My research statement

Touch is commonly assumed to be the most fundamental sensory modality.  Consider how heavily infants rely on touch.  They reach out their arms to identify their mother, feel the warmth of her skin, and hold the breast to receive milk.  Babies smile when they are gently stroked.  These examples indicate the importance of touch in recognizing the physical world and also in bonding emotionally with others. 

However, touch is the least understood of the sensory modality modalities. Haptics (touch engineering) research has been called an “emerging research field” for decades.  Touch screens are already widely used as an input device of smartphones or tablet PCs.  IBM considers that cognitive computing will be a life-changing innovation, and in 2012, they predicted that computers with tactile feedback of material properties would be achieved within five years.  The recent release of the Apple Watch that produces emotional haptic feedback is an indication of the potential scope of haptics applications.

The long-term goals of my research are to identify the computational basis of tactile perception in humans, and to engineer artificial systems that are capable of recording, synthesizing, and presenting tactile stimuli.  Ultimately, this research leads to the development of the platform for touch-oriented (visceral) media design. 

[History of my research 2008-2014]

To achieve my research goal, I have conducted research projects under multiple disciplines, from cellular mechanosensation, structural biomechanics of the skin and, sensor engineering to acquire softness information of the skin.

In the cellular biomechanics project, I have conducted basic studies on the Merkel cell, which is the most sensitive touch receptor in the skin.  I showed, for the first time in the history, that the Merkel cell is touch-sensitive machinery that transduces a gentle touch stimulus into neural signals in the brain (Nature 2014).  These findings support the hypothesis that Merkel cells have an active computational role in extracting features, such as edges and surface shapes from physical contact.

Finger mechanics project, we tested a hypothesis whether fingerprint structure of the fingered may amplify the amount of stress concentration in the skin, leading to clear identification of the geometry contacting to the finger. Collaborating with Takashi Maeno and Takayuki Shinmi in Keio University, we found that fingerprint structure does help collect geometric information from outside body. This result is consistent with the ability of human touch identification to geometric information.  (Neuroscience 2013, Transaction on Virtual Reality Society of Japan 2011).

I also identified how we people can feel skin softness in fingertip. Skin is complex material so that its deformation is totally non-linear phenomenon. But we human can easily tell the difference between smooth, soft skin and rough, plump skin. To understand this daily life experience, I hypothesized that perceptual skin softness comes from the mechanical structure of the skin: stiff thin surface (know as stratum corneum in skin biology) and soft inner tissue (the complex of epidermis, dermis and subcutaneous tissue). Preparing sixty-five kinds of different skin softness models made with urethane resin of different surface thickness and stiffness, and psychological evaluation revealed that both surface and inner tissue stiffness can affect our perceptual softness. By collaborating with Dr. Sadao Omata in Nihon University, skin softness sensor was developed for discriminating skin softness models and its discrimination rate was over 90%. Based on this result, my developed skin softness sensor has been installed in cosmetic company and still being used for evaluating actual human skin softness (Skin Research and Technology, 2011)

Where my passion to haptics research comes from? The answer is the discovery of a novel tactile phenomenon, which I named the Fishbone Tactile Illusion, in which flat surface is felt as it were indented (Experimental Brain Research, 2011). I found this tactile illusion when I was in graduate school and totally fascinated by this phenomenon. One of my ultimate goal is to explain this phenomenon using the knowledge in peripheral nervous system in tactile sensation, biomechanics of the skin, signal processing in the dorsal horn of spiral cord, and somatosensory cortex in the central nervous system.