Method of making a flexible substrate containing self-assembling microstructures

An article comprising

• (a) a substrate comprising a first amorphous thermoplastic layer having embossed on a first surface thereof a plurality of recesses of predetermined dimensions, each recess having a flat bottom surface, the length and width of said flat bottom surface each being about 1000 μm or less;
• (b) a plurality of microstructures respectively disposed within said recesses, said microstructures having dimensions complementary to the dimensions of said recesses;
• and
• (c) a planarization layer disposed over said microstructures and said first surface of said amorphous thermoplastic substrate.

A method for forming an amorphous thermoplastic product having precise embossed surfaces requiring sharp angles and flatnesses, comprising the steps of:

• providing a continuous press having a pair of opposed belts, at least one of said belts having a predetermined pattern;
• passing a web of amorphous thermoplastic material between said opposed belts;
• heating said material to at least above its glass transition temperature to the embossing temperature of said amorphous thermoplastic material;
• applying pressure to said amorphous thermoplastic material through said belts sufficient to emboss said predetermined pattern on a surface thereof;
• said pattern including an array of sparced receptor recesses having a depth between 5 and 100 μm, an upwardly tapered wall at an angle of 20°-70°, a flat bottom parallel to the top surface of said material, said bottom wall having a major dimension of 1000 μm or less;
• and
• cooling said amorphous thermoplastic material to below its glass transition temperature.

A method of assembling a microstructure on a substrate, said substrate comprising a top surface with at least one recessed region thereon, said method comprising the steps of:

• 1) providing a slurry comprising a plurality of shaped blocks and a fluid;
• 2) transferring said slurry over said substrate at a rate at which at least one of said shaped blocks will self align and be disposed into a recessed region;
• and 3) subjecting said substrate with said shaped blocks disposed therein to elevated temperatures for subsequent processing, and
• wherein the substrate employed in the method comprises a first layer of an amorphous polymeric material, said material having a glass transition temperature Tg and an embossing temperature Te, at which Te the elastic modulus of the substrate is less than about 1×108 dynes/cm2 and the viscoelastic index of the substrate is greater than about 0.3, and said substrate being capable of subsequent processing at a processing temperature Tp, such that after about one hour at Tp the substrate has a dimensional stability of <0.01% change in dimension, an elastic modulus of greater than about 1010 dynes/cm2, and a viscoelastic index of less than about 0.1.