Author Archive

Art in Science Competition Winner and runners up announced at MicroTAS 2019

Lab on a Chip and the National Institute of Standards Technology (NIST) presented the Art in Science award at the µTAS 2019 Conference on the 30th October 2019 at the Lab on a Chip/Royal Society of Chemistry booth. The award highlights the aesthetic value in scientific illustrations while still conveying scientific merit. The competition received many fantastic submissions this year which were judged by Jeanne Andres, Lab on a Chip Executive Editor, Greg Cooksey, NIST representative and Hang LuLab on a Chip Associate Editor .

Greg Cooksey and Maria Southall (Lab on a Chip Deputy Editor) announced the winner of the competition was Joesph de Rutte (UCLA) with his entry “A Cell’s World” and presented Mr de Rutte with his award and certificate.

A Cell’s World  

Joseph de Rutte, UCLA, USA

Fluorescent image of uniform droplets formed using structured microparticles. Fluorescently labeled particles are suspended in a water solution and agitated with oil and surfactant. This platform is used to encapsulate single-cells and measure their secretions.
Fluorescent image of uniform droplets formed using structured microparticles. Fluorescently labeled particles are suspended in a water solution and agitated with oil and surfactant. This platform is used to encapsulate single-cells and measure their secretions.
Greg Cooksey (NIST), Joseph de Rutte (UCLA, winner) and Maria Southall (Lab on a Chip)
Left to right: Greg Cooksey (NIST), Joseph de Rutte (UCLA, winner) and Maria Southall (Lab on a Chip)

The runners up are:

Laura Barillas, Leibniz Institute for Plasma Science and Technology (INP), Germany
MicroQuasar – Laura Barillas, Leibniz Institute for Plasma Science and Technology (INP), Germany
Sensing in Three-Dimensions
Sensing in Three-Dimensions – Michael Restaino, University of Maryland, USA
Stars and Diamonds made out of bone cells
Stars and Diamonds made out of bone cells – Charlotte Yvanoff, Vrije Universiteit Brussel, Belgium

 

A big thank you to all the contributors this year!

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MicroTAS 2019 Student Mixer

Written by Darius Rackus

Do you know which country has an airport with an IATA code of “OMG”? How about when the most recent Swiss canton joined the Swiss Confederacy? Or do you know where the article first describing a miniaturized total analysis system was published? For trivia boffins and scientists in microfluidics, these were the types of questions asked at the third annual student mixer at the International Conference on Miniaturized Systems for Chemistry and Life Sciences (microTAS).

For the past three years, microTAS has been hosting networking events for postgraduate students and female faculty. This year, students were invited to a pub quiz where they could not only test their trivia knowledge but also meet peers from different labs and different countries.

Over 200 students showed up for the night, and at least 150 participated in the quiz. The one rule given was that teams had to include students from at least two different countries and students were quick to form very diverse teams. The winning team had students representing Switzerland, China, Japan, and Israel. While there was lots of Swiss chocolate to be won, the main benefit was making new connections, which can sometimes be daunting at large international conferences.

The event was hosted by the Chemical and Biological Miniaturization Society (CBMS) and prizes were sponsored by the Royal Society of Chemistry, the journal Analytical Chemistry (ACS), and Dolomite. The winning team took home microfluidics-branded hoodies and 400 g each of fine Swiss chocolate. Of course, winning isn’t everything and networking events like this are great opportunities for connecting early career researchers. Hopefully this will continue to be a fixture of future microTAS conferences.

MicroTAS student mixer. Photo credit: André Kling

For the curious, the answers to the questions are a) Namibia (Omega Airport), b) Canton Jura was formed and joined in 1979, and c) Manz, Graber and Widmer coined the term “µTAS” in their 1990 Sensors and Actuators B publication


About the webwriter

Darius Rackus (right) is a postdoctoral researcher in the Dittrich Bionalytics Group at ETH Zürich. His research interests are in developing integrated microfluidic tools for healthcare and bioanalysis

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Emerging Investigators Series – Ye Ai

 

