Droplet microfluidic systems, where water-in-oil emulsion droplets can function as pico-liter-volume bioreactor, enables single-cell-resolution studies at extremely high throughput. Almost all liquid handling steps can now be conducted in droplet microfluidics format. These features make this technology extremely popular for broad ranges of microbiology and biotechnology applications, especially when the sample diversity to be screened is extremely high, in other word when the library to be screened is large. However, major challenges that prevent the even more wide-spread use of these technologies are the relatively high error rates in many droplet manipulation steps, as well as the challenges in sequentially conducting several different droplet manipulation steps often required in many biological assays of interest. Here, I present several innovations in droplet microfluidics technologies that reduce the operational errors in droplet manipulation steps as well as enable stable operations over long periods of time, and thus reducing the error rates in high-throughput multi-step screening applications.

Development of biochips enabling distortion-free imaging in the microchannel filled with a culture medium (water) is required to investigate behavior of living cells in micro and nano environments. Fluoropolymer CYTOP is a promising material as a platform of biochips for the distortion-free imaging, because the refractive index of CYTOP (1.34) is almost same as 1.33 of water. In this study, we have developed a new 3D fabrication method for CYTOP by two-photon polymerized structures using a femtosecond laser as molds, which will be used for fabrication of micro and nano environment platforms for super-resolution bioimaging.

Microneedles are medical microdevices that provide a pathway across the skin barrier to exchange fluids or compounds with the body for drug delivery or biosensing. This talk will highlight some of the research results on hollow microneedles and associated microfluidics phenomena including manufacturing methods for hollow microneedles. It further discusses the use of these needles to characterize the diffusion of compounds in biological tissues and the mechanics of fluid absorption biological tissue upon injection. Sensing applications of hollow microneedles include continuous glucose monitoring and a point-of-care sensing platform technology for therapeutic drug monitoring in tiny fluid volumes.

I will present our work on scanning, non-contact microfluidic technologies that can dynamically shape liquids over surfaces without needing physical walls unlike standard microfluidics, which are typically closed. These technologies form ‘hydrodyamic flow confinements’ on a surface by the flow of a shaping liquid around a processing liquid. In this talk, I will discuss how these open-space embodiments enable chemical and biochemical reactions to be performed locally on immersed surfaces completely eliminating gas–liquid interfaces thereby providing new opportunities for handling, analyzing and interacting with biological samples. I will then describe two key application themes that my team has been pursuing in recent years. First is the precise patterning of surfaces with proteins and other biomolecules in an additive and subtractive manner, forming complex gradients on surfaces, and their interactions with cells on surfaces for use in biopatterning and measuring reaction kinetics. Second, I will present new concepts around tissue microprocessing for spatial multi-omic analysis of biopsy samples for possible use in pathology.

Thrombus formation is a physiological response to damage in a blood vessel. Monitoring thrombus formation is challenging, due to the limited imaging options available to analyze flowing blood. In this work, we use a visible-light optical coherence tomography (vis-OCT) system to monitor the dynamic process of the formation of thrombi in a microfluidic blood vessel-on-chip (VoC) device. Inside the VoC, thrombi form in a monolayered channel of endothelial cells perfused by human whole blood. We show that the correlation of the vis-OCT signal can be utilized as a marker for thrombus formation and can track and quantify its growth over time. We validate our results with fluorescence microscopic imaging of fibrin and platelets.

We present a microfluidic method for sorting micro/nano particles by optical radiation pressure. First, we create a narrow particle train in the middle of a microfluidic channel by laminar flow of micro/nano particles aqueous suspension. Then, we launch laser light from the side of the channel orthogonal to the flow. The particles experience optical scattering force and deviate the flowing position from the original train. The end of the channel splits into two branches. Depending on the shape, size, or color, only the particles experiencing strong optical force travel into the one of the exit branches, and the rest flows into another. To enhance the accuracy and resolution of particle sorting, we use parabolic fluid flow speed gradient in the channel.

We report a new electrochemical bio-microelectromechanical system that will enable biofluids analysis without pretreatment steps and lies in the use of an array of microelectrodes modified with bioelectronic nano-films. The multi-sensor array generates a set of complex electrochemical signals that is analyzed by using intelligent machine learning algorithms (‘chemometrics’). Here, we demonstrate the in-situ detection of: (1) the neurotransmitter dopamine in undiluted urine (a biomarker for adrenal cancer); (2) the antipsychotic clozapine in blood to provide improved schizophrenia treatment outcomes; and (3) the drug hydroxyurea in blood to enable optimized treatment of children affected with sickle cell disease.

We present our laboratory’s ongoing work in developing techniques based on commercially available screen-printing inks and threads to realize electronic components and multi-level circuits on clothing, where the fabric serves as the substrate for textile-based printed circuit boards. We investigate various limitations of commercially available scree-printing inks, including the physical properties of traces such as their resistance, clearance limit, resolution, ink penetration depth, flexibility, and stretchability. We also investigate the solderability of the inked traces and threads, ability to make custom components such as resistors and capacitors, durability of traces under flexing, and attachment techniques to surface mount components.

