Smart Polymers as Adaptive and Programmable Substrates for Electronics

Date

Dec 12, 2016

Time

4:30 PM - 5:30 PM

Speaker

Dr. Jonathan Reeder

Affiliation

The University of Texas at Dallas, Department of Materials Science and Engineering, Texas, USA

Language

en

Main Topic

Materialien

Other Topics

Materialien, Physik

Host

Kristina Krummer

Description

The planar and brittle nature of traditional electronics precludes them from intimately interfacing with the soft, curvilinear surfaces which are ubiquitous about our daily life. Here we present two methods for transforming planar electronics into 3D structures via reconfiguration of shape memory polymer (SMP) substrates. Temperature-responsive SMP substrates with a glass transition above room temperature are used as the substrate. Heating the substrate above its glass transition temperature reduces the modulus two orders of magnitude, allowing the application of an external force to deform predefined sections out-of-plane. The shape fixing properties of the substrate allow the deformed, out-of-plane state to be “locked in” by cooling to room temperature. Arrays of 3D electronic whiskers are assembled via the application of warm air and exhibit multiple sensing modalities based on the change in resistivity of Au serpentines in response to strain and temperature. Thiol-click polymer substrates are synthesized with a glass transition of 55 °C and 3x3 arrays of SMP cantilevers (150 µm x 2mm) are laser machined into the substrate. The application of 70 °C air from the backside of the substrate softens the substrate and forces the array of cantilevers out-of-plane to angles reaching 90° from the substrate surface, as determined by the air velocity and substrate thickness. The relationship between deployment angle and both substrate thickness and air velocity is shown for ranges of 25-125 µm and 1-75 m/s, respectively. Photolithographically defined strain gages patterned at the hinges of the cantilevers enable tracking of the angular deflection of the 3x3 array of flanges. Tip deflections and temperature changes as small as 5 µm and 0.5 °C, respectively, enable sensing of surface topologies, material stiffness, friction, and ambient temperature We also report on the synthesis and characterization of a photopatternable thiol-epoxide/acrylate SMP. A linear thiol-epoxide polymerization generates OH’s which enable the grafting of an acrylate crosslinker onto the linear backbone. Subsequent photosensitization and UV exposure reacts the acrylate groups and forms a thermoset network. Thermomechanical testing shows that this material exhibits an over two-order-of-magnitude drop in modulus (2 GPa to 8 MPa) when heated from 20 to 45°C. This adaptive material system is amenable to conventional lithography techniques, and future work aims to develop a photopatterning process for producing sub-10µm SMP features.

Links

• Seminars at the IFW

Last modified: Dec 12, 2016, 8:48:17 AM