BOM: one exocortex v0 visual prototype
Prices are US retail as found in October 2026. Verified means the price was read on the listing itself. Unverified means it is an estimate, because the listing showed no price or was blocked. Check every unverified line before ordering. The contact stems are not a line item: they are printed as part of each SLA tile. No EEG electronics are included.
Quantities come from the design:
- 16 tiles × 64 = 1,024 contacts.
- 2 M2 screws + 2 inserts per tile.
- 3.4 cm³ of resin per tile (54 cm³ for 16, report.json), about 6 mL each with supports, plus coupons and wash losses.
- PETG: 207 g for the shell (band 102 cm³ + crown 61 cm³ + crown supports), plus the fixtures and placer (about 125 g).
(a) Consumed by the prototype
| part no. | item | qty | unit | vendor / listing | price | buy | consumed | status / note |
|---|---|---|---|---|---|---|---|---|
| EXO-201 ball | 3.0 mm solid brass ball, H62 | 1,200 | ea | uxcell 400-pack ×3 (Amazon) | ~$25 / 400 | $75.00 | $75.00 | unverified. Alternative: Boca Bearings grade 500, $73.02 / 1,000 (verified, but only 500 in stock, so 2 packs = $146). 1,024 + 8 % spares |
| EXO-2xx | ABS-like resin, 1 kg, dark grey / black | 1 | kg | Elegoo ABS-Like V2.0 | $31.99 | $31.99 | $8.00 | verified price; black not confirmed. About 0.25 kg used: 16 tiles × 8 mL + coupons + supports |
| EXO-100/101 | PETG 1.75 mm, black, 1 kg | 1 | kg | Overture PETG | ~$18 (Amazon) / $29.99 (Newegg) | $18.00 | $3.80 | Amazon price unverified, Newegg $29.99 verified. About 210 g for the shell (incl. supports); the fixtures come out of the same spool |
| EXO-120 | rib-knit cuffed beanie, black | 1 | ea | Carhartt A18 Acrylic Watch Hat | $8.99–19.99 | $8.99 | $8.99 | verified: Walmart $8.99, Gemplers $19.99 (closeout) |
| LIB-INS-M2x3 | M2 × 3 × Ø3.2 brass heat-set insert | 32 | ea | generic M2 × 3 × 3.2, 100-pack | ~$8 / 100 | $8.00 | $2.56 | unverified. Use M2 × 3: the boss hole is 3.0 deep with a 0.6 mm skin outside, so ruthex RX-M2x4 (4 mm) is too long |
| LIB-BHCS-M2x4 | M2 × 4 button head screw, black | 32 | ea | HH Fasteners M2 assortment (180 pcs) | ~$10 | $10.00 | $1.80 | unverified. M2 × 4: a 1.5 mm grip (carrier + foot) leaves 2.5 mm in a 3 mm insert. Check the assortment has button heads at 4 mm, or buy M2 × 4 ISO 7380 separately |
| EXO-130 | helmet retention dial (ratchet cradle) | 1 | ea | UltAlt retention dial, 2-pack | ~$12 / 2 | $12.00 | $6.00 | unverified. 50–62 cm. Its clips go into the two shell slots behind the ears |
| EXO-111/112 | helmet pad kit with hook-and-loop dots | 1 | set | OutdoorMaster universal pad kit | ~$10 | $10.00 | $10.00 | unverified. Crown pads cut to the layout's pad Ø; headband strips along the rim |
| EXO-121 | woven label "exocortex" | 1 | order | Dutch Label Shop custom woven labels | ~$20 / order (min 5) | $20.00 | $20.00 | unverified (the currency on the page may not be USD). 10–14 days to produce: the longest lead item, order on day 1 |
| CON-EPX | 2-part 5-minute epoxy | 1 | ea | any hardware-store epoxy | ~$6 | $6.00 | $2.00 | unverified. Band/crown lap joint, luer adapter seal. The cups' reinforcing wick uses the tile resin itself |
| CON-GLD | metallic gold paint marker | 1 | ea | Molotow ONE4ALL metallic gold | ~$7 | $7.00 | $1.00 | unverified. Touch-up only |
| CON-PRM | flat black spray primer (optional) | 1 | ea | Rust-Oleum Painter's Touch 2X Flat Black 249846, 12 oz | $7.99 | $7.99 | $2.00 | verified. Scuff-sand first. Only if the shell's print lines show through the knit |
| total (a) | $214.97 | $141.15 |
Against the $100–150 target: the materials the prototype actually uses come to about $141, inside the target. The cash outlay is about $215, because resin, filament, inserts and screws come in packs. The brass balls are 53 % of the consumed cost.
The cheaper ball would be gold-coloured solid ABS (about $8 per 1,000 if a no-hole 3 mm pack can be found). That would bring the consumed total to about $75 and cut 110 g of mass. However, nothing verified matched: the 3 mm gold listings found were beads with holes. Brass also keeps the conductive path to v1.
