Matthew P. Horning

Detection of malarial byproduct hemozoin utilizing its unique scattering properties

The scattering characteristics of the malaria byproduct hemozoin, including its scattering distribution and depolarization, are modeled using Discrete Dipole Approximation (DDA) and compared to those of healthy red blood cells. Scattering (or dark-field) spectroscopy and imaging are used to identify hemozoin in fresh rodent blood samples. A new detection method is proposed and demonstrated using dark-field in conjunction with cross-polarization imaging and spectroscopy. SNRs greater than 50:1 are achieved for hemozoin in fresh blood without the addition of stains or reagents. The potential of such a detection system is discussed.

Nanogap quantum dot photodetectors with high sensitivity and bandwidth

We report high-performance nanoscale photodetectors utilizing annealed nanocrystal quantum dots (QDs) within a nanoscale metal electrode gap. By optimizing the nanogap size and fabrication process, the device demonstrates a significantly better sensitivity (noise equivalent power=7.76×10−14 W/Hz1/2) and bandwidth (≥125 kHz) than previously reported nanoscale photodetectors. Furthermore, by utilizing a lateral photoconduction structure and a self-assembled layer of QDs, the detector fabrication is highly compatible with many substrates and device architectures.

Automated microscopy and machine learning for expert-level malaria field diagnosis

The optical microscope is one of the most widely used tools for diagnosing infectious diseases in the developing world. Due to its reliance on trained microscopists, field microscopy often suffers from poor sensitivity, specificity, and reproducibility. The goal of this work, called the Autoscope, is a low-cost automated digital microscope coupled with a set of computer vision and classification algorithms, which can accurately diagnose of a variety of infectious diseases, targeting use-cases in the developing world. Our initial target is malaria, because of the high difficulty of the task and because manual microscopy is currently a central but highly imperfect tool for malaria work in the field. In addition to diagnosis, the algorithm performs species identification and quantitation of parasite load, parameters which are critical in many field applications but which are not effectively determined by rapid diagnostic tests (RDTs). We have built a hardware prototype which can scan approximately 0.1 μL of blood volume in a standard Giemsa-stained thick smear blood slide in approximately 20 minutes. We have also developed a comprehensive machine learning framework, leveraging computer vision and machine learning techniques including support vector machines (SVMs) and convolutional neural networks (CNNs). The Autoscope has undergone successful initial field testing for malaria diagnosis in Thailand.

A nano-scale quantum dot photodetector by self-assembly

Modern CMOS transistors will not scale well in the next decade due to leakage currents, sources of variation, and platform requirements. To keep the cost per transistor decreasing, and to realize the feasibility of ultra-high density integrated circuits, low power techniques and efficiency optimization are being explored to counter these problems. Parallel to the development of electronic VLSI, using photons as a means of carrying information has been an appealing approach, due to the high speed and broad bandwidth of light, and the elimination of on-chip parasitic and electro-magnetic interference as its electronic counterpart. This paper focuses on photonic integrated circuits to solve the high-density problem, and presents a design for a nano-scale QD optical transducer (QDOT) that will function as a near-field photodetector and that can easily interface into a self- assembled QD integrated circuit (QDIC). The optical transducer consists of a QD between two metal electrodes. The tunneling current between the metal electrodes is mediated by the QD and can be gated by changing the optical signal intensity impinging on the QD. The device can be fabricated via self-assembly using QDs. In this method, a chemistry linker such as DNA or APTES is covalently bound to pre- defined zones on a substrate. The global location of these zones is defined via electron-beam lithography (EBL). Numerical simulations are discussed and ideal characteristics of the device are presented.