A team of scientists from Imperial College London has introduced CrystalTac, a family of vision-based tactile sensors (VBTSs) developed using rapid monolithic manufacturing techniques.
(A) C-Sight, IMM mechanism. (B) C-Tac, MDM mechanism. (C) C-SighTac, IMM + MDM mechanism. (D) Vi-C-Tac, MDM + MFM mechanism. (E) Vi-C-Sight, IMM + MFM mechanism. The diagram for each design illustrates its unique internal structure and material assignment. Image Credit: Wen Fan, Imperial College London.
Vision-based tactile sensors have seen increasing adoption in robotics due to their ability to capture detailed contact information. These sensors are typically classified based on the type of tactile features they detect, and each category demands a distinct structural design to translate physical contact into optical data. However, the complexity of these designs often challenges conventional manufacturing methods, especially in balancing flexibility, cost, and consistency.
Previous work has suggested that monolithic manufacturing—using multimaterial 3D printing—can help overcome these challenges. Yet, bridging the gap between sensor design and actual production has remained a bottleneck.
Thereby, we develop the CrystalTac family, a series of VBTSs designed with on-demand sensing mechanisms and fabricated through rapid monolithic manufacturing. The CrystalTac family aims to highlight the potential of rapid monolithic manufacturing techniques in VBTS development and inspire further research in tactile sensing and manipulation.
Wen Fan, Study Author and Researcher, Imperial College London
The research followed a structured approach. First, the team reviewed existing VBTSs, categorizing them based on their core sensing mechanisms. They then evaluated the feasibility of producing these mechanisms using monolithic manufacturing, assessing both technological and practical considerations.
Building on these findings, they created the CrystalTac lineup: C-Tac, C-Sight, C-SighTac, Vi-C-Tac, and Vi-C-Sight. Each sensor in the series is designed around a specific tactile sensing principle and built to demonstrate how flexible, design-led creation can be achieved with rapid 3D printing.
To validate their work, the researchers conducted a series of experiments to assess the sensors' performance, manufacturing cost, and design adaptability. They also introduced novel marker designs and refined sub-component manufacturing methods to support future scalability and broader applications. The results showed that the CrystalTac series performs reliably and meets its intended design goals.
What sets CrystalTac apart is its flexibility. The designs are meant to serve as open templates rather than rigid blueprints, allowing others in the robotics community to adapt and expand upon them.
In future work, we aim to advance the new CrystalTac series by enhancing the capabilities of monolithic manufacturing in terms of production quality and efficiency, as well as multimaterial printing for VBTSs. These technologies can be seamlessly integrated with tactile sensory enhancements in dexterous hands to perform tasks such as human–computer interaction or dexterous manipulation.
Wen Fan, Study Author and Researcher, Imperial College London
The paper was co-authored by Wen Fan, Haoran Li, and Dandan Zhang. Fan and Li received partial funding through the CSC scholarship program, and the team also acknowledged support from the Royal Society Research Grant (RGS/R1/221122).
Journal Reference:
Fan, W., et al. (2025) CrystalTac: Vision-Based Tactile Sensor Family Fabricated Via Rapid Monolithic Manufacturing. Cyborg and Bionic Systems. doi.org/10.34133/cbsystems.0231.