Nucleic acid testing (NAT) is currently the most sensitive method available for identifying infectious pathogens. Nevertheless, NAT-based diagnoses developed to date mostly require sophisticated infrastructures, reagents, and skilled technicians. While readily available in reference laboratories, NATs such as PCR remain inaccessible in resource-limited settings. Although extensive efforts have been undertaken toward point-of-care (POC) molecular diagnosis, a fully validated ‘sample-in-answer-out’ NAT system has not developed due to significant challenges of portability, sample preparation, and throughput. In this talk, I will discuss several low-cost field-deployable NAT devices and systems developed in our lab in the past 8 years, especially for infectious diseases in resource-limiting areas. These NAT devices could be loaded with easily-obtainable raw samples such as finger-prick blood, making diagnostic testing faster and easier for identifying pathogens like Malaria, HIV and SARS-COV-2.

Calorimetry is a label-free technique to study molecular interaction and measure their enthalpy changes in solution. We have developed a microfluidic calorimetry platform that uses optical means to measure these enthalpy changes in sub-nanoliter aqueous droplets. Thermochromic liquid crystals act as optical transducers to convert temperature changes caused by the reaction heat to a shift in their reflectance spectrum. We implemented large area fiber coupled LED illumination optics and multi spot detection along the microfluidic channel to measure the temperature changes in moving microfluidic droplets. To calibrate the temperature response of our system we implemented localized laser heating of individual droplets at 1464nm and monitored the heat dissipation of those droplets in the microfluidic channel. We showed that we can observe milli-Kelvin temperature changes in droplets with millisecond time resolution.

Accurate diagnosis of periprosthetic joint infections is a major challenge worldwide. The detection of persistent infections during the two-stage revision process with the current clinical procedure to determine the perfect time for reimplantation shows enormous subjectivity and leads to wrong decisions.

As part of the BoneSens research project, which aims to develop a novel digitized spacer system for continuous, longitudinal monitoring of infection status in vivo (multi-parametric data acquisition: temperature measurements; images of the inner joint skin and spectral evaluation of the bacterial load), this study investigates the potential of light scattering as a diagnostic tool using a random forest (RF) approach.

Bacterial suspensions of different concentrations (e2, e4, e6, e7, e8 of Staphylococcus Aureus in Dulbecco’s Modified Eagle’s Medium) were illuminated by the radiation of a broadband light source to detect scattering patterns with an angle of 90 degrees. In the next step, calculations of amplitude, standard deviation, and AUC values form the basis for the classification of bacterial loads by an RF algorithm.

Based on the graphical results of light scattering, bacterial loads may show differentiation with a lower limit of 104 CFU/ml. The calculated values enable a more sensitive classification of concentrations of 10² CFU/ml with an accuracy of up to 98%. Out of 200 measurements to be analyzed, only four were incorrectly assigned, whereby a differentiation is made between critical (bacterial load is underestimated; 1 out of 4) and non-critical errors (bacterial load is overestimated; 3 out of 4).

This paper introduces an optimized and affordable optofluidic add-on device for continuous and rapid light sheet imaging of C. elegans. Platform utilizes an optofluidic chip with integrated PDMS microlens to generate a light-sheet and rapidly images worms flowing in a microchannel via a regular microscope. Validation results on control and 6-OHDA-exposed worms demonstrates the ability of platform in qualitative and quantitative imaging of neuronal degenerations at different ages. The developed affordable platform enables a conventional fluorescent microscope to offer high-content and high-throughput light-sheet images of C. elegans populations which is invaluable to aging, neurodegeneration, and drug discovery studies.

Progress achieved in the field of stem-cell technology allows the reprogramming of patient-derived cells, obtained from urine or skin biopsies, into induced pluripotent stem cells that can then be differentiated into any cell types. Within this framework, techniques, being able to accurately and non-invasively characterize cell structure, morphology, and dynamics, represent very promising approaches to identify disease-specific cell phenotypes. Consequently, we will present how a label-free optofluidic platform, based on quantitative-phase digital holographic microscopy along with various experimental developments in microfluidics, constitutes a very appealing cell imaging methodology to identify, through the measurement of biophysical properties, specific cell phenotypes.

This study aimed to fabricate a droplet-based microfluidic glucose sensor using gold nanoparticles at Linoleic acid (GNPs@LA). A rapid and biocompatible method was employed to synthesize GNPs@LA. These GNPs@LA exhibit fluorescence at an excitation wavelength of 405 nm. To address the challenge of working with two immiscible solutions, namely the glucose solution and GNPs@LA, we have fabricated a droplet-based microfluidics sensor. Subsequently, the fluorescence spectra of the GNPs@LA droplets were measured. The proposed sensor utilizes the interaction between glucose and GNPs@LA, in which the fluorescence spectra's peak intensity reduces with an increase in the glucose concentration.