2014 12-22 - functional analysis of a sterilizer (rb)

Functional analysis of a sterilizer
Renata Bertocchi
Open Source for
Biomedical Engineering - OS4BME

Projecting an UVC Sterilizer:
Analysis of real needs
Analysis of physical principles
The Project
Mechanics
Electronics
Software

Lack of hygienic condition:
35.3 million people living with HIV/AIDS worldwide
in 2012
1.6 million people died of AIDS-related illnesses
worldwide in 2012
More than 780,000 people die every year due to
the consequences of hepatitis B
Ebola: over 4,500 deaths in ten months
WHO Data

Main blood diseases vectors:
Surgical tools
Dentist tools
Podiatrist tools

“An estimated 4,100 children under the age of five die
each day from diarrhea globally. Malnutrition, due
to dirty water, inadequate sanitation, and hygiene,
is estimated to lead to death in an additional 2,350
children under the age of five each day.”
WHO data

Water crisis caused by:
Climate change
World population growth
Bad management

Water crisis (2008)

Water crisis (2025)

UV radiation

UV radiation: brief history
All started in 1672 with Isaac Newton’s decomposition of light

UV radiation: brief history

UV radiation inactivation

UVC uses
Air sterilization (typically in cellular culture
systems)
Water sterilization (aquriums and bioreactors)
Surface sterilization (surgical rooms, surgical tools)

UVC uses

UVC material interaction
Absorption can cause an increase of temperature which
can damage material like polymers.

Polymers tend to
lose their properties
because the
presence of
impurities causes
photodegradation.

Even if penetration is very
negligible (75 µm), UV
irradiation can degrade
wood surfaces more than
visible light.
Material containing
cellulose is generally
bleached

Glass has nearly zero
transmission level
Glass solarization
Textiles generally
lose their colours
exciting cromophores

Transparent material to UVC are mainly soft glass
(Sodium-Barium), quartz glass, Teflon
Metal are generally UV stable, some of them have
good reflective coefficient (Aluminium)

Material choice and dimensioning
Aluminium Dimensions
- ρ = 70-80% - lamp size
- low cost - surgical tools
dimensions
- low weight

Material choice and dimensioning
Aluminium
1) 2) 3)
- cheap - less processing - ready-to-use
- need of processing - round angles - round angles
- big quantities - big quantities - expensive

Dimensioning: 3D-modelling

blue print

3D printed parts

UVC LED
- power output
- shape
- viewing angle
- cost

The lamp
- size
- power
- shape
- useful life

Modelling the system
k = 2*10-4
m2
/J

Aluminium ρ = 70-
80%

µController

Arduino is
Open-source
Easy to use
Low cost

Arduino (www.arduino.cc) uses
a simple Integrated Development
Environment (IDE) allowing all
kinds of users to write programs
using a language similar to C/C++.

Finally...
We have a surface sterilization system safe and low-
cost, capable of sterilize surgical tools in 1 h (30 min
per part).

Sterilization: regulations &
standards
Case of study: UVC sterilizer
UVC is an emerging method of sterilization and
there is not a precise regulation to observe. This
implies more caution and a long research for articles
and footprints of who has already work on it.

standards
About sterilization of health care products...
Over 60 ISO rules!!!

standards
Case of study: UVC sterilizer
Radiation

standards
Case of study: UVC sterilizer – gluing the pieces...
Choosing is fundamental
- to save time in consulting
- ISO rules are not free...

About water sterilization

“At sufficiently high doses, all waterborne enteric
pathogens are inactivated by UV radiation.” WHO

Problems:
- filtration
- flux
- UVC interaction with glass

References:
1. Many data from www.who.inc
2. Scientific America, some articles about water crisis
3. Ultraviolet Germicidal Irradiation Handbook - UVGI
for Air and Surface Disinfection. Kowalski,
Wladyslaw
4. www.arduino.cc
5. www.wikipedia.org
6. Philips lamp catalogue and Omron µSwitch catalogue

Thank you for yourThank you for your
attention!attention!

2014 12-22 - functional analysis of a sterilizer (rb)

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