Aadhar Jain

Optofluidic opportunities in global health, food, water and energy.

Optofluidics is a rapidly advancing field that utilizes the integration of optics and microfluidics to provide a number of novel functionalities in microsystems. In this review, we discuss how this approach can potentially be applied to address some of the greatest challenges facing both the developing and developed world, including healthcare, food shortages, malnutrition, water purification, and energy. While medical diagnostics has received most of the attention to date, here we show that some other areas can also potentially benefit from optofluidic technology. Whenever possible we briefly describe how microsystems are currently used to address these problems and then explain why and how optofluidics can provide better solutions. The focus of the article is on the applications of optofluidic techniques in low-resource settings, but we also emphasize that some of these techniques, such as those related to food production, food safety assessment, nutrition monitoring, and energy production, could be very useful in well-developed areas as well.

Gel-based optical waveguides with live cell encapsulation and integrated microfluidics.

In this Letter, we demonstrate a biocompatible microscale optical device fabricated from agarose hydrogel that allows for encapsulation of cells inside an optical waveguide. This allows for better interaction between the light in the waveguide and biology, since it can interact with the direct optical mode rather than the evanescent field. We characterize the optical properties of the waveguide and further incorporate a microfluidic channel over the optical structure, thus developing an integrated optofluidic system fabricated entirely from agarose gel.

Optimal Intensity and Biomass Density for Biofuel Production in a Thin-Light-Path Photobioreactor

Production of competitive microalgal biofuels requires development of high volumetric productivity photobioreactors (PBRs) capable of supporting high-density cultures. Maximal biomass density supported by the current PBRs is limited by nonuniform distribution of light as a result of self-shading effects. We recently developed a thin-light-path stacked photobioreactor with integrated slab waveguides that distributed light uniformly across the volume of the PBR. Here, we enhance the performance of the stacked waveguide photobioreactor (SW-PBR) by determining the optimal wavelength and intensity regime of the incident light. This enabled the SW-PBR to support high-density cultures, achieving a carrying capacity of OD730 20. Using a genetically modified algal strain capable of secreting ethylene, we improved ethylene production rates to 937 μg L(-1) h(-1). This represents a 4-fold improvement over a conventional flat-plate PBR. These results demonstrate the advantages of the SW-PBR design and provide the optimal operational parameters to maximize volumetric production.

Stacked optical waveguide photobioreactor for high density algal cultures.

In this work, an ultracompact algal photobioreactor that alleviates the problem of non-optimal light distribution in current algae photobioreactor systems, by incorporating stacked layers of slab waveguides with embedded light scatterers, is presented. Poor light distribution in traditional photobioreactor systems, due to self-shading effects, is responsible for relatively low volumetric productivity. The optimal conditions for operating a 10-layer bioreactor are outlined. The bioreactor exhibits the ability to sustain uniform biomass growth throughout the bioreactor for 3 weeks, and demonstrates an 8-fold increase in biomass productivity. Using a genetically engineered algal strain, constant secreted ethylene production for over 45 days is also demonstrated. Since the stacked architecture leads to improved light distribution throughout the volume of the bioreactor, it reduces the need for culture mixing for optimum light distribution, and thereby potentially reducing operational costs.

Integrated hollow fiber membranes for gas delivery into optical waveguide based photobioreactors

Compact algal reactors are presented with: (1) closely stacked layers of waveguides to decrease light-path to enable larger optimal light-zones; (2) waveguides containing scatterers to uniformly distribute light; and (3) hollow fiber membranes to reduce energy required for gas transfer. The reactors are optimized by characterizing the aeration of different gases through hollow fiber membranes and characterizing light intensities at different culture densities. Close to 65% improvement in plateau peak productivities was achieved under low light-intensity growth experiments while maintaining 90% average/peak productivity output during 7-h light cycles. With associated mixing costs of ∼ 1 mW/L, several magnitudes smaller than closed photobioreactors, a twofold increase is realized in growth ramp rates with carbonated gas streams under high light intensities, and close to 20% output improvement across light intensities in reactors loaded with high density cultures.

