Flexible Hybrid Electronics

SoCCsopFlexible electronics have the potential to transform computing by enabling bendable systems with arbitrary shapes. Physical flexibility combined with the cost and weight advantages opens a wide range of form factors and application areas, including wearable electronics, prosthetics, medical sensing, rollable displays, and internet of things (IoT).
Close to 100 million people suffering from physical impairments can benefit from flexible electronics. However, the performance and capabilities of purely flexible electronics are very limited. For example, silicon technology offers 14nm feature size with over 1GHz frequency, whereas the feature sizes of thin-film transistors (TFT) range from 8µm to 50µm, and frequencies hardly reach 10MHz. Therefore, practical use of flexible electronics is largely limited to sensors and displays. Emerging flexible hybrid electronics (FHE) can target this problem by integrating traditional rigid ICs and printed electronics on a flexible substrate. This hybrid approach combines the processing and storage capabilities of silicon ICs with the physical and cost benefits of flexible electronics. Hence, FHE exhibit an inherent design trade-off between flexibility and computational efficiency (more rigid ICs).
At eLab, we are working on methodologies and tools for the design and optimization of Systems-on-Polymer (SoPs), which will enable new form factor computer systems. We coined the term SoP to refer to fully integrated FHE systems capable of sensing, computing, and communication.

Our first patent on this topic is filed in August 2015! Check our overview paper for more information

Ujjwal Gupta, Jaehyun Park, Hitesh Joshi, Umit Y. Ogras. “Flexibility Aware Systems on Polymer: Concept to Prototype,” in IEEE Trans. on Multi-Scale Computing Systems, December 2016.
Ujjwal Gupta, Sankalp Jain, Umit Y. Ogras, “Can Systems Extended to Polymer? SoP Architecture Design and Challenges,” in Proc. of the Intl. SoC (System-on-Chip) Conference, September 2015. 
ACM SIGDA newsletter column on FHE: Ganapati Bhat, Umit Y. Ogras, “What is Flexible Hybrid Electronics?,” ACM/SIGDA e-Newsletter, vol. 49, no. 11, November 2019.

Sizhe An, Umit Ogras, What is EDA for Wearable Flexible Healthcare Devices? ACM SIGDA newsletter column, February 2022.

Please see the new video demonstrations of energy harvesting using flexible piezo-electric patches and wearable IoT prototype:

Besides introducing the concept of Systems-on-Polymer, this paper presents an approach to place rigid ICs onto flexible substrates to minimize the loss of flexibility. We use bending forces and cantilever beam concept to model flexibility and solve this optimization problem, as illustrated below.

Energy Harvesting using Flexible PV-cells:  Wearable devices interweave technology into daily life in a myriad of applications including health monitoring, smart watch, and fitness tracker. Widespread adoption of these devices is hindered by the duration they can operate without recharging. Since the weight, size and flexibility constraints limit the total battery capacity, it is imperative to leverage ambient energy sources, such as solar energy, body heat and motion. We demonstrates how to maximize the energy harvested using flexible photo-voltaic cells.
Poster Presented at ES-Week 2017:
Jaehyun Park, Hitesh Joshi, Hyung Gyu Lee, Sayfe Kiaei, and Umit Y. Ogras. “Flexible PV-cell Modeling for Energy Harvesting in Wearable IoT Applications,” at CODES+ISSS, October 2017.
The corresponding paper received the 2017 CODES+ISSS Best Paper Award. It is published in ACM Tran. on Embedded Comp. Sys. (ESWEEK Special Issue), October 2017.

Interesting video on flexible electronics ecosystem: