Author Archive

Avoiding air bubbles when filling microfluidic chips by use of an ultrasonic bath

Leonie Bastin1 and Karen Alim1,2

1 Max Planck Institute for Dynamics and Self-Organization, Göttingen, Germany

2 Physics Department, Technical University of Munich, Germany

Why is this useful?

In microfluidic devices with small structures, air bubbles are often trapped at interfaces, corners or structures within the channel. The presented method is reproducible, fast, and only requires an additional ultrasonic bath. Vibrations from the ultrasonic bath detach the bubbles from surfaces. By flushing the chip with water at the same time, the bubbles are transported out.

What do I need?

  • An ultrasonic bath
  • The microfluidic device
  • A syringe filled with water

What do I do?

  1. Connect the syringe to the microfluidic device.
  2. Lay the device into the ultrasonic bath and turn it on.
  3. Manually fill the device with water, varying the pressure in pulses of around a second in length (see inset in Figure 1A). Use high flow rates! In our case, we used flow rates of approximately 50 microliters per second during the pulses.
  4. Before the syringe is empty, turn off the ultrasound bath, take the device out and check whether there is any air left in the channel.
  5. If there is air left in the chip, press some water through with high speed when the device is not laying in the ultrasound bath.
  6. If there are still bubbles left, repeat the procedure.
  7. Once no bubbles are left in the chip, insert the syringe for your experiment on the other side of the chip. To avoid the appearance of new bubbles, press out some of the liquid so that a drop appears at the outlet before you insert the syringe.

 

Figure 1: (A) Schematic drawing of the setup. The tubing at the outlet is optional if you fill the chip with water. The manual pressure pulses are sketched in the inset. (B) Photo of the setup without tubing at the outlet. (C) Fluorescence microscopy image of a chip filled with fluorescein to visualise the structure that is shown in D and E only filled with water. The center part is filled with 100 micrometer wide PDMS-pillars, which are arranged in a hexagonal structure. (D) Photo of a small region of the chip when filled with water without using the ultrasound method. Many air bubbles are visible between the pillar structures (arrows). (E) Photo of the same region after using the ultrasound method. No air bubbles are left in the chip.

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Outstanding Reviewers for Lab on a Chip in 2019

We would like to highlight the Outstanding Reviewers for Lab on a Chip in 2019, as selected by the editorial team, for their significant contribution to the journal. The reviewers have been chosen based on the number, timeliness and quality of the reports completed over the last 12 months.

We would like to say a big thank you to those individuals listed here as well as to all of the reviewers that have supported the journal. Each Outstanding Reviewer will receive a certificate to give recognition for their significant contribution.

Dr Daniel Citterio, Keio University, ORCID: 0000-0001-7420-045X

Dr David Collins, University of Melbourne, ORCID: 0000-0001-5382-9718

Dr David Eddington, University of Illinois at Chicago, ORCID: 0000-0002-6346-5193

Dr Mathieu Hautefeuille, National Autonomous University of Mexico, ORCID: 0000-0003-3918-0320

Dr Wolfgang Keil, Institute Curie

Dr Séverine  Le Gac, University of Twente, ORCID: 0000-0002-4546-6184

Dr Rebecca  Pompano, University of Virginia, ORCID: 0000-0002-8644-9313

Dr Julien Reboud, University of Glasgow, ORCID: 0000-0002-6879-8405

Dr Yi-Chin Toh, Queensland University of Technology, ORCID: 0000-0002-4105-4852

Dr Victor Ugaz, Texas A&M University, ORCID: 0000-0001-9361-9950

Dr Jeremiah Zartman, University of Notre Dame, ORCID: 0000-0001-7195-7203

We would also like to thank the Lab on a Chip board and the Lab on a Chip community for their continued support of the journal, as authors, reviewers and readers.

If you would like to become a reviewer for our journal, just email us with an application form and an up-to-date CV or résumé. You can find more details in our author and reviewer resource centre.

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Emerging Investigators Series – Jacqueline Linnes

Dr. Jacqueline Linnes is an Assistant Professor in the Weldon School of Biomedical Engineering at Purdue University. She received her B.S. in Engineering from the Purdue University and Ph.D. in Biongineering from the University of Washington. She was a Fogarty Postdoctoral Fellow at the Division of Global Health Equity within Brigham and Women’s Hospital/Harvard Medical School and continued her postdoctoral training at Boston University in Biomedical Engineering. She has received numerous awards including the Mandela Fellows Global Innovation Challenge Award (2017), Fast Company’s World Changing Ideas Finalist (2018), and Marta E. Gross Assistant Professorship of Biomedical Engineering (2018).

