Abstract
Stable positioning between a measurement probe and its target from sub- to few micrometer scales has become a prerequisite in precision metrology and in cellular level measurements from biological tissues. Here we present a 3D stabilization system based on an optoelectronic displacement sensor and custom piezo-actuators driven by a feedback control loop that constantly aims to zero the relative movement between the sensor and the target. We used simulations and prototyping to characterize the developed system. Our results show that 95 % attenuation of movement artifacts is achieved at 1 Hz with stabilization performance declining to ca. 70 % attenuation at 10 Hz. Stabilization bandwidth is limited by mechanical resonances within the displacement sensor that occur at relatively low frequencies, and are attributable to the sensor's high force sensitivity. We successfully used brain derived micromotion trajectories as a demonstration of complex movement stabilization. The micromotion was reduced to a level of ∼1 µm with nearly 100 fold attenuation at the lower frequencies that are typically associated with physiological processes. These results, and possible improvements of the system, are discussed with a focus on possible ways to increase the sensor's force sensitivity without compromising overall system bandwidth.
Highlights
Environmental or user-generated vibrations can be detrimental in measurements that require stable contact at themicrometer scale between the measurement probe(s) and its target
Such applications are becoming increasingly common in metrology, microelectronics and cellular level measurements from biological tissues
We have developed an active 3D stabilization system to actively compensate for the movement artifacts
Summary
Environmental or user-generated vibrations can be detrimental in measurements that require stable contact at the (sub)micrometer scale between the measurement probe(s) and its target Such applications are becoming increasingly common in metrology, microelectronics and cellular level measurements from biological tissues. Even when an experimental animal is securely fixed to the experimental setup to prevent its movements the brain undergoes constant micromotion that makes recording electrical activity of the nerve cells challenging This micromotion results from periodic physiological processes, such as cardiac and respiratory functions, and transient movements generated by the activity of muscles in the head. Successful demonstration of active stabilization based on the physiological signals [2,4] or direct measurements of the brain micromotion have been previously presented [2] These methods are constrained to one dimensional movement along the electrode axis, which may limit their general use
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