Fig. 2: Synthesis and material characterization of the 3D printable tissue adhesive.

a Illustrated schematic of the tissue adhesive synthesis process. Polyurethane (PU), acrylic acid (AA), and photoinitiators are combined in a precursor solution and exposed to UV light to activate a one-pot nonspecific polymerization reaction, resulting in poly(acrylic acid) (PAA) grafted to and entangled with PU. The unincorporated reagents are removed via dialysis with ethanol followed by water. The purified material is then redissolved and functionalized with N-hydroxysuccinimide (NHS) esters using 3-(dimethylamino)propyl)carbodiimide (EDC) as a coupling agent, yielding PU-PAA-NHS. b-c FTIR spectra for materials prepared using different precursor compositions. Each spectrum was normalized based on the peak at 2900 cm⁻¹. d ¹H NMR spectra for tissue adhesive samples with varying degrees of NHS functionalization. Each spectrum was normalized based on the peak around 2.22 ppm (attributed to PAA), and the degree of NHS functionalization was estimated by integrating the NHS alkyl peak around 2.76 ppm with respect to the normalized peak. e Apparent viscosity of tissue adhesive inks as a function of shear stress for varying polymer concentrations. f Shear storage modulus as a function of shear stress for varying polymer concentrations. g Filament width as a function of printing speed for the tissue adhesive ink comprising 15 w/w % PU-PAA and 5 w/w % PU extruded through a 200 µm-diameter nozzle under 250 kPa of pressure. Values represent the mean (n = 3 independent samples). Source data are provided as a Source Data file.