In this work, we present a single pole magnetic tweezers (MT) device designed for integration with substrate deformation tracking microscopy (DTM) and/or traction force microscopy (TFM) experiments intended to explore extracellular matrix rheology and human epidermal keratinocyte mechanobiology. Assembled from commercially available off-the-shelf electronics hardware and software, the MT device is amenable to replication in the basic biology laboratory. In contrast to conventional solenoid current-controlled MT devices, operation of this instrument is based on real-time feedback control of the magnetic flux density emanating from the blunt end of the needle core using a cascade control scheme and a digital proportional-integral-derivative (PID) controller. Algorithms that compensate for an apparent spatially non-uniform remnant magnetization of the needle core that develops during actuation are implemented into the feedback control scheme. Through optimization of PID gain scheduling, the MT device exhibits magnetization and demagnetization response times of less than 100 ms without overshoot over a wide range of magnetic flux density setpoints. Compared to current-based control, magnetic flux density-based control allows for more accurate and precise magnetic actuation forces by compensating for temperature increases within the needle core due to heat generated by the applied solenoid currents. Near field calibrations validate the ability of the MT device to actuate 4.5 μm diameter superparamagnetic beads with forces up to 25 nN with maximum relative uncertainties of +/-30% for beads positioned between 2.5 and 40 μm from the needle tip.

中文翻译：

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具有磁通密度反馈控制的电磁镊子

在这项工作中，我们提出了一种单极磁镊（MT）设备，旨在与基底变形跟踪显微镜（DTM）和/或牵引力显微镜（TFM）实验集成在一起，旨在探索细胞外基质流变学和人类表皮角质形成细胞力学生物学。MT设备由市售的现成电子硬件和软件组装而成，可以在基础生物学实验室中复制。与传统的螺线管电流控制MT设备相比，该仪器的操作基于使用级联控制方案和数字比例积分微分的从针芯钝端发出的磁通密度的实时反馈控制。 （PID）控制器。补偿在致动期间形成的针芯的明显的空间上不均匀的剩余磁化的算法被实施到反馈控制方案中。通过优化PID增益调度，MT设备显示的磁化和退磁响应时间小于100毫秒，并且不会在较大的磁通密度设定值范围内出现过冲。与基于电流的控制相比，基于磁通密度的控制通过补偿由于施加的螺线管电流产生的热量而导致的针芯内的温度升高，从而实现了更准确，更精确的磁致动力。近场校准可验证MT设备的致动能力4。