Dr. Ye Ai is currently an Associate Professor at Singapore University of Technology and Design (SUTD). He obtained his B.S. in Mechanical Engineering from Huazhong University of Science and Technology (China) in 2005 and his Ph.D. in Mechanical and Aerospace Engineering from Old Dominion University (USA) in 2011. Prior to joining SUTD as an assistant professor in 2013, he worked as a postdoctoral researcher at the Bioscience Division of Los Alamos National Laboratory from June 2011 to January 2013. He was a visiting scholar at Massachusetts Institute of Technology (MIT) from August 2014 to July 2015. He was promoted to associate professor with tenure in September 2019. Dr. Ai’s research interest focuses on developing novel microfluidic technologies for particle/cell manipulation and single cell analysis. His research team is also striving to translate their innovative microfluidic technologies to commercial market through collaborations with industry.

Read Dr Ai’s recent Emerging Investigator Series paper: Microfluidic impedance cytometry device with N-shaped electrodes for lateral position measurement of single cells/particles in the most recent issue of Lab on a Chip, and find out more about him and his work below.

 

 

  1. Your recent Emerging Investigator Series paper focuses on measuring the lateral position of single cells or particles. How has your research evolved from your first article to this most recent article?

My first research article when I was a PhD student was to develop a finite element model with dynamically deformed mesh that can simulate the transient motion of finite-size particles in microscale fluid flows. My PhD research mainly focused on electrokinetics for manipulating particles, cells and ions in micro/nanoscale. My postdoctoral training at the Bioscience Division of Los Alamos National Laboratory exposed me to a lot of biological problems, in particular the need in high-throughput cellular analysis at the single cell level. My previous research experience has somehow shaped my current research focus into single cell manipulation and analysis using novel microfluidic technologies when I become an independent principal investigator in Singapore.

  1. What aspect of your work are you most excited about at the moment?

I am most excited to apply our developed microfluidic technologies for solving real biomedical problems and enabling new biological studies. As an example, in 2017 my team published our single cell sorting technology using a highly focused acoustic beam in Lab Chip (DOI: 10.1039/c7lc00678k). Later, I was approached by quite a number of research teams worldwide who wanted to try our sorting technology. These email communications have encouraged me to apply our developed prototype for real biomedical problems. Right now, I have established collaboration with a few biomedical research institutes in Singapore and we have found that our sorting technology is not causing any cell damage, which is however challenging for conventional FACS machine. We currently have the idea to commercialize this single cell sorting technology. Let us see what is going to happen in the next few years.

  1. In your opinion, what are the key considerations when designing a microfluidic platform for real-time measurements?

My research team is currently developing both hydrodynamic and acoustic cell sorting platforms. The conventional way to quantify the sorting performance (e.g. purity and recovery) is to run additional cell analysis of collected samples, typically using a flow cytometer. In this work (DOI: 10.1039/c9lc00819e), we designed and validated a new impedance cytometry device that enables the measurement of the lateral positions and physical properties of individual particles and cells. The integration of this new device with any cell sorting platform will allow the evaluation of the sorting performance to be implemented in the same system.

The key consideration of integrating these real-time measurements really depends on whether there is a critical need. But I do see a lot of sorting applications need these real-time, in-line measurements for the purposes of quality control and workflow simplification. And any integration will somehow complicate the system and increase the cost, so the other key consideration is the ease of integration. Integration of electronics is generally easier compared to optics, and we are measuring intrinsic biophysical properties rather than labelling approaches; therefore, I do see great opportunities to integrate our new impedance cytometry device with a variety of cell sorting platforms.

  1. What do you find most challenging about your research?

The microfluidics and Lab on a chip research area is interdisciplinary in nature. My challenge is always to find the right people (e.g. students, postdoctoral fellows, collaborators) and secure sufficient resources to work on real impactful research problems.

  1. How do you spend your spare time?

I am trying to make a balance between work and personal life, so I mainly spend my spare time with my family members, especially my second kid is only 8 months old. I also spend some of my spare time to do physical exercise, which can help relax and leave some time for free thinking.

  1. Which profession would you choose if you were not a scientist?

I rarely thought about this before. Perhaps I would choose to be a doctor.

  1. Can you share one piece of career-related advice or wisdom with other early career scientists?

Based on my own experience, it is important to define a unique research domain based on your own expertise and the surrounding research ecosystem when early career scientists start their independent research. It is also wise to have a clear vision about what you want to achieve in the next five years.

