Compliance detection becomes very essential in minimally invasive surgery (MIS). It can help in detection of cancerous lumps and/or for deciding on tissue healthiness. In this paper, a micromachined piezoresistive tactile sensor, with two serpentine springs and 500-μm cubic mesas, has been designed for detecting the compliance of soft tissue independent of the applied distance between the sensor and the tissue. The measuring range of the sensor is chosen to be associated with the soft-tissue properties. The sensor parameters are optimized to give high sensitivity and linearity of the sensor output. The design is simulated using ANSYS for checking the sensor performance. Then, the sensor is fabricated and tested by three types of specimens, namely, specimen chips with known stiffness, silicone rubber specimens, and chicken organ specimens (leg and heart). For the specimen chips and silicone rubber specimens, the sensor distinguished between different stiffnesses independent of the applied displacement in the range of 50-200 μm. The sensor measured Young's modulus up to 808 kPa with an average error of ±7.25%. For the chicken leg and heart, the sensor distinguished between them under the applied displacement from 100 to 200 μm, and they were calculated as 12 ±1 kPa and 81 ±8 kPa, respectively.

The tensile strength of a silicon nanowire (SiNW) that had been integrated into a silicon-on-insulator (SOI)-based microelectromechanical system (MEMS) device was measured using electrostatic actuation and sensing. SiNWs of about 150 nm diameter and 5 μm length were batch-fabricated into a 5-μm-thick SOI device layer. Since there was no interface between the SiNW and the MEMS device and the alignment was perfect, the SiNW integration into an SOI-MEMS was expected to be useful for developing highly sensitive biochemical sensors or highly reliable torsional mirror devices. The SiNW was tensile tested using the electrostatic MEMS testing device. The integration was achieved using a combination of anisotropic and an isotropic dry etching of silicon, with an inductively coupled plasma reactive ion etching. A fabricated silicon beam of 800 nm square was thinned by a sacrificial oxidation process. The tensile strength of the wire was 2.6–4.1 GPa, which was comparable to that of microscale silicon MEMS structures. The reliability of such a thin device was successfully verified for future applications of the device structures.

To clarify the physiological and pathological roles of gut-liver-axis (GLA) in the human body, a GLA microphysiological system (GLA-MPS) holds great potential. However, in current GLA-MPSs, the importance of a physiologically relevant flow for gut and liver cells' cultivation is not fully addressed. In addition, the integration of individual organ perfusion, circulation flow, and organ tissue functions in a single device has not been achieved. Here, we introduce a GLA-MPS by integrating two cell-culture chambers with individually applied perfusion flows and a circulation channel with an on-chip pneumatic micropump under cell-culture chambers via a porous membrane for interconnecting them. We analyzed the fluid shear stress (FSS) with computational fluid dynamics simulations and confirmed that the physiologically relevant FSS could be applied to the gut (Caco-2) (8 × 10−3 dyn cm−2) and liver (HepG2) cells (1.2 × 10−7 dyn cm−2). Under the physiologically relevant flow, the Caco-2 and HepG2 cells in the GLA-MPS maintained a cell survival rate of 95% and 92%, respectively. Furthermore, the expression of functional proteins such as zonula occludens 1 (in Caco-2) and albumin (in HepG2) was enhanced. To demonstrate the GLA interaction, the inflammatory bowel disease was recapitulated by applying lipopolysaccharide for only Caco-2 cells. The inflammatory proteins, such as inducible nitric oxide synthase, were induced in Caco-2 and HepG2 cells. The presented GLA-MPS can be adapted as an advanced in vitro model in various applications for disease modeling associated with inter-tissue interactions, such as inflammatory disease.

We propose a method of submicroparticle pattern formation with high productivity, flexibility, and accuracy. The proposed process is composed of template-assisted self-assembly for particle self-assembly and a subsequent two-step transfer of the assembled particles. Optimization of the process parameters was performed by carrying out experiments to evaluate the effects of the parameters on the yields of each process. Polystyrene particles that are 500 nm in diameter were used, and a silicon wafer was used as a target substrate in the experiments that are described in this paper. In the self-assembly process, 70% of the pattern was successfully self-assembled on a silicon template substrate. In the first transfer step, a transfer yield of 79% was obtained with a self-assembled-monolayer-coated polydimethylsiloxane carrier substrate. In the second transfer step, a transfer temperature of 115 provided the maximum transfer yield of 85%. The overall process yield of 48% was achieved by the optimized process parameters, and it was successfully demonstrated that the proposed method can fabricate any submicroparticle pattern.