Magnetic sensing is present in our everyday interactions with consumer electronics and demonstrates the potential for the measurement of extremely weak biomagnetic fields, such as those of the heart and brain. In this work, we leverage the many benefits of microelectromechanical system (MEMS) devices to fabricate a small, low-power, and inexpensive sensor whose resolution is in the range of biomagnetic fields. At present, biomagnetic fields are measured only by expensive mechanisms such as optical pumping and superconducting quantum interference devices (SQUIDs), suggesting a large opportunity for MEMS technology in this work. The prototype fabrication is achieved by assembling micro-objects, including a permanent micromagnet, onto a postrelease commercial MEMS accelerometer using a pick-and-place technique. With this system, we demonstrate a room-temperature MEMS magnetic gradiometer. In air, the sensor’s response is linear, with a resolution of 1.1 nT cm⁻¹, spans over 3 decades of dynamic range to 4.6 µT cm⁻¹, and is capable of off-resonance measurements at low frequencies. In a 1 mTorr vacuum with 20 dB magnetic shielding, the sensor achieves a 100 pT cm⁻¹ resolution at resonance. This resolution represents a 30-fold improvement compared with that of MEMS magnetometer technology and a 1000-fold improvement compared with that of MEMS gradiometer technology. The sensor is capable of a small spatial resolution with a magnetic sensing element of 0.25 mm along its sensitive axis, a >4-fold improvement compared with that of MEMS gradiometer technology. The calculated noise floor of this platform is 110 fT cm⁻¹ Hz^−1/2, and thus, these devices hold promise for both magnetocardiography (MCG) and magnetoencephalography (MEG) applications.

磁感应存在于我们与消费电子产品的日常互动中，并展示了测量极弱生物磁场（例如心脏和大脑的磁场）的潜力。在这项工作中，我们利用微机电系统 (MEMS) 设备的许多优点来制造一种小型、低功耗且价格低廉的传感器，其分辨率在生物磁场范围内。目前，生物磁场只能通过昂贵的机制来测量，例如光泵浦和超导量子干涉装置 (SQUID)，这表明 MEMS 技术在这项工作中具有很大的机会。原型制造是通过使用拾放技术将微型物体（包括永久微磁体）组装到发布后的商用 MEMS 加速度计上来实现的。有了这个系统，我们展示了室温 MEMS 磁梯度仪。在空气中，传感器的响应是线性的，分辨率为 1.1 nT cm^-1，跨越 3 个十倍频程的动态范围至 4.6 µT cm ^-1，并且能够在低频下进行偏共振测量。在具有 20 dB 磁屏蔽的 1 mTorr 真空中，传感器在共振时实现了 100 pT cm ^-1分辨率。该分辨率与MEMS磁力计技术相比提高了30倍，与MEMS梯度计技术相比提高了1000倍。该传感器具有沿其敏感轴为 0.25 mm 的磁性传感元件的小空间分辨率，与 MEMS 梯度计技术相比，提高了 4 倍以上。该平台的计算本底噪声为 110 fT cm ⁻¹  Hz ^−1/2，因此，这些设备有望用于心磁图 (MCG) 和脑磁图 (MEG) 应用。