George T.-C. Chiu

• PhD
• Professor (Full) at Purdue University West Lafayette

We consider the problem of learning the dynamics of a linear system when one has access to data generated by an auxiliary system that shares similar (but not identical) dynamics, in addition to data from the true system. We use a weighted least squares approach, and provide a finite sample error bound of the learned model as a function of the numbe...

This paper proposes an improved height profile model for drop-on-demand 3D printing with UV curable ink. It is extended from a previously validated model and computes height profile indirectly from volume and area propagation to ensure volume conservation. To accommodate 2D patterns using multiple passes, volume change and area change within region...

This paper proposes an improved model of height profile for drop-on-demand printing of UV curable ink. Unlike previous model, the proposed model propagates volume and covered area based on height difference between adjacent drops. Height profile is then calculated from the propagated volume and area. Measurements of 2-drop and 3-drop patterns are u...

This paper proposes a height profile model for drop-on-demand printing of UV curable ink. Existing models includesuperposition of single drops, numerical models, and graphic-based model. They are either too complicated or over simplified.Graphic model intends to find a sweet spot in between, however, accuracy is marginally improved from superpositi...

Lateral flow assay (LFA) color signal quantification methods were developed by utilizing both International Commission on Illumination (CIE) LAB (CIELAB) color space and grayscale intensity differences. The CIELAB image processing procedure included calibration, test, control band detection, and color difference calculation, which can minimize the...

Hydrogels with particulates, including proteins, drugs, nanoparticles, and cells, enable the development of new and innovative biomaterials. Precise control of the spatial distribution of these particulates is crucial to produce advanced biomaterials. Thus, there is a high demand for manufacturing methods for particle-laden hydrogels. In this conte...

Selective sensing of trace hydrogen gas is highly desirable in leak detection applications, and it has recently come to the fore to an even larger degree due to the great potential of hydrogen in the current energy transition. One difficulty of room-temperature hydrogen sensing in an open environment is the potential interference from multiple othe...

Many materials have been explored for the purpose of creating structures with high radiative cooling potential, such as nanocellulose-based structures and nanoparticle-based coatings, which have been reported with environmentally friendly attributes and high solar reflectance in current literature. They each have their own advantages and disadvanta...

Most industrial processes are not fully-automated. Although fast and low-level control can be handled by controllers, initializing and adjusting the reference, or setpoint, values, are commonly tasks assigned to human operators. A major challenge is the control policy variation among operators. In turn this can result in inconsistencies in the fina...

Collaborative robots, or cobots, have been developed as a solution to the growing need for robots that can work alongside humans safely and effectively. One emerging technology in robotics is the use of Discrete Variable Stiffness Actuators (DVSAs), which enable robots to adjust their stiffness in a fast-discrete manner. This enables cobots to work...

Applications of drop-on-demand inkjet printing in dosage-matter manufacturing and scalable patterning are attributed to its capacity for producing consistent dosages with high placement accuracy. In practice, with the same drop jetting profile, drop volume and drop jetting velocity are affected by variations in ink properties and environmental cond...

Recent advances in biomaterials and 3D printing/culture methods enable various tissue-engineered tumor models. However, it is still challenging to achieve native tumor-like characteristics due to lower cell density than native tissues and prolonged culture duration for maturation. Here, we report a new method to create tumoroids with a mechanically...

Precision livestock farming (PLF) offers a strategic solution to enhance the management capacity of large animal groups, while simultaneously improving profitability, efficiency, and minimizing environmental impacts associated with livestock production systems. Additionally, PLF contributes to optimizing the ability to manage and monitor animal wel...

We consider the problem of learning the dynamics of a linear system when one has access to data generated by an auxiliary system that shares similar (but not identical) dynamics, in addition to data from the true system. We use a weighted least squares approach, and provide finite sample error bounds of the learned model as a function of the number...

In a variety of human-in-the-loop systems, variations among human operators can result in inconsistencies in process operation and product quality. While a variety of methods exist to mitigate this issue, they often require some model of the relationship between the human input and system output; unfortunately, obtaining such a model continues to b...

Consistent dosages with high deposition accuracy are critical for drop-on-demand(DoD) inkjet printing to be used in additive manufacturing and device characterization. Practically, drop volume and drop jetting velocity are subject to process uncertainties, such as applied pressure fluctuation and variation in printheads, for which open-loop approac...

Thin and lightweight radiative cooling paints are needed for many weight-sensitive applications. However, it is difficult to achieve high solar reflectance with thin layers. This work develops ultrawhite hBN-acrylic paints that achieve solar reflectance of 97.9% and sky window emissivity of 0.83 with only 150 μm thickness and 0.029 g/cm² weight, re...

In the modern industrial setting, there is an increasing demand for all types of sensors. The demand for both the quantity and quality of sensors is increasing annually. Our research focuses on thin-film nitrate sensors in particular, and it seeks to provide a robust method to monitor the quality of the sensors while reducing the cost of production...

