Molecular recognition using nanomechanical photothermal spectroscopy

尽管具有体积小、灵敏度高、基于阵列的检测和低功耗等优点，但微悬臂梁等微型传感器仍然是一种实验室工具。这主要是由于检测缺乏选择性和重复性，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一个反复出现的问题，例如那些基于分子吸附引起的质量、电学、光学和机械性质变化的平台。重复性问题产生于作为选择性吸附目标分子的基础的化学/生物界面缺乏一致性。这些问题可以通过将悬臂梁的物理灵敏度与基于物理的正交信号产生相结合来克服，例如中红外光谱。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了微小的温度变化，可以检测到悬臂梁的弯曲。这项技术既不需要标记，也不需要受体，并且只依赖于分子的物理性质。因此，这项技术结合了悬臂梁的极高灵敏度和分子识别的极高选择性的分子振动。通过从共振频率变化同时监测被吸附的质量，克服了重复性的挑战。这项技术有可能利用纳米悬臂研究单个分子。除了作为化学和生物传感的平台外，这个概念还可以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.