Step by step assembly of the TetrODrive
Parts and materials can be found here
Tetrode twisting is explained in more detail in this JOVE paper: Nguyen et al. Micro-drive Array for Chronic in vivo Recording: Tetrode Assembly. J. Vis. Exp. (26), e1098, doi:10.3791/1098 (2009)
GitHub: Open Ephys tetrode twister, Open Ephys webpage
We placed the twister on a laboratory lifting table for easy height adjustments pointing towards a custom-made fixation cross on the top to separate the four wires. A hook, that collects the wires, is fixed to the twister clamp. The tetrode ends at the hook will be used for attachment to the EIB.
- prepare a clean and dust-free environment
- cut 40 cm tungsten wire
- twister settings: 80 forward, 20 backward settings differ depending on the length and the used material of the wires. Initially play around with the settings.
- after twisting but still clamped inside using a heat gun (220-degree Celsius, might vary depending on insulation) from three different sides slowly (5 s) up and down, airflow output low, a few cm distances
- afterwards release tension by slowly lifting the table and cut tetrode at the side of the fixation cross
- handle tetrodes extremely careful, and only touch them with forceps at the ends which are cut away later, insulation can break very easily
- fixate each wire from the backside with a golden pin into the appropriate hole holding a forceps (each wire in a separate one, indicated in figure for our EIB: 1-4, ..., 17-20,...)
- the golden pins fit perfectly and do not need additional steps for fixation (silicone layer is later added for protection)
also check for cross-links, wire ends shouldn't touch each other
backside of EIB
- use the provided designs files to order the EIB at some of the proposed vendors
- we used a reflow soldering process to connect a male Hirose DF 12 connector to the EIBs you can use any other EIB, that do not need manual fixation of the connector, we would suggest a zero insertion force connector over an omnetics plug to minimize plugging force
We included a short reflow tutorial in case you want to use this process
- with all the tetrodes (up to 8) fixed on the EIB apply the silicone protective coating from the front and backside of the EIB to the golden pins
- solder reference and ground electrodes before or during the surgery, the reference electrode should be placed as close as possible without picking up the same signal as the tetrodes
The intan headstage has an omnetics connector. Therefore, we use a permanently intan headstage attached adapter that has a female Hirose DF 12 connector and an Omnetics connector.
- general explanation of how to handle, polish and cleave fibers can be found in the Thorlabs documentation
- to reduce autofluorescence we used a steel ferrule for fiber photometry, for regular optogenetic stimulation we used a ceramic ferrule
- since the fiber will be going in a loop from the EIB to the microdrive it is important that the fiber is long enough
- for protection we insert it in a kevlar protective tubing
- the length without kevlar protection should be also long enough: since it has to enter the cannula of the microdrive and protrude to the appropriate in vivo length
- cut protective tubing. push kevlar slightly out (5-10 mm), cutaway 10 mm from the other side, fixate kevlar fibers and push fiber inside the tube, move Kevlar fibers so that both ends have kevlar fibers outside,
glue the kevlar fibers of the one end to the ferrule, the other end kevlar fibers will be glued later to the guide cannula of the microdrive
- the procedure is described in the ReadMe
- here are the design files and 3D print files
in this wiki, we additionally provide photographs of the illustrations in the paper
every UV glue step is accompanied by immediate UV lamp hardening
you should have the following previous parts prepared
- 3D printed body and head
the assembly is very quick
-
enlargening of the holes in the body and head: with a manually operated handheld drill holder (not mechanically)
-
body:
middle screw hole --> 0.8 mm drill, followed by M1x0.25 thread tapping
thread tapping carefully: 3D print must be dry and UV light-cured, don't apply strong pressure, repeatedly (4-5 times) remove and clear resin dust from the tap
two outer holes --> 1 mm drill, for insertion of metal cannulas
use a piece of the metal cannula to ensure its smooth movement
- head
same as in body: two outer holes --> 1 mm drill, for insertion of metal cannulas for metal cannulas
use a piece of the metal cannula to ensure its smooth movement
a 10 mm long M1 screw is screwed into the middle hole (without any previous modification to the middle head hole)
fixate nut from the bottom and glue the nut to the screw (careful: apply UV glue only on nut/screw fixation, the screw has to turn freely)
- cut (using electric drill/grinder/cutter e.g. Proxonn) two stainless steel tubing pieces (1 mm diameter, hollow inside): approximate 10 and 15 cm
- deburr the cannula ends to prevent damage to the tetrode isolation layer (using electric drill/grinder/cutter e.g. Proxonn + sandpaper)
- check for obstructions in the cannula (using a small drill < 1mm diameter)
this is a useful tool for cutting: attach a cutter tip instead of the here displayed one
- insert cannulas into microdrive head and screw a few turns to merge the head with the body
-
fixate the cannulas to the head and body: apply a small amount of UV glue on the marked positions (black circles) of the cannulas
-
seal the two lower holes (screw and support cannula) with e.g. tape
you should have the following parts prepared
- assembled TetrODrive (body + head merging)
- optical fiber in protective Kevlar tubing attached to the ferrule
- EIB with fixated tetrodes and protective silicone
- the optical fiber should be inserted and marked at the appropriate protrusion length that is needed from the bottom of the TetrODrive
- take the fiber out again and cut it to the appropriate length
- tetrodes are inserted with forceps (apply force only at the tips that are later cutaway)
- optical fiber is inserted between the tetrodes
- glue the kevlar, the optical fiber itself, and the tetrodes to the guide cannula at the microdrive head
-
distribute the tetrodes equally around the fiber with a sharpened toothpick or with forceps touching the protruding area that is later cutaway
-
now very carefully with the tiniest drop of UV glue using an insect pin or sharpened toothpick apply UV glue at the base of the fiber and tetrode (where fiber and tetrode leave the microdrive)
-
use a very small amount of UV glue to prevent diameter increase and don't apply UV glue at the tip of the fiber
-
using carbide-tipped scissors the tetrodes are cut to a length of approximately 500 micrometers (or a bit less: 300 micrometers) longer than the fiber tip, cut with a slight angle to lower the chances of cross-links
-
now the ferrule of the optical fiber is glued to the EIB backside (for better adhesion: it helps to roughen the area to be glued on the EIB with a sharp blade)
-
dip the electrode tips into a gold plating solution and use the NanoZ (Multi Channel Systems) to lower the impedance to around 150 kOhm
-
settings NanoZ: plating current: -0.015 microA, 1 s, 30 runs
-
check for cross-links that could occur due to over plating
-
measure the optical output through the microdrive implanted optical fiber to later estimate the in vivo used light intensity
the custom-head plate allows head-fixation and space for TetrODrive insertion
we milled the head plate out of an aluminum alloy plate
-
Parafilm as a protective layer allows an easy adaption of the implants spatial orientations
-
it is fast applied and taken off without any additional weight and increased size of a cap
-
a thin-layer is robust enough for wire and fiber protection
