Modeling and simulation has become indispensable in many fields to analyze systems and to design new products. Our research comprises physics-based modeling and reliable design intended for various applications: aerospace and defense, automotive, computers and telecommunications, portable electronics, and biomedical applications.
Objective: To develop and employ validated electrical, mechanical, and thermal models and design tools to achieve high-performance, low-power, manufacturable, and reliable flexible wearable electronic systems and demonstrators.
Approaches: Modeling of curved substrates by solving Maxwell’s equations, Finite Volume Method (FVM) for multi-physics modeling, sequential process modeling and residual stresses, design for stretchability, material, geometry, and process design guidelines.
Process simulation model to predict shapes and stresses
Antenna bending experiment and simulation
Multi-physics platform and Co-simulation
Design requires various levels of abstraction to ensure minimum product re-spins, protection of intellectual property and a seamless flow from application to manufacturing to product realization. Process Design Kits (PDK), which has been the hallmark of the CMOS semiconductor industry has been adopted for more than 20 years ago, and has been the key for creating several fabless design houses. Unlike the semiconductor industry where a single foundry is responsible for the complete IC process, the flexible wearable electronics industry has a fragmented foundry where multiple manufacturers provide processes that cater to sub-elements of a system, but not the system in its entirety. Unlike a wafer fab with an investment of billions of dollars, a combination from hundreds of foundries each with an investment of few million dollars is required to realize these systems. In addition, different foundries could provide substrates such as PEN, PET, Kapton, glass or paper to realize components such as resistors, inductors, capacitors, filters, antennas, sensors, batteries etc. Such implementations will lead to large deformation unlike any other system today and therefore addressing the associated mechanical, thermal, and electrical issues becomes critical. As the technologies evolve, new printing methods and materials will emerge with superior properties. To enable seamless deployment of the flexible wearable technologies, a framework is required where the design rules for each process can be captured, models can be developed and details can be hidden, so that a designer can seamlessly integrate various components into the system as part of the design process. Needless to say, such a framework should be standardized to interact with commercial design environments using mainstream design tool suites.
- Manufacturing Process Simulation
When devices are attached, when passives, conductors, batteries, sensors, and other elements are printed, and when various components are encapsulated, significant thermo-mechanical stresses develop in the flexible wearable electronic system. These stresses are influenced by, among other factors, the coefficient of thermal expansion mismatch among different materials, the time-, temperature-, and direction-dependent thermo-mechanical properties of various materials, the process temperature profiles, the cure kinetics and shrinkage of polymers, etc. Physics-based virtual manufacturing tools can simulate various process steps and determine residual shape and stresses in the flexible hybrid electronic system, even before physical porotypes are built. Such upfront process-simulation models and tools can save significant cost and time by eliminating trial-and-error manufacturing approaches and by resulting in high-yield, fast turn-around flexible wearable electronics products.
- Reliable Design
The microelectronic industry has traditionally relied upon thermal cycling, temperature/humidity, drop/impact, and other tests for qualification purposes. Although such tests are necessary for component, subsystem, and system qualification, physics-based reliability assessment models and tools can upfront insight into various failure mechanisms. Our focus will be to bend, twist, and stretch flexible wearable electronic systems, and subject them to thermal cycling, vibration, shock/impact, field-use and other conditions through numerical simulations. Such virtual reliability models and tools will be able to predict potential failure mechanisms and locations, operational life, and limits on their stretch, twist, and bend capabilities even before experimental prototyping and physical testing, The models and tools, once validated, will be generic in nature and can be used to assess a wide range of material, geometry, process, and application parameters from the standpoint of reliability.
Flexible wearable electronics requires detailed simulations of electrical, mechanical and thermal characteristics of the components to ensure that they are reliable and perform appropriately. Since these structures can be bent, twisted, stretched and washed their electrical, mechanical and thermal properties are tightly coupled to each other. This requires a multi-physics simulation environment.
The capabilities required for multi-physics simulation in the context of these systems include: i) exchanging model structures between electrical, mechanical and thermal tools, ii) mapping simulation results between tools, such as for example mapping of stress and deformation data from mechanical simulation to electrical and thermal simulation where the simulators are capable of reading and interpreting the data (ex: impact of stress on electrical properties of materials), iii) automated iterative solving between the different simulation tools including convergence checks, so that user intervention is minimized, and iv) a simple and user-friendly method to specify a range of bending, twisting and stretching conditions.
Our focus is to develop a multi-physics simulation environment by working with EDA companies by enhancing the current capabilities available in commercial tools.