Light-driven levitation of ultralight macroscopic plates / John Cortes.

Format:

Book

Manuscript

Thesis/Dissertation

Author/Creator:

Cortes, John, author.

Contributor:

Bargatin, Igor, degree supervisor.

Turner, Kevin, degree committee member.

Hu, Howard H., degree committee member.

University of Pennsylvania. Mechanical Engineering and Applied Mechanics, degree granting institution.

Language:

English

Subjects (All):

Penn dissertations--Mechanical engineering and applied mechanics.

Mechanical engineering and applied mechanics--Penn dissertations.

Local Subjects:

Penn dissertations--Mechanical engineering and applied mechanics.

Mechanical engineering and applied mechanics--Penn dissertations.

Physical Description:

xv, 139 leaves : illustrations (chiefly color) ; 29 cm

Production:

[Philadelphia, Pennsylvania] : University of Pennsylvania, 2019.

Summary:

The term "Micro-flyers" has generally been associated with centimeter-scale devices such as robotic insects or miniaturized drones. Due to manufacturing and aerodynamics challenges, propulsion at even smaller, sub-centimeter scales has historically been very difficult. In this thesis, we present the novel idea that light-driven photophoretic force can be used as a means of propulsion, which can then be used to levitate ultralight plates under several ambient and reduced pressure conditions.

The photophoretic force is generated by a difference in temperature in a solid body or within the walls of a channel. We have used this unique phenomenon to develop micro-hovercrafts, which range from a few millimeters up to a centimeter in size and can hover hundreds of microns above an engineered low-stiction substrate at atmospheric pressure conditions. Under these conditions, gas flows from the cold end to the hot end, where a carbon nanotube layer absorbs incident light and heats up, resulting in the thermal transpiration flow. This flow then creates an overpressure underneath the plate, which causes it to lift-off and maintain a hovering gap between 300 µm and 600 µm for extended periods of time.The photophoretic force is generated by a difference in temperature in a solid body or within the walls of a channel. We have used this unique phenomenon to develop micro-hovercrafts, which range from a few millimeters up to a centimeter in size and can hover hundreds of microns above an engineered low-stiction substrate at atmospheric pressure conditions. Under these conditions, gas flows from the cold end to the hot end, where a carbon nanotube layer absorbs incident light and heats up, resulting in the thermal transpiration flow. This flow then creates an overpressure underneath the plate, which causes it to lift-off and maintain a hovering gap between 300 µm and 600 µm for extended periods of time.

The ultralight plates consist of a microfabricated plate metamaterial called nanocardboard, which is made from two face sheets interconnected by channels and features wall thicknesses in the 35-100 nm range, giving them areal densities as low as 0.5 g/m2.

We also show the plate's capabilities to fly at heights above 10 mm above a fine metal mesh at reduced pressures (as low as 10 Pa inside of a small vacuum chamber), which shows the potential of mid-air levitation without the dependence on a solid substrate. Not only can the plates fly at reduced pressures, but they also display the ability to liftoff and move a payload. We have developed theoretical models which are able to predict both the low-height hovering behavior as well as the reduced pressure capabilities of our ultralight plates. We show that our plates are excellent candidates for a novel approach to conducting atmospheric research in the Earth's mesosphere as well as the Martian surface (given their ranges of ambient pressure).

Notes:

Ph. D. University of Pennsylvania 2019.

Department: Mechanical Engineering and Applied Mechanics.

Supervisor: Igor Bargatin.

Includes bibliographical references.

Other Format:

Online version: Cortes, John. Light-driven levitation of ultralight macroscopic plates.

OCLC:

1142099424