Performance improvement of photocurable methacrylate resins with fillers for custom-fit earphones
Bibliographic record
Abstract
Custom-fit earphones are an emerging class of wearable technology composed of a malleable prepolymer resin.The earphones are molded during a 60 second curing process to the exact shape of one's ear, delivering a snug fit.The resin is composed of a mixture of methacrylates, cured into a photocurable thermoset, similar to dental composites.Enclosed in the earphones are blue LEDs (=470 nm) which initiates curing.Two key issues were identified.Photopolymerization is highly exothermic, making the process unsafe for users.The cured resin also exhibits volumetric shrinkage resulting in poor resin-sleeve adhesion.This study aims at developing the ideal prepolymer mixture: one that has a low temperature increase (exotherm) and minimal shrinkage while maintaining high mechanical strength and degree of cure (conversion).Exotherms were determined by a customized apparatus used to cure the resin while recording temperature.With the help of a 3D printer, parts were constructed and used as the sample holder that had the same volume as an ear sleeve.The rest of the apparatus consisted of blue LED arrays, LCD display, thermocouple, a microcontroller, and MATLAB interface.Volumetric shrinkage was determined using density measurement via Archimedes method and pycnometry.Material strength was determined using tensile tests.Degree of cure was determined via vinyl conversion using FT-IR spectroscopy.The monomers diurethane dimethacrylate (UDMA), urethane acrylate methacrylate (UAM), bisphenol A glycidyl methacrylate (BisGMA) and bisphenol A dimethacrylate (BisDMA) were used as the main monomer in conjunction with crosslinkers 1,6-hexanediol dimethacrylate (HDDMA), trimethylolpropane triacrylate (TMPTA) and trimethylolpropane trimethacrylate (TMPTMA).Results showed high exotherm for crosslinkers (>27.3C).Replacing small molecule crosslinkers with oligomeric crosslinkers such as poly(ethylene glycol) diacrylate (PEGDA) and poly(ethylene glycol) diacrylate (PEGDMA) showed less pronounced exotherms.BisGMA:PEGDA in a 1:2 ratio resulted in an exotherm of 19.3C and was used as the baseline for filler introduction.Inorganic fillers including fumed silica (FS), silica gel (SG), and commercial ground silica MIN-U-SIL US 5 (m) and 15 (m) silica were pre-treated and mixed with the baseline resin at several loadings.FS/resin blends showed a decreased exotherm (13.6C at 25% wt.) while SG/resins blends showed an increased exotherm (30.0C at 25 wt.%).All filled samples had lower volumetric shrinkage compared to the baseline (5.1%).Degree of cure increased with filler loading for FS (40% at 25 wt.%) and SG (40% at 25 wt.%)) and remained neutral for the rest compared to the baseline (28%).FS and SG filled resins had tensile
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".