We study the problem of estimating an unknown parameter in a distributed and online manner. Existing work on distributed online learning typically either focuses on asymptotic analysis, or provides bounds on regret. However, these results may not directly translate into bounds on the error of the learned model after a finite number of time-steps. I...

Hydrogels with embedded functional particulates are widely used to create soft materials with innovative functionalities. In order to advance these soft materials to functional devices and machines, critical technical challenges are the precise positioning of particulates within the hydrogels and the construction of the hydrogels into a complex geo...

Formaldehyde, a compound commonly employed in many construction materials, paints, and plastics, has been linked to deleterious health effects. Thus, monitoring the presence of formaldehyde in interior locations is increasingly important when it comes to public health. Currently, there is a crucial need for a low-cost, small-scale, selective, and s...

Public health depends on reliable, low-cost methods of measuring indoor air quality (IAQ), and carbon dioxide (CO2) is often used as a surrogate measure for IAQ. Thus, there is an increasing interest in developing inexpensive CO2sensors that can be seamlessly integrated into existing ventilation systems for smart and connected healthy buildings. To...

We study the problem of identifying the dynamics of a linear system when one has access to samples generated by a similar (but not identical) system, in addition to data from the true system. We use a weighted least squares approach and provide finite sample performance guarantees on the quality of the identified dynamics. Our results show that one...

We consider the problem of learning the dynamics of autonomous linear systems (i.e., systems that are not affected by external control inputs) from observations of multiple trajectories of those systems, with finite sample guarantees. Existing results on learning rate and consistency of autonomous linear system identification rely on observations o...

Indoor air quality (IAQ) has been a growing concern in recent years, only to be expedited by the COVID-19 pandemic. A common provisional measure for IAQ is carbon dioxide (CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), which is commonly used to inform the ventilation control of buildings...

Electrodes fabricated from electronically active polymers offer some benefits over those fabricated with common metals, including an appreciable resistance to corrosion and lower density. These benefits, and potentially others, manifest the advantages of using conductive polymers in lieu of metals for the mass production of ignition systems. In thi...

Carbon dioxide (CO2) has been linked to many deleterious health effects, and it has also been used as a proxy for building occupancy measurements. These applications have created a need for low-cost and low-power CO2 sensors that can be seamlessly incorporated into existing buildings. We report a resonant mass sensor coated with a solution-processa...

Due to the nascency of bacteriophage-based pathogen detection technologies, several practical hurdles stand in the way between providing promising proof-of-concept data and development of robust detection platforms. One such hurdle, and the focus of this work, is the development of methods for transitioning laboratory stocks of bacteriophage into f...

This paper proposes an improved model of height profile for drop-on-demand printing of UV curable ink. Unlike previous model, the proposed model propagates volume and covered area based on height difference between adjacent drops. Height profile is then calculated from the propagated volume and area. Measurements of 2-drop and 3-drop patterns are u...

In this paper, a low cost, single camera, double mirror system that can be built in a desktop nail printer will be described. The usage of this system is to capture an image of a fingernail and to generate the 3D shape of the nail. The nail’s depth map will be estimated from this rendered 3D nail shape. The paper will describe the camera calibratio...

Nitrate sensors are commonly used to reflect the nitrate levels of soil conditions in agriculture. In a roll-to-roll system, for manufacturing Thin-Film nitrate sensors, varying characteristics of the ion-selective membrane on screen-printed electrodes are inevitable and affect sensor performance. It is essential to monitor the sensor performance i...

Automating the assessment of sensor quality in the production of thin-film nitrate sensors can yield significant advantages. Currently, the inspection process is extremely time and labor intensive, requiring technicians to manually examine sensors from each batch to determine their performance. Not only is manually examining sensors costly, it also...

Mercury (Hg) and Arsenic (As) have been recognized as chemical threats to human health. Still, the detection of lower contamination levels using traditional image analysis remains challenging due to the small number of available data samples and the insufficient utilization of the spatial information contained in the sensor pad images. To overcome...

In one of our previous paper [1] proposed in the last year, we described the color management pipeline that applied to our nail inkjet printer. However, the resulting prints are not as vivid as we would like to have since those prints are not well saturated. In this paper, we propose a saturation enhancement method based on the image segmentation a...

In this paper, we introduce an eight-channel paper-based microfluidic device that aims to detect multiple chemicals at once. The microfluidic device we propose is fabricated by wax printing on filter paper, which is trouble-free to handle, low cost, and easy to fabricate. As a hydrophobic material, wax (solid ink) defines the hydrophilic channels f...

The standoff detection of energetic materials is a critical challenge in national security and defense. The detection of solid energetic materials is particularly challenging, as these materials have extremely low vapor pressures at room temperature. Accordingly, the species have very low vapor phase concentrations. This letter presents a bifurcati...

Drop formation models are essential for the control of drop-on-demand (DoD) inkjet printing process. Traditional numerical models are difficult to implement in real-time control. In this paper, an equivalent circuit model (ECM) is developed to motivate the implementation of a data-driven ARX model combined with a drop volume adjuster to estimate dr...

