Memsensor-Integrated Microrobots for Passive Detection of H₂O₂

Abstract

A memsensor (a memory sensor) is designed as a sensor with/in memory, which can work in a passive mode and, hence, is particularly suitable for environments where a local/onboard power supply is hardly available for such a scenario: the microrobot will carry such sensors and move to a specific region where the physical quantities of interest are in the intermediate range. The sensors will be collected back with the robot to understand the information about the location where they have been staying. In this report, molybdenum disulfide (MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) memsensors are integrated on microrobots for hydrogen peroxide (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) detection in a passive mode. The sensing is based on the reactivity of a MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanoflake to H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , which is an indicator of the existence of tumor cells in their microenvironment. The sensor has a crossbar configuration and is microfabricated with Au/MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Au. Due to its irreversible structure, calibration is done at a lower concentration of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and confirmed at a higher one while the effective sensing range is in between. Experiments show that the proposed calibration and sensing method has an acceptable resolution of 200 nmol/L to 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> mol/L. Compatibility of the fabrication processes of the sensors to that of helical magnetic microrobots is excellent based on the first trial.