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New thematic collection open for submissions – Single Cell Analysis

We are delighted to announce a new thematic collection in Lab on a Chip, focusing on multimodal single cell analysis, with Professors Daniel T. Chiu and Pratip K. Chattopadhyay as thought leaders.

Daniel Chiu

Professors Chiu and Chattopadhyay describe the current challenges in the field in their recent editorial in Lab on a Chip on “The Next Frontier in Single Cell Analysis: MultiModal Studies and Clinical Translation”:

Biological processes are inherently complex. Stochasticity, redundancy, plasticity, and noise are built into fundamental cellular activities from gene transcription to protein expression. A major challenge in biomedical research is to untangle this complexity. Microarray technology influenced biological research because it demonstrated clearly the wide selection of cellular molecules available for measurement and provided an efficient means to query them. However, microarrays require a large amount of material and assay large numbers of cells together in bulk.

Single cell analysis overcomes the problems of bulk measurements, but for many years the only available technology—flow cytometry—was incapable of highly multiplexed measurements. The current movement in single cell analysis is multimodal characterization. These approaches, which are rapidly replacing one-dimensional single cell analysis in biomedical research, simultaneously combine measurements of transcription with post-transcriptional regulation, epigenetic modifications, and surface protein expression. It is possible that lipid and metabolite composition, and/or cellular morphology may also be analyzed with the transcriptome or proteome.

We now have a dizzying array of tools that provide us with the potential to comprehensively and accurately characterize the cells involved in a biological process. We are a step away from using these tools widely and efficiently to impact clinical care, but there are large obstacles we must break down first. With a better understanding of the complexity ingrained in cellular systems, how do we smartly choose subsets of markers and cell types to survey, remembering that samples from patients are often limited as are research budgets? Once we know what to measure, there is the critical question of how to measure it, since there are a myriad of technical platforms and data analysis tools from which to choose. As we make measurements, how do we ensure that they are robust—are there general validation and quality control principles we can establish, or are such measures wholly platform-specific? Finally, are highly multiplexed, single cell technologies valuable only as a screening tool to identify simple biomarkers, or can these highly complex technologies (and their associated data analysis algorithms) be used directly for clinical diagnostics?

We invite review and research manuscripts that suggest answers to these questions and related issues for inclusion in a thematic collection focused on multimodal single cell analysis. If you are interested in submitting to the collection please contact the Editorial Office.

This collection open for submissions now, and into 2020.

 

If you’re interested in this topic, you can read our previous thematic collection on droplet-based single-cell sequencing here. The articles are free to read until November 15th 2019.

 

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Wearable-Implantable Sensors Thematic Collection-open for submissions

We are very pleased to announce a new Thematic Collection on Wearable and Implantable sensors!

Cover Image from 10.1039/C7LC00914C

Cover image for 10.1039/C7LC00914C

A ‘super-team’ of Lab on a Chip authors (10.1039/c7lc00914c) recently wrote, “Wearable sensing technology has recently and rapidly moved from largely a vision of science fiction to a wide array of established consumer and medical products. This explosion of wearable sensors can be attributed to several factors, such as affordability and ergonomics provided by advances in miniaturized electronics, the proliferation of smart-phones and connected devices, a growing consumer desire for health awareness, and the unmet need for doctors to continuously obtain medical quality data from their patients.”

Following this, we at Lab on a Chip have been inspired to create an Editors’ Choice collection highlighting some of our favourite recent papers in the area and to also seek more contributions in this area. The collection will feature a series of papers that address aspects of the issues involved in creating wearable or implantable sensors and their applications for diagnostics, medicine and therapeutics, health awareness and other novel applications.

Below is a selection of content highlights featured in the collection so far. In addition, all papers are free to read until 31st October 2019*.

Wearable sensors: modalities, challenges, and prospects

J. Heikenfeld, A. Jajack, J. Rogers, P. Gutruf, L. Tian, T. Pan, R. Li, M. Khine, J. Kim, J. Wang and J. Kim

 

Flexible plastic, paper and textile lab-on-a chip platforms for electrochemical biosensing

Anastasios Economou, Christos Kokkinos and Mamas Prodromidis

 

Microfluidic neural probes: in vivo tools for advancing neuroscience

Joo Yong Sim, Jae-Woong Jeong, et al.

