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UID:event-19@tuemeche.nl
DTSTAMP:20261008T003056Z
DTSTART;TZID=Europe/Amsterdam:20260930T160000
DTEND;TZID=Europe/Amsterdam:20260930T173000
SUMMARY:Controlling water-in-water droplets and extracellular environment
 s in microfluidics
DESCRIPTION:Speaker: Chris Li\nHost: Hans Wyss\n\nMany important processe
 s in nature happen in water. In living cells\, biological fluids\, and so
 ft materials\, molecules do not always stay evenly mixed. Under certain c
 onditions\, one liquid can separate into two liquid phases. This process 
 is called liquid–liquid phase separation. It can also occur in fully aq
 ueous systems\, where two water-rich phases form because they contain dif
 ferent polymers or salts. This leads to the formation of water-in-water d
 roplets.\nWater-in-water droplets provide a gentle and biocompatible envi
 ronment. Unlike water-in-oil droplets\, they do not require an oil phase 
 and are therefore attractive for biological studies. However\, they are d
 ifficult to control because their interface is very weak. Their size\, st
 ability\, composition\, and surrounding environment are hard to regulate 
 over time. This limits their use in both basic research and biological ap
 plications.\nThe aim of this thesis was to develop a simple and reliable 
 microfluidic platform to produce\, trap\, and control water-in-water drop
 lets. Microfluidics allows liquids to be handled in very small channels w
 ith precise control. In this work\, water-in-water droplets were formed d
 irectly inside dead-end chambers connected to a main channel. The main ch
 annel continuously supplied a controllable aqueous environment. As a resu
 lt\, droplets could form in place and remain stable without oil\, surfact
 ants\, or complex flow control.\nThis design has an important advantage. 
 Because the droplets remain connected to the surrounding aqueous phase\, 
 their chemical environment can be changed in real time. For example\, pol
 ymer concentration\, salt concentration\, or pH can be adjusted in the ma
 in channel and then influence the droplets inside the chambers. The platf
 orm was first tested using a PEG/dextran aqueous two-phase system. Drople
 t size and composition could be controlled in a stable and reproducible w
 ay. The same design was then applied to more complex phase-separating sys
 tems\, including coacervate droplets and droplets with internal sub-compa
 rtments.\nAfter establishing droplet control\, the platform was used for 
 cell studies. Cells were guided into the dead-end chambers by a dextran c
 oncentration gradient. This gradient generated a physical driving force t
 hat moved cells into the chambers without direct mechanical pushing. By a
 djusting the gradient\, the number of cells in each chamber could be cont
 rolled. This allowed reliable confinement of single cells or small cell g
 roups. The method worked for both fission yeast and leukemia cells.\nCell
 s trapped in the chambers could then be enclosed inside PEG–dextran wat
 er-in-water droplets. This created a controllable three-dimensional extra
 cellular environment around the cells. By changing the polymer concentrat
 ion outside the droplets\, physical properties such as density and viscos
 ity could be tuned. In this way\, the position and behavior of cells insi
 de the droplets could also be regulated. The platform therefore combined 
 cell capture\, droplet formation\, and extracellular-environment control 
 in one system.\nThe final part of the thesis studied how cells respond wh
 en the surrounding fluid becomes more viscous. This question is important
  because many biological environments are thick\, crowded\, and physicall
 y complex. Using fission yeast as a model organism\, the platform allowed
  extracellular fluid viscosity to be changed under controlled conditions.
 \nThe results showed that extracellular viscosity can strongly affect cel
 l growth and division. Above a certain threshold\, cells could no longer 
 divide normally. Below this threshold\, cells adapted by increasing the v
 iscosity of their cytoplasm. This internal response was linked to preserv
 ed glucose-transporter activity and continued growth. Further experiments
  showed that glucan and trehalose are important for this adaptation. When
  their production was disrupted\, cells became less tolerant to high extr
 acellular viscosity.\nThis thesis provides a new fully aqueous microfluid
 ic platform for controlling water-in-water droplets and cell microenviron
 ments. It also shows that cells can respond to physical changes outside t
 he cell by tuning their own internal material properties.\n\nMore info: h
 ttps://tuenl.sharepoint.com/sites/intranet-mechanical-engineering/_layout
 s/15/Event.aspx?ListGuid=9bfaaae6-070c-4371-810d-a43d7ee02bf2&ItemId=244
LOCATION:Atlas 0.710
URL:https://tuemeche.nl/peoplepages/event.php?id=19
CATEGORIES:PhD Defense
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