Microfluidics - Applications in food processing

1. MICROFLUIDICS
Applications in Food Processing
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2. 3
INTRODUCTION
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01
The science of designing, manufacturing and
operating processes and devices with small
amounts of fluids in laminar regime
MICROFLUIDICS
02
■ Lab on a chip
■ Dimensions - few millimeters to micrometers
■ One transverse dimension < 1 mm
MICROFLUIDIC DEVICES

3. 4
FUNDAMENTALS
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SCALING LAW
CONTINUUM
ASSUMPTION
DIMENSIONLESS
NUMBERS
01
03
02

4. 5
CONTINUUM ASSUMPTION
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L =10 nm
d= 0.3 nm
N = (
𝑳
𝒅
)ᶾ = 4x10⁴
Standard deviation = 𝑵
Average number of molecule = N
Mean free path, 𝐿^(−1) = λ
Representative physical length scale, 𝐿^(−1) = 𝐿
=
𝑵
𝑵
=
𝟏
𝑵
= 0.5
Relative uncertainty (%)
Knudsen number, Kn =
𝝀
𝑳 ≤ 0.01
Continual flow
01
02
Is continuum valid for microsystems? Yes
Bruus (2007), Tabeling (2005)

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SCALING LAW
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‘Scaling law’ : The law of the variation of physical quantities with the size l of the system
1. Effect of size reduction? 2. Governing forces?
Example: Gravity and capillary forces
F= 𝒎 ∗ g
m 𝒎 V 𝒎
𝑳𝟑
m – Mass, kg
g - Acceleration due to gravity, m/𝒔𝟐
Capillary forces scales 𝒎 L
Macroscopic scale =
𝑳𝟑
𝑳
̴ 𝑳𝟐
Microscopic scale L  0
V – Volume, 𝒎𝟑
L – Characteristic length scale, m
01
02 Surface forces scales 𝒎 𝑳𝟐
Volume forces scales 𝒎 𝑳𝟑
L  0
𝑳𝟐
𝑳𝟑 =
𝟏
𝑳
𝑳𝟐
𝑳𝟑 =
𝟏
𝑳
̴ ꝏ
Surface forces are dominating
Bruus (2007), Tabeling (2005)

6. 7
DIMENSIONLESS NUMBERS
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Relative importance of two competing phenomena in a fluid flow system
We Ca
Pe
FRR
Reynolds number
Weber number Capillary number
Pe´clet number
Flow rate ratio
Re
Re =
𝝆𝑼 𝒍
𝝁
We =
𝝆𝑼𝟐 𝒍
𝜸
Ca =
𝝁𝑼
𝜸
Pe =
𝑼 𝒍
𝑫
FRR =
𝑄𝑎
𝑄0
Skurtys and Aguilera (2008)

7. 8
CONTD….
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Liquid 1
Liquid 2 Diffusion region
T- Sensor
U - Characteristic velocity of the flow
l - Characteristic length of the channel
D - Diffusion coefficient
𝝉 – Time scale
Pe´clet number,
01 Pe =
𝑼 𝒍
𝑫
 Relative importance between diffusion and convection
Pe =
𝝉𝑫𝒊𝒇𝒇𝒖𝒔𝒊𝒐𝒏
𝝉𝑪𝒐𝒏𝒗𝒆𝒄𝒕𝒊𝒐𝒏
Pe >> 1 𝒎 𝝉𝑫𝒊𝒇𝒇𝒖𝒔𝒊𝒐𝒏 >> 𝝉𝑪𝒐𝒏𝒗𝒆𝒄𝒕𝒊𝒐𝒏
Pe << 1 𝒎 𝝉𝑫𝒊𝒇𝒇𝒖𝒔𝒊𝒐𝒏 << 𝝉𝑪𝒐𝒏𝒗𝒆𝒄𝒕𝒊𝒐𝒏
 Diffusion requires longer channel
 Diffusion requires shorter channel
Bruus (2007), Tabeling (2005)

