Here I will present the optoelectronic responses of nanotube/silicon heterojunctions, allotropic transformation of sp2 carbon, and well-defined suspended nano/microscale networks on 3D flexible substrates. The first portion of the talk will focus on a radically unconventional, voltage-tunable, sharply non-linear and extremely sensitive photo-response in nanotube/Si heterojunctions with high photo-responsivity. The scalability of our technique is demonstrated by fabricating an array of 250,000 micron-scale photo-active junctions covering a centimeter-scale wafer. I also present bidirectional phototransistors, and novel logic elements such as a mixed optoelectronic AND gate, a 2-Bit optoelectronic ADDER/OR gate, and a 4-Bit optoelectronic D/A converter [Nature Photonics (2014)]. The second portion of the talk will focus on inter-allotropic transformations/hybridizations of specific types that appear uniformly across large-area carbon networks, using moderate alternating voltage pulses. By controlling the pulse-magnitude, small-diameter single-walled carbon nanotubes can be transformed predominantly into larger diameter single-walled carbon nanotubes, multi-walled carbon nanotubes of different morphologies, multi-layered graphene nanoribbons, or structures with sp3-bonds. This re-engineering of carbon bonds evolves via a coalescence-induced reconfiguration of sp2-hybridizion, terminates with negligible introduction of defects, and demonstrates remarkable reproducibility [Nature Communications (2014)]. The last part of the presentation will focus on a new nanostructured transfer paradigm to print scalable and well-defined suspended nano/microscale networks on 3D patterned flexible substrates with micro- to nanoscale precision. The underlying printing/transfer mechanism, as well as the mechanical, electromechanical, and mechanical resonance properties of the suspended networks are characterized, including identifying metrics relevant for reliable and sensitive device structures [Scientific Reports (2015)].