# A cost-effective laboratory device for single slow micro compression testing of soft materials in the small-strain region

## TL;DR

A low-cost device for testing soft materials under small strain was developed and shown to be accurate and reliable.

## Contribution

A cost-effective and precise micro-compression testing system for small-strain mechanical evaluation of soft materials.

## Key findings

- The device achieved 1 µm displacement and 0.01 N force detection accuracy.
- It showed ±2.0% agreement with commercial MTS systems in force-displacement comparisons.
- PDMS specimens tested with the device had ±0.05% error compared to standard specimens.

## Abstract

•Developed a low-cost micro compression tester for small-strain region.•Achieved high resolution: 1 µm displacement and 0.01 N force detection accuracy.•Verified ± 2.0 % agreement with commercial MTS through force–displacement comparison.•Performed compression tests with standard PDMS specimens (ASTM D575-91)•Easy-to-fabricate and cost-effective system broadly applicable in MEMS research.

Developed a low-cost micro compression tester for small-strain region.

Achieved high resolution: 1 µm displacement and 0.01 N force detection accuracy.

Verified ± 2.0 % agreement with commercial MTS through force–displacement comparison.

Performed compression tests with standard PDMS specimens (ASTM D575-91)

Easy-to-fabricate and cost-effective system broadly applicable in MEMS research.

In various microscale applications, accurate evaluation of the mechanical properties of materials under small-strain and low-force conditions is important. However, conventional universal testing machines (UTM) are expensive and difficult to operate reliably under low-force conditions, making them unsuitable for small-strain testing. To overcome these limitations, we developed a cost-effective device for single slow micro-compression testing (MCT) to measure the mechanical properties of materials in the small-strain region. The MCT consists of a force sensor (FlexiForce A301-1, Tekscan, USA), an Arduino-based signal acquisition module, and a high-precision z-stage. The displacement control accuracy of the z-stage was verified using a laser displacement meter (LK-G10, Keyence, Japan), and the experimental results confirmed displacement and force resolutions of 1 µm and 0.01 N, respectively. Under no-load conditions, the force–displacement error between the MCT and a commercial universal testing machine (MTS, AMETEK LRX-plus, LLOYD INSTRUMENTS, UK) was within ± 2.0 %. In addition, standard and one-third-size PDMS (polydimethylsiloxane) specimens were fabricated according to ASTM D575-91 and tested using both systems; the error between the two specimens was within ± 0.05 %. From the linear region in the small-strain range, the Young’s modulus of the miniature specimen was estimated, showing a percentage error of + 2.2 % from reported values, confirming high precision and reliability.

The developed device, with a total fabrication cost below USD 1,500, provides cost-effectiveness, precision, and repeatability, enabling applications in polymer MEMS and soft robotics.