  Soft material research has seen significant growth in recent years, with
emerging applications in robotics, electronics, and healthcare diagnostics
where understanding material mechanical response is crucial for precision
design. Traditional methods for measuring nonlinear mechanical properties of
soft materials require specially sized samples that are extracted from their
natural environment to be mounted on the testing instrument. This has been
shown to compromise data accuracy and precision in various soft and biological
materials. To overcome this, the Volume Controlled Cavity Expansion (VCCE)
method was developed. This technique tests soft materials by controlling the
formation rate of a liquid cavity inside the materials at the tip of an
injection needle, and simultaneously measuring the resisting pressure which
describes the material response. Despite VCCE's early successes, expansion of
its application beyond academia has been hindered by cost, size, and expertise.
In response to this, the first portable, bench-top instrument utilizing VCCE is
presented here. This device, built with affordable, readily available
components and open-source software, streamlines VCCE experimentation without
sacrificing performance or precision. It is especially suitable for
space-limited settings and designed for use by non-experts, promoting
widespread adoption. The instrument's efficacy was demonstrated through testing
Polydimethylsiloxane (PDMS) samples of varying stiffness. This study not only
validates instrument performance, but also sets the stage for further
advancements and broader applications in soft material testing. All data, along
with acquisition, control, and post-processing scripts, are made available on
GitHub.