(b) Placer tooling (one-time; reused for every helmet)
| part no. | item | qty | unit | vendor / listing | price | buy | status / note |
|---|---|---|---|---|---|---|---|
| PNP-LM4 | LM4UU linear bushing | 2 | ea | eBay 10-pack | $16.99 / 10 | $16.99 | verified |
| PNP-SH4 | Ø4 chromed shaft, 300 mm (cut into 2 × 93) | 1 | ea | VXB 4 × 300 mm linear shaft | ~$10 | $10.00 | unverified. A 150 mm length (PBC NIM04SS-0150) is too short for two shafts |
| PNP-SPR | compression spring, OD 6 × 0.5 wire × 25 free, stainless | 2 | ea | Amazon 304 springs, 5-pack | ~$7 | $7.00 | unverified. Buy OD 6, not OD 5: an OD 5 × 0.5 spring has a 4.0 ID and binds on the Ø4 shaft. Measure the rate (target 0.55 N/mm each) |
| PNP-PMP | 12 V diaphragm vacuum pump, > 350 mmHg | 1 | ea | SparkFun ROB-10398 | $25.50 | $25.50 | verified, in stock. About 47 kPa, enough (0.05 N grip). BODENFLO BD-05T033B (−55 kPa) costs $105 and isn't needed |
| PNP-PSU | 12 V 2 A adapter, 5.5 × 2.1 centre positive | 1 | ea | Parts Express 120-078 | $7.98 | $7.98 | verified |
| PNP-LUR | female luer lock × 1/8 in barb | 2 | ea | Chromtech P-859 | $1.05 | $2.10 | verified per piece. Check for a minimum order or shipping charge |
| PNP-NDL | blunt luer-lock needles, assortment incl. 16 G and 18 G | 1 | kit | McMaster-Carr needle assortment (12) | ~$15 | $15.00 | unverified. 16 G (OD 1.65 / ID 1.19) is the design size. The 1 in length works but shortens the Z reach by 12.7 mm, so the 1/2 in is preferred |
| PNP-HOS | silicone tube 3 × 5 mm | 2 | m | Newegg Business 9B-2ZU-0074-00300 | $6.85 | $6.85 | verified |
| PNP-FLT | inline filter (aquarium air-line type) | 1 | ea | generic | ~$5 | $5.00 | unverified. Keeps resin dust and debris out of the pump. Vacuforce VFD0204 ($32.20) needs 4 mm push-in fittings |
| PNP-SW | KW10 hinge-lever microswitch | 1 | ea (10-pack) | Amazon 10-pack | ~$8 | $8.00 | unverified. Omron D2F-01L is about $1.33 each at TME. Wire C + NO to the probe header |
| PNP-DWL | Ø2 × 8 dowel pin (fixture A/B) | 2 | ea | McMaster-Carr ISO 2338 2m6 × 8 | ~$6 / pack | $6.00 | unverified |
| PNP-210 | 3 mm black acrylic, 12 × 12 in | 1 | sheet | J Tech Photonics 1/8 in black acrylic | $16.99 | $16.99 | verified (sale). The tray needs 173.5 × 146.5. Cast or extruded isn't stated; both cut on a diode laser if opaque |
| EXO-310 | PETG sheet 0.040 in (1.0 mm), 8 × 12 in, 5-pack | 1 | pack | Walmart 207926167 | $5.89 | $5.89 | verified. Clear only, for the thermoforming study coupons |
| total (b) | $133.30 |
Small hardware from stock: 2 × M3 × 4 set screws, 2 × M2 × 8 for the switch, 2-core 26 AWG lead with a 2.54 mm housing for the probe header.
(c) Already on hand (not purchased)
| item | used for |
|---|---|
| Ender-3 V3 SE printers | shell (EXO-100/101), placer (PNP-100…102), fixture (PNP-200), tray base (PNP-211) |
| SLA printer + wash/cure station, IPA, nitrile gloves | tiles EXO-201…216, coupons EXO-300/301/311 |
| 3018 CNC (GRBL 1.1 board with a probe header) | placer; spindle kept for milling the MDF forming mould EXO-320 |
| diode laser engraver | PNP-210 tray (black acrylic only) |
| soldering iron with heat-set tip | M2 inserts |
| hex keys 1.3 / 1.5 / 2.5, M3 tap, cut-off wheel, sandpaper, kitchen scale, luggage scale, calipers | assembly, calibration, pull-out tests |
| scrap MDF | EXO-320 forming mould (research only) |
Future: electrically functional prototypes (estimates, not quotes)
Architecture: one 64-channel AFE on a small rigid "tile pod" per tile (electronics-roadmap.md).
| item | per 64-ch tile | ×16 (1,024 ch) | note |
|---|---|---|---|
| AFE, option 1: Intan RHD2164 (64 ch, BGA) | $534 | $8,544 | verified price, but listed out of stock indefinitely. Bare die ($479) needs wire bonding. Supply risk: check before designing around it |
| AFE, option 2: 8 × TI ADS1299 (8 ch, 64-TQFP) | $577 (qty 1) | $6,838 (128 × $53.42 at qty 100) | Digi-Key, from an undated cached copy; verify. Large: 8 chips per tile |
| kirigami / comb FPC, 2-layer polyimide (prototype run of 5) | $20–60 | $300–700 | unverified, typical JLCPCB/PCBWay flex pricing |
| 2 × ZIF 40-way 0.5 mm, Hirose FH12-40S-0.5SH(55) | $1.70–3.00 | $27–48 | LCSC $0.86 (verified); Digi-Key about $1.50 (estimate, 12-week lead time in cache) |
| tile pod PCB, 4-layer + assembly | $50–150 | $400–1,200 | unverified |
| 64 spring contact pins (gold-plated pogo, P50/P75 class) | $6–32 | $100–500 | unverified |
| electrode surface: gold plating of brass balls (batch), or Ag/AgCl sintered tips | $50–320 | $150–1,500 | unverified. Ag/AgCl pellets about $2–5 each |
| hub: MCU + digital isolation + battery + charger | $30–60 | $60–150 | unverified |
| acquisition controller | (pod → MCU over SPI) | Intan C3008 1,024-ch recording controller: quote only | or an open-source hub (e.g. an Open Ephys–class board) |
| total | ≈ $750–1,300 | ≈ $9,000–13,000 (+ controller if C3008) | parts only, excluding NRE, test and certification |
A single 64-channel functional tile is the right next step. It proves contact mechanics, noise and the interconnect at under about $1.3k. Scaling to 1,024 channels costs as much as the AFE silicon, about $7–9k of chips.