Our group is interested in finding out how the contact between soft or biological materials on various surfaces can be monitored and controlled. We develop instruments, devices and methods to measure friction when objects are simply put in contact or even sliding over random surfaces.

The output of our studies drives the development of two main applications. The first one is the design of soft robotics sensors that can monitor the nature of the object and its state of contact (sliding or firmly attached) when grasping objects. And the second one is surface haptics device which are able to change in real time the frictional conditions of a fingertip and creates compelling sensations of texture and shape via what we call surface haptic devices. Learn more about some of our ongoing projects.

This group is part of the Human-Robot Interaction section of the Cognitive Robotics Department at the TU Delft and we collaborate closely with the Delft Haptics lab.

Graduation projects

If you are interested to pursue your Master thesis with us, and learn more about haptic devices, the sense of touch or contact mechanics of soft robots, email to Michaël.


Our group studies the mechanics linked to tactile perception. Our approach lies at the intersection of the observation of tactile interaction with high precision devices, the design of haptic interfaces for reproducing realistic tactile sensations and the psychophysical study of human perception.

Surface Haptics

We design bespoke surface haptic devices to produce tactile sensation directly on the user's fingertip.

Tactile Sensing

We design and develop soft tactile sensors using color-mixing principle to measure the 3d interactions between the sensor and the object. By using a new color-mixing based signal processing methods, we developed a soft tactile sensor that is able to estimate the 3d forces and deformations of the contact with different objects. Known strategies of human processing and perception of tactile input can be also applied to the sensor, which resulted in a new signal processing methods that is able to extract the frictional resistance of a material, within the first millisecond of a contact with an object, before even a frictional force is present.

Contact mechanics

Ultrasonic friction modulation of the bare fingertip touching a glass plate has the potential of bringing haptic feedback to touchscreens. The physical underpinning of the phenomena that creates this reduction of friction has been elusive to researchers. In order to draw a greater understanding of the physics at play, we developed an imaging system that is able to capture the motion of the skin with a 1µs resolution. The results from this study showed that the skin is actually bouncing on an air cushion. This air cushion limits the contact between the plate and the skin thus reducing the friction experienced by a bare fingertip.

Interaction design

We study how to create compelling sensations using surface haptics. Directly modifying friction of the bare finger sliding on glass opens a whole new range of possible interactions that were not achievable with force-feedback or vibrotactile stimulation. We explore the design space of tactile stimuli that can be produced with friction modulation to enable the production of virtual relief, texture and buttons on touchscreens.


Zhaochong Cai