Description
Figures and relevant data from the paper "Broadband Electromagnetic Properties of Engineered Flexible Absorber Materials" are found here . The paper was published on Advanced Materials Technologies in 2023. ABSTRACT: Flexible and stretchable materials have attracted significant interest for applications in wearable electronics and bioengineering fields. Recent developments also incorporate mounted and embedded microwave circuits, components, and systems with engineered flexible materials that operate over a broadband frequency range (~1 to 100 GHz). Here we demonstrate a simple, low-cost, flip-chip technique where flexible materials are placed on top of coplanar waveguide (CPW) transmission lines for material property measurement. We apply on-wafer error correction and de-embedding techniques to determine broadband electromagnetic properties of the material-loaded transmission line segments. Finite-element simulations of material-loaded devices were employed along with the broadband measurements to estimate the electromagnetic material properties. To demonstrate this technique, we fabricated flexible polydimethylsiloxane (PDMS) composites with varying concentrations of Barium Hexaferrite (BaM) nanoparticles for potential applications in electromagnetic shielding and quantified the complex permittivity and permeability of the composites up to 110 GHz using our broadband scattering-parameter measurements. We fit the frequency-dependent permeability to models describing the ferromagnetic resonance of barium hexaferrite (BaM) nanoparticles in PDMS and estimated the constituent nanoparticle properties using the Maxwell-Garnett mixing model. This study paves way to exploit a wide range of engineered materials in flexible, wearable, and biomedical electronics applications and presents a convenient methodology to extract important broadband electromagnetic properties for applications such as electromagnetic shielding.
Resources
| Name | Format | Description | Link |
|---|---|---|---|
| Figure 1: Reference chip, air and composite loaded test chips subject to measurement. | PNG | PDMS composites with 30% and 60% (weight ratio) barium hexaferrite were directly placed on test chips with CPWs for flip chip measurements. The Reference die is used for on-wafer calibration with necessary devices to perform multiline through-reflect-line (mTRL) and series resistor calibration [Orloff2011]. Test chip has 8 identical transmission lines of 11 mm. Schematic diagrams of the top-view and cross section of the composite (superstrate) loaded transmission line are shown on the bottom and right-hand of the image. | Open resource |
| Figure 2: Frequency dependent R, L, C, G (per unit length) transmission line model that is used for simulations and calculations | PNG | The image depicts the electric field vectors for gold transmission lines on quartz substrate that are exaggerated for clarity (Image not to scale). The fields emanate from the signal line and ends on ground planes. | Open resource |
| Differential substrate capacitance vs. substrate permittivity | CSV | The impact of substrate and superstrate material properties on CPW transmission line capacitance, inductance, and resistance calculated from finite-element simulations. | Open resource |
| Differential superstrate capacitance vs. superstrate permittivity | CSV | The impact of substrate and superstrate material properties on CPW transmission line capacitance, inductance, and resistance calculated from finite-element simulations. | Open resource |
| Differential inductance vs. superstrate permeability | CSV | The impact of substrate and superstrate material properties on CPW transmission line capacitance, inductance, and resistance calculated from finite-element simulations. | Open resource |
| Figure 4: Material loaded transmission lines and de-embedding in test wafer | PNG | The cables and probes from the vector network analyzer (VNA) are connected to the reference plane during measurement. The TRL calibration procedure translates 50 Ohm reference plane to probe pads. The air-loaded distance (L) of the transmission line is de-embedded to obtain RLCG distributed circuit parameters for BaM material loaded CPW space. | Open resource |
| Calculated and measured distributed circuit parameters - Inductance per unit length | CSV | Figure%205a.csv | Open resource |
| Calculated and measured distributed circuit parameters - Resistance per unit length | CSV | Figure%205b.csv | Open resource |
| Frequency dependence of the capacitance per unit length | CSV | Frequency dependence for the bare test chip (air), two PDMS samples, three 30% BaM samples, and the BaM 60% sample. These values are obtained by fixing RL and optimizing CG to fit the measured, de-embedded data. The conductance is negligible when compared to capacitance values. | Open resource |
| Frequency dependence of the conductance per unit length (LDUT) | CSV | Frequency dependence for the bare test chip (air), two PDMS samples, three 30% BaM samples, and the BaM 60% sample. These values are obtained by fixing RL and optimizing CG to fit the measured, de-embedded data. The conductance is negligible when compared to capacitance values. | Open resource |
| Calculated real effective permittivity (εeff) vs. frequency | CSV | Real permittivity for two PDMS samples, three 30% BaM samples, and the BaM 60% sample. | Open resource |
| Calculated imaginary effective permittivity (εeff) vs. frequency | CSV | Imaginary permittivity for two PDMS samples, three 30% BaM samples, and the BaM 60% sample. | Open resource |
| Calculated and extracted real part of effective permeability for samples | CSV | Calculated effective permeability (μeff) vs. frequency for three 30% BaM samples, and the BaM 60% sample. | Open resource |
| Calculated and extracted imaginary part of effective permeability for samples | CSV | Calculated effective permeability (μeff) vs. frequency for three 30% BaM samples, and the BaM 60% sample. | Open resource |
| Estimates for the free-space attenuation constant for engineered BaM-PDMS composites | CSV | Figure%209.csv | Open resource |
| Readme File for Figures with Description | Text | README.txt | Open resource |