Microengineering Devices Lecture 03

Study Notes

Focus on fabrication techniques for MEMS-based sensors relevant in medical diagnostics.
Importance of non-invasive methods for monitoring health, especially glucose levels in diabetes.

VOCs are organic compounds that evaporate at room temperature; examples include ethanol, acetone, methanol, and petrol.
Higher concentrations of specific VOCs can indicate certain health conditions, e.g., diabetes patients exhaling more acetone.

Mimics the human sense of smell using arrays of microsensors to detect and differentiate odors.
Brains process patterns of smells; equivalent in e-nose is establishing an artificial neural network for pattern recognition.

Microengineering knowledge is crucial for creating arrays of micro and nanosensors to detect specific VOCs.
Techniques include bulk micromachining and surface micromachining.
Critical to select proper sensing materials; common options include indium tin oxide and zinc oxide.

VOC sensing has dual significance: environmental monitoring and medical diagnosis.
Different diseases result in distinct VOC profiles, necessitating precise sensing technologies.

Air pollutants linked to respiratory and cardiovascular illnesses, as well as cancer risk.
VOCs are harmful and common in many environments, such as newly painted areas emitting strong VOCs.

Two types of sensors explored:
- VOC sensors for detecting volatile organic compounds.
- Gas sensors for a broader spectrum of gaseous detection.
Emphasis on design strategies to ensure flexibility and durability in sensor substrates.

Understanding microengineering principles plays a vital role in advancing sensor technology for non-invasive disease diagnosis and environmental safety.

Diabetic individuals exhale higher concentrations of acetone compared to healthy individuals, which can be detected by specific sensors.
Designing effective sensors requires expertise in microengineering and microtechnology to create nano-sized sensor arrays.
Larger dimension sensors can be designed but may lack the precision needed for certain applications.

Air pollutants include carbon monoxide, particulate matter, ozone, lead, sulfur dioxide (SO2), nitrogen dioxide (NO2), and volatile organic compounds (VOCs).
Water pollution involves contaminants such as bacteria, parasites, and chemicals, with concerns like antibiotic resistance.
VOCs can lead to various health issues, including respiratory illnesses, cardiovascular diseases, nausea, skin irritation, and cancer risk.
Newly painted surfaces can emit VOCs, highlighting the importance of avoiding exposure to such environments.

VOCs: Organic compounds that can evaporate at room temperature; examples include petrol, diesel, ethanol, acetone, methanol, butanol, and isopropyl alcohol.
The concentration of VOCs in exhaled breath varies based on individual health conditions, presenting an opportunity for non-invasive disease diagnosis.
A person’s breath contains VOCs in the parts per million (PPM) range, with unique profiles for different diseases.

VOC sensing plays a crucial role in environmental monitoring and medical diagnostics.
Two types of sensors discussed:
- VOC sensors specifically for detecting volatile organic compounds.
- Gas sensors for detecting various gases and pollutants.

Different approaches for sensor fabrication:
- Bulk micromachining for traditional sensor designs.
- Combination of bulk and surface micromachining for enhanced sensor capabilities.
Common sensing materials include indium tin oxide and zinc oxide, utilized in semiconducting oxides to improve sensor performance.

For flexible sensors, choosing the appropriate substrate is vital to prevent cracking and ensure durability.
Familiarity with design software such as SolidWorks or CATIA is beneficial but not essential for microengineers.