Abstract: In one aspect, the present disclosure provides a nozzle for 3-D printing. The nozzle may include a first nozzle tip defining a first outlet, where the first nozzle tip includes a first channel extending therethrough. The nozzle may further include a second nozzle tip defining a second outlet, where the second nozzle tip includes a second channel extending therethrough, and where the first channel surrounds the second outlet. The second nozzle tip may be retracted longitudinally with respect to the first nozzle tip such that the second outlet of the second nozzle tip is located in the first channel.

Abstract: A 3D printed core-shell filament comprises an elongated core radially surrounded by an outer shell with a barrier layer in between, where the elongated core comprises a ductile polymer and the outer shell comprises a stiff polymer having a Young's modulus higher than that of the ductile polymer. A lightweight lattice structure may comprise a plurality of the 3D printed core-shell filaments deposited in layers.

Abstract: Provided are devices and methods that combine material anisotropy with nonlinear structural design to produce structures that precisely and sequentially actuate in response to multiple stimuli, such as water or non-polar solvents. These devices and methods can include bistable anisotropic elements that convert to monostable element upon exposure to a particular stimulus, and anisotropic distortions can be harnessed to change the geometric properties of the element to cross phase boundaries and trigger shape changes at precise times. One can incorporate complex logic into these devices and methods.

Abstract: A 3D printed core-shell filament comprises an elongated core radially surrounded by an outer shell with a barrier layer in between, where the elongated core comprises a ductile polymer and the outer shell comprises a stiff polymer having a Young's modulus higher than that of the ductile polymer. A lightweight lattice structure may comprise a plurality of the 3D printed core-shell filaments deposited in layers.

Abstract: In one aspect, the present disclosure provides a nozzle for 3-D printing. The nozzle may include a first nozzle tip defining a first outlet, where the first nozzle tip includes a first channel extending therethrough. The nozzle may further include a second nozzle tip defining a second outlet, where the second nozzle tip includes a second channel extending therethrough, and where the first channel surrounds the second outlet. The second nozzle tip may be retracted longitudinally with respect to the first nozzle tip such that the second outlet of the second nozzle tip is located in the first channel.

Abstract: A foam structure with nominally aligned arrays of carbon nanotube is described. The foam structure also includes a functionalization substance associated or attached to carbon nanotube surfaces.

Abstract: A method for making a multilayer foam structure of nominally-aligned carbon nanotubes (CNTs) is disclosed. The method comprises synthesizing a layer of CNTs and sandwiching the layer of CNTs between two polymeric layers, or between two metallic layers or foils.

Abstract: An energy absorbing cell has a first structural element, a second structural element disposed parallel to and spaced apart from a first structural element, a first intermediate member, and a second intermediate member. Each intermediate member is disposed at an angle between the structural elements. A first end and a second end of each intermediate member are respectively attached to the structural elements. The intermediate members are formed from an elastic material. The angles of the intermediate members are selected such that application of a compressive force to displace the structural elements toward one another triggers a snap-through instability in both intermediate members. The energy absorbing cell is used, singly or in combination with one or more other energy absorbing cells, to form energy absorbing structures, such as vehicle bumpers or highway barriers, adapted to control the deceleration of an object impacting the energy absorbing structure.

Abstract: Syntheses of carbon nanotubes (CNT) are disclosed. The syntheses can take place on a thermally oxidized silicon surface placed inside a furnace prior to a reaction. The setup can have many variables that could affect the resulting CNT arrays, including flow rate and composition of carrier gas, flow rate and composition of precursor solution, and temperature. By varying such variables the density of the resulting CNT arrays can be controlled.

Abstract: A foam structure with nominally aligned arrays of carbon nanotube is described. The foam structure also includes a functionalization substance associated or attached to carbon nanotube surfaces.

Abstract: A filamentary structure extruded from a nozzle during 3D printing comprises a continuous filament including filler particles dispersed therein. At least some fraction of the filler particles in the continuous filament comprise high aspect ratio particles having a predetermined orientation with respect to a longitudinal axis of the continuous filament. The high aspect ratio particles may be at least partially aligned along the longitudinal axis of the continuous filament. In some embodiments, the high aspect ratio particles may be highly aligned along the longitudinal axis. Also or alternatively, at least some fraction of the high aspect ratio particles may have a helical orientation comprising a circumferential component and a longitudinal component, where the circumferential component is imparted by rotation of a deposition nozzle and the longitudinal component is imparted by translation of the deposition nozzle.

Abstract: A method for controlling the microstructural arrangement of nominally-aligned arrays of carbon nanotubes (CNTs) and a foam structure of CNTs are disclosed. The method includes a functionalization of CNT surfaces, for example, a non-covalent functionalization. The non-covalent functionalization of CNT surfaces can be obtained by way of a wetting process, for example by the use of a solution of surfactant or silica (SiO2) nanoparticles to wet the CNTs. In particular, the CNT array is first detached from the growth substrate and then a functionalization substance (surfactant or SiO2) is added to the CNT array. The functionalization substance can be dissolved in a volatile solvent, such that CNT arrays densify after the solvent evaporates. A method for synthesizing nominally-aligned arrays of carbon nanotubes (CNTs) is further disclosed, wherein the synthesizing method is combined with the wetting process.

Abstract: Syntheses of carbon nanotubes (CNT) are disclosed. The syntheses can take place on a thermally oxidized silicon surface placed inside a furnace prior to a reaction. The setup can have many variables that could affect the resulting CNT arrays, including flow rate and composition of carrier gas, flow rate and composition of precursor solution, and temperature. By varying such variables the density of the resulting CNT arrays can be controlled.

Abstract: Syntheses of carbon nanotubes (CNT) are disclosed. The syntheses can take place on a thermally oxidized silicon surface placed inside a furnace prior to a reaction. The setup can have many variables that could affect the resulting CNT arrays, including flow rate and composition of carrier gas, flow rate and composition of precursor solution, and temperature. By varying such variables the density of the resulting CNT arrays can be controlled.

Abstract: Syntheses of carbon nanotubes (CNT) are disclosed. The syntheses can take place on a thermally oxidized silicon surface placed inside a furnace prior to a reaction. The setup can have many variables that could affect the resulting CNT arrays, including flow rate and composition of carrier gas, flow rate and composition of precursor solution, and temperature. By varying such variables the density of the resulting CNT arrays can be controlled.

Abstract: Syntheses of carbon nanotubes (CNT) are disclosed. The syntheses can take place on a thermally oxidized silicon surface placed inside a furnace prior to a reaction. The setup can have many variables that could affect the resulting CNT arrays, including flow rate and composition of carrier gas, flow rate and composition of precursor solution, and temperature. By varying such variables the density of the resulting CNT arrays can be controlled.

Abstract: A method for making a multilayer foam structure of nominally-aligned carbon nanotubes (CNTs) is disclosed. The method comprises synthesizing a layer of CNTs and sandwiching the layer of CNTs between two polymeric layers, or between two metallic layers or foils.