The Internet of Things (IOT) is a widely engaging topic in various research areas related to wearable, clinical applications. Biomedical system such as personal health monitors in real-time is feasible through IOT systems. Wearable bioelectronics have received great deal of attention in the past decade due to their great potential in personalized health management through non-invasive monitoring of health indicators.
Fusion of physical and chemical sensing onto a single platform cannot only provide information for physical parameter such as Electrocardiogram (ECG) but also offer more insightful and detailed chemical parameters from biofluids such as sweat for more comprehensive evaluation of personal health state. From monitoring glucose and lactate level with ECG, biosensor can prevent the exerciser from hypoglycemic shock during intense exercise.
Although wearable sensors based on stretchable electronics have been developed recently, the approach of stretchable biosensor is restricted to large deformation. Brittle materials such as SU-8 and Parylene are used as encapsulation layer for biosensors detecting analytes in sweat. For high integrity of stacked layers under strain, stretchable conductor comprised with intrinsically stretchable components can be an alternative for stretchable electrode.
In this work, stretchable electrode is fabricated to monitor biochemical and biophysical information using Ag flake and elastomeric material, Eco-flex, with encapsulation of photo-patterned PDMS. Through photo-patterned PDMS encapsulation, the variation of normalized resistance of conductor decrease in stretching condition resulted from micro-crack induced by the strain.
In addition, stretchable enzymatic biosensor detecting analytes such as glucose and lactate in sweat is fabricated via Ag stretchable electrode with photo-patterned PDMS. Electrodeposition is carried out on Au modified electrode to stably deposit polymers for functionalizing at active sites. Also humidity and pH sensor for assistant sensor is fabricated to precisely detect the biochemical information. Glucose and lactate concentration is measured under 40% strain. The stretchable biosensor functionalized by PEDOT:PSS shows lower site impedance than conventional Ag/Agcl electrode , thereby it can be used as the electrode to monitor ECG in real time as well.