 

Passive sweat collection and colorimetric analysis of biomarkers relevant to kidney disorders using a soft microfluidic system

Yi Zhang, John A. Rogers, et al.

 

Complete validation of a continuous and blood-correlated sweat biosensing device with integrated sweat stimulation

A Hauke, J. Heikenfeld, et al.

 

Interested in submitting to the collection?

We are interested in contributions of review and research articles in this area and this collection is now open for submissions into 2020. If you’re interested in contributing to this collection, please contact the Editorial Office.

*Access is free through an RSC account (free to register)

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Hooked on a Feeling: measuring cell-substrate adhesion with ISFET devices

By developing an ion-sensitive field-effect transistor with small gate dimensions, scientists at the University of Applied Sciences Kaiserslautern in Germany were able to measure cell-substrate adhesion on the single cell scale.

To survive, most mammalian cells attach to other cells and the extracellular environment in order to regulate their growth, proliferation, and migration. Electrical impedance spectroscopy is one way to quantitatively monitor cell-substrate interactions. The strength of cellular adhesion to a substrate with integrated electrodes can be measured by comparing the ratio of the readout voltage to the applied alternating current. Yet this method is limited groups of many cells as the size of the microelectrode must be larger than 100 μm in diameter. Smaller features are subject to greater interface impedance between the electrode and liquid media and this background impedance overwhelms the desired cell-substrate measurements. Suslorapova and colleagues thus used an ion-sensitive field-effect transistor (ISFET) with small gate dimensions to overcome this limitation. The group was able measure the effects of enzymatic digestion with trypsin and an apoptosis-inducing drug on single cell detachment using the ISFET devices with a 16 by 2 square micron gate.

The authors create an equivalent circuit model to interpret recorded impedance spectra from their single cell and small cell groups grown in contact with the field-effect transistor devices. The seal resistance and membrane capacitance parameters which can be extracted from the measured transistor transfer function (TTF) provide measures of cell shape and adhesion to the substrate. Changes in TTF correspond to adhesion of individual cells on top of the ISFET gates. This platform and the model developed to interpret TTF signal opens exciting avenues to monitoring cell adhesion in high throughput yet still at single cell resolution.

Download the full research paper paper for free* for a limited time only!

Electrical cell-substrate impedance sensing with field-effect transistors is able to unravel cellular adhesion and detachment processes on a single cell level
A. Susloparova , D. Koppenhöfer , J. K. Y. Law , X. T. Vu and S. Ingebrandt. Lab Chip, 2015, 15, 668-679. DOI: 10.1039/C4LC00593G

*Access is free until 27.03.15 through a publishing personal account. It’s quick, easy and free to register!

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Saving Stripes: using gratings to prevent destructive air-water interfaces

Researchers at National Taiwan University design grating structures to prevent air-water interfaces from destroying lipid bilayers, enabling robust bioassays of synthetic membranes.

Supported lipid bilayers (SLBs) are useful as platforms to simulate cell membranes for evaluating transport of toxins and viral particles1 and screening new pharmaceutical reagents. Yet a significant challenge is maintaining the integrity of SLBs throughout an experiment. Air-water interfaces, commonly formed during reagent changes and rinses, peel apart SLBs and delaminate them from the substrate. Strategies to preserve SLB integrity involve coating SLBs with polymers to increase their rigidity or adding proteins and sugars to form protective layers with a high bending modulus above the membrane. These methods modify the chemical structure and environment of SLBs, preventing analysis of membrane properties and specific assays of membrane-tethered species. Thus, Chung-Ta Han and Ling Chao developed a substrate with patterned gratings to prevent air-water interfaces from directly contacting SLBs when an air bubble is introduced into a microchannel with SLBs.Han2015_Figure2

The grating structures, fabricated by standard photolithography, are perpendicular to fluid flow in the microchannel and act as obstacles to air-water interfaces contacting SLBs directly by a ‘tenting’ mechanism (see figure at right). Holding the obstacle height constant at 2 μm, Han and Chao evaluated obstacle spacing at different flow rates influenced SLB stability after treatment with an air bubble. 40 μm spacing was found to efficiently preserve SLBs from air-water interfaces at a practical range of flow rates: 60 – 6000 mm/min. The authors also confirmed the integrity of the membranes by comparable diffusivity measurements within the SLBs before and after air-bubble treatment. Finally, the authors demonstrated that air bubbles did not affect receptor-ligand interactions between species embedded in the SLBs and surrounding buffer when SLBs were protected using the microfabricated obstacles.

