Force sensing microinstrument for measuring tissue properties and pulse in microsurgery

Miniaturized and "smart" instruments capable of characterizing the mechanical properties of tiny biological tissues are needed for research in biology, physiology, and biomechanics, and can find very important clinical applications for diagnostics and minimally invasive surgery (MIS). We are developing a set of robotic microinstruments designed to augment the performance of surgeons and clinicians during MIS. These microtools are intended to restore (or even enhance) the finger palpation capabilities that the surgeon exploits to characterize tissue hardness and to measure pulsating vessels in traditional surgery, but which are substantially reduced in MIS. This paper describes the main applications and the performance of a prototype miniature robotic instrument consisting of a microfabricated microgripper, instrumented with semiconductor strain-gauges as force sensors. The experimental set-up used for the in vitro tests reported in this paper consists of the microprobe mounted on a workstation and teleoperated. A haptic interface provides force feedback to the operator. We have demonstrated that the system can discriminate, both qualitatively and quantitatively, tiny skin samples based on their different elastic properties, and "feel" microvessels on the basis of pulsating fluid flowing through them.