Nutrilyzer: A Mobile System for Characterizing Liquid Food with Photoacoustic Effect

In this paper, we propose Nutrilyzer, a novel mobile sensing system for characterizing the nutrients and detecting adulterants in liquid food with the photoacoustic effect. By listening to the sound of the intensity modulated light or electromagnetic wave with different wavelengths, our mobile photoacoustic sensing system captures unique spectra produced by the transmitted and scattered light while passing through various liquid food. As different liquid foods with different chemical compositions yield uniquely different spectral signatures, Nutrilyzers signal processing and machine learning algorithm learn to map the photoacoustic signature to various liquid food characteristics including nutrients and adulterants. We evaluated Nutrilyzer for milk nutrient prediction (i.e., milk protein) and milk adulterant detection. We have also explored Nutrilyzer for alcohol concentration prediction. The Nutrilyzer mobile system consists of an array of 16 LEDs in ultraviolet, visible and near-infrared region, two piezoelectric sensors and an ARM microcontroller unit, which are designed and fabricated in a printed circuit board and a 3D printed photoacoustic housing.

In Situ UV Disinfection of a Waveguide-Based Photobioreactor

Compact waveguide-based photobioreactors with high surface area-to-volume ratios and optimum light-management strategies have been developed to achieve high volumetric productivities within algal cultures. The light-managing strategies have focused on optimizing sunlight collection, sunlight filtration, and light delivery throughout the entire bioreactor volume by using light-directing waveguides. In addition to delivering broad-spectrum or monochromatic light for algal growth, these systems present an opportunity for advances in photobioreactor disinfection by using germicidal ultraviolet (UV) light. Here, we investigated the efficacy of in situ, nonchemical UV treatment to disinfect a heterotrophic contaminant in a compact photobioreactor. We maintained a >99% pure culture of Synechocystis sp. PCC 6803 for an operating period exceeding 3 weeks following UV treatment of an intentionally contaminated waveguide photobioreactor. Without UV treatment, the culture became contaminated within only a few days (control). We developed a theoretical model to predict disinfection efficiency based on operational parameters and bioreactor geometry, and we verified it with experimental results to predict the disinfection efficiency of a Bacillus subtilis spore culture.

StressPhone: smartphone based platform for measurement of cortisol for stress detection(Conference Presentation)

Anxiety disorders are estimated to be the most common mental illness in US affecting around 40 million people and related job stress is estimated to cost US industry up to

Hollow Fiber Membrane (HFM) Facilitated CO2 Delivery to a Cyanobacteria Layer for Biofuel Production

300 billion due to lower productivity and absenteeism. A personal diagnostic device which could help identify stressed individuals would therefore be a huge boost for workforce productivity. We are therefore developing a point of care diagnostic device that can be integrated with smartphones or tablets for the measurement of cortisol - a stress related salivary biomarker, which is known to be strongly involved in bodys fight-or-flight response to a stressor (physical or mental). The device is based around a competitive lateral flow assay whose results can then be read and quantified through an accessory compatible with the smartphone. In this presentation, we report the development and results of such an assay and the integrated device. We then present the results of a study relating the diurnal patterns of cortisol levels and the alertness of an individual based on the circadian rhythm and sleep patterns of the individual. We hope to use the insight provided by combining the information provided by levels of stress related to chemical biomarkers of the individual with the physical biomarkers to lead to a better informed and optimized activity schedule for maximized work output.

Thermal and Optical Analysis of a Stacked Photobioreactor Design

Photosynthetic bacteria have been shown to be advantageous organisms for biofuel production due to high CO2 fixation efficiencies, fast growth rates, and lower water requirements. Recently, cyanobacteria been metabolically engineered to efficiently secrete their products into a surrounding solution. This has the advantage of potentially eliminating the requirement to harvest and post-process the organisms in order to extract a biofuel, which is one of the most energy and water expensive processes in most biodiesel production strategies. Lagging behind the development of these organisms however has been the development of new photobioreactor (PBR) strategies that can efficiently delivery light and inorganic carbon to the bacteria while extracting the secreted product and O2 from the solution phase. Hollow fiber membranes (HFMs) are a method for bubble-less gas exchange that has been shown to be effective at enhancing mass transfer in applications such as wastewater and landfill treatment. HFM technology could be used to overcome the mass transport challenges associated with photobioreactors. HFM modules have been used to increase mass transfer of CO2 to the bulk media in bench scale PBRs; however, the use of HFM fibers as both a mean to exchange and deliver a gas phase throughout a PBR has not been explored. We have characterized the passive transport along a single fiber in a miniature reactor in previous work. Here we extend our work to arrays of HFM fibers. We performed a range of experiments to characterize bacteria growth rate and distribution as a function fiber spacing and active transport through the fibers, and report optimized values for these variables.Copyright