(6kc) Soft, Stretchable Wearable Platforms for Sensing and Energy Harvesting Applications

The human sweat represents an interesting biofluid due to its ease of collection and presence of biomarkers related to dehydration, physical fatigue, mental stress, and various diseases. Recently reported technologies for analyzing sweat rely either on active, battery-powered electronics for electrochemical detection or passive, colorimetric chemistries for visual readout. Complex construction and large size/weight represent disadvantages of the former; semi-quantitative operation and limited scope of measurable biomarkers are limitations of the latter. I introduce the first example of a unique, unconventional class of battery-free, wireless, flexible, lightweight, skin interfaced platform that perform sensing via schemes inspired by electrochemical biofuel cells and colorimetric assays embedded in chrono-sampling microfluidic networks with broad functionality in sweat analysis. NFC electronics, biofuel cells and microfluidics results in a wearable chemical sensor which is several orders lighter, cheaper and smaller than reported alternatives with no apparent effect on its performance. A demonstration device allows simultaneous monitoring of sweat rate/loss, along with quantitative measurements of pH and of lactate, glucose and chloride concentrations using biofuel cell and colorimetric approaches. Systematic studies of the electronics designs, the microfluidic systems and the integration schemes establish the key design considerations and performance attributes. Capabilities in measurements with short- and long range wireless reader systems in the context of personalized fitness monitoring suggest a broad range of application possibilities. Human trials involving measurements of sweat glucose and lactate concentrations and comparisons to levels in the blood over a period of two days highlight the ability for long-term monitoring of sweat analytes as a potentially non-invasive means to track corresponding blood concentrations. These successful studies represent the first examples of skin interfaced sweat sensors with multi-day operational use.

In addition to realizing new sensing platforms, developing viable wearable energy sources remain another key challenge hampering the widespread growth of the wearable sensors field. Most prior efforts rely on bulky coin batteries which severely compromise wearability. Efforts focused on developing thin, stretchable batteries and super capacitors address this issue but at the cost of limited energy capacity and frequent recharging. Various forms of wearable energy harvesters that harness energy from body heat, movement and sun demonstrate potential for powering wearable electronics. However, many of the energy harvesters and storage systems rely on toxic chemicals which pose serious health concerns. I describe the fabrication, characterization, and real-life application of a highly biocompatible, soft, stretchable electronic-skin-based biofuel cell (E-BFC) that scavenges energy from lactate present in human sweat. The E-BFC exhibits a power density of ~1.2 mWcm-2, representing the highest power density recorded by a wearable biofuel cell to date. Such performance is achieved via a unique combination of lithographically-patterned stretchable electronic framework and screen-printed, densely-packed three-dimensional carbonnanotube-based bioanode and cathode array arranged in a stretchable “island-bridge” configuration. The E-BFC maintains its performance even under repeated strains of 50% and can power a Bluetooth Low Energy (BLE) radio. This is the first example of a wearable biofuel cell powering a BLE radio. Such systematic studies and demonstrations mark a significant breakthrough in the field of wearable biofuel cells.

Selected Publications: (Total papers: 38; H-index: 26; Total citations: 2583)

Full List:
https://scholar.google.com/citations?hl=en&user=FYgDmoAAAAAJ&view_op=lis...
1. “Battery-free, skin-interfaced microfluidic/electronic system for simultaneous electrochemical, colorimetric & volumetric sweat analysis” A. J. Bandodkar et al, Sci. Adv. (under review).
2. “Soft, stretchable, high power density electronic skin-based biofuel cells for scavenging energy from human sweat”, A. J. Bandodkar, J.-M. You, N.-H. Kim, Y. Gu, R. Kumar, A. M. V. Mohan, J. Kurniawan, S. Imani, T. Nakagawa, B. Parish, M. Parthasarathy, P. P. Mercier, S. Xu and J. Wang, Energy Environ. Sci., 2017,10, 1581.
3. “All-printed magnetically self-healing electrochemical devices”, A. J. Bandodkar, C. S. López, A. M. V. Mohan, L. Yin, R. Kumar and J Wang, Sci. Adv. 2016, 2, e1601465.
4. “A wearable chemical–electrophysiological hybrid biosensing system for real-time health and fitness monitoring”, S. Imani, A. J. Bandodkar, V. Mohan, R. Kumar, S. Yu, J. Wang, P.P. Mercier, Nat. Commun. 2016, 7, 11650.
5. “Highly Stretchable Fully-Printed CNT-based Electrochemical Sensors and Biofuel Cells: Combining Intrinsic and Design-induced Stretchability”, A. J. Bandodkar, I. Jeerapan, J. M. You, R. N. Flores and J. Wang, Nano Lett. 2016, 16, 721.
6. “All-Printed Stretchable Electrochemical Devices”, A. J. Bandodkar, R. Nuñez-Flores, W. Jia and J. Wang, Adv. Mat. 2015, 27, 3060.

Keywords: Wearable chemical sensors, biofuel cells, microfluidics, colorimetric assays, wireless electronics, printed devices.

Research Interests: Wearable chemical sensors, implantable chemical sensors, biofuel cells, batteries, energy harvesting, stretchable devices, self-healing systems.

Teaching Interests: Teachers and mentors are important pillars in one’s success and I owe my accomplishments to the teachers in my past and present who instilled scientific curiosity in me, taught me technological skills, helped me overcome my weaknesses, and guided me in tackling challenging tasks. A major motivation for me to become a faculty is to partake into the noble gesture of teaching and guide young minds towards a successful, fruitful and content life. During my PhD and now as a postdoc, I have mentored 14 undergraduate students of which 4 are currently PhD students in top tier schools; 3 work in industry and 7 are currently pursing undergraduate degrees. I have also been a TA for two graduate level courses (~50 students in each course). Apart from helping students understand the concepts during office hours, I also taught the class when the concerned professor was travelling. Considering my ability to explain complex scientific concepts in a simple manner to people without STEM background and my passion to motivate people towards research, I was invited as a guest lecturer for an undergraduate course (~150 students) on “Designing Information” at the UC San Diego’s Fine Arts Department. During this lecture, I illustrated the different ways in which wearable devices offer an exciting avenue for achieving personalized Internet of Things and how these devices are having an impact in today’s day and age. The overwhelming feedback and interest and curiosity ignited in the Fine Arts students, who before the lecture had given little thought to wearable devices and their impact, was quite satisfying to me. In fact, one of the students even collaborated with me on a project that combined chemical sensors with fine arts – a truly unique learning for both of us. In addition to these, I have also been invited as a speaker at the University’s undergraduate outreach events to motivate and encourage young minds to take up careers in the STEM fields.

As a faculty I would be thrilled to teach courses on mass and heat transfer, thermodynamics, electrochemistry, chemical sensors, nanobiotechnology and surface science. Additionally, I would be excited to be involved in committees focused on increasing student participation in STEM fields.