Design and control of an air-jet lump display

A common surgical task is identifying hard lumps embedded in soft tissue. During open procedures, surgeons can localize lumps using the distributed tactile feedback provided through manual palpation with the fingers. Tactile displays developed to restore tactile feedback for both traditional and robot-assisted minimally invasive surgery (RMIS) are designed generically to provide a wide range of tactile sensations to the finger, and as such, are often bulky and electro-mechanically complex. We developed a novel adjustable aperture air-jet pneumatic lump display that directs a thin stream of pressurized air through an aperture onto the fingerpad. The display is designed to produce the sensation of a lump to the finger, with minimal hardware requirements. It has two degrees of freedom, enabling independent control of pressure and aperture size. We describe the design of the display and demonstrate the process through which the output of the display can be controlled, using two different methods for adjusting aperture size. The output of the pneumatic air-jet lump display is quantitatively measured with capacitive tactile sensor arrays, and results show that the display is capable of changing both the size and pressure of the output.