FedFwd: Federated Learning without Backpropagation

In federated learning (FL), clients with limited resources can disrupt the training efficiency. A potential solution to this problem is to leverage a new learning procedure that does not rely on backpropagation (BP). We present a novel approach to FL called FedFwd that employs a recent BP-free method by Hinton (2022), namely the Forward Forward algorithm, in the local training process. FedFwd can reduce a significant amount of computations for updating parameters by performing layer-wise local updates, and therefore, there is no need to store all intermediate activation values during training. We conduct various experiments to evaluate FedFwd on standard datasets including MNIST and CIFAR-10, and show that it works competitively to other BP-dependent FL methods.Comment: ICML 2023 Workshop (Federated Learning and Analytics in Practice: Algorithms, Systems, Applications, and Opportunities

Aptamer-functionalized Si-nanonet electrolyte-gate field-effect transistor (EGT) for detection of SARS-CoV-2 virus

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DC and AC Sensing Characteristics of a Si-nanowire BioFET for Urea Detection

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Sensing Characteristics of SARS-CoV-2 Spike Protein Using Aptamer-Functionalized Si-Based Electrolyte-Gated Field-Effect Transistor (EGT)

The sensing responses of SARS-CoV-2 spike protein using top-down-fabricated Si-based electrolyte-gated transistors (EGTs) have been investigated. An aptamer was employed as a receptor for the SARS-CoV-2 spike protein. The EGT demonstrated excellent intrinsic characteristics and higher sensitivity in the subthreshold regime compared to the linear regime. The limit of detection (LOD) was achieved as low as 0.94 pg/mL and 20 pg/mL for the current and voltage sensitivity, respectively. To analyze the sensing responses of EGT in detecting the aptamer–SARS-CoV-2 spike protein conjugate, a lumped-capacitive model with the presence of an effective dipole potential and an effective capacitance of the functionalized layer component was employed. The aptamer-functionalized EGT showed high sensitivity even in 10 mM phosphate-buffered saline (PBS) solution. These results suggest that Si-based EGTs are a highly promising method for detecting SARS-CoV-2 spike proteins

Hydrogel-coated nanonet-based field-effect transistors for SARS-CoV-2 spike protein detection in high ionic strength samples

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An Ultrasensitive Silicon-Based Electrolyte-Gated Transistor for the Detection of Peanut Allergens

The highly sensitive detection of peanut allergens (PAs) using silicon-based electrolyte-gated transistors (Si-EGTs) was demonstrated. The Si-EGT was made using a top-down technique. The fabricated Si-EGT showed excellent intrinsic electrical characteristics, including a low threshold voltage of 0.7 V, low subthreshold swing of <70 mV/dec, and low gate leakage of <10 pA. Surface functionalization and immobilization of antibodies were performed for the selective detection of PAs. The voltage-related sensitivity (SV) showed a constant behavior from the subthreshold regime to the linear regime. The current-related sensitivity (SI) was high in the subthreshold regime and then significantly decreased as the drain current increased. The limit of detection (LOD) was calculated to be as low as 25 pg/mL based on SI characteristics, which is the lowest value reported to date in the literature for various sensor methodologies. The Si-EGT showed selective detection of PA through a non-specific control test. These results confirm that Si-EGT is a high-sensitivity and low-power biosensor for PA detection

Improvement of Electrical Characteristics and Stability of Amorphous Indium Gallium Zinc Oxide Thin Film Transistors Using Nitrocellulose Passivation Layer

In this research, nitrocellulose is proposed as a new material for the passivation layers of amorphous indium gallium zinc oxide thin film transistors (a-IGZO TFTs). The a-IGZO TFTs with nitrocellulose passivation layers (NC-PVLs) demonstrate improved electrical characteristics and stability. The a-IGZO TFTs with NC-PVLs exhibit improvements in field-effect mobility (μ_FE) from 11.72 ± 1.14 to 20.68 ± 1.94 cm²/(V s), threshold voltage (<i>V</i>_th) from 1.85 ± 1.19 to 0.56 ± 0.35 V, and on/off current ratio (<i>I</i>_on/off) from (5.31 ± 2.19) × 10⁷ to (4.79 ± 1.54) × 10⁸ compared to a-IGZO TFTs without PVLs, respectively. The <i>V</i>_th shifts of a-IGZO TFTs without PVLs, with poly­(methyl methacrylate) (PMMA) PVLs, and with NC-PVLs under positive bias stress (PBS) test for 10,000 s represented 5.08, 3.94, and 2.35 V, respectively. These improvements were induced by nitrogen diffusion from NC-PVLs to a-IGZO TFTs. The lone-pair electrons of diffused nitrogen attract weakly bonded oxygen serving as defect sites in a-IGZO TFTs. Consequently, the electrical characteristics are improved by an increase of carrier concentration in a-IGZO TFTs, and a decrease of defects in the back channel layer. Also, NC-PVLs have an excellent property as a barrier against ambient gases. Therefore, the NC-PVL is a promising passivation layer for next-generation display devices that simultaneously can improve electrical characteristics and stability against ambient gases

Hydrogel-gated silicon nanotransistors for SARS-CoV-2 antigen detection in physiological ionic strength

The recent COVID-19 outbreak has strongly pushed the field of biosensors, resulting in multiple new approaches for quantitative virus detection. Among them, those using nanostructured field-effect transistors (FETs) as transducers provide an ultrasensitive approach requiring simple setups for their miniaturization toward point-of-care diagnostics of the disease. However, this type of biosensors suffer from limited sensitivity when it comes to analyzing biofluids due to their shortened screening length in presence of complex liquids with high ionic strength. In this work we propose a solution to this problem, which consists on the surface modification of the FETs with a hydrogel based on star-shaped polyethylene glycol and loaded with specific antibodies against SARS-CoV-2 spike protein. The hydrogel increases the effective Debye length, allowing to preserve the sensitivity in high ionic strength solutions. We provide the demonstration employing silicon nanonet-based FETs for the detection of viral antigens in buffer and in saliva, as well as cultured viral particles. We finally discriminate positive and negative patient samples (nasopharyngeal swab), and propose the theoretical frame that discusses the mechanism of the sensitivity preservation based on the presence of the pegylated hydrogel

Diagnosis of the patients in the development (hospital 1) and external validation (hospital 2) datasets.

Diagnosis of the patients in the development (hospital 1) and external validation (hospital 2) datasets.</p

Agreement of CFS score based on NEI scale among investigators after consensus meeting.

Agreement of CFS score based on NEI scale among investigators after consensus meeting.</p