Client Citation Analysis
The Dropometer measured ink surface tension by pendant drop during ink formulation. It did not measure viscosity, which came from an A&D SV-1A viscometer. It measured no contact angles, coating thickness or electrochemical behaviour.
Surface tension of the prepolymerized PNIPAAm hydrogel ink, before and after adding 2.4 µL of Triton X-100. The paper reports 70 mN/m before and about 30 mN/m after.
Can a temperature responsive PNIPAAm hydrogel be inkjet printed and photopolymerized on printed graphene electrodes, and how does the coating change electrochemical selectivity?
The printed coating blocked negatively charged redox species near neutral pH and let positive ones through. At pH 2 this selectivity reversed, while temperature had no relevant effect.
This paper uses pendant drop surface tension to qualify an inkjet ink for printed electrochemical sensors.
Surface tension of the prepolymerized PNIPAAm ink, measured by pendant drop on the Dropometer. The authors report 70 mN/m before surfactant and about 30 mN/m after adding 2.4 µL Triton X-100.
Ink viscosity came from an A&D SV-1A viscometer. Electrode coverage was checked by optical and digital microscopy. Sensor behaviour came from cyclic voltammetry on two potentiostats.
Surface tension of the hydrogel inkjet ink before and after surfactant addition.
Ink viscosity, raised from 0.9 to about 1.8 mPa s by controlled prepolymerization.
Drop on demand printing of graphene, insulator and hydrogel layers with DMC-11610 cartridges.
UV light for ink prepolymerization and for curing during printing.
Cyclic voltammetry of bare and coated graphene electrodes.
Visual inspection of electrodes and hydrogel coverage.
pH of electrolyte solutions.
The Dropometer measured the surface tension of the hydrogel inkjet ink by pendant drop. The paper names it as the Dropometer pendant droplet analyzer from Droplet Lab, Canada.
Before surfactant, the prepolymerized ink measured 70 mN/m, which the authors judged not printable. After adding 2.4 µL of Triton X-100, it measured about 30 mN/m, which they judged printable.
The Dropometer did not measure viscosity; a separate A&D viscometer did. It also measured no contact angles, layer thickness or electrochemical response, which drive the paper's main conclusions.
The paper does not report drop volume, needle size, temperature, replicates, drop age or fitting model for the surface tension readings.
The surface tension reading confirmed when the ink reached a printable range, one of two rheology checks before printing. It supports ink formulation, not the pH switchable sensing result.
Need to confirm a new ink or coating liquid is in its printable surface tension range before it reaches the printhead? See how the Dropometer handles this measurement.
Adding 2.4 µL Triton X-100 lowered ink surface tension from 70 to about 30 mN/m, measured on the Dropometer.
A controlled UV prepolymerization raised viscosity from 0.9 to about 1.8 mPa s, measured on an A&D viscometer.
Printing the hydrogel into grid cavities gave far more even coverage. On one electrode with six printed layers, thickness ranged from about 1 to 14 µm.
Near neutral pH, the coating blocked ferricyanide but passed ruthenium hexaammine. At pH 2, the pattern reversed, while 4 °C to 80 °C changed little.
With the coating, 5 mM ascorbate was hardly detected at pH 7.4, while 1 mM dopamine gave a clear oxidation signal.
No figure in this paper contains Dropometer data; the surface tension values appear only in the text of Section 3.1. The paper is published under CC BY-NC-ND 4.0, so we link to figures rather than reproduce or adapt them.
Shows the printed graphene electrodes and how the grid improved hydrogel coverage. It contains no Dropometer data. Source: Scotti and Lesch, Electrochimica Acta 2026, CC BY-NC-ND 4.0.
Inkjet printheads only jet inks within a set surface tension and viscosity window. Measuring both lets a lab confirm a new functional ink is printable before loading a cartridge.
The authors treated 70 mN/m as not printable and about 30 mN/m as printable for their setup.
Just 2.4 µL of Triton X-100, added to an example batch built on 4 mL of stock solution, produced the reported drop in surface tension.
Surface tension and viscosity were measured on separate instruments and adjusted by separate steps.
This water based ink started at 70 mN/m before surfactant
Surfactant lowers tension; prepolymerization raises viscosity
Check both before printing a reactive ink
Extra catalyst and photoinitiator were added after the surfactant. Measure the final ink, not only an intermediate.
Drop volume, temperature, drop age and replicates were not reported. Logging them makes your values comparable across batches.
It measured the surface tension of the hydrogel inkjet ink by pendant drop. The ink measured 70 mN/m before surfactant and about 30 mN/m after adding 2.4 µL Triton X-100.
No. Viscosity was measured on an A&D SV-1A viscometer. The paper reports no contact angle measurements, and its wetting comments draw on earlier work and microscopy.
The authors found the ink at 70 mN/m was not printable on their inkjet setup. A small surfactant addition brought it to about 30 mN/m, which they judged printable.
No. The surface tension measurement supported ink formulation only. The selectivity came from cyclic voltammetry, and the authors say its origin remains unclear.
Use the formal reference below when citing the original paper.
Scotti, S., & Lesch, A. (2026). Fully inkjet-printed poly(N-isopropylacrylamide)/graphene electrodes for electroanalytical sensing with pH switchable selectivity. Electrochimica Acta, 576, 149649. https://doi.org/10.1016/j.electacta.2026.149649
Scotti and Lesch, Electrochimica Acta 2026, 576, 149649. DOI: 10.1016/j.electacta.2026.149649