学和生物传感的平台外，该概念还可用于研究分子的热特性。

Despite advantages such as small size, high sensitivity, array-based detection, and low power consumption, miniature sensors such as microcantilevers still remain as a laboratory tool. This is mainly due to the lack of selectivity and reproducibility in detection, especially when detecting small molecules. Selectivity challenge has been a recurring problem with indirect sensing platforms such as those based on variations in mass, electrical, optical, and mechanical properties induced by molecular adsorption. Reproducibility issues arise from the lack of uniformity in chemical/biological interfaces that serves as the basis for selective adsorption of target molecules. These problems can be overcome by combining the physical sensitivity of a cantilever with an orthogonal, physics-based signal generation, for example, mid-infrared spectroscopy. Resonant excitation of vibrational modes of molecules adsorbed on a bimaterial cantilever creates small temperature changes that can be detected as bending of the cantilever. This technique is label-free as well as receptor-free and depends only on the physical properties of the molecules. The technique, therefore, combines the extremely high sensitivity of the cantilever with very high selectivity of molecular vibrations for molecular recognition. The reproducibility challenge is overcome by monitoring the adsorbed mass simultaneously from resonance frequency variation. The technique has the potential of investigating a single molecule using a nanocantilever. In addition to serving as a platform for chemical and biological sensing, the concept can be used for investigating the thermal characteristics of molecules.