In this protocol we demonstrate how to fabricate a micro-drive array for chronic electrophysiological recordings in rats.
At this point the drive array is ready to be loaded with tetrodes. Fabrication of tetrodes, how to load them into the micro-drives, and how to prepare the drive array for surgical implantation are the subjects of a subsequent video article.
Figure 1. Model of finished micro-drive array. A micro-drive array consists of several major components: a plastic drive base; a collector cannula from which the tetrodes enter the brain; 21 micro-drives that each drive a single tetrode; an electrode interface board that connects to pre-amplifiers.
Figure 2. Custom micro-drive screws. A. Technical drawings of the custom screw design. The screw features a threaded part (M1.2×0.25; 1.2 mm diameter, 0.25 mm / turn), a half-cylinder head that matches our custom made screw driver and a smooth part with lip (see detail). B. Model of complete micro-drive. The support tube and custom screw are connected with dental cement. The lip on the screw is embedded in the dental cement and allows for free rotation while driving the support tube up or down.
Additional Files
We designed the printed drive base, the protective cone and the mold for construction of the micro-drives in SolidWorks 2008 3D CAD software:
The 3D printing service bureau can not handle native Solidworks files directly, but rather requires the design files in stereolithography CAD format (STL). For people who do not have access to Solidworks software, but still would like to use the printed parts used in the video article we include the designs in STL format as well:
Fixes to these files, and additional models, are tracked on github.
This protocol describes the general features of the micro-drive building process. It has been successfully modified to produce drive arrays with multiple recording targets or smaller arrays for recordings in mice. In addition to recording from the hippocampus, many researchers use these drives to target cortical and sub-cortical structures. The use of longer screws may be required in order to record from deeper brain structures. With extensive modification to the drive base, motorized drives my be used in lieu of manually-turned ones, allowing more precise, remote tetrode adjustment (Yamamoto and Wilson, 2008). Customized stationary guide cannula arrangements have been used in place of the circular main cannula to achieve spatial control over the distribution of tetrodes in the cortex and hippocampus.
We would like to acknowledge Linus D. Sun and Jeenah Jung, who originated the use of computer-designed, 3-D printed drives in our lab for recording from mice. In addition, we would like to acknowledge all past and present Wilson Lab members for their contributions to micro-drive and tetrode technology development in the lab.
3D-printed plastic parts | Material | American Precision Prototyping (www.approto.com) | Parts are printed by stereolithography (SLA) using DSM 14120 ‘ABS-like’, DSM 11120 ‘Watershed’ or Accura 55 resins. Request high resolution, no sandblasting. | |
stainless steel tubing | Material | Small Parts (www.smallparts.com) | Cut to custom length and deburred. Sizes: 13 Ga (1pc @ 10 mm), 15 Ga (1pc @ 50 mm), 20 Ga thin wall (21pcs @ 5 mm), 23 Ga (21pcs @ 14 mm) | |
Dental cement powder | Material | A-M Systems (www.a-msystems.com) | 525000 | |
Dental cement solvent | Material | A-M Systems | 526000 | |
Electrode interface board | Material | Neuralynx (www.neuralynx.com) | EIB-81 | |
micro-drive screws | Material | Advanced Machining and Tooling (www.amtmfg.com) | Custom made screws with M1.2×0.25 threads (1.2mm major diameter; 0.25 mm thread pitch) | |
‘Tap-Ease’ tapping lubricant | Tool | AGS Company | TA-2 | Available from MSC Industrial Supply (www.mscdirect.com) |
Polyimide tubing | Material | IWG High Performance Conductors (www.iwghpc.com) | Sizes: 30 Ga (outer diam: 0.0071″, inner diam: 0.0116″) 5 mil (nominal outer diam: 0.0055″, wall: 0.0010″) | |
Cordless drill/driver | Tool | DeWalt (www.dewalt.com) | DC750KA | Any drill/driver with low-speed setting will do. |
Variable-Speed Rotary Tool Kit with Flex-Shaft | Tool | Dremel (www.dremel.com) | 3956-02 | |
Razor blades | Tool | VWR (www.vwr.com) | 55411-050 | |
Watch glass | Tool | VWR | 66112-107 | |
Tap for custom screws | Tool | Balax | 01302 | M1.2×0.25 Thredfloer thread-forming tap. Available from MSC Industrial Supply. |
Taps | Tool | Small Parts | HSBT-0172, HSBT-0080 | 1-72, 0-80 bottoming taps |
Pin vise | Tool | Vargus | 3SHC1–I | To hold taps. Available from MSC Industrial Supply |
Drill bits | Tool | Small Parts | Sizes: 65, 61, 1.55mm | |
Benchtop vise | Tool | Panavise | 301 | Available from DigiKey (www.digikey.com). |
No.2 Dumont forceps | Tool | Stoelting (www.stoeltingco.com) | 52100-27 | Used for inserting 20 Ga thin wall sleeves. |
5-minute epoxy | Tool | Allied Electronics (www.alliedelec.com) | ||
Accu-Tek Carbofib Tip Tweezers | Tool | Aven (www.aveninc.com) | 18768 (Pattern 304) | Used for handling polyimide tubing. |
Micro Dissecting Scissors | Tool | Biomedical Research Instruments (www.biomedinstr.com) | 25-1000 | Used for cutting polyimide carrier tubes |
Xcelite 378M Pliers | Tool | Newark | 96F8903 | Used for handling stainless steel tubing and for construction of custom screwdriver. |
mini pin vise | Tool | MSC Industrial Supply (www.mscdirect.com) | 00920314 | Used as a handle for custom made screwdriver. |