V4 tactile cost reduction: PVDF, pressure cells, and harness

Checked: 2026-10-23 Scope: one right-hand V4 glove; 20 independent PVDF vibration channels at 4 kHz/channel and 20 independent pressure locations at 50 Hz/channel. Purpose: identify a commercially sourceable, lower-cost construction while preserving the existing six keyed GH branch interfaces and 20+20 channel contract. Purchase status: research only; no purchase, supplier outreach, or canonical hardware change.

Decision

The closest low-risk alternate is a 28 µm poled PVDF sheet with screen-printed silver ink from PolyK, selected as the 200 × 135 mm variant of SKU PVDF-Ag-120u-A. The product page lists 28 µm film, 5 µm silver ink, d31 >25 pC/N, d33 >20 pC/N, and compatibility with TE 1-1004347-0; it displays $180 before the stated $30 international UPS charge. The exact thickness/size variant price, current stock, VAT, and Bulgaria landed cost need a cart or quote check. The electrical and attachment construction remains the same class as the current TE sheet, so this is the first alternate to coupon. The displayed amount is the full sheet purchase cash outlay; unused area is not treated as free material or a per-glove saving.

TE/MEAS LDT0-028K (1002794-0, distributor alias 11028362-00) is rejected as a same-capability cost win pending fit. HESTORE lists €5.660 each at quantity 20, or €113.20 for 20, with more than 10 in stock and more than 2,000 on a 10–15 working-day route. The part retains 28 µm PVDF and screen-printed silver electrodes but changes the mechanical stack to a 125 µm polyester substrate plus protective coating, a 13 × 25 mm film outline, approximately 205 µm total thickness, and 0.5 nF typical capacitance. It is a coupon-only fallback. Its theoretical €70.99 difference against the observed €184.19 TE sheet is excluded from the released-glove savings target because the 13 × 25 mm / 205 µm construction is not the current 10 × 14 mm bare-film / 40 µm design class.

The LDT candidate is a process-saving pilot, not an assumed drop-in. The current V3/V4 cell calls for a 10 × 14 mm bare-film blank, a 40 µm finished TE silver-ink sheet, staggered opposite-face tab joints, and a pressure stack beneath the PVDF. The LDT part has a 125 µm polyester carrier, larger outline, fixed contacts, and a different bending boundary condition. Its candidate cell is roughly 165 µm thicker than the current 40 µm sheet. Preserve all 20 channels only after footprint fit, comfort, pressure/PVDF cross-talk, 4 kHz response, polarity, continuity, and flex endurance pass on the actual glove; until then, count no LDT saving.

There is no manufacturer-verified evidence in this bounded search for a three-times cheaper, same-construction PVDF sheet. The useful low-risk cash-outlay candidate is the lead wire: Adafruit sells 30 AWG stranded silicone wire in 2 m pieces and 50 ft spools with 0.8 mm OD, inside the JST GH contact window. Quote six pre-terminated GH branch harnesses and a 20-cell cut/lead-prep service as the remaining route to a complete-device reduction. Keep the GH connector pin map unchanged.

Current area and cost baseline

The local V3 starting files carried into V4 define 20 PVDF blanks at 10 × 14 mm, for 2,800 mm² of film. TE 1-1004347-0 is an 8 × 5.5 in (203 × 140 mm) sheet, with 28 µm PVDF and 40 µm finished thickness for the silver-ink version. Gross sheet utilization is therefore 9.85%; using the 190 × 127 mm silver-electrode area gives 11.60%. The geometry is area-inefficient because the purchase is a general-purpose sheet, not because the 20 locations need a large electrical active area. A 200 × 135 mm sheet has 27,000 mm² gross area and raises ideal utilization only to 10.37%; area alone cannot produce a 3× saving.

