GelTech Labs

Manual and automated free swell measurement of potassium polyacrylate

Tested March 2026

Summary

A trained operator and Carousel each ran a 72 h free swell test on potassium polyacrylate in 0.9% NaCl, three replicates per method, at the same 10 timepoints. Mean swelling didn't differ between methods (paired t-test, p = 0.365). Replicates spread less on Carousel, a mean SD of 2.17 g/g against 6.10 g/g by hand, and a run took about 30 minutes of hands-on time against about 5.7 hours.

What it means for your lab

Tighter replicates make smaller differences between formulations visible, and hours of skilled bench time go back to your scientists.

~3×lower replicate variability on Carousel than by hand

Replicate spread by hand and on Carousel

Peak swelling, three replicates per arm (g/g)

Manual 39 to 60 g/gMean SD 6.10 g/g · coefficient of variation >22%
Carousel 38 to 45 g/gMean SD 2.17 g/g · coefficient of variation <10%
0204060

Both arms n = 3 at the same 10 timepoints over 72 h. A paired t-test found no difference in mean swelling (p = 0.365).

2.17 vs 6.10 g/gmean SD across 10 timepoints, Carousel against manual
p = 0.365no difference found in mean swelling
~30 min vs ~5.7 hhands-on time per 72 h run

Results

Swelling ratio is reported in g/g. Both methods reached a similar range, and the spread between replicates, measured as standard deviation (SD), is where they differ.

72 hours of free swell, manual and Carousel

Manual

Carousel

Swelling ratio (g/g) · mean ± SD band, n = 3 per arm · 0.9% NaCl · room temperature · cube-root time axis · SD at 72 h: 10.5 g/g manual, 3.3 g/g Carousel

Materials and methods

One material, measured two ways: three replicates by hand and three on Carousel. Both arms used the same chambers, mesh, fluid, timepoints and blotting sponge, so the handling was what differed.

Manual trained operator, by hand

A trained operator lifted, blotted and weighed each of three chambers at every timepoint, about 5.7 hours of hands-on time per 72 h run. Peak swelling ranged from 39 to 60 g/g.

Carousel automated immersion and weighing

Carousel immersed and weighed each of three chambers on schedule, about 30 minutes of hands-on time per 72 h run. Peak swelling ranged from 38 to 45 g/g.

Free swell · 72 hoursFree swell, gravimetric

Setup. About 75 mg of KPA powder per chamber, in injection-molded PP chambers with 200 µm PP mesh, immersed in 0.9% NaCl at room temperature.

Readout. Swelling ratio (g/g) at 5, 10 and 30 min and 1, 2, 4, 8, 24, 48 and 72 h, blotted with the same PVA sponge before each weighing.

Free swell, gravimetric. Both arms n = 3, under matched conditions.

Variability · mean SD across 10 timepointsPaired t-test on the means

Error bars: SD · 6.10 ± 3.41 g/g manual against 2.17 ± 1.24 g/g Carousel

Paired t-test on the means. p = 0.365: no difference found in the two arms' means

Results summary

Measure	Manual	Carousel
Peak swelling (g/g)	39 to 60	38 to 45
Mean SD, 10 timepoints (g/g)	6.10 ± 3.41	2.17 ± 1.24
Hands-on time per 72 h run	~5.7 h	~30 min

Methods. Commercial KPA powder, about 75 mg per chamber, in injection-molded PP chambers with 200 µm PP mesh, in 0.9% NaCl at room temperature. Both arms n = 3, sampled at 5, 10 and 30 min and 1, 2, 4, 8, 24, 48 and 72 h, and blotted with the same PVA sponge before each weighing. Hands-on time covers setup, sample handling and weighing per 72 h run. Timepoint means compared by paired t-test: p = 0.365, no difference found. Bench data, March 2026.