Work

Fused filament fabrication of gyroid TPU/MWCNT nanocomposite sensors with tunable piezoresistive response: Proof-of-concept integration into a 3D-printed smart midsole

Year: 2026

Type: article

Abstract: Functional architected polymer nanocomposites that combine mechanical compliance, tunable electrical conductivity, and piezoresistive response are highly attractive for wearable electronics and personalized sensing technologies. However, the coupled effects of conductive-network density and lattice geometry on the electromechanical performance of fused-filament-fabricated (FFF) elastomers remain insufficiently understood. Here, thermoplastic polyurethane (TPU) containing 2, 3, and 4 wt% multiwalled carbon nanotubes (MWCNTs) was melt-extruded into conductive filament feedstock and printed into gyroid triply periodic minimal surface (TPMS) lattices with unit cell sizes of 4, 5, and 6 mm. Increasing MWCNT loading improved electrical transport and increased Young’s modulus from 14.22 ± 0.60 MPa at 2 wt% to 19.16 ± 0.59 MPa at 3 wt%, with a comparable value of 18.89 ± 1.45 MPa at 4 wt%, while elongation at break decreased from 660 ± 41% to 503 ± 34.03%. Fracture-surface scanning electron microscopy revealed composition-dependent morphological differences, while the complementary electrical and spectroscopic analyses supported the observed structure-property trends. Under compression, the gyroid lattices showed stable piezoresistive responses governed by filler loading and architecture. Among the investigated configurations, the selected TPU/MWCNT (2 wt%) sensor with a 5 mm nominal UCS exhibited an apparent gauge factor of 1.24 ± 0.03, hysteresis of 8.17 ± 0.74%, and stable short-term cyclic response over 100 cycles. The sensor-screening results are based on one independently fabricated sensor per composition-UCS combination, with repeated loading cycles used to assess short-term cycle-to-cycle variation. Four sensing elements based on the selected configuration were integrated into a wireless 3D-printed midsole for a proof-of-concept demonstration involving one instrumented shoe and one controlled step. The system enabled real-time acquisition and qualitative visualization of normalized relative-resistance changes associated with the temporal loading sequence. The signals were not calibrated into plantar-pressure units and therefore demonstrate relative loading detection rather than quantitative plantar-pressure measurement.

Source: Materials Today Communications

DOI: 10.1016/j.mtcomm.2026.115990