The retained procurement observation is €184.19 per TE sheet, with stock and price captured 2026-10-22 and current stock unresolved. TE’s current product page identifies the matching product family as 1-1004347-0-M / internal 11027667-00, “28UM AG INK FILM 8 X 5.5”, and currently directs buyers to distributor inventory. Farnell’s current listing showed 12 pieces, a 43-week manufacturer lead-time field, and €264.89 ex VAT at quantity one; its quantity-50 price was €184.36 ex VAT. Treat both as live observations with distributor and date risk, not as a stable contract price. Every sheet price is a full purchase cash outlay; the 2,800 mm² allocated blank area is a planning measure, not a material saving.

Candidate comparison

Pressure media and electrodes

Adafruit 1361 is a 280 × 280 mm, 0.1 mm, pressure-sensitive conductive sheet listed at $4.95 (quantity 10–99 $4.46, 100+ $3.96). The page currently reports out of stock. It gives <500 Ω·cm volume resistivity and <31,000 Ω/sq surface resistivity, but the product is a hobby material with batch and hysteresis variation. One sheet has ample area for 20 separate 8 × 10 mm islands; qualify resistance-versus-force on the selected batch before production. For one glove, the cash outlay is the full purchased sheet unless a supplier quotes cut pieces from its stock.

Adafruit 1168 is a 200 × 200 mm woven copper/nickel-plated polyester fabric, listed at $4.95 and currently shown in stock. The product description gives less than 1 Ω/ft in any direction. One sheet has ample area for 40 separate 8 × 10 mm pressure electrodes (3,200 mm² total, 8% ideal area use). This is the most economical exact electrode source found; retain perimeter-only bonding and batch continuity checks. The $4.95 is the one-glove purchase cash outlay; area allocation is not a saving.

Adafruit 1167 silver-plated knit fabric is listed at $9.95 for 200 × 200 mm and less than 1 Ω/ft, but the current Adafruit page reports out of stock. It is a viable comfort/elasticity comparison coupon and is not required for the first cost build.

Leads, attachment, harness, and labor

Alpha Wire 5851 BK005 remains a technically appropriate lead source: 30 AWG, 7/38 stranded silver-plated copper, PTFE, 100 ft (30.48 m), 600 V, 200 °C maximum. Mouser currently lists $143.30 per 100 ft spool with 7 in stock and a 12-week factory lead-time field for larger replenishment; DigiKey lists the same electrical construction and $166.10. A 100 mm average lead length for 80 cell leads consumes 8.0 m and allocates about $37.61 of the Mouser spool; 150 mm consumes 12.0 m and allocates about $56.42. Measure the actual route before choosing a cut length. For a one-glove purchase, the cash outlay is the full $143.30 spool. The 8–12 m figures are allocation planning only and are not savings.

Adafruit 2051 is a lower-cost same-interface candidate for a few-meter build: the manufacturer page lists 30 AWG stranded silicone wire, 2 m length, 0.8 mm outside diameter, 331 Ω/km resistance, -60 to 200 °C, and nominal 600 V at $0.75 per piece (quantity breaks $0.68 at 10–99 and $0.60 at 100+). Adafruit also lists 50 ft versions such as 3164 at $4.95. JST’s official GH contact specification for SSHL-002T-P0.2 accepts AWG 30–26 and insulation OD 0.76–1.0 mm, so 30 AWG / 0.8 mm is inside the specified crimp window. The fetched Adafruit page does not publish conductor metal or strand count, so qualification must include crimp bellmouth/strain-relief inspection, pull force, bend cycling at the GH exit, continuity/isolation, and the existing pin-map check. Six 2 m color pieces would provide 12 m for $4.50 at unit pricing if the selected colors are available; a pair of 50 ft spools would be $9.90. Against the full $143.30 Alpha spool cash outlay, those purchases reduce the material cash outlay by $138.80 or $133.40 respectively before freight/VAT. Charge the full purchased pieces/spools to the one-glove build.

MG Chemicals 8331D-14G is a 1:1 silver conductive epoxy with room-temperature cure. Current distributor observations range from about $130.37 to $210.55 per 14 g syringe, with stock and export restrictions varying. Forty controlled tab dots use a small fraction of a syringe; for a one-glove purchase, the cash outlay is the full syringe unless the assembler quotes use from its stock. Dot mass is a separate allocation metric, not a saving. A mechanical crimp/fold attachment is a documented alternative for metallized PVdF and can remove the 40-dot dispense/cure operation, but it needs a tab fixture, pull test, flex test, and contamination/short inspection before adoption.

