David was a charter member of Xerox PARC and is currently a Research Fellow. His fields of expertise include acousto-optic interactions, electron spin resonance and fundamental aspects of disordered semiconductors, laser-induced thin-film crystallization, scanning tunneling microscopy, heteroepitaxial growth, and new fabrication methods, design and use of complex "smart matter" systems. One of his projects -- which exemplified the fabrication and programming of smart matter -- involved moving paper precisely, using arrays of analog sensors and computer-actuated air jets fabricated in printed circuit board technology. The system consists of hundreds of agents which can each sense, act and compute locally, yet work together with minimal global information to provide precise, coherent behaviors. More recent work has involved similar aggregations of electro-physical agents to allow parallel, redundant printing systems to be composed in a hypermodular fashion. David holds over 120 US patents. He is a Fellow of the APS and has been an Editorial Board Member of Applied Physics Letters and Divisional Associate Editor of Physical Review Letters. He thrives on learning new concepts and using them in novel ways.