Manipulation at the sub-micron scale often requires force-sensing capabilities of milli-to nanonewton forces. This article presents a novel design of a compliant load cell with mechanically adjustable stiffness. The system enables adapting force sensitivity to the requirements of a specific application. The principle of the stiffness adjustment is based on a preloaded spring, that stores the potential energy used to compensate the effort needed to deflect the compliant structure of the load cell. Unlike Micro-Electro-Mechanical Systems (MEMS), the new mechanism can be fabricated at the centimeter-scale. This reduces the fragility of the system and facilitates interchange of end-effectors. A main advantage of this solution is the possibility to use one common force sensing device for diverse applications at various scales, such as in biotechnology, semiconductor nanoprobing or microassembly. We describe the analytical model of the load cell and use it to simulate the performance of the stiffness adjustment mechanism. The analytical results are then validated by finite element method (FEM) and experiments performed on a large-scale stainless-steel prototype. Empirical results show that the overall stiffness can be tuned to near-zero and beyond, resulting in a bistable mode. The presented model brings freedom for designing the sensitivity adjustment, and the experimental part shows the ability to reduce the stiffness of the prototype by approximately 200-fold, achieving a force sensing resolution of 0.41 $\mu N$

亚微米级的操纵通常需要几毫米到纳米牛顿力的力感应能力。本文介绍了一种具有机械可调节刚度的顺应性称重传感器的新颖设计。该系统可以使力敏感度适应特定应用的要求。刚度调节的原理基于预加载的弹簧，该弹簧存储势能，用于补偿使测力传感器的柔顺结构偏转所需的力。与微机电系统（MEMS）不同，新机制可以在厘米级上制造。这减少了系统的脆弱性，并促进了末端执行器的互换。该解决方案的主要优点是可以使用一个通用的力感测设备在各种规模的各种应用中使用，例如生物技术，半导体纳米探测或微装配。我们描述了称重传感器的分析模型，并用它来模拟刚度调节机构的性能。然后，通过有限元方法（FEM）验证了分析结果，并在大型不锈钢原型上进行了实验。实验结果表明，总体刚度可以调整为接近零甚至更高，从而产生双稳态模式。提出的模型为设计灵敏度调整带来了自由，实验部分显示了将原型的刚度降低大约200倍的能力，实现了0.41的力感测分辨率 然后，通过有限元方法（FEM）验证了分析结果，并在大型不锈钢原型上进行了实验。实验结果表明，总体刚度可以调整为接近零甚至更高，从而产生双稳态模式。提出的模型为设计灵敏度调整带来了自由，实验部分显示了将原型的刚度降低大约200倍的能力，实现了0.41的力感测分辨率 然后，通过有限元方法（FEM）验证了分析结果，并在大型不锈钢原型上进行了实验。实验结果表明，总体刚度可以调整为接近零甚至更高，从而产生双稳态模式。提出的模型为设计灵敏度调整带来了自由，实验部分显示了将原型的刚度降低大约200倍的能力，实现了0.41的力感测分辨率$\mu ñ$