This platform uses integrated barriers to protect SLBs from air-water interfaces, creating SLBs with native properties to study biomolecule behavior within membranes and perform high throughput analytical assays utilizing synthetic membranes.

Download the full article now – free* access for a limited time only!

Using a patterned grating structure to create lipid bilayer platforms insensitive to air bubbles
Chung-Ta Han and Ling Chao. Lab Chip, 2015, 15, 86 – 93.
DOI: 10.1039/c4lc00928b
[1] I. Kusters, A. M. Van Oijen and A. J. Driessen, ACS Nano, 2014, 8, 3380-3392.

*Access is free until 06.02.15 through a registered RSC Publishing account.

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Cytometry Unplugged: acoustophoretic focusing enables impedance-based particle sizing and counting

Groups collaborating across Sweden, Denmark, and Korea develop a chip-integrated acoustic focusing technique to precisely arrange particles for fast sizing and counting using impedance analysis.

The size and number of particles in a mixture can be quickly determined using a Coulter counter. Changes in resistance across a Coulter counter orifice through which particles pass correspond to the volume particles occupy as they displace the ionic carrier fluid (impedance spectroscopy). As fabrication methods transition to planar electrode formats to facilitate device development, the precise position of particles in the orifice becomes crucial to obtaining accurate results. Using planar electrodes on the channel bottom, the electric field across the orifice varies and thus sizing information from amplitude changes in impedance depend on consistent particle positioning. Previous methods using fluid flow focusing require complex fabrication steps and suffer from ion diffusion between virtual channel boundaries (fluid-fluid interfaces). Thus, Carl Grenvall in the Biomedical Engineering department in Lund University and his colleagues developed an acoustic actuation method to focus particles into the middle of the channel before they pass into the sensing aperture containing planar electrodes.

The team used two different frequencies to form standing waves in horizontal and vertical directions of the ‘prefocusing channel’ to guide particles to the center of the aperture where impedance was analyzed. Concentration studies helped determine the optimal density of particles to enable rapid sample analysis yet prevent formation of doublets. Confocal imaging confirmed simulation results to show distribution of focused particles and narrow confinement – 2.04% coefficient of variation after removing doublets, which is on par with other experimental and commercial cytometry platforms. The group was able to discriminate particle sizes from 3, 5, and 7 μm as well as separate 7 μm beads in a diluted blood sample. This demonstration of efficient particle focusing in two dimensions is an exciting development to create integrated simple-to-manufacture microchip impedance microscopy platforms. Standing wave acoustophoresis is gentle on cells as several studies even reporting in-field cell culturing1, thus suggesting further opportunities for integration of microscale cytometers into microscale experimental platforms.

Download the full paper for free* for a limited time only!

Two-dimensional acoustic particle focusing enables sheathless chip Coulter counter with planar electrode configuration
Carl Grenvall, Christian Antfolk, Christer Zoffmann Bisgaard, and Thomas Laurell. Lab Chip, 2014, 14, 4629 – 4637.
DOI: 10.1039/c4lc00982g

*Access is free through a registered publishing personal account until 03/02/2015.

[1] M. A. Burguillos, C. Magnusson, M. Nordin, A. Lenshof, P. Augustsson, M. J. Hansson, E. Elmer, H. Lilja, P. Brundin and T. Laurell, PloS one, 2013, 8, e64233.

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Sorting by Surfing: particles separate by riding acoustic waves

Collaborators across the University of Augsburg, Harvard University, and the University of Glasgow create a fluorescence-activated cell sorter relying on acoustofluidics to guide particles to their final location.

Traditional fluorescence-activated cell and droplet sorting (FACS, FADS) machines are expensive and require considerable time for analysis as well as maintenance (i.e., rinsing and cleaning of tubing to prepare for RNase-free processing). Cheap and disposable microfluidic devices can alleviate the expense and maintenance required, but still lag in particle sorting speed because they depend on fluidic, dielectric, and magnetic actuation to direct particles after fluorescence interrogation.

