  Recently, vision-based tactile sensors (VBTSs) have gained popularity in
robotics systems. The sensing mechanisms of most VBTSs can be categorised based
on the type of tactile features they capture. Each category requires specific
structural designs to convert physical contact into optical information. The
complex architectures of VBTSs pose challenges for traditional manufacturing
techniques in terms of design flexibility, cost-effectiveness, and quality
stability. Previous research has shown that monolithic manufacturing using
multi-material 3D printing technology can partially address these challenges.
This study introduces the CrystalTac family, a series of VBTSs designed with a
unique sensing mechanism and fabricated through rapid monolithic manufacturing.
Case studies on CrystalTac-type sensors demonstrate their effective performance
in tasks involving tactile perception, along with impressive cost-effectiveness
and design flexibility. The CrystalTac family aims to highlight the potential
of monolithic manufacturing in VBTS development and inspire further research in
tactile sensing and manipulation.
