Aspects of the disclosure relate to demarcation templates for demarcating a test area on a test surface and for providing visual guidance to a user to precisely and accurately swab the test surface in order to determine the presence and/or concentration of an analyte of interest on the test surface. In one aspect, the analyte of interest is a hazardous contaminant. Some templates can include alignment markings around the border demarcating the test area to provide such guidance to users, and can include graphical use instructions on a removable central portion of the template. The template can be adhesive to be securely fixed to the test surface for accurate demarcation of the test area throughout sampling.

The present disclosure describes systems and methods for centering a circular object, such as a petri dish, between a plurality of pins. For example, in one embodiment, a method comprises placing a circular object on a rotatable platform surrounded by three moveable pins. In order to roughly center the circular object, the method further comprises moving, for a first time, all of the pins toward the circular object until at least two out of the three pins are touching the circular object. In order to more accurately center the circular object, the method further comprises: moving all of the pins away from the circular object so that it can be rotated without substantial inference; rotating the platform approximately 60 degrees, wherein rotating the platform causes the circular object to also rotate by approximately 60 degrees; and moving, for a second time, all of the pins toward the circular object.

Aspects of the disclosure relate to demarcation templates for demarcating a test area on a test surface and for providing visual guidance to a user to precisely and accurately swab the test surface in order to determine the presence and/or concentration of an analyte of interest on the test surface. In one aspect, the analyte of interest is a hazardous contaminant. Some templates can include alignment markings around the border demarcating the test area to provide such guidance to users, and can include graphical use instructions on a removable central portion of the template. The template can be adhesive to be securely fixed to the test surface for accurate demarcation of the test area throughout sampling.

The present disclosure describes systems and methods for centering a circular object, such as a petri dish, between a plurality of pins. For example, in one embodiment, a method comprises placing a circular object on a rotatable platform surrounded by three moveable pins. In order to roughly center the circular object, the method further comprises moving, for a first time, all of the pins toward the circular object until at least two out of the three pins are touching the circular object. In order to more accurately center the circular object, the method further comprises: moving all of the pins away from the circular object so that it can be rotated without substantial inference; rotating the platform approximately 60 degrees, wherein rotating the platform causes the circular object to also rotate by approximately 60 degrees; and moving, for a second time, all of the pins toward the circular object.

A microfluidic chip suitable for controlling movement and detecting position of a microfluid includes a first substrate, a second substrate, first scan lines, first signal lines, second scan lines, second signal lines, actuating units, and heating units. The first scan lines and the first signal lines are disposed on the first substrate. The second scan lines and the second signal lines are disposed on the second substrate. The actuating units each have a first active device and a driving electrode. The first active device is electrically connected to one of the first scan lines, one of the first signal lines, and the driving electrode. The heating units are respectively disposed corresponding to the actuating units, and each have a second active device and a negative temperature coefficient thermistor. The second active device is electrically connected to one of the second scan lines and one of the second signal lines.