The rising development of biosensors offers great potential for health, food, and environmental monitoring. However, in many colorimetric platforms, there is a performance limitation stemming from the tendency of traditional Au nanoparticles toward nonspecific aggregation in response to changing ionic strength (salt concentration). This work puts f...

The prediction and measurement of vibrations of the low-frequency transverse modes of tensioned webs are of increasing interest for process monitoring, quality control, and process stability in roll-to-roll flexible hybrid and stretchable electronics manufacturing, nano-manufacturing, coated layer patterning, and other continuous manufacturing tech...

Hydrogel-based soft materials have been used in numerous applications in healthcare, food, pharmaceutical, and cosmetic industries. Manufacturing hydrogels whose functional properties and compositions are voxelized at superior spatial resolutions can significantly improve current applications as well as will enable a new generation of soft material...

In this article, we propose an iterative learning control (ILC) algorithm for a class of periodic processes with a variable time-delay that is greater than one iteration of the process. We propose a definition of the time delay as the sum of an integer and a residual such that the two components can be estimated separately. This structure enables t...

Hardware cost and manufacturing process variation constrain the use of Machine Learning (ML) in low-cost sensor applications. This paper describes a novel method to manage some of those critical limitations. Reference Calibration Mapping (RCM) is a method that creates a reference space from a single sensor and then transforms the output from the re...

Infectious diseases and environmental pollution caused by toxic chemical agents such as heavy metals are significant concerns in the global world. For example, Mercury (Hg) and Arsenic (As) have been recognized as chemical threats for human health. It is difficult to achieve multiple detections of different types of targets in lateral flow strips b...

Drop-on-demand (DoD) inkjet printing is used in precise-dosage deposition applications where consistent drop volume is important. Existing drop volume regulation in DoD inkjet printing are mainly open-loop approaches that are not effective in compensating for uncertainties during high volume printing applications. In this paper, a real-time image-b...

This paper proposes a height profile model for drop-on-demand printing of UV curable ink. Existing models include superposition of single drops, numerical models, and graphic-based model. They are either too complicated or over simplified. Graphic model intends to find a sweet spot in between, however, accuracy is marginally improved from superposi...

Presented here is the description of a software-based noise source detector that was developed to simplify the printing noise source identification process. The typical noise sources studied here were high frequency, stick-slip (squeaking) noises associated with rollers along the paper path. The detector was built by combining several digital signa...

The increasing incidence of infectious outbreaks from contaminated food and water supply continues imposing a global burden for food safety, creating a market demand for on‐site, disposable, easy‐to‐use, and cost‐efficient devices. Despite of the rapid growth of biosensors field and the generation of breakthrough technologies, more than 80% of the...

The increasing incidence of infectious outbreaks from contaminated food and water supply continues imposing a global burden for food safety, creating a market demand for on‐site, disposable, easy‐to‐use, and cost‐efficient devices. Despite of the rapid growth of biosensors field and the generation of breakthrough technologies, more than 80% of the...

During twin-roll steel strip casting, molten steel is poured onto the surface of two casting rolls where it solidifies to form a steel strip. The solidification process introduces a two-phase region of steel known as mushy steel which has a significant effect on the resulting quality of the manufactured steel strip. Therefore, an accurate model of...

The inside back cover picture shows the relationship between burning rate and equivalence ratio for aluminum bismuth (III) oxide nanothermite and highlights the correlation between this relationship and the ability of the material to controllably fracture silicon substrates when the material is confined. Details are discussed in the article by Eric...

Nanothermites have shown the potential to controllably fracture substrates in applications such as electromechanical systems security. In prior work, both equivalence ratio and material formulation have been varied to tailor fracturing performance. In this paper, material confinement was utilized to further tailor the fracturing performance of alum...

Smart devices employing interconnected sensors for feedback and control are being rapidly adopted. Many useful applications for these devices are in markets that demand cost-conscious solutions. Traditional machine learning based control systems often rely on multiple measurements from many sensors to achieve performance targets. An alternative met...

In this paper we propose an iterative learning control (ILC) algorithm for a class of periodic processes with a variable time-delay that is greater than one iteration in length. We estimate the delay by separating it into two components: an estimate based on the number of iterations contained within a single delay period and an estimate defined as...

This work demonstrated printed metallic bridge wire and spark gap igniters suitable for use with energetic materials. These devices were fabricated from an aqueous dispersion of silver nanoparticles on a flexible, mesoporous substrate using a piezoelectric inkjet printer. This manufacturing process resulted in precise samples fabricated without the...

Vibration-based sensing modalities traditionally have relied upon monitoring small shifts in natural frequency in order to detect structural changes (such as those in mass or stiffness). In contrast, bifurcation-based sensing schemes rely on the detection of a qualitative change in the behavior of a system as a parameter is varied. This can produce...

The Earth is at a sociotechnical crossroads with humanity hanging in the balance – and high-tech agriculture can help bail us out. Human population growth, increasing urbanization and rising incomes is likely to drastically increase demand for animal agriculture in the coming decades. The US Department of Agriculture (USDA) predicts the need to dou...