  In the past two decades, there has been a continuous rise in the deployment
of robots fulfilling social roles that expands across various industries such
as guides, service providers, and educators. To establish robots as integral
allies in daily life, it is essential for them to deliver positive and
trustworthy experiences, achieved through seamless and satisfying interactions
across diverse modalities and communication channels. In the realm of
human-robot interactions, touch plays a pivotal role in facilitating meaningful
connections and communication. To delve into the significance of haptic
technologies and their impact on interactions between humans and social robots,
an exploration of the existing literature is essential, since the research
about touch is the most underrepresented between the other communication
channels (facial expressions, movements, vocals etc). A systematic literature
review has been carried out, identifying 42 articles with the Preferred
Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), related to
touch and haptic technologies and interaction between humans and social robots
in the twenty years (2001 -2023). The results show the main differences, pros
and cons between the materials and technologies that have been primary used so
far, the qualitative and quantitative research that links the HRI touch studies
with the human emotion and also the types of touch and repeatability of those
methods. The study identifies research gaps and outlines future directions,
while it serves as a guide for anyone who will be interesting in conducting HRI
touch research or build a haptic system for a social robot.
