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Tech seminar on EES
Transcript of Tech seminar on EES
Epidermal Electronic Systems
Materials, Mechanics and Design
Design of components
Epidermal electronic system (EES) is a class of integrated electronic systems that are ultra thin, soft, and lightweight, and can be mounted on to the epidermis and yet provides robust, intimate contact to the skin.
All the components in EES are mounted on a thin layer of PolyDiMethylSiloxane (PDMS) using a method called Micro-transfer printing
In a typical EES the effective modulus (EEES) and bending stiffness (EIEES), are more important than stretchability.
The materials and mechanics ideas presented here enable intimate, mechanically “invisible,” tight and reliable attachment of high performance electronic functionality with the surface of the skin in ways that bypass limitations of previous approaches.
Swathi B Ayas
It’s a wireless device, nearly weightless and requires such less power that it can fuel itself with miniature solar collectors.
This technology blurs the gap between conventional electronics and biology
a. Materials used b. Mechanism employed
1. What is epidermal electronics ?
2. How are such nano circuits made ?
3. Applications and advantages.
4. Deformations and Limitations.
5. Conclusion and credits.
Typically, small numbers of bulk electrodes are mounted on the skin via adhesive tapes, mechanical clamps or straps, or penetrating needles, often mediated by conductive gels, with terminal connections to separate boxes that house collections of rigid circuit boards, power supplies, and communication components.
Epidermal electronics has a different approach, The electrodes, electronics, sensors, power supply, and communication components are configured together into ultrathin, low-modulus, lightweight, stretchable “skin-like” membranes that comfortably laminate onto the surface of the skin by soft contact
PDMS adds to the flexibility of the silicon and avoids adhesion losses due to stretching and bending when applied to skin.
These small flexible electronic circuits are thinner than a human hair and have the same bendable, stretchable, and compressible properties as human skin!
Adhesion to the skin due to very strong Van der Walls forces.
Electronics in this form can even be integrated directly with commercial temporary transfer tattoos as a substrate alternative to polyester or PVA. The result, is of interest as a way to conceal the active components and to exploit low-cost materials.
Materials and Components
The active elements use electronic materials, such as silicon and gallium arsenide, in the form of filamentary serpentine Nano ribbons and Nano membranes. The result is a high-performance system that offers reversible, elastic responses to large strain deformations
PDMS is used because it is Hydrophobic, Inert, Non toxic, and highly Non Inflamable
Mechanism of Adhesion
the approximate expression EEES = Eint (1 + Ld/Ls), where
is the effective modulus of the interconnects,
is the characteristic device size, and
is the distance between devices
EEES value can be reduced by minimizing Eint or reducing the Ratio Ld : Ls
The strech ability of the system defines the value of EIEES or bendability.
EIEES depends solely on the thickness of the system and is inversely proportional. Increase in thickness decreases the bending capacity.
Applications and Advantages
1. Monitoring Physiological parameters in BioMedical applications
a. ECG b. EEG c. EMG
2. Nano sensors and Power cells
3. Human Computer Interfacing
Monitoring Physiological Activity
EES offers a wireless method of obtaining patient data and vital statistics. EES does not hinder patient movement and is much more comfortable than conventional methods. Additionally PDMS is inert and does not cause any allergic reactions.
This can be used to measure different parameters of the human body. Such as the Heart rate using and ECG, The muscle strain using an EMG or study faint brain waves using an EEG.
All materials used in the EES are Bio compatible and even after 24 hours of continuous wearing and usage showed no signs of irritation.
Nano sensors and Power cells
The response varies with the amount of deformation because of the dependence of the RF inductance on geometry. For example, at tensile strains of ~12% the resonance frequency shifts by ~30%.
Many different sensors are possible with EES, including resistance-based temperature sensors built with electrodes of Platinum, In-plane strain gauges based on carbon- black-doped silicones, LEDs, photo detectors and silicon FS photovoltaic cells.
Such cells can generate a few tens of microwatts. By increasing the areas or areal coverage we can improve the output, but not without compromises in size and mechanics
Deformations and Limitations
Increasing the thickness of the EES causes decrease in bending and elasticity of the System.
Only low power consuming circuits can be implemented and the power supply must have a significant duration of operation.
Because EES is as thin as the epidermis it cannot retain shape when removed
Additional Applications of EES
Patients with sleep apnea.
Babies who need neonatal care.
For making electronic bandages which help skin heal from wounds and burns.
Physiological status monitoring.
Controlling voice and motion activated video games
Many of the EES concepts are fully compatible with small scale integrated circuits that can be released from ultrathin body silicon-on-wafer substrates. For long-term use, materials and device strategies to accommodate the continuous efflux of dead cells from the surface of the skin and the processes of transpiration will be needed.