  Biological muscles have always attracted robotics researchers due to their
efficient capabilities in compliance, force generation, and mechanical work.
Many groups are working on the development of artificial muscles, however,
state-of-the-art methods still fall short in performance when compared with
their biological counterpart. Muscles with high force output are mostly rigid,
whereas traditional soft actuators take much space and are limited in strength
and producing displacement. In this work, we aim to find a reasonable trade-off
between these features by mimicking the striated structure of skeletal muscles.
For that, we designed an artificial pneumatic myofibril composed of multiple
contraction units that combine stretchable and inextensible materials. Varying
the geometric parameters and the number of units in series provides flexible
adjustment of the desired muscle operation. We derived a mathematical model
that predicts the relationship between the input pneumatic pressure and the
generated output force. A detailed experimental study is conducted to validate
the performance of the proposed bio-inspired muscle.
