TITLE: Multifiber Array Fabrication
AUTHORS: Mai-Anh Vu, mwhowe

[DESCRIPTION]
We have developed a multi-fiber photometry approach to monitor dopamine release with sub-millimeter spatial resolution and sub-second temporal resolution at over 50 locations simultaneously throughout the striatum in awake, behaving mice expressing a fluorescent sensor. This protocol includes the array fabrication and pre-implant mapping steps. Please contact us (mwhowe@bu.edu) if you are interested in using this technique. 

[STEPS]
SECTION: Fabrication steps
1. Cut fibers into several ~3 cm pieces using the ThorLabs fiber scribe
SECTION: Fabrication steps
2. Secure the grid to the Helping Hands using one of the clamps and paper tape
SECTION: Fabrication steps
3. Under the microscope, load fibers into the desired holes in the first row of the grid. The design of these implants is completely flexible; our designs are meant to target the striatum with maximal coverage with no overlap in the collection fields of individual fibers.
SECTION: Fabrication steps
4. Rotate the grid such that the fibers are now parallel to the lab bench.
SECTION: Fabrication steps
5. Under the microscope, push/pull the fibers to the desired depths on the implanted side beneath the grid.
SECTION: Fabrication steps
6. Rotate the grid such that the top is visible, and apply UV glue to the loaded holes
SECTION: Fabrication steps
7. Under the microscope, push/pull the fibers to the desired depths on the implanted side beneath the grid.
SECTION: Fabrication steps
8. Verify that the lengths are correct, and then cure.
SECTION: Fabrication steps
9. Repeat steps 2-7 for the remainder of the rows. Note that we do this row by row, but column-by-column or hole-by-hole is possible.
SECTION: Fabrication steps
10. Once all fibers are loaded and secured, gather the fiber distal ends into a ~1cm section of polyamide tube.
SECTION: Fabrication steps
11. Fill the tube with instant glue and let dry.
SECTION: Fabrication steps
12. Cut with a fresh razorblade – this cross-section is the imaging surface.
SECTION: Fabrication steps
13. Polish first with the 6 micron polishing paper, and then the 3 micron to create a smooth, uniform fiber bundle surface for imaging.
SECTION: Fabrication steps
14. Mount a large diameter post (this can be a blunted, sanded section of a needle) on one side of the grid to facilitate holding during implantation. 
SECTION: Calibration steps (mapping the fiber grid location to imaging surface)
15.7. Repeat for the columns.
SECTION: Calibration steps (mapping the fiber grid location to imaging surface)
15.6. Repeat for the remainder of the rows

SECTION: Calibration steps (mapping the fiber grid location to imaging surface)
15.5. Now slot the piece of paper between rows 2 and 3, such that rows 1 and 2
are exposed, and rows 3 onward are covered, and repeat step 16.4

SECTION: Calibration steps (mapping the fiber grid location to imaging surface)
15.4. Shine the LED light on the exposed fibers and note (taking a picture is useful) the illuminated ends in the imaging surface
SECTION: Calibration steps (mapping the fiber grid location to imaging surface)
15.3. Under the dissection microscope, using a piece of paper (material #14 above) bent to 90 degrees, slot it between the first and second rows such that rows 2 onwards are covered.



SECTION: Calibration steps (mapping the fiber grid location to imaging surface)
15.2. Mount the USB digital microscope camera underneath so you have a clear view of the imaging surface
SECTION: Calibration steps (mapping the fiber grid location to imaging surface)
15.1. Flip the multifiber array upside down, so the implanted ends are upwards.
SECTION: Calibration steps (mapping the fiber grid location to imaging surface)
15. The overall idea will be to use the LED penlight to illuminate the implanted ends and note which fibers in the imaging surface are lit. Do this by sequentially uncovering one row at a time, and then one column at a time, such that each fiber in the imaging surface has a row and column coordinate in the grid. An example way to do this is as follows: