PrimaThrone¶

PrimaThrone is an open-source testing chair design for use in neurobehavioural research with non-human primates (NHPs).

Motivation¶

Neuroscientific research in NHPs requires a range of esoteric products, that manufacturers are able to charge exorbitant prices for. The NHP testing ‘chair’ is one such item, with each unit typically costing around $14,000, while the cost of the materials is less than $1,000.

Typical NHP chair designs (McMillan, Bloomsmith & Prescott, 2017) consist of two main parts: a box structure that the animal can climb into and sit in with only the head exposed, and a base structure that is used to elevate the box and is typically on lockable casters for transportation. The main constraints on the materials and construction of NHP chairs is that they need to be able to safely and comfortably contain an adult NHP, while also withstanding the high temperature and pressure of facility cage wash systems. However, they also need to be light enough to move around fairly easily and designed with ease of use and the safety of researchers in mind. NHP chairs for use in MRI scanners places additional constraints on material choices and dimensions, which this design is not intended for.

Commercial options¶

If your lab has the money, it’s always nice to buy ready-made solutions so that you can focus on science instead of engineering! The table to the right lists some commercial options for typical NHP behavioural testing chairs.

Manufacturer	Design	Material	Cost
Crist Instruments	Enclosed	Polycarbonate	$14,000
Rogue Research	Enclosed	Polycarbonate	$14,000
Plas-Labs	Shelf	Polycarbonate
GreyMatter Research	Enclosed	Polycarbonate	$9,000
Primate Products	Open
UniFab	Open	Stainless steel
Applied Prototypes	Enclosed	Polycarbonate

Materials¶

Polycarbonate

Polycarbonate (e.g. ‘Lexan’) is a popular choice of panel material for constructing the box section of NHP chairs, since it is available in a clear format that allows researchers visual access to the animal once seated in the chair. Polycarbonate panels are inexpensive and can be cut to custom shapes using a water-jet cutter (although they cannot be laser cut). The downside of polycarbonate is that it becomes brittle through repeated exposures to high-temperature cage wash systems, which combined with the mechanical forces applied to it will eventually result in cracks, especially around screw holes. The use of nylon or other non-metal screws and hardware, and larger through-holes (rather than tapped holes) can ameliorate this problem.

Aluminium

A more durable alternative to polycarbonate is aluminium, with the obvious trade-off that you won’t be able to see through it. Using a marine-grade aluminium alloy like 5052 for the side panels of the chair box will improve the chair’s structural stability and chemical resistance, while vent holes cut in these panels can give some visibility and improve air flow.

T-slot profile

Extruded aluminium ‘t-slot’ profile is a simple and cost effective means of constructing the chair base. Many companies offering NHP chairs commercially will use t-slot, although this construction method is less durable than a welded frame, and may require re-tightening over time. A benefit of t-slot profile is that it is easy to attach additional components to the chair, such as guides to help position the chair in a stable and reproducible manner in the testing rig.

Hardware

In addition to the t-slot hardware and locking casters needed for the base, a hinge and latches are needed for the rear door, handles for moving the chair around, corner brackets for attaching the panels to each other, and a removable waste pan.

Bill of materials

Product ID	Vendor	Material	Description	Quantity	Cost each ($)	Cost sum	Part
	TAP plastics	Polycarbonate	Sheet, 3/8”, 12 x 21”	1	$33.12	$33.12	Front panel
	TAP plastics	Polycarbonate	Polycarbonate sheet, 3/8”, 12 x 26”	1	$12	$12.00	Rear door
	TAP plastics	Polycarbonate	Polycarbonate sheet, 3/8”, 12 x 8”	1	$12	$12.00	Rear panel
	TAP plastics	Polycarbonate	Polycarbonate sheet, 3/8”, 12 x 26”	1	$12	$12.00	Neck plate A
	TAP plastics	Polycarbonate	Polycarbonate sheet, 3/8”, 12 x 26”	1	$12	$12.00	Neck plate B
	TAP plastics	Polycarbonate	Polycarbonate sheet, 3/8”, 12 x 26”	1	$12	$12.00	Neck plate C
	Midwest Steel	Aluminium 5052	Aluminium 5052 sheet, 3/8”, 16 x 16”	1	$37.24	$37.24	Base panel
	Midwest Steel	Aluminium 5052	Aluminium 5052 sheet, 3/8”, 11 x 26”	2	$48.70	$97.40	Side panels
	Midwest Steel	Aluminium 5052	Aluminium 5052 sheet, 3/8”, 12 x 10”	1	$21.95	$21.95	Seat
1605A77	McMaster-Carr	Stainless steel (316)	Piano hinge, 2” wide, 3ft long	1	$40.38	$40.38	Rear door
1794A55	McMaster-Carr	Stainless steel (304)	Tight-hold draw latches	2	$11.18	$22.36	Rear door
1726A92	McMaster-Carr	Stainless steel (316)	Stainless Steel, 5” pull handles	2	$10.06	$20.12	Handles
91185A819	McMaster-Carr	18-8 Stainless steel	Plastic grip thumb screws	5	1.75	$8.75	Seat adjustment
	McMaster-Carr		Bolts			$0.00
	McMaster-Carr	Aluminium 5086	5086 Aluminum 2x2” corner bracket, 11” long	2	$28.73	$57.46	base brackets
	McMaster-Carr	Aluminium 5086	5086 Aluminum 1x1” corner bracket, 14” long	2	$18.41	$36.82	front brackets
	McMaster-Carr	Aluminium 5086	5086 Aluminum 1x1” corner bracket, 14” long	2	$18.41	$36.82	top brackets
23085T24	McMaster-Carr	Rubber + Steel	5” square stem casters	2	$24.25	$48.50	Wheels
23085T34	McMaster-Carr	Rubber + Steel	5” square stem casters with brakes	2	$35.86	$71.72	Wheels
98164A209	McMaster-Carr	Stainless steel	1/4”-20 bolts, 3/8”	80		$0.00	Fasteners
	8020	Anodized aluminium	1010: t-slot profile, 14.5”	4	$5.29	$21.16	Frame struts
	8020	Anodized aluminium	1010: t-slot profile, 16” long	4	$5.63	$22.52	Frame struts
	8020	Anodized aluminium	1010: t-slot profile, 15.5” long	4	$5.51	$22.04	Frame struts
	8020	Anodized aluminium	4119: 2-hole inside corner bracket	8	$2.90	$23.20	Fasteners
	8020	Anodized aluminium	4151: 5-hole corner plate	8	$6.30	$50.40	Fasteners
	8020	Anodized aluminium	10 series t-slot nuts	80	$0.21	$16.80	Fasteners
					TOTAL =	$731.96

Custom Parts¶

The design files for cutting the panels out of your selected material (e.g. plate aluminum and/or polycarbonate) are provided via the links below.

GrabCAD Download

PrimaThrone MRI¶

A horizontal training chair was designed as a low-cost, easy to assemble solution to allow researchers to train animals for awake fMRI outside of the scanner environment. The outer dimensions and shape of the box are similar to those of commercial horizontal fMRI chairs, but the use of commercially available extruded aluminium profile frame and off-the-shelf hardware greatly simplifies assembly, lowers cost, and speeds up construction. The panels are 3/8” polycarbonate, which can be custom cut to the required shapes (including bevel and mitre cuts) by vendors listed or possibly by your institution’s machine shop (water jet cutting is recommended). The only additional custom machining required is the drilling of through-holes in the polycarbonate.

The chair design includes the following features:

Safety
- sliding neck plate on the front panel
- rear drop-down door with latches for locking in both open and shut positions
- drop-down door will not fully close without user intervention (no trapped tails!)
Adjustability
- floor insert and drip tray, adjustable to multiple different heights
- adjustable headpost crossbar with lever locks
- optional response lever attachments to front panel
Ease of use
- handles on the top of the chair frame for ease of lifting
- removable drip tray is easy to empty

The following bill of materials provides suggested vendors for purchasing the aluminium extrusion and hardware parts. Custom cut polycarbonate is available from various vendors suggested here:

