The mechanical imaging of lumps in tissues via surface measurements can permit the noninvasive detection of disease-related differences in body tissues, and can aid the documentation of tissue changes over time. This has motivated the development of new electronic sensing methods for mechanical imaging. Conventional tactile sensors are rigid, unable to conform to curved geometries, and are not adaptable to the shapes of all body parts, limiting their applicability in biomedical sensing applications. To address these needs and limitations, we developed a mechanical imaging method and system for capturing tissue properties during automatic or human-guided palpation. It combines extremely compliant capacitive tactile sensors based on soft polymers and microfluidic electrodes with custom electronic data acquisition hardware, and new algorithms for enhanced tactile imaging by reference to nominal tissue responses. We demonstrate that this method is able to perform mechanical imaging of simulated tumors (lumps), yielding images that accurately reflect lump size, independent of embedding depth. In addition, as a proof of concept, we show that informative tactile images can be obtained when the sensor is worn on a human finger, which palpates the tissue, pointing toward the potential use of sensors that could be integrated in a hand worn device for use in many existing clinical practices of palpation. As we demonstrate, soft capacitive sensors can accurately image lumps in soft tissue provided that care is taken to control and compensate for electrical and mechanical background signals. The results underline the utility of such sensors for applications in medical imaging or clinical practices of palpation.