Lothar Schmid, David Weitz, and Thomas Franke overcame these issues by using traveling surface acoustic waves (SAWs) to drive particles into select channels based on readout of a fluorescent signal. The group oscillated PDMS structures from below by embedded interdigitated transducers to achieve focused acoustic radiation forces which gently moved droplets and cells via acoustic streaming.

The group was able to achieve sorting independent of cell size and compressibility on the order of 3000 particles/second into multiple outlet channels. This fast separation of particles given fluorescence signal readout enables efficient sorting of populations which vary widely in shape and volume. Further, the particles did not have to be first encapsulated into drops. This simplification avoids biohazard aerosol formation, provides higher signal to noise on the fluorescent signal interrogation, and streamlines the separation process. The group demonstrated gentle sorting of melanoma cells in a single fluid based on metabolic activity and membrane integrity. It will be exciting to see how acoustic streaming can further be used to direct particles to aid rare cell separations and cell isolations from complex samples.

You can download the full article for free* until the 24th October 2014:

Sorting drops and cells with acoustics: acoustic microfluidic fluorescence-activated cell sorter
Lothar Schmid, David A. Weitz, and Thomas Franke. Lab Chip, 2014, 14, 3710-3718.
DOI: 10.1039/C4LC00588K

*Access is free through a registered RSC account – click here to register

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Whole-in-One: one chamber to amplify DNA from single cells

Researchers at Virginia Tech create an elegant device to perform DNA amplification starting from whole cells by taking advantage of diffusivity differences in PCR components.

Diffusion can be friend or foe in the microscale regime, depending on the application. For active mixing, relying on diffusion can lengthen reaction time and thereby decrease reaction efficiency. But for separating reaction products, low ratios of convection to diffusion (Péclet number) enable control over elements based on their diffusivity[1]. Professors Luke Achenie and Chang Lu from the chemical engineering department at Virginia Tech took advantage of this diffusion-enabled control to combine cell lysis and PCR reactions in ‘one pot’ with temporal separation of how components add to the chamber due to diffusivity differences. Separation of cell lysis and DNA amplification steps in PCR is important as many traditional chemical reagents for cell lysis inhibit polymerases used in PCR and Phusion polymerases tolerant to surfactant lysis reagents are incompatible with downstream SYBR green dyes.

The device consists of a single reaction chamber connected on both sides to two separate loading chambers. A hydration line ensures minimal evaporation during the PCR cycle in the main chamber. The loading chambers are opened in sequence to let molecules into the reaction chamber via two-layer control valves. The substantial difference in reagent diffusivity in the lysis and amplification processes allow diffusion gradients to drive molecules from new solutions contacting the reaction chamber and replace reagents from previous steps without disturbing the DNA of interest. Taq polymerase and proteins are two orders of magnitude larger in diffusivity than typical (50 kb) DNA fragments, while primers, dNTPs, and lysis buffers are three orders smaller. Relying solely on diffusion to deliver reagents to the main chamber increases the time of the reaction, but this can be addressed by elevating the temperature or increasing concentration of starting reagents in the loading chambers.

The authors showed the functionality of their device with purified human genomic DNA as well as single cells. This work opens up new capabilities to perform multi-step preparation and amplification assays for DNA in a single chamber starting directly from few cells to a single cell.

Download the full article today – for free*

Diffusion-based microfluidic PCR for “one-pot” analysis of cells

Sai Ma, Despina Nelie Loufakis, Zhenning Cao, Yiwen Chang, Luke E Achenie and Chang Lu
DOI:10.1039/C4LC00498A

References: [1] T. M. Squires and S. R. Quake, Reviews of Modern Physics, 2005, 77, 977.

*Access is free through a registered RSC account until 19th September 2014 – click here to register

About the Webwriter


Sasha is a PhD student in bioengineering working with Professor Beth Pruitt’s Microsystems lab at Stanford University. Her research focuses on evaluating relationships between cell geometry, intracellular structure, and force generation (contractility) in heart muscle cells. Outside the lab, Sasha enjoys hiking, kickboxing, and interactive science outreach.

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