Bill of materials

Vendor	Part #	Description	Function	Qty	Price	Total
McMaster	47065T244	10 series, 3-way corner	Rear panel corners	4	$10.65	$42.60
McMaster	3136N42	T-slot plastic pull handles	Top handles	4	$13.98	$55.92
McMaster	47065T959	Flanged bearing	Headpost slide	2	$46.16	$92.32
McMaster	47065T771	Bearing pads	Headpost slide	6	$2.14	$12.84
McMaster	60585K31	Bearing brake	Headpost slide	2	$10.77	$21.54
McMaster	47065T239	2” corner bracket	Rear door corners	4	$5.25	$21.00
McMaster	93650A145	1/4” polyurethane washers	Washers for bolts	4	$8.82	$35.28
McMaster	3136N22	2” end cap	Headpost end cap	2	$1.50	$3.00
McMaster	3136N2	1” end cap	Headpost end cap	2	$1.20	$2.40
McMaster	98164A211	316 SS 1/4”-20 screws, 1/2” long		10	$0.33	$3.30
McMaster	91735A546	316 SS 1/4”-20 screws, 1.5” long		12	$0.59	$7.08
McMaster	92185A540	316 SS 1/4”-20 screws, 3/4” long		4	$0.31	$1.24
McMaster	3136N147	T-slot rubber bumpers		8	$3.29	$26.32
8020	14011	Inline pivot	Front panel corners	4	$17.75	$3.00
8020	4136	2” gusseted corner	Rear to top connection	2	$5.65	$3.00
8020	2107	Deadbolt latch	Rear door latch	2	$18.90	$37.80
8020	1030-S	1 x 3” profile, 20”	Tray rails	2	$12.95	$25.90
8020	1002-S	1x1” smooth, 12”	Rear door top	2		$0.00
8020	1020	1x2” profile, 14”	Headpost slide	1	$7.41	$7.41
8020	1010	1x1” profile, 12”	Rear door verticals	2		$0.00
8020	1003-S	1x1” profile, 10”	Read door top	1	$4.25	$4.25
8020	1002-S	1x1” smooth, 10”	Rear door bottom	1	$4.25	$4.25
8020	2059	Slide bearing pad	Rear door slide	4	$6.05	$24.20
8020	1010	1x1” profile, 15”	Rear vertical	2	$5.40	$10.80
8020	1010	1x1” profile, 10”	Rear horizontal	2	$4.25	$8.50
Mid West Steel	1/4” 5052 aluminium	12.75 x 28”	Bottom panel	1	$43.49	$43.49
Mid West Steel	3/8” 5052 aluminium	10 x 26”	Insert tray	1	$46.52	$46.52
Tap Plastics	3/8” polycarbonate	12 x 26”	Side panels	2	$32.39	$64.78
Tap Plastics	3/8” polycarbonate	12 x 10”	Rear door	1	$12.46	$12.46
Tap Plastics	3/8” polycarbonate	12.75 x 24”	Top panel	1	$32.29	$32.29
Tap Plastics	3/8” polycarbonate	12 x	Neck plate A	1		$0.00
Tap Plastics	3/8” polycarbonate	10 x	Neck plate B	1		$0.00
Grainger	11K114	9 x 26” display pan	Drip tray	1	$23.66	$23.66
					TOTAL =	$677.15

In order to make this design MRI-compatible, it is recommended to use fiberglass structural profile in the place of the aluminium. Since fiberglass profile is not readily available with T-slots, all screw holes would need to be drilled and tapped. However, this is a feasible approach to constructing a MRI-compatible chair with greater strength and rigidity than chairs where the polycarbonate panels are directly bolted or glued together.

Trolley for horizontal chairs¶

Trolleys for transporting horizontal NHP chairs between the animal’s home room and the lab can be constructed from commercially available aluminum t-slot profile and non-magnetic parts (for use in the MRI magnet room). These carts can therefore be safely wheeled into an MRI scanner room and locked in place next to the patient bed in order to minimize the distance when transferring animals for MRI studies. This trolley design positions the chair door at the correct height for transferring animals directly into the chair from the bottom row of an Allentown quad home cage, but can be easily modified to suit other caging systems by simply changing the height and base width (to maintain stability) of the aluminum profile.

The table below lists the components used for construction of a trolleys. However, before ordering it should be noted that assembly involves the following additional steps:

Tapping

All T-slot aluminium profile pieces need both end holes tapped with 1/4”-20 threads (except for the 2x1 profile). This optional service can be requested from vendors like 8020 at an extra cost and slight additional delay to shipping. Alternatively, this can be done by hand using the appropriate tap, wrench, and lubricant.

