Building An Open-source Robotic Stereotaxic Instrument

Summary

This protocol includes the designs and software necessary to upgrade an existing stereotaxic instrument to a robotic (computer numeric controlled; CNC) stereotaxic instrument for around $1,000 (excluding a drill).

Abstract

This protocol includes the designs and software necessary to upgrade an existing stereotaxic instrument to a robotic (CNC) stereotaxic instrument for around $1,000 (excluding a drill), using industry standard stepper motors and CNC controlling software. Each axis has variable speed control and may be operated simultaneously or independently. The robot's flexibility and open coding system (g-code) make it capable of performing custom tasks that are not supported by commercial systems. Its applications include, but are not limited to, drilling holes, sharp edge craniotomies, skull thinning, and lowering electrodes or cannula. In order to expedite the writing of g-coding for simple surgeries, we have developed custom scripts that allow individuals to design a surgery with no knowledge of programming. However, for users to get the most out of the motorized stereotax, it would be beneficial to be knowledgeable in mathematical programming and G-Coding (simple programming for CNC machining).

The recommended drill speed is greater than 40,000 rpm. The stepper motor resolution is 1.8°/Step, geared to 0.346°/Step. A standard stereotax has a resolution of 2.88 μm/step. The maximum recommended cutting speed is 500 μm/sec. The maximum recommended jogging speed is 3,500 μm/sec. The maximum recommended drill bit size is HP 2.

Introduction

Stereotactic rodent surgery is used in a wide variety of neuroscience applications, including lesioning¹, iontophoresis², microwire implantation³, stimulation⁴, and thin skull imaging⁵. However, there are major hurdles facing those who wish to apply these techniques, including the steep learning curve for performing accurate stereotactic surgery and the high probability of human error. Human errors include measurement and calculation failures, as well as the low accuracy and replicability of human movements. In an effort to reduce these confounding errors, stereotactic surgeons would benefit from a system that ens....

Protocol

1. Wire the bipolar stepper motors by screwing the wires into the connectors supplied with the driver board. Wire colors on bipolar stepper motors are standardized (Figure 1).
   Note: The described stepper motors have a resolution of 1.8°/step, geared to 0.346°/step. A standard stereotax has 3 mm/360° of travel. The final resolution is 2.88 μm/step. The motors are also capable of fractional stepping.
   1. Connect the green wire to A+, connect the black wire to A-, connect the red wire to B+ and connect the blue wire to B-.
2. Slide the couplers over the stepper motors, being careful to align the mounting holes, and ....

Results

The end result of the surgery designed in the methods will be a rat skull with a sharp edge craniotomy, and 3 skull holes (Figure 17). Note that the skull used to demonstrate the surgery was much wider than the prototypical rat skull. The sharp edge craniotomy may be used to insert a microwire array into the brain, for high density neural recordings. The CNC stereotax may also be used to lower the array with great precision. Software is included in this protocol that allows the surgeon to define the para.......

Discussion

The use of automated surgery equipment helps to eliminate some of the most common problems in neuroscience research. First, the tool paths are 100% reproducible. Every cut is guaranteed to be in the same location relative to Bregma. Second, it should reduce experimenter error. Although many researchers are highly skilled surgeons, it takes an exceptional amount of practice to become even a competent surgeon. This device will allow new students to quickly and easily perform highly accurate surgeries. Third, motorized surg.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
1x Standard U Frame Stereotax	Kopf	Kopf	This protocol should work with most existing stereotaxic devices.
3x 12 V, 1.6 A, 233 oz-inch Geared Bipolar Stepper Motor	Phidgets	Robot Shop	Any high torque geared stepper motor should do.
1x 3 Axis CNC Stepper Motor Driver Board Controller	Toshiba	Ebay	Any 3 Axis CNC driver should do. Linked Item includes Mach3 CNC software.
2x Arm Couplers: medial-lateral (ML) & dorsal-ventral (DV)	custom machined	Part Drawings	These must be machined by your local machine shop. (costs will vary)
1x anterior-posterior (AP) Coupler	custom machined	Part Drawings	These must be machined by your local machine shop. (costs will vary)
3x Motor to Stereotax Collar	custom machined	Part Drawings	These must be machined by your local machine shop. (costs will vary)
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12x NF10-32 Cup Point Set Screws	McMaster Carr	½” Length	You will need 6 of each.
¼” Length
12x M3 Socket Head Screws (20 mm)	McMaster Carr	20mm Length	You will need 4 for each motor
1x Micro-Motor Drill	Buffalo Dental	X50	Any Micromotor drill will work.  At least 38,000 rpm recommended
1x 12 V DC Power Supply	12 Volt Adapters	12v DC – 7 Amp	Any 12 V DC PSU should work (ensure amperage rating is higher than the sum of the motors’ amperage).
1x Extra Large Probe Holder	Stoelting	Stoelting
1x Grade B Rat Skull	Skulls Unlimited	Skulls Unlimited
Mach 3 Mill	ArtSoft USA	Trial Download	Any Standard CNC controlling software should work.
Surgery Designer	Kevin Coffey David Barker	MATLAB File Exchange	These codes are available to modify. We accept no responsibility for your use or modification of code.