Temperature gradient sensing mechanism using liquid crystal droplets with 0.1-mK-level detection accuracy and high spatial resolution

Abstract

We proposed the detection mechanism of the micro-levels of temperature gradient in a micro-electromechanical system using the unidirectional rotation of cholesteric-liquid crystal (Ch-LC) droplets. Ch-LC droplets in the presence of an isotropic phase subjected to a heat flux rotate with a speed proportional to the magnitude of the temperature gradient. We further quantified the temperature gradient-to-torque conversion efficiency to apply the thermomechanical cross-correlation to the detection of temperature gradient. Then, we observed the rotational behavior of Ch-LC droplets after introducing them onto model devices containing patterned Au thin-film electrodes. Direct electric current applied to these Au electrodes results in unidirectional rotation of the Ch-LC droplets in response to heat flux generated from the Au electrodes. By evaluating the possible temperature gradient detection resolution using Ch-LC droplet rotation, we show that Ch-LC droplets can achieve both high spatial resolution (~ 10 µm) and high detection accuracy (~ 0.1 mK/µm).

Heads or tails: investigating the effects of amphiphile features on the distortion of chiral nematic liquid crystal droplets

“…[29][30][31] It is, however, difficult to extract information about the analyte identity purely from the final texture of a nematic LC, save a few exceptions: for example, recent work has shown that specific information about the volatile compounds that are being sensed can be extracted based on the dynamics of the LC response 9,32 or by attaching specific antibodies to the interface. 26 CLCs and CLC-derived materials, however, can instead show gradients of response on their own 11,17,[33][34][35][36] owing to distortions induced in the helical structure that change the reflected color. These color changes are potentially more amenable to eventual sensing applications without targeting specific molecules, often able to be read out by the unaided eye 33,35 and without the traditional crossed polarizer set-ups necessary with nematic LC materials.…”

Biosensing with Oleosin‐Stabilized Liquid Crystal Droplets

“…[2][3][4][5][6][7][8][9] Many of the same characteristics of LCs that make them amenable to use in displays (high responsiveness to external stimuli and optical feedback) can be applied in sensing technology to provide clear, rapid feedback about a system. Classically used for temperature sensing applications, [10][11][12][13][14] LCs have more recently found use in detecting the presence or absence of amphiphiles [3] or harmful volatile compounds [5,7,[15][16][17] that can contaminate a system. Most reported sensing applications use nematic liquid crystals (NLCs), ordered fluid phases that often function based on a change of the LC alignment [2,18,19] or loss of the LC phase altogether.…”

Vertical Contact‐Separation Process of Liquid Crystal Micro‐Droplets for Chirality Sensing Mechanism

“…To directly detect chirality in solution, the VCSP of liquid crystal micro-droplets (LCμDs) can serve as a novel chirality sensing mechanism. We have recently reported that cholesteric liquid crystals (LCs) are responsive to external stimuli such as light [13], electric fields [14], and heat flux [15][16][17][18]. Achiral nematic LCs, composed of rod-like molecules with their long axes aligned along a specific direction at equilibrium, exhibit spontaneous twisting of the director along an axis when doped with chiral compounds [19].…”