Existing nonverbal communication systems typically result in high uncertainties, cumbersome response time, or are bulky and unsuitable for use on curvilinear regions of the body, such as the face. We introduce skin-like, conformable devices together with non-contact optical methods for full-field strain mapping and rigorous theoretical models to offer a system capable of predictable, spatiotemporal, biokinematic assessment of the face. The enabling advances in engineering science include mass-manufacturable microfabrication of soft, piezoelectric interfaces to the skin; three-dimensional reconstruction of soft-tissue surfaces in vivo under dynamic deformation conditions; extensive theoretical modeling of complex epidermis-device mechanical interactions; and algorithms for real-time detection and classification of distinct epidermal deformation signatures. Preliminary studies on healthy and amyotrophic lateral sclerosis subjects demonstrate reliable performance that establishes potential viability for use in clinically-realizable nonverbal communication technologies.