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Capillary number ,
04
Flow rate ratio, FRR =
𝑄𝑎
𝑄0
05
Ca =
𝝁𝑼
𝜸
Reynolds number,
02 Re =
𝝆𝑼 𝒍
𝝁
< 2,100
 L 𝒎 0 - Inertial effects are irrelevant
 D-100 𝝁 m, 𝝁 =𝟏𝟎−𝟑
𝑷a.s, v=0.1 m/s, Re =1
 To evaluate the detachment forces
Weber number,
03 We =
𝝆𝑼𝟐 𝒍
𝜸
U - Characteristic velocity of the flow
l - Characteristic length of the channel
D - Diffusion coefficient
𝝆 - Fluid density
𝝁 - Fluid viscosity
𝜸 - Interfacial tension
CONTD….
 Multiphase systems with higher viscosity
 𝝁 =𝟏𝟎−𝟑
𝑷a.s, v=0.1 m/s , 𝜸 = 40 m N/m, Ca - 𝟏𝟎−𝟐
 Structures - desired sizes and shapes
Droplets, bubbles, micro-/nanoparticles and self-assembled structures
Skurtys and Aguilera (2008)

9. 10
MICRODEVICE GEOMETRIES
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 Co-flow and flow-focusing
 Shear-induced geometries
Capillaries assemblies
01
CONTD….
Co-flow capillary tubes Flow-focusing capillary tubes
Utada et al., (2005)

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CONTD….
 a. T-junction & Y-junction,
 b. Cross-junction
 Shear-induced geometries
Planar geometries
02 a. b.
T-junction Y-junction Cross-junction
Ushikubo et al., (2015)

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 Interfacial tension-induced
Terrace geometry
03
CONTD….
Micro channel
Terrace
Well Dispersed phase Continuous phase
Disk-shaped droplet Interfacial force
Sugiura et al., (2000)

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Regimes in shear-induced geometries
CONTD….
01 Interfacial tension > Shear forces
Squeezing
02 Continuous phase flow
Dripping
03 Interfacial and viscous forces
Jetting
Ushikubo et al., (2015)

13. 14
MICROMACHINING PROCESS
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Etching
Photolithography
Injection
molding
Laser ablation
3D printing
Mechanical
micromachining
http://www.scme-nm.org/

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Rpm- 1200-4800
t= 30- 60 s
0.5 – 2.5 μm
Hexamethyldisalizane
Coat
Expose
Si-Wafer
(H₂O₂)
PHOTOLITHOGRAPHY
Mercury vapour arc lamp – 365 nm / EUV
ArF – 193 nm/ KrF – 248 nm
6000 wafers/ day
Spin - coat
SU-8
OSTE, HSQ
http://www.scme-nm.org/

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Crosslinking
Ionized water
Develop
Immersion develop Spray-on develop
Mold
Polydimethylsiloxane (PDMS) + SYLGARD
Vacuum – Air
Heat - Cure
Hard- bake
PDMS Circuit
Plasma
CONTD….
KOH, EDP and TMAH
http://www.scme-nm.org/

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ETCHING
Removal of layers using chemicals
Methods?
Surface & Bulk Etch
1. Wet method 2. Dry methods
 Chlorine and Fluorine-based (w/ w.o oxygen.)
 Cold SF6:O₂
 XeF₂ (Xenon Difluoride)
Crystalline silicon substrate Silicon
1 2
 Potassium Hydroxide (KOH)
 Ethylene Diamine Pyrocatechol (EDP)
 Tetramethyl Ammonium Hydroxide (TMAH)
http://www.scme-nm.org/

