Lintec of America, Inc.

Chi Huynh

Masaharu Ito

Techniques are described for transferring nanofiber forests using transfer films that either lack a conventional adhesive at the substrate—nanofiber forest interface or that include a diffusion barrier that prevents diffusion of adhesive molecules (or other polymer molecules mobile at ambient temperatures) into the nanofiber forest. These techniques can be applied to single layer nanofiber forests or stacks of multiple nanofiber forest. By selecting the bond strength between the nanofiber forest and the transfer films, the nanofibers can be aligned in a common direction that includes, but is not limited to, perpendicular to a substrate or transfer film.

Transferring nanofiber forests between substrates

Techniques are described for transferring nanofiber forests using transfer films that either lack a conventional adhesive at the substrate-nanofiber forest interface or that include a diffusion barrier that prevents diffusion of adhesive molecules (or other polymer molecules mobile at ambient temperatures) into the nanofiber forest. These techniques can be applied to single layer nanofiber forests or stacks of multiple nanofiber forest. By selecting the bond strength between the nanofiber forest and the transfer films, the nanofibers can be aligned in a common direction that includes, but is not limited to, perpendicular to a substrate or transfer film.

Methods and systems are described for continuously densifying at least one nanofiber sheet using heat and an applied force that can include both compressive and tensile components. Nanofiber sheets densified using these techniques have a more uniform and more highly aligned microstructure than nanofiber sheets densified using a solvent alone. As a result, the nanofiber sheets of the present disclosure have, for example, higher tensile strength and better electrical conductivity than nanofiber sheets densified using other techniques.

Densifying a nanofiber sheet using heat and force

A nanofiber forest that includes a pattern or shape can be transferred to a substrate. The nanofiber forest can be configured to have any perimeter and/or internal shape or pattern using a stencil technique and/or using an engraving technique. This pattern can be transferred as a 'negative image' of a corresponding pattern in a stencil or as a 'positive image' by engraving the pattern directly into the nanofiber forest. For either type of pattern formation, the patterned nanofiber forest is transferred by applying a substrate to the pattern or to a nanofiber forest covered by a patterned stencil. Pressure is then applied causing the exposed surface of the nanofiber forest or pattern of nanofiber forest to adhere to the substrate.

Patterning a nanofiber forest

Techniques are described for transferring nanofiber forests using transfer films that either lack a conventional adhesive at the substrate&#x2014;nanofiber forest interface or that include a diffusion barrier that prevents diffusion of adhesive molecules (or other polymer molecules mobile at ambient temperatures) into the nanofiber forest. These techniques can be applied to single layer nanofiber forests or stacks of multiple nanofiber forest. By selecting the bond strength between the nanofiber forest and the transfer films, the nanofibers can be aligned in a common direction that includes, but is not limited to, perpendicular to a substrate or transfer film.

A nanofiber forest is described that has been processed to increase a number of nanofibers per unit area (referred to as 'areal density' or, equivalently, 'density') compared to the nanofiber forest in its as-synthesized state. This increase in areal density is accomplished by physically manipulating a deformable substrate on which the nanofiber forest is disposed. At a high level, this physical manipulation begins by transferring the nanofiber forest from a growth substrate to a deformable substrate. A surface area of the deformable substrate is reduced relative to a surface area of the substrate when the nanofiber forest was attached. This reduction in area causes the nanofibers in the forest to move closer to one another, thus increasing the number of nanofibers per unit area.

Densifying a nanofiber forest

A nanofiber sheet is described that is composed of a substrate and a layer of oriented nanofibers. Nanofibers of the sheet can be oriented in a common direction. In some orientations, light absorbent sheets can absorb over 99.9%, and in some cases over 99.95%, of the intensity of light incident upon the sheet. Methods for fabricating a light absorbent sheet are also described.

Nanofiber sheet

A nanofiber structure is described that is composed of a substrate and a layer of oriented nanofibers. Nanofibers of the layer can be oriented in a common direction. An angle of the common direction can be selected so that nanofibers of the sheet are oriented at an angle with respect to an underlying substrate even if the underlying substrate is not planar. The angle can be used to adapt the sheets to demands as a thermal interface material.

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Richardson, TX, United States of America

Chi Huynh