Laboratory for Dynamics of Machines and Structures 
Single-process 3D-printed smart pad with CNN-based touch localization and force classification
 T. Barši Palmić, E. Podlipnik and J. Slavič
Virtual and Physical Prototyping, 2026

download pdf   https://doi.org/10.1080/17452759.2026.2640277

More research on: 3D printing,
Abstract
Multi-material 3D-printing enables the single-process embedding of piezoresistive sensors producing multi-functional, fully 3D-printed, smart structures without manual assembly or specialized equipment. However, the low sensitivity and manufacturing variability yield unreliable signals, limiting 3D-printed sensors to simple demonstrations rather than complex sensing tasks. This work introduces a single-process, 3D-printed structure with inherently poor sensing capability that is transformed into a highly accurate smart pad with functional tap localization using a convolutional neural network (CNN). The structure consists of a thermoplastic polyurethane (TPU) pad with up to four embedded piezoresistive sensors fully fabricated through material extrusion (MEX). The CNN processes measured time-series signals to predict the tap location and classify the force magnitude. The 4-sensor smart pad reliably distinguishes individual taps with millimeter accuracy (3.56 mm mean accuracy), enabling touch-pad applications with force classification (>98.7% accuracy). The single-sensor smart pad maintains functional performance (6.32 mm mean accuracy), proving that machine learning compensates for the extreme sensor reduction. This work establishes a rapid-prototyping platform for application-specific CNN-enhanced smart structures in human-machine interfaces, soft robotics, and structural health monitoring.
Authors

Researcher

Tibor Barši Palmić, PhD

  Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
  tibor.barsi@fs.uni-lj.si
  +386 1 4771 228
tibor-barsi    
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Professor

Janko Slavič, PhD

  Ladisk, Faculty of Mechanical Engineering, University of Ljubljana
  janko.slavic@fs.uni-lj.si
  +386 1 4771 226
jankoslavic     jankoslavic    
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