Volflex++ is a shape-changing haptic interface that can generate the physical characteristics, such as shape and rigidity, of virtual objects using an array of newly developed non-expandable balloons. To alter the rigidity of each non-expandable balloon, the volume of air in it is controlled through a linear actuator and a pressure sensor based on Hooke’s law. Furthermore, to change the volume of each balloon, its exposed surface area is controlled by using another linear actuator with a trumpet-shaped tube. A position control mechanism is constructed to display virtual objects using the balloons. The 3D position of each balloon is controlled using a flexible tube and a string.

Voflex++ aims to show that soft robotic structures with controllable materiality and shape-change can be combined with Virtual Reality to create new physical-virtual objects.



Overview of the system


Non-expandable balloon. On the left, the air-bag. On the right, the cover made of a latex balloon.



Change of Volume

Each balloon can dynamically change their volume, from null to large (c.a. 40 mm)

Four types of volume changes: from null (left) to large (right).



Change of Rigidity

Each balloon can change its rigidity, from very soft one (corresponding to an internal pressure of 5-10 kPa) to a very stiff one (c.a. 35 kPa).

Three types of volume changes: soft (left), medium (center), stiff (right).



Change of Position

The position in space of each balloon can be modified. In this way, different three-dimensional shapes can be presented.

(under development)


Model-based Shape-changing Interfaces

A proof-of-concept application. A virtual flat surface, with dynamic size and rigidity, can be presented physically through Volflex++.

To expand the possibilities, we developed a physical sound model of a membrane. Depending on the settings of the surface (size and rigidity) the sound model will change accordingly.

This proposed approach can lead to a new type of shape-changing haptic interfaces, that couple physical and virtual objects not only through visually but also sonically.

To enable the interaction, we developed an embedded touch detector using the air-pressure sensor attached to each balloon.


Touch Detection with Capacitive Sensing

We are developing a novel touch detector using capacitive sensing.



Alberto Boem, Yuuki Enzaki, Hiroaki Yano, Hiroo Iwata. 2019. Human Perception of a Haptic Shape-changing Interface with Variable Rigidity and Size. In Proceedings of the IEEE Conference on Virtual Reality and 3D User Interfaces, Osaka (JP), 2019. To appear. [pdf]

Alberto Boem, Hiroo Iwata. 2018. Encounter-type Haptics for Virtual Reality Musical Instruments. In Proceedings of the IEEE Conference on Virtual Reality and 3D User Interfaces, Reutlingen (DE), 2018. DOI:10.1109/VR.2018.8446549 [pdf]


Volflex is a haptic technology envisioned by Prof. Hiroo Iwata and developed at the Virtual Reality Lab of the University of Tsukuba (JP).

This new version was first developed by Naoki Takizawa.