The current factory scope asks for six keyed tactile harnesses, 20 PVDF lead-prep subassemblies, and 20 tactile laminate cut kits. The lowest-risk labor reduction is to retain the existing GHR-06V-S ×1, GHR-08V-S ×4, GHR-14V-S ×1 and SSHL-002T-P0.2 ×52 electrical interface and request a supplier quote for six continuity-tested, label-ready branch harnesses. The quote should state six branch quantities, 80 cell-lead tails, the existing pin map, adjacent-isolation test, and per-branch inspection record. This removes repeated hand crimp/label/continuity work without changing the board.

For any PVDF cut service, retain the same two PVDF signal/return conductors in each four-wire cell bundle and preserve the current branch map. For the LDT coupon, the supplier or integrator must document how its contacts are terminated to the existing harness wire and provide pull/continuity/isolation results. The LDT’s crimp tabs are a process advantage only if the contact-to-wire operation is faster and more reliable than the current silver-epoxy joint.

Cost interpretation

The evidence supports a lower cash outlay from Adafruit 30 AWG wire versus the full Alpha spool, while preserving the JST GH contact size/OD window pending crimp and bend qualification. The LDT’s €71 difference is a theoretical comparison only and contributes zero to the released-glove target until its 13 × 25 mm / 205 µm stack passes fit. PolyK may offer a modest same-class sheet saving if the 28 µm / 200 × 135 mm variant is confirmed, but the full sheet purchase remains chargeable. The complete-device 3× target needs a factory labor quote and process change; PVDF area allocation alone does not support it.

For a one-glove build, charge the whole purchased sheet, wire piece/spool, fabric sheet, or epoxy syringe unless the assembler quotes a cut length or consumable use from its own stock. Consumption allocations stay in the model as planning metrics and are never counted as purchase savings.

Qualification gates

1. Buy or obtain one current TE reference coupon, two PolyK 28 µm silver sheet coupons, and two LDT0-028K units. Record lot/date, thickness, dimensions, electrode construction, and polarity direction before assembly.
2. Build the same 8 × 10 mm pressure cell under each PVDF option. For PolyK, keep the 10 × 14 mm blank and staggered opposite-face tabs. For LDT, preserve the full contact area first; test a paper fit against every finger, thumb, palm, and heel position before trimming any part.
3. Measure open-circuit pulse amplitude, polarity, capacitance, leakage, and noise with the same impact fixture and 4 kHz acquisition path. Compare each candidate to the TE reference at all 20 channel inputs.
4. Measure pressure force response, hysteresis, repeatability, and PVDF-to-pressure cross-talk at the same 20 locations. Record local thickness and crease clearance.
5. Run continuity, adjacent isolation, shared VEXC/GND return, branch-map, and contact pull checks on the full six-harness arrangement. Keep the existing six GH sockets and pin map.
6. Crimp the Adafruit 30 AWG / 0.8 mm wire into SSHL-002T-P0.2; inspect bellmouth and insulation support, pull the contact, cycle the branch at the GH exit, and repeat continuity/isolation checks. Preserve the existing labels, pin map, and four-wire cell bundle.
7. Flex the assembled coupon and inspect silver/electrode/contact joints, cover, and strain relief at the chosen bend radius. Release a replacement only after the measured signal, comfort, and joint survival meet the TE reference acceptance record.

Source status and open quote fields

Source URLs, extracted fields, evidence class, and unresolved fields are in sources.json. Open fields are: PolyK exact variant price/stock and lot certificate; Bulgaria VAT and delivery for all US/UK sources; HESTORE shipping; current TE distributor stock; Adafruit conductor metal/strand construction and Bulgaria shipping; Precision Acoustics quotation; Adafruit 1361 replenishment; a pre-cut 28 µm silver-metallized PVDF quote; and factory pricing for pre-terminated harnesses and PVDF lead-prep service.

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