Single-process 3D-printed smart pad with CNN-based touch localization and force classification

Barši Palmić, Tibor (author), Podlipnik, Enej (author), Slavič, Janko (author)

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.

• Language: English
• Keywords: multi-material 3D-printing, smart structures, piezoresistive sensors, convolutional neural networks, impact detection
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FS - Faculty of Mechanical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 15 str.
• Numbering: Vol. 21, no. 1, art. e2640277
• PID: 20.500.12556/RUL-181418
• UDC: 681.586:004.92
• ISSN on article: 1745-2759
• DOI: 10.1080/17452759.2026.2640277
• COBISS.SI-ID: 274318851
• Publication date in RUL: 07.04.2026

Record is a part of a journal

• Title: Virtual and physical prototyping
• Publisher: Taylor & Francis
• ISSN: 1745-2759
• COBISS.SI-ID: 514087705

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: 3D-tisk z zaznavali, pametne strukture, piezorezistivni senzorji, konvolucijske nevronske mreže, zaznavanje trka, procesiranje signalov, strojno učenje

Projects

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: P2-0263
• Name: Mehanika v tehniki

• Funder: ARIS - Slovenian Research and Innovation Agency
• Project number: L2-60140
• Name: Aktivni samozavedni 3D-tiskani dinamski sistemi in strukture