[2] He and his team built the world's smallest synthetic electrically powered rotational nanomotor,[3] the smallest fully integrated FM radio receiver,[4][5] a nanomechanical mass balance with single-atom sensitivity,[6] voltage-controllable nanoscale relaxation oscillators,[7][8] and a nanoscale thermal rectifier[9] useful for phononic circuitry He and his team invented the nanomanipulator,[10][11] suspended graphene grid,[12][13] and the graphene liquid cell[14] and graphene flow cell,[15] all of which have greatly advanced transmission electron microscopy.
As a graduate student, Zettl closely collaborated with two-time Physics Nobel Laureate John Bardeen.
Charge density wave statics and nonlinear dynamics Zettl discovered chaotic response[18] and period doubling routes to chaos[19] in dynamic charge density wave (CDW) systems driven by an rf field, and found that mode locking completely freezes out all internal fluctuations of the collective mode condensate.
Zettl was the first to intercalate high-Tc superconductors with foreign molecules[32] which allowed Cu-O planes to be physically and electronically separated.
Zettl also produced high quality single crystals[33] of fullerene superconductors which facilitated a host of detailed transport and thermodynamic measurements.
Zettl revealed the elastic properties of high-Tc materials,[34] and determined the effective dimensionality of fullerene superconductors via paraconductivity measurements.
[38] Zettl discovered that CNTs could be stable in a fully collapsed state,[39] which led to a refined quantification[40] of the interlayer interaction energy in graphite; this important parameter had previously been surprisingly ill-defined experimentally.
Zettl was the first to synthesize boron nitride nanotubes (BNNTs),[1] for which (in sharp contrast to CNTs), the electronic and optical properties are relatively insensitive to wall number, diameter, and chirality.
[46] He also developed methods to functionalize the outer surfaces of BNNTs,[47][48][49] and fill them with foreign chemical species[50][51] creating new structures including silocrystals.
[52] Zettl showed experimentally that an electric field could be used to modulate the electronic band gap of BNNTs (giant Stark effect).
Other inventions by Zettl that resulted were surface-tension-powered relaxation oscillators,[7] tunable resonators,[55] nanocrystal-powered linear motors,[56] a fully integrated nanoradio receiver,[3] a nanoballoon actuator,[57] and nano-scale electrical[58] and thermal[59] rheostats.
Zettl used the nanomanipulator to perform the first electron holography experiments[60] on nanoscale materials, which quantified quantum mechanical field emission from CNTs.
Zettl also developed nanomechanical biological probes,[61] tailored nanopores,[62][63][64] and highly efficient wideband graphene-based mechanical energy transducers.