Drilling

The 4 x 27” long T-slot profile pieces need to have 1/4” through holes drilled through them as indicated by the red lines in the design file below. A T-slot drill jig can be purchased from McMaster-Carr for use with a hand drill, but a drill press is recommended for this. A tip is to use the 2x2” t-slot plates to clamp pairs of t-slot profile together and drill 2 at a time in order to ensure good alignment of through holes.

Waterjet

The rear plate is waterjet cut from 0.25” thick 5052 plate aluminium (for marine-grade corrosion resistance). This can usually be done by your institutional machine shop, or outsourced to a commercial shop like Xometry for faster turnaround. The digital template file (.DXF) for this part can be downloaded here.

GrabCAD Download

These customizations can alternatively be requested at the time of order from companies such such as 8020 (although this will add to the shipping time).

Bill of materials

Vendor	Part #	Description	Qty	Price	Total
8020	4176	10 Series 3 Hole - Inside Corner Bracket	2	$3.85	$7.70
8020	4167	10 Series 4 Hole - Square Flat Plate	6	$4.80	$28.80
8020	4123	10 Series 6 Hole - Tee Flat Plate	2	$7.30	$14.60
8020	1003S	10 series, 1x1 - 10.75” long	11	$2.47	$27.17
8020	1010	10 series, 1x1 - 12.75” long	6	$2.93	$17.58
8020	1010	10 series, 1x1 - 27” long	2	$5.06	$10.12
8020	1003S	10 series, 1x1 - 27” long	2	$7.01	$14.02
8020	1020	10 series, 2x1 - 26” long	2	$7.93	$15.86
8020	1010	10 series, 1x1 - 26” long	2	$5.85	$11.70
8020	2570	10 series, 45 deg support, 12”	2	$15.35	$30.70
8020	4134	10 series, 4 hole wide gusseted corner	2	$5.65	$11.30
8020	4136	10 series, 4 hole tall gusseted corner	2	$5.65	$11.30
8020	4132	10 series, 2 hole gusseted corner	4	$3.95	$15.80
8020	2570	1010 45 degree support, 12”	2	$15.35	$30.70
8020	4132	10 series, 1x1 bracket	2	$3.95	$7.90
8020	3675	1/4”-20 T-slot nuts, 18-8 stainless	60	$0.61	$36.60
MedCaster	NM-05QD0-125-TL-TPS1	Non-magnetic locking 5” casters	4	$41.00	$164.00
McMaster	47065T244	10 series, 3-way corner	8	$10.65	$85.20
McMaster	98164A211	316 Stainless Steel 1/4”-20 screws, 1/2” long	24	$0.33	$7.92
McMaster	91735A546	316 Stainless Steel 1/4”-20 screws, 1.5” long	10	$0.59	$5.90
McMaster	92185A540	316 Stainless Steel 1/4”-20 screws, 3/4” long	10	$0.31	$3.10
McMaster	90107A029	316 Stainless Steel 1/4” washers	100	$7.11	$7.11
McMaster	47065T362	Anti-slip T-slot insert, 6’	1	$16.68	$16.68
McMaster	3136N42	T-slot plastic pull handles	2	$13.98	$27.96
McMaster	3136N147	T-slot rubber bumpers	4	$3.29	$13.16
McMaster	3136N22	T-slot 2 x 1” end caps	2	$1.50	$3.00
McMaster	47065T242	10 series, 2-way corner	2	$7.38	$14.76
McMaster	3618T13	316 Stainless Steel chain, 1/8, 1ft	1	$5.97	$5.97
McMaster	6043T12	S-biner, stainless	4	$1.67	$6.68
Xometry	5052 Aluminum	Waterjet cut 15 x 24”, 1/4” thick	1	$163.88	$163.88
				TOTAL =	$817.17

Note that the most expensive components are the non-magnetic casters. An cheaper option could be to purchase an alternative caster (such as the regular version of the same MedCaster nylon 5” locking casters: NG-05QDP125-TL-TP01), and transfer the NHP chair from the transport trolley to an MR-compatible trolley before entering the magnet room if needed.