Large Area Flexible and Stretchable Sensors Actuators and Electronics

TITLE: Large Area Flexible and Stretchable Sensors Actuators and Electronics

Advisors: Sameer R Sonkusale

Researchers: Pooria Mostafalu, Shideh Kabiri Ameri, Meera Punjiya

Sponsor: DARPA, NSF EFRI, Qatar Foundation

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There is a great need to develop sensors and circuits that are flexible and conformal for wearable and implantable biomedical applications. In one of the projects, funded through the NSF Emerging Frontiers in Research and Innovation (EFRI) program, our team is working on integrated sensors, electronics and actuators on flexible and stretchable substrates that are also biocompatible for real-time monitoring and treatment of chronic wounds. The smart dressing is expected to communicate the status of the wound wirelessly to the caregiver, who can trigger an on-demand drug release from the built-in reservoir on the dressing. The smart dressing is also expected to have its own energy source or have mechanisms for wireless energy harvesting. Sensors range from dissolved oxygen, pH, strain and temperature. Treatment appears in the form of electrical stimulation of wound, delivery of oxygen and chemical growth factors and draining of the excess fluid from the wound. We are also working on the next generation of ingestible soft capsule endoscope, where there is a need to make transparent flexible sensors and electronics for monitoring the gastric environment. In some of these applications, there is also a need to make these sensors on biodegradable and biocompatible substrates using low cost processes that do not rely on expensive cleanroom facilities.


We are investigating several innovative bioflex devices and systems. For smart bioflex wound dressing, we have developed electrochemical sensors on paper and textile for detection of oxygen and pH in the wound. Paper or fabric is an abundant, naturally renewable, low cost, biocompatible and biodegradable material suitable for biomedical applications. We utilize a low cost fabrication approach that does not require expensive facilities for making paper based devices. It utilizes stencil-based patterning of conductive inks for realizing interconnects on paper using adhesive tapes and origami for shaping. We demonstrate nanomaterial growth directly on paper substrate through templated electrodeposition process for realization of nanowire electrode array on paper for the first time. These electrodes have high surface area and lower electrode impedance with many applications in healthcare and energy. We have also worked on using spray painting through shadow stencil mask for patterning hydrophobic and hydrophilic regions on paper to realize paper-based microfluidics. Beyond paper/fabric as substrates, we are also exploring new materials such as parylene, an FDA approved transparent and biocompatible polymer and emerging bioresorbable and biodegradable polymer blends such as poly(glycerol sebacate)(PGS)/poly(ε-caprolactone)(PCL) for making chemical and mechanical sensors. We are also exploring all-paper based printed circuit board for realization of electronics for readout and wireless transmission. On the electronics front, we are working on energy efficient circuits for wireless power telemetry using inductive coupling, and wireless communication using standard Radio Frequency Identification (RFID) /Medical implant communication systems (MICS) spectrum. This is in addition to innovative front end circuitry on CMOS for readout voltage and current signals from sensors built on flexible substrates. We are also exploring bioflex devices for saliva based diagnostics of medical conditions such as cancer and for management of chronic conditions like diabetes.


Nanowire electrode array on paper has been for biopotential (e.g. ECG) recording; these electrodes provide excellent dry contact without the need for a wet gel adhesive for wearable monitoring. We have also demonstrated a paper-based battery using such nanowire electrodes on paper for harvesting energy from natural acidic environments such as stomach acid. This is an innovative way to power up an ingestible sensor without the need for any external battery. We have demonstrated flexible oxygen sensors utilizing paper as a flexible, biocompatible and biodegradable substrate for wound dressing at conferences MMB 2013 and BIOCAS 2014 where it received the best paper award. We have even demonstrated a galvanic cell for power generation utilizing biological fluid as an unlimited source of electrolyte (Biosensors and Bioelectronics 2014).


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