IRI Filler Pro - Measured data of the reference device
Confidential - under NDA - YAVU - 2026-08-10 This is the authoritative source for every dimension and force in this project. Anything not listed here as measured is an assumption and is labelled as such.
Where these numbers come from
Court-appointed expert report by Dr. Wilhelm Hartwich, Munich - publicly appointed and sworn expert (IHK Munich/Upper Bavaria for medicinal products, medical devices, foodstuffs, cosmetics). Report "Antwort BU1" of 19 August 2022, 16 pages, in proceedings before the Amtsgericht Düsseldorf, ref. 48 C 511/20.
Instrument: force gauge Sauter FK 250, calibrated by KERN & SOHN GmbH, calibration certificate F81-110-KERN-22-07/1 of 20 July 2022.
Three YAVU pens were measured, ten readings each. The case was decided in YAVU's favour in January 2023.
1 - Measured directly
Instruments named in the report: vernier caliper Preisser Inox (0.025 mm resolution), 10x magnifier, scale, ruler - and for forces the Sauter FK 250 force gauge, calibrated by KERN.
| Quantity | IRI-228 | IRI-171 | IRI-139 |
|---|---|---|---|
| Syringe inner diameter | 3.60 mm | 3.60 mm | 3.60 mm |
| Max. plunger travel | 6.60 mm | 5.60 mm | 5.00 mm |
| Syringe head outer diameter | 8.60 mm | - | - |
| Operating force to cock the spring, mean of 10 | 75 N (69-81) | 84 N (77-87) | 66 N (62-72) |
| Release button force, mean of 10 | 60 N (53-65) | 60 N | 62 N |
| Device mass | 315 g | 319 g | 322 g |
(The same report also measured two competitor devices. Those figures are third-party data from court proceedings and are not reproduced here - they are not needed to build this device.)
The 3.60 mm inner diameter is a direct caliper measurement. It is the number the whole drive sizing rests on, and it does not need to be measured again.
The expert concluded that the YAVU pens "exceed the commercially available comparison pens in ejection performance".
2 - Calculated inside the report
| Quantity | Value | Method |
|---|---|---|
| Max. ejectable volume | 0.067 / 0.057 / 0.051 ml | r² x 3.14 x travel, stated verbatim: "1.80² x 3.14 x 6.60 = 67 µl" |
| Nozzle orifice | 0.18 mm | Proportion from a magnified photograph |
The report notes the orifice was "just about visible as a hole" - so the 0.18 mm carries noticeably more uncertainty than the 3.60 mm. Please verify it on your own sample.
What follows for us
| Quantity | Value |
|---|---|
| Effective plunger area (from Ø 3.60 mm) | 10.18 mm² |
| Stroke for one 60 µl shot | 5.90 mm |
| Cumulative travel to empty a 0.3 ml chamber | 29.5 mm (5 shots) |
| Nozzle area | 0.0254 mm² |
| Static pressure implied by the operating force (75 N / 10.18 mm²) | 74 bar - a LOWER BOUND, see below |
3 - NOT in the report at all - assumption, flagged as such
All 18 pages were searched. The report contains no numeric value for pressure (bar/MPa), jet velocity (m/s), energy (J), or spring travel. "Pressure" appears only qualitatively, e.g. "with high pressure at high firing speed". The ejection test was a visual comparison - dyed liquid into shower gel in a glass, judged by eye. Conclusive for the comparison, but it yields no number.
2.25 J, 354 bar and 265 m/s are one assumption, not three pieces of evidence. They are
mathematically the same statement: 2.25 J delivered into 60 µl gives 354 bar, and
v = sqrt(2p/ρ) gives 266 m/s from that. The source document calls it an impulse simulation.
The 74 bar figure is a lower bound, for two reasons. First, the shot is an impact, so the dynamic peak is higher than any static equivalent - and how much higher was never measured. Second, the 75 N was measured at the cocking lever (strap and carabiner at the lever end), so it is the operating force at the hand, not necessarily the spring force: a lever ratio would put the real spring force above it.
The true firing pressure lies somewhere between 74 and 354 bar. This single unknown is the last thing standing between us and a firm drive specification. It is the one measurement we would like from the bench test.
How to close it: an in-line pressure transducer at the chamber during a shot, or measure the jet velocity optically, or measure penetration depth in a standardised gel against the reference device. Any one of the three closes it.
4 - What this means for the drive
Force at the plunger = pressure × 10.18 mm²:
| Pressure | Force |
|---|---|
| 74 bar (static equivalent of the existing spring) | 75 N |
| 150 bar | 153 N |
| 250 bar | 254 N |
| 354 bar (upper bound, simulated) | 360 N |
Even at the upper bound the requirement is 360 N over a 5.9 mm stroke. A short stroke is
the favourable regime for a voice coil - short coil, high force density. See
VOICE_COIL_DRIVE.md.
5 - What this means for the firmware
The nozzle is 0.18 mm, not the 0.117 mm previously assumed. At 266 m/s the flow through that orifice is 6 771 µl/s, so 60 µl takes 8.9 ms - about 148 µs per µl ideal, and roughly 175-200 µs/µl with a realistic discharge coefficient for crosslinked HA.
VcShotConfig::us_per_ul has been corrected from 450 to 180. It remains a bench
calibration value, settable at runtime via setVoiceCoilCalibration() and persisted in NVS -
no firmware rebuild needed.
It is now held per chamber. The 0.18 mm figure above belongs to the 0.3 ml chamber. The
5 ml refill chamber has a different (probably narrower) nozzle that has never been measured,
so firmware carries a placeholder for it until you measure it - see docs/CHAMBER_SELECTION.md.
Both values are set independently via setChamberCalibration().
6 - Handling note
These figures come from a court file. Please treat the spring force values with particular care: they are the measured differentiator against competitor devices and were, until now, kept internal at YAVU. They are disclosed to you because they bound the firing pressure and you cannot size a drive without that bound.
Source: firmware repo docs/MEASURED_DATA.md · confidential · NDA