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Etch Rinse Dry
 Etchant solution
 Concentration (wt %)
 Temperature (ºC)
 Etch rate (μm/ min)
 Quick-Dump-Rinse (QDR)
 Ultra-clean deionized water
 T : 50 – 80º C
 D.I. water: 25 psi
 Spin Rinse Dryer (SRD)
 Higher rotational speed
 Heated Nitrogen
 N₂: 4–6 CFM, 30–35 psi
 DI: 1.5–2 GPM, Max 25–30 psi
WET ETCH PROCESS
http://www.scme-nm.org/

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DRY ETCH PROCESS
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Physical etch process
Chemical etch process
Reactive Ion Etching (RIE)
Size: 2 to 20 μm
10 kV, 2.45 GHz
O₂
0.07 mbar
RF Power Supply
Vacuum
Chamber
http://www.scme-nm.org/

19. 20
APPLICATIONS
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Emulsions
01
10 - 100 μm
1. Concept for preparing double
emulsions using T-shaped
microchannels
2. Multiple emulsions: a. single, b. double, c.
triple, d. quadruple and e. quintuple emulsion
Okushima et al., (2004), Abate and Weitz (2009)

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CONTD….
4. Microfluidic production of solid fat microparticles
3. Multiple emulsions: Capillary microfluidic device for double and multiple emulsion
 O/W/O, W/O/W, A/O/W
 Increases the system stability
 Protects from external agents
 Oxygen, light, reacting environment
 Release of the compound in the target site
 Temperature, pH, presence of enzymes
Kim et al., (2013), Chu et al., (2007), Utada et al., (2005)

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Microgels
02
CONTD….
Oil
105 μm
200 μm
50 μm
Alginate
Solution
Alginate
droplet
CaCl₂ solution
CaCl₂ droplet
Microbeads
1. Production of alginate microgels by coalescence of biopolymer and cross-linking agent
2. In situ mixture
CaCl₂ solution
Alginate solution
Oil
Winding channel
Shintaku et al., (2007), Choi et al., (2007)

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CONTD….
3. Internal and external gelation
Mixing
03
3 mm
2.2 mm
0.3 m
Re∼100
Re∼10
Re∼10
Chen et al., (2021), Cai et al., (2017)

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MICROFLUIDIC CHIPS
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1. Droplet generator chip – one channel design
Company Microfluidic ChipShop, Germany
Input Channel Width 140 µm
Collection Channel Width 420 µm
Channel Depth 140 µm
Material Topas, PC
Price 42.20€ per Chip/ Rs. 3535.30 per chip
https://www.microfluidic-chipshop.com/

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2. Droplet generator chip – Multi channel design
Company Microfluidic ChipShop, Germany
Input Channel Width 80 µm
Collection Channel Width 240 µm
Channel Depth 80 µm
Material Topas, PC
Price 42.20€ per Chip/ Rs. 3535.30 per chip
https://www.microfluidic-chipshop.com/
CONTD….

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3. Micro mixer – Diffusion mixer
Company Microfluidic ChipShop, Germany
Input Channel Width 100/ 200 µm
Output Channel Width 200 µm
Channel Width Mixer 200 µm
Channel Depth 100 µm
Material Zeonor, PC
Price 42.20€ per Chip/ Rs. 3535.30 per chip
https://www.microfluidic-chipshop.com/
CONTD….

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4. Micro mixer – Herringbone mixer
Company Microfluidic ChipShop, Germany
Input Channel Width 300 µm
Output Channel Width 600 µm
Channel Width Mixer 600 µm
Channel Depth 200 µm
Material Zeonor, PC
Price 42.20€ per Chip/ Rs. 3535.30 per chip
https://www.microfluidic-chipshop.com/
CONTD….