Dr. Linnes’s research lab develops real-time detection technologies to prevent, diagnose, and better understand the pathogenesis of diseases. This work emphasizes the translation of fundamental microfluidics and biological assays into point-of-care diagnostics using human-centered design principles. Her extensive experience in translational research includes co-founding and managing early-stage field-testing and user feedback for two startup companies. She has co-developed point-of-care health diagnostics, wearable devices, and water purification technologies for use in the US, Bolivia, Nicaragua, Kenya, Zambia, and Haiti.

Read Dr Linnes’s Emerging Investigator article “Microfluidic Rapid and Autonomous Analytical Device (microRAAD) to Detect HIV from Whole Blood Samples” and find out more about her in the interview below.

 

Your recent Emerging Investigator Series paper focuses on detecting HIV using a microRAAD. How has your research evolved from your first article to this most recent article?

As a PhD student, I published on the causes of bacterial adhesion to proteins adsorbed to medical devices (in 2012). These infections are incredibly difficult to detect and I found that I didn’t want to just study the causes of infections but to develop the diagnostic tools themselves. I now use the molecular biology and surface analysis skills that I developed in my PhD to create point-of-care diagnostic devices in my own lab. A critical shift in my thinking came when I realized that both the technical skills and the problem solving mindset that I learned in my PhD research were transferable to entirely different fields. In my two postdocs, I worked on Global Health projects ranging from infection control to point-of-care diagnostic devices.  Now in my own research lab, we focus on developing, integrating and automating real-time detection technologies including point-of-care diagnostics and wearable devices, to meet the needs of underserved populations. This article is an example of a sample-to-answer test we developed to automate molecular detection of a pathogen (HIV) from whole blood sample at the point-of-care.

 

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

I started my lab in 2015 with the vision that we could automate molecular detection in point-of-care diagnostics, so that the dvices could be used by anyone, anywhere in the world. I love that we have pulled together individuals with expertise in so many different fields from materials science, to electrical engineering, to molecular biology in order to make this technology work. A huge contingent of my lab and Dr. Stanciu’s lab, and at all levels, from undergraduate researchers to PhD’s have contributed to this project. Now we are bringing in more expertise in translational clinical research. I am currently in Kenya and just handed over a batch of these microRAADs to my colleague, Dr. Eddy Odari at Jomo Kenyatta University of Agriculture and Technology. Dr. Odari will be testing the MicroRAADs using real patient samples and I can’t wait to find out the results.

 

In your opinion, what is the biggest advantage to using your microRAAD compared to other methods of detecting HIV?

I know there’s still a ways to go, but I believe that the microRAAD platform will ultimately bridge the gap between laboratory-based molecular detection instruments and truly point-of-care diagnosis of HIV in the field.

 

What do you find most challenging about your research?

Designing technologies sample-to-answer molecular diagnostics that are both highly sensitive and remain robust and accessible to the clinicians, technicians, and patients who need them is incredibly challenging. In my lab, we find it critical to test out our ideas and prototypes via formal and informal usability studies to understand what can be done practically in the field settings that they are designed for. We redesign anything that isn’t actually usable in the real world.

 

At which upcoming conferences or events may our readers meet you?

I am at the 4th Africa International Biotechnology and Biomedical Conference in Nairobi and Mombasa, Kenya, and this October I will be attending the 2019 Biomedical Engineering Society Annual Meeting in Philadelphia, USA, and the 2019 MicroTAS conference in Basel, Switzerland.

 

How do you spend your spare time?

I have a 5 year old and a 3 year old so “spare time” is perhaps an overstatement, but we spend a lot of time outdoors at parks and playgrounds and my husband and I built a tree house in our backyard this summer.

 

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

That’s a tough one. I love my job as a biomedical engineering faculty member. I do think it would be fantastic to work at a science museum developing and building exhibits and outreach activities.

 

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

Don’t underestimate the power that people play in your research. Play well with others, find a place that supports you in your efforts, seek out excellent employees and mentees, and make sure to invest in their development and in your own. Whenever possible, work directly with the people that you ultimately want to use your technology. It is both incredibly motivating and absolutely critical to making an impact that reaches beyond the confines of your own lab.

Dr Jacqueline Linnes

Dr Jacqueline Linnes (Picture credit: Purdue University photo/Rebecca Wilcox)

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