We present a technique for the directed assembly and self-assembly of micrometer-scale structures based on the control of specific DNA linkages between colloidal particles. The use of DNA links combined with polymer brushes provides an effective way to regulate the range and magnitude of addressable forces between pairs (and further combinations) of different particles. We demonstrate that the autoassembly of alternate microbeads as well as their directed assembly, by using laser tweezers, is reversible. The key to reversibility is preventing the particles from falling into their van der Waals well at close distances. This goal is achieved by the use of adsorbed polymers that limit the number of DNA bridges to one to three between adjacent particles.

We report on NMR studies of (TMTSF)2PF6 with field aligned along the a and b axes. We observe no change in the Knight shift on cooling well into the superconducting state, consistent with an equal spin paired triplet state. Nuclear spin lattice relaxation measurements show an increase just below Tc which we associate with a Hebel–Slichter (HS) peak and suggest P wave pairing that is nodeless. An additional study of the critical field as a function of pressure shows a strong enhancement as pressure is reduced toward the critical pressure, Pc, for spin density wave formation. We find that the superconducting Tc is not reduced as the SDW phase is entered. However, Hc2 is increased and there is a strong upward curvature of Hc2 along all axes as pressure is decreased toward Pc. We suggest that near Pc, there is a coexistence region consisting of stripes (slabs) of commingled SDW and superconducting regions and that the application of a magnetic field further finely divides the superconductor.