# Fully Screen-Printed Pressure Sensing Insole—From Proof of Concept to Scalable Manufacturing

## TL;DR

Researchers developed a low-cost, scalable method to manufacture flexible pressure-sensing insoles using screen-printed graphene and carbon composites for wearable gait monitoring.

## Contribution

A fully screen-printed, scalable pressure-sensing insole with practical manufacturing guidelines for wearable electronics.

## Key findings

- The insole achieved a sensitivity of 10.5 ± 2.8 Ω per 100 N and a sheet-to-sheet coefficient of variation of 22.1%.
- Static-load tests showed coefficients of variation as low as 4% at 500 g and a detection limit of ~0.1 N.
- Composite pastes with carbon fillers improved sensor repeatability and sensitivity.

## Abstract

What are the main findings?

Influence of composite formulation, screen mesh density, electrode geometry, lamination, and screen-printing parameters on the resistive response under pressure.

Scalable fabrication method for flexible pressure-sensing insole based on contact resistance between graphene nanocomposite layer and silver electrode.

What are the implications of the main findings?

Practical process and design guidelines for manufacturing printed pressure sensor insoles for wearable gait monitoring and biofeedback applications.

Feasibility demonstration of a fully screen-printed multilayer insole architecture compatible with compact readout electronics and everyday footwear.

Continuous plantar-pressure monitoring is important for objective gait analysis and early detection of abnormal loading; however, many existing solutions remain laboratory-bound (force plates and instrumented walkways) or rely on costly in-shoe multilayer sensor arrays. Here, we developed and optimized a fully screen-printed pressure-sensing insole based on carbon–polymer nanocomposite layers, with an emphasis on manufacturability and process control to bridge the gap between proof-of-concept force-sensitive resistor (FSR)-based insoles and scalable printed-electronics manufacturing workflows. Composite pastes containing carbon fillers (graphene nanoplatelets, carbon black, and graphite) were formulated to improve sensor repeatability and sensitivity. Sensors were characterized under compression loads from 100 N to 1300 N, showing a sensitivity of 10.5 ± 2.8 Ω per 100 N and a sheet-to-sheet coefficient of variation of 22.1% in resistance response. The effects of paste composition, screen mesh density, electrode layout, and lamination on sensitivity and repeatability were systematically evaluated. In addition, correlation analysis of resistance values from integrated quality-control meanders proved useful for monitoring screen-printing process stability. The final insole integrates printed carbon sensing pads and contacts, a dielectric spacer, and an adhesive layer in a thin, flexible format suitable for integration with wearable electronics. In practical static-load tests, repeated manual placement of weights yielded coefficients of variation as low as 4% at 500 g and a detection limit of ~0.1 N, comparable to a very light finger touch. These results demonstrate that low-cost screen-printed electronics can provide robust pressure sensing for wearable plantar-pressure monitoring.