Measurement in liquid media is a major challenge in real-time detection using resonant cantilevers. This is addressed in the present study by fabricating sub-micron thick cantilevers followed by functionalization for biomolecule detection.

The fabricated cantilever resonator beams of thickness 165 nm were used for measurements in two systems: (i) human immunoglobulin (HIgG) as the antibody on the cantilever sensing mouse immunoglobulin (MIgG) as corresponding antigen, and (ii) detection of triglyceride (TG) based on the enzymatic hydrolysis with lipase, using tributyrin as a model. In both cases, the beams were functionalized for covalent bonding of the protein receptor. The label-free detection was carried out by measuring the shift in resonance frequency at higher modes, using a laser Doppler vibrometer in liquid and in air.

The calibration showed a linear correlation between the bioanalyte concentration and change in the resonance frequency. Notably, detection of antigen mass as low as 434 59fg and triglyceride concentration in the nM range with limit of detection as 7 nM in liquid interface was achieved, greatly improving the sensitivity of bioanalyte detection in liquid samples.

Although frequency-based methods are highly sensitive, the issues with measurement liquid medium limit their application. In the present report, these issues were addressed by fabricating sub-micron thick cantilever beam, choosing an appropriate functionalization method without affecting the sensitivity, and measurement at higher modes. These have resulted in circumventing issues like damping and hydrodynamic loading thus improving its potential as real-time sensor.

液体介质中的测量是使用共振悬臂进行实时检测的主要挑战。这在本研究中通过制造亚微米厚的悬臂然后进行生物分子检测的功能化来解决。

制造的厚度为 165 nm 的悬臂谐振器光束用于在两个系统中进行测量：（i）人免疫球蛋白（HIgG）作为悬臂传感小鼠免疫球蛋白（MIgG）上的抗体作为相应的抗原，以及（ii）甘油三酯（TG）的检测) 基于脂肪酶的酶促水解，使用三丁酸甘油酯作为模型。在这两种情况下，光束都被功能化用于蛋白质受体的共价键合。无标记检测是通过在液体和空气中使用激光多普勒振动计测量更高模式下共振频率的变化来进行的。

校准显示生物分析物浓度与共振频率变化之间存在线性相关性。值得注意的是，在液体界面实现了低至434 59fg的抗原质量和nM范围内的甘油三酯浓度的检测，检测限为7 nM，大大提高了液体样品中生物分析物的检测灵敏度。

尽管基于频率的方法非常敏感，但测量液体介质的问题限制了它们的应用。在本报告中，这些问题通过制造亚微米厚悬臂梁、在不影响灵敏度的情况下选择合适的功能化方法以及在更高模式下进行测量来解决。这些已经导致规避了阻尼和流体动力载荷等问题，从而提高了其作为实时传感器的潜力。