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REFERENCES
 Abate, AR, and DA Weitz. 2009. "High‐order multiple emulsions formed in poly (dimethylsiloxane)
microfluidics." Small 5 (18):2030-2032.
 Bruus, Henrik. 2007. Theoretical microfluidics. Vol. 18: Oxford university press.
 Cai, Gaozhe, Li Xue, Huilin Zhang, and Jianhan Lin. 2017. "A review on micromixers." Micromachines 8 (9):274.
 Chen, Minjun, Guido Bolognesi, and Goran T Vladisavljević. 2021. "Crosslinking strategies for the microfluidic
production of microgels." Molecules 26 (12):3752.
 Choi, Chang-Hyung, Jae-Hoon Jung, Young Woo Rhee, Dong-Pyo Kim, Sang-Eun Shim, and Chang-Soo Lee. 2007.
"Generation of monodisperse alginate microbeads and in situ encapsulation of cell in microfluidic device."
Biomedical microdevices 9 (6):855-862.
 Chu, Liang‐Yin, Andrew S Utada, Rhutesh K Shah, Jin‐Woong Kim, and David A Weitz. 2007. "Controllable
monodisperse multiple emulsions." Angewandte Chemie 119 (47):9128-9132.
 He, Shan, Nikita Joseph, Shilun Feng, Matt Jellicoe, and Colin L Raston. 2020. "Application of microfluidic
technology in food processing." Food & function 11 (7):5726-5737.

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 Kim, Shin-Hyun, Jin Nam, Jin Woong Kim, Do-Hoon Kim, Sang-Hoon Han, and David A Weitz. 2013. "Formation
of polymersomes with double bilayers templated by quadruple emulsions." Lab on a Chip 13 (7):1351-1356.
 Microfluidic ChipShop, Jena, Germany, <https://www.microfluidic-chipshop.com/>
 Neethirajan, Suresh, Isao Kobayashi, Mitsutoshi Nakajima, Dan Wu, Saravanan Nandagopal, and Francis Lin. 2011.
"Microfluidics for food, agriculture and biosystems industries." Lab on a Chip 11 (9):1574-1586.
 Okushima, Shingo, Takasi Nisisako, Toru Torii, and Toshiro Higuchi. 2004. "Controlled production of
monodisperse double emulsions by two-step droplet breakup in microfluidic devices." Langmuir 20
(23):9905-9908.
 Shintaku, Hirofumi, Takeo Kuwabara, Satoyuki Kawano, Takaaki Suzuki, Isaku Kanno, and Hidetoshi Kotera. 2007.
"Micro cell encapsulation and its hydrogel-beads production using microfluidic device." Microsystem
technologies 13 (8):951-958.
 Skurtys, O, and JM Aguilera. 2008. "Applications of microfluidic devices in food engineering." Food Biophysics 3
(1):1-15.
 Southwest Center for Microsystems Education (SCME), University of New Mexico, Albuquerque, New Mexico,
United States, http://www.scme-nm.org/.
CONTD….

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CONTD….
 Sugiura, Shinji, Mitsutoshi Nakajima, Jihong Tong, Hiroshi Nabetani, and Minoru Seki. 2000. "Preparation of
monodispersed solid lipid microspheres using a microchannel emulsification technique." Journal of colloid
and interface science 227 (1):95-103.
 Tabeling, Patrick. 2005. Introduction to Microfluidics: OUP Oxford.
 Ushikubo, FY, DRB Oliveira, M Michelon, and RL Cunha. 2015. "Designing food structure using microfluidics."
Food Engineering Reviews 7 (4):393-416.
 Utada, Andrew S, Alberto Fernandez-Nieves, Howard A Stone, and David A Weitz. 2007. "Dripping to jetting
transitions in coflowing liquid streams." Physical review letters 99 (9):094502.
 Utada, Andrew S, Elise Lorenceau, Darren R Link, Peter D Kaplan, Howard A Stone, and DA Weitz. 2005.
"Monodisperse double emulsions generated from a microcapillary device." Science 308 (5721):537- 541.
 Zhang, Hong, Ethan Tumarkin, Ruby May A Sullan, Gilbert C Walker, and Eugenia Kumacheva. 2007.
"Exploring microfluidic routes to microgels of biological polymers." Macromolecular rapid communications 28
(5):527-538.

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THANK
YOU