Zeming Song

Origami lithium-ion batteries

There are significant challenges in developing deformable devices at the system level that contain integrated, deformable energy storage devices. Here we demonstrate an origami lithium-ion battery that can be deformed at an unprecedented high level, including folding, bending and twisting. Deformability at the system level is enabled using rigid origami, which prescribes a crease pattern such that the materials making the origami pattern do not experience large strain. The origami battery is fabricated through slurry coating of electrodes onto paper current collectors and packaging in standard materials, followed by folding using the Miura pattern. The resulting origami battery achieves significant linear and areal deformability, large twistability and bendability. The strategy described here represents the fusion of the art of origami, materials science and functional energy storage devices, and could provide a paradigm shift for architecture and design of flexible and curvilinear electronics with exceptional mechanical characteristics and functionalities.

Folding Paper-Based Lithium-Ion Batteries for Higher Areal Energy Densities

Paper folding techniques are used in order to compact a Li-ion battery and increase its energy per footprint area. Full cells were prepared using Li4Ti5O12 and LiCoO2 powders deposited onto current collectors consisting of paper coated with carbon nanotubes. Folded cells showed higher areal capacities compared to the planar versions with a 5 × 5 cell folded using the Miura-ori pattern displaying a ~14× increase in areal energy density.

Kirigami-based stretchable lithium- ion batteries

We have produced stretchable lithium-ion batteries (LIBs) using the concept of kirigami, i.e., a combination of folding and cutting. The designated kirigami patterns have been discovered and implemented to achieve great stretchability (over 150%) to LIBs that are produced by standardized battery manufacturing. It is shown that fracture due to cutting and folding is suppressed by plastic rolling, which provides kirigami LIBs excellent electrochemical and mechanical characteristics. The kirigami LIBs have demonstrated the capability to be integrated and power a smart watch, which may disruptively impact the field of wearable electronics by offering extra physical and functionality design spaces.

Origami-enabled deformable silicon solar cells

Deformable electronics have found various applications and elastomeric materials have been widely used to reach flexibility and stretchability. In this Letter, we report an alternative approach to enable deformability through origami. In this approach, the deformability is achieved through folding and unfolding at the creases while the functional devices do not experience strain. We have demonstrated an example of origami-enabled silicon solar cells and showed that this solar cell can reach up to 644% areal compactness while maintaining reasonable good performance upon cyclic folding/unfolding. This approach opens an alternative direction of producing flexible, stretchable, and deformable electronics.

Microscale Silicon Origami.

A new methodology to create 3D origami patterns out of Si nanomembranes using pre-stretched and pre-patterned polydimethylsiloxane substrates is reported. It is shown this approach is able to mimic paper-based origami patterns. The combination of origami-based microscale 3D architectures and stretchable devices will lead to a breakthrough on reconfigurable systems.

Printing Stretchable Spiral Interconnects Using Reactive Ink Chemistries

Stretchable electronics have important applications in health monitoring and integrated lab-on-a-chip devices. This paper discusses the performance of serpentine stretchable interconnects printed using self-reducing, silver reactive inks. It details process optimization, device fabrication, and device characterization, while demonstrating the potential applications for reactive inks and new design strategies in stretchable electronics. Devices were printed with an ethanol stabilized silver diamine reactive ink and cycled to stretch ratios of 140 and 160% over 1000 cycles with less than 2.5% variation in electrical resistance. Maximum deformation before failure was measured at 180% elongation. Additionally, interconnect deformation was compared to finite element analysis (FEA) simulations to show that FEA can be used to accurately model the deformation of low-strain printed interconnects. Overall, this paper demonstrates a simple and affordable route toward stretchable electrical interconnects.

Two-dimensional (2D) in-plane strain mapping using a laser scanning technique on the cross-section of a microelectronics package

Strain distribution exists in all microelectronic devices, including emerging flexible[1] and foldable[2] electronics. When a device is subject to bending or elevated temperature, the mechanical and electrical properties change. In some cases induced or applied strain can cause the device to fail[3-5]. For this reason, accurate strain mapping techniques are of great interest[6] to the electronics industry and could provide a detailed understanding of the strain distribution across a device. This understanding will help improve the structure or layout design of mechanical and electronic devices. The laser scanning technique demonstrated in this work could potentially provide a solution to map the two dimensional (2D) strain distribution within an electronic package. We have validated the strain sensitivity and spatial resolution of features for the device in a previous report[7, 8] and are now applying the technique to a practical microelectronic package sample. Here, we demonstrate 2D strain mapping capability by preforming 2D scans across the composite solder bump region at room temperature and an elevated temperature.

2D Grating Pitch Mapping of a through Silicon Via (TSV) and Solder Ball Interconnect Region Using Laser Diffraction: IEEE Electronic Components and Technology Conference, 2016

Planar Strain mapping of interconnects, such as Ball Grid Arrays (BGA) and Through-Silicon Vias (TSVs), is an important step in the development and testing of electronics packages, as excessive strain can lead to device failure. Today, the two most widely adopted methods of experimental strain field measurement, Digital Image Correlation and Moiré Interferometry, encounter limitations when the average strain magnitude drops below 1μm on thermally loaded samples. DIC provides only limited fields of view and increases measurement complexity, while Moiré Interferometry suffers from resolution near material interfaces. If well bonded to a surface, changes in periodicity of a thin diffraction grating can be strongly dependent on the strain field. The local grating periodicity, can then be measured using laser diffraction. We present a means of mapping the pitch of a grating bonded to the surface of a through-silicon via interconnect in two dimensions over a wide field of view, with a high degree of repeatability at room and elevated temperature.