Optimizing Calibration sets you up for success
Force measurements made with the system are based on measurement of deflected light of a conjugated laser which reflects off a polished AFM chip. Thus, if the laser is focused on different spots on the AFM chip, the amount of deflected light will differ and a consistent measure of force between two different myofibrils will not be possible. There are several techniques that will help the user optimize not only the magnitude of the signal but also the repeatability.
- Make use of the 820A XYZ motion controller
Many researchers who have experience working with tooling attached to motorized micropositioners are used to making manual adjustments of position either via joystick or keypad. Those with sufficient experience can adeptly navigate the probes/tooling quickly and accurately use them to attach to a sample. However, placing the tooling back in the exact calibration spot in 3D space after navigating to pick up a myofibril requires a level of expertise that few can achieve manually. The 820A XYZ motion controller provides a means of remembering various points in 3D space which the user can return to at their convenience with a precision of less than 1um.
Additionally, the motion controller has a software interface that is fully integrated with the data acquisition software. It allows movements of very precise magnitudes to be made which is useful for fine adjustments and delicate operations such as sample attachment.
- Location, Location, Location
Since we have the ability to make precise movements of the micropositioners, we should strive to optimize the relative position of the AFM cantilever in 3D space. The focal point of the conjugated laser spot is set to be approximately 500-600um from the face of the optical periscope. To set this distance we should focus on the bottom edge of the optical periscope and use a lower powered objective to set the cantilever distance from it. This distance can be easily measured with the included HSVL software. The size of individual myofibrils typically requires a very high powered objective to be used in order to visualize clearly, which typically means a small FOV. It can help to have the periscope in the FOV for reference, but this may require adjusting the focal distance of the laser inside the 470A sensor head. Please speak with Aurora Scientific directly about customizing this distance based on the needs of your existing microscope.