arXiv subjects

Benjamín J. Alemán

Publications and source records attributed to Benjamín J. Alemán.

5 recordsLinked to original sources

arXiv2025

An Electrochemical Appraisal of Coffee Qualities

Despite coffee's popularity, there are no quantitative methods to measure a chemical property of a black coffee drink in situ and relate it to a flavor experience. Here we show that cyclic voltammetry can be used in coffee without any additional sample preparation to directly measure the strength of a coffee beverage and, separately, how dark the coffee has been roasted; these two properties are implicated in the sensory profile of the beverage. We show that the current passed for the cathodic features that precede hydrogen evolution are linearly related to beverage strength. The same features are suppressed with subsequent cycling, and we show that the magnitude of suppression is directly related to roast color, which dictates the ensemble chemical composition and thus flavor of the beverage. Together, this voltametric analysis decouples beverage strength from roast color and offers a new strategy for rapidly assessing chemical properties of coffee that correlate to flavor.

physics.pop-ph↗

arXiv2023

Validating an algebraic approach to characterizing resonator networks

Resonator networks are ubiquitous in natural and engineered systems, such as solid-state materials, neural tissue, and electrical circuits. To understand and manipulate these networks, it is essential to characterize their building blocks, which include the mechanical analogs of mass, elasticity, damping, and coupling of each resonator element. While these mechanical parameters are typically obtained from response spectra using least-squares fitting, this approach requires a priori knowledge of all parameters and is susceptible to large error due to convergence to local minima. Here we validate an alternative algebraic means to characterize resonator networks with no or minimal a priori knowledge. Our approach recasts the equations of motion of the network into a linear homogeneous algebraic equation and solves the equation with a set of discrete measured network response vectors. For validation, we employ our approach on noisy simulated data from a single resonator and a coupled resonator pair, and we characterize the accuracy of the recovered parameters using high-dimension factorial simulations. Generally, we find that the error is inversely proportional to the signal-to-noise ratio, that measurements at two frequencies are sufficient to recover all parameters, and that sampling near the resonant peaks is optimal. Our simple, powerful tool will enable future efforts to ascertain network properties and control resonator networks.

physics.data-an↗

arXiv2023

Spatial mapping and analysis of graphene nanomechanical resonator networks

Nanoelectromechanical (NEMS) resonator networks have drawn increasing interest due to their potential applications in emergent behavior, sensing, phononics, and mechanical information processing. A challenge toward realizing these large-scale networks is the ability to controllably tune and reconfigure the collective, macroscopic properties of the network, which relies directly on the development of methods to characterize the constituent NEMS resonator building blocks and their coupling. In this work, we demonstrate a scalable optical technique to spatially map graphene NEMS networks and read out the fixed-frequency collective response as a single vector. Using the response vectors, we introduce an efficient algebraic approach to quantify the site-specific elasticity, mass, damping, and coupling parameters of network clusters. We apply this technique to accurately characterize single uncoupled resonators and coupled resonator pairs by sampling them at just two frequencies, and without the use of curve fitting or the associated a priori parameter estimates. Our technique may be applied to a range of classical and quantum resonator systems and fills in a vital gap for programming NEMS networks.

cond-mat.mes-hall↗

arXiv2018

A fast, sensitive, room-temperature graphene nanomechanical bolometer

Bolometers are a powerful and vital means of detecting light in the IR to THz frequencies, and they have been adopted for a range of uses from astronomical observation to thermal imaging. As uses diversify, there is an increasing demand for faster, more sensitive room-temperature bolometers. To this end, graphene has generated interest because of its miniscule heat capacity and its intrinsic ultra-broadband absorption, properties that would allow it to quickly detect low levels of light of nearly any wavelength. Yet, graphene has disappointed its expectations in traditional electrical bolometry at room temperature, because of its weakly temperature-dependent resistivity and exceptionally high thermal conductivity. Here, we overcome these challenges with a new approach that detects light by tracking the resonance frequency of a graphene nanomechanical resonator. The absorbed light heats up and thermally tensions the resonator, thereby changing its frequency. Using this approach, we achieve a room-temperature noise-equivalent power of 7 pW/Hz^1/2, a value 100 times more sensitive than electrical graphene bolometers, and speeds (1.3 MHz) that greatly surpass state-of-the-art microbolometers.

cond-mat.mes-hall↗

arXiv2012

Electron spin resonance of nitrogen-vacancy centers in optically trapped nanodiamonds

Using an optical tweezers apparatus, we demonstrate three-dimensional control of nanodiamonds in solution with simultaneous readout of ground-state electron-spin resonance (ESR) transitions in an ensemble of diamond nitrogen-vacancy (NV) color centers. Despite the motion and random orientation of NV centers suspended in the optical trap, we observe distinct peaks in the measured ESR spectra qualitatively similar to the same measurement in bulk. Accounting for the random dynamics, we model the ESR spectra observed in an externally applied magnetic field to enable d.c. magnetometry in solution. We estimate the d.c. magnetic field sensitivity based on variations in ESR line shapes to be ~50 microTesla/Hz^1/2. This technique may provide a pathway for spin-based magnetic, electric, and thermal sensing in fluidic environments and biophysical systems inaccessible to existing scanning probe techniques.

